i remember hearing that having 20 in wheels will cause there to be a loss in power bc of more rotating mass? is this true and if so, how much power loss we lookin at here, a noticable difference? thanx.

I've heard the same but I was told that it wouldn't be that much of a differance... now if you have 2 cars that are evenly matched up then thats where it matters and counts. I really dunno though.

It depends on the weight of the wheels and of course the tire size if you go with a tire/wheel with a larger diameter than stock. If your rear wheels with tires weigh 30lbs more than the stockers then that's the same difference between the stock driveshaft and a 1 piece aluminum driveshaft. I think anyone with a 1 piece shaft will tell you there is a noticeable difference.

So I would say yes the difference is noticeable.

ORIGINAL: |UCF|chron

i remember hearing that having 20 in wheels will cause there to be a loss in power bc of more rotating mass? is this true and if so, how much power loss we lookin at here, a noticable difference? thanx.


yes you will see a noticeable diff in power, but i'd be more concerned about your LSD. according to the manual, running tires other than 17" or 18" will cause a permanent loss of effectiveness in your LSD...

A typical set of 20's is significantly heavier than the OEM wheels. You should expect to see a loss of 10-15 HP at the wheels on a Dyno.

Of course, there are some 20's which are even heavier than that, and there are some which are lighter.

If you go with larger diameter TIRES (outside diameter) that has the same effect as changing your rear-end gears, but this won't show an HP change on the dnyo. Also, keep in mind that this is an uncommon practice. When one buys 20's, you generally get very low-profile tires so the OD is the same as stock.

I don't belive the line in the manual about loss of LSD effectiveness with different wheel sizes. It just doesn't make any sense.

My 20's aren't that much heavier than stock bullits, and I couldn't feel any noticeable difference in the switch...

jay
That is just it! MOST of the people that are claiming 20" lose all this performance HAVE NEVER BOLTED A SET UP!

Yes IF there was a substantial weight increase with 20” rims over the stock rims one would lose some performance! But if the weight between the different size rims is close the added traction with a bigger foot print that most 20" can give you over stock tires is easily over shadows any performance loss one could feel because they have inadequate or marginal horse power! Is every 20” rim made the best rims we can bolt on our cars? Absolutely NOT! There is always a trade-off. One must ask what they want from their car or the add-ons that they install. And anyone that will boldly make a statement that “All 20” rims will make your car lose performance has no more of a clue then the guy that states 20” rims are the best size rims for ALL performance aspects. Neither of those ends of the spectrum is correct. Somewhere in the middle lies the truth about 20”s and performance!
05SDI

Erm I got some actual dyno #'s from when I just got bigger tires when my mustang was rather new. I had the stock crapellis 235/50/17 and I did 306.8 rwhp, I changed to 255/40/17 hankooks and my rwhp dropped to 298. Remember if I am not mistaken every lb you add in rotational weight is = to 4x non-rotational weight.

Att. Andrew

every lb you add in rotational weight is = to 4x non-rotational weight

Well, it changes with speed = inertia

I believe that you could have seen a change in the dyno numbers. But assuming the tire sizes are correct the 235/50/17 Pirelli was not the stock tire the stock tire was 235/55/17 and they were 27.1” tall. When you changed to 255/40/17 Hankooks you tire height dropped to about 25” tall. What did you change on either the dyno set up or calibration to make up for the 8% difference in the two tire sizes? (if your 235/50/17 tire size was correct then it is closer to 5% difference in tire size) Now the HP numbers you have given are within 3% and that can be the difference in either weather or a clean air filter.
Now IF you had stock 18” wheels and you mistakenly typed 235/50/17 instead of 235/50/18 and you lost HP when you bolted on a set of 17” wheels, this would be quite humorous to me!

I have always said dynos don’t win races!! They are just a tool to inform you of one aspect of how a vehicle could perform.

you will likely lose 10-20rwhp, depending on what wheels, how wide, and how much rubber is on them...not the end of the world by any means, but quite noticeable when pulling hard to redline

Oh my do I remember this discussion not too very long ago. It got a bit ugly. Check out the previous thread and see if it helps you any. There is much to read but trust me, its all good!!! lol

http://www.mustangforums.com/m_2149636/tm.htm

One other thing, it doesnt start off talking about the 20's but it certainly changes gears and gets heavy into 20's. ;)

OH! Thanks Stowes for rescuing that thread as it was trying to die a peaceful death! lol
I’m guessing this one will end with the same people arguing the same points and ending with the same conclusions!
I think some know how I stand on this issue! lol!!!!

To be continued I’m sure…..

ORIGINAL: Sleeper05

you will likely lose 10-20rwhp,



Were in the heck did you pull those numbers from?

SO your saying someone with a good CAI & tune wearing 20" will be even in RWHP as a 100% stock GT?

I THINK NOT!

All you guys saying larger rims hurt performance; Here is your perfect example:
Do you have any proof that the GT’s with 18" rims are slower then the GT’s with 17" rims......

I THINK NOT!

Oh and the saga continues....

ORIGINAL: 05SDI

OH! Thanks Stowes for rescuing that thread as it was trying to die a peaceful death! lol
I’m guessing this one will end with the same people arguing the same points and ending with the same conclusions!
I think some know how I stand on this issue! lol!!!!

To be continued I’m sure…..




Awww man, Im sorry :( Ya gotta admit, it was good reading material though!! LOL BTW, you held your own very well so let the arguing begin!! LOL LOL (its all good)

ok well, heres the thing, i dont have the GT, so the power loss would be even more noticable for me wouldnt it? 20s look really really nice on the s197, but will the power loss be worth it (if any?) or shoulod i just look for nice 18s or 17s?

ORIGINAL: 05SDI
Were in the heck did you pull those numbers from?

SO your saying someone with a good CAI & tune wearing 20" will be even in RWHP as a 100% stock GT?

I THINK NOT!

All you guys saying larger rims hurt performance; Here is your perfect example:
Do you have any proof that the GT’s with 18" rims are slower then the GT’s with 17" rims......

I THINK NOT!


A good CAI + Tune is worth 25 or so HP on average. I'd say a 10 HP loss is about right for the average set of 20's. Thus, the modded car with the 20's would still be better off than a stock GT, but by less of a margin than he otherwise would.

Go to the "other forum" (m o d u l a r f o r d s). There are numerous firsthand dyno experiences described there. The proof of the power loss is EMPIRICAL.

By the way, I HAVE weighed the OEM wheels, and they only differ by about half a pound each between 17" and 18". That's not enough to see a significant change in performance. However, I have handled and weighed some 20" wheels that were 18 lbs HEAVIER than the oem wheels. Ouch!!!!

The issue is the WEIGHT of the wheel-tire combo. Of course, there are heavy wheels in all sizes. However, the logic goes like this: The TYPICAL 20" wheel, or "Dub" if you prefer that term, is not made with performance in mind. It is designed for style. As such, weight is a very minor concern, if it is a concern at all. Thus the AVERAGE 20" wheel is significantly heavier than the OEM 17" and 18" wheels. Think about it, the average person cares about what their wheels look like. You might ask your buddies or your fellow forum members "what do you think about these wheels for my car" and then point to a picture. You see guys like Chip Foose design wheels on TV. He gets out a sketch pad and draws what he thinks looks good. That's shopping based on LOOKS. How often do you see someone shop around for wheels by asking for weights? Or even better, moment of inertia? That information is difficult to find becasue the average customer doesn't care about those specs. Consequently they are also less important for the wheel makers.

A 20" wheel is not a performance wheel, at least not on these cars. The 20 will leave you with a very thin sidewall, which in addition to making your ride uncomfortable, also greatly reduces the torsional sidewall give in the tires--and that is key to getting a good hookup on the drag strip. Take a look at what the serious drag racers are doing: They ditch the OEM wheels and they go through a lot of effort to modify the rear end so they can put on 16" or 15" wheels in the back. That lets them put some serious wrinkle-wall tires on there.

Sure, you could get your 20's with some nice, wide, grippy tires. And that might be better than stock for traction (Due to the tires and the extra width). But getting the same type of tire on 18" or 17" rims would be even better. Then you'd have the added contact area and the sticky rubber but less of the weight. The serious racers known this. That's why they run 15" Bogarts that weight half what the OEM wheels do, and give them a nice fat wrinkewall sidewall.

BUT, a lot of people don't do that becasue 20" wheels are the hot style these days. And there's nothing wrong with that. Just about everything on these cars is a compromise of one sort or another. If you like your 20's, great! More power to you. But understand that if your wheels are particularly heavy (which most 20s are) then you will loose some power becasue of it.

UCF you would be wise to pay close attention to the actual weight of any 20" rims you are looking at. We added the same rim/tire set up as my car to my wife’s V6 convertible and I assume because she drives as one might consider "normal" that acceration was not something she complained about with the new 20" rims. Having to dodge pot holes was! I will add that acceleration, or lack there of, was one of the 3 things she did mention when she drove it home the first day we got the car a few months back. But she had gotten used to driving our GT with over 500hp so there was quite a step to the new V6! If you are coming from 16's or 17's I think the biggest thing you'll notice (OVER THE LOSS OF PERFORMANCE sorry I had to throw that in lol) is the ride. Now we lowered her car by installing Eibach pro spring kit and Tokico D-Spec (same as mine) when we went to the 20" so there was a very noticeable ride difference! I had to run here D-Specs about a half a turn out to get the same ride she liked on my car.
Please don't think I feel I'm some guru on rims and tires and I'm far from it! I just don't appreciate broad statements from people that have never had any first hand experience with actually using these but yet they claiming that just because we bolt on a set of 20" rims our cars can't perform anymore! Yes there are better rims out there for all out performance but Stock Mustang rims and tires are NOT them!
To any of the nay sayers:
Did I claim that 20's made my wife’s car quicker? NO As a matter of fact every time I drive her car and go and punch out in it, right about the time the RPM get close to 5300 or so I get the impression in my mind of the little engine cowering down hands up screaming NO! NO! Please stop, what did I do to you! LOL! So I don't drive her car hard at all! It's just not any fun! More then once I have forgotten which car I was in and started to ease into the throttle to pass and though what the heck! Then just laugh because I realize I left those extra 300+ ponies back in the garage. Funny thing, I don't thing I have ever though I was in her car while actually having been in mine!

CrazyAl

And that is the true argument! It is weight that robs horsepower NOT necessarily rims size!

I could confuse the issue by saying even in drag racing if I showed up with either of our cars and ran passes where the only thing I changed was rear tires, for example 215/65/16 (stock on some V6 Mustangs) and made passes with a set of 285/30/20 that the traction I would gain at the launch would never be over came by the hp I would be robbing as the car accelerates down the track!
Now this IS speculation on my part and next summer because my wife’s car isn’t banned from the track (lol) I will practice this theory!

Again my point isn’t that 20’s are the best, my point is and always has been some 20’s are NOT as bad as some people claim!

ORIGINAL: 05SDI


ORIGINAL: Sleeper05

you will likely lose 10-20rwhp, depending on what wheel, how wide, and how much rubber


Were in the heck did you pull those numbers from?


moment of inertia of a 17in rim @ 20lb = 5.0173 lb ft^2
moment of inertia of a 20in rim @ 20lb = 6.9444 lb ft^2

the 20in rim will require 38.4% more power to accelerate at the same rate.
now increase the actual mass of the larger rim to 25lb (only fair that the 20 weighs just 5lbs more)...
I= 8.68 lb ft^2...requiring 73% more torque to turn
now add the fact that the rubber is centered further out, so lets just round to 85% more.

that tiny little increase in diameter suddenly made that wheel twice as hard to turn (requiring twice as much torque), and since horsepower and torque are directly proportional at a given rpm, you also need twice as much horsepower to accelerate the rate at which the wheel spins.

you will lose 10-20rwhp depending on teh bolded variables



crazyal--while weight does have an large affect on power loss, the moment of inertia of the wheel is mass * radius^2...so the radius has an exponentially greater effect on power loss. granted, however, radii do not change much (a couple inches max), while weight might increase 2-fold with big rims.

ORIGINAL: 05SDI
I could confuse the issue by saying even in drag racing if I showed up with either of our cars and ran passes where the only thing I changed was rear tires, for example 215/65/16 (stock on some V6 Mustangs) and made passes with a set of 285/30/20 that the traction I would gain at the launch would never be over came by the hp I would be robbing as the car accelerates down the track!
Now this IS speculation on my part and next summer because my wife’s car isn’t banned from the track (lol) I will practice this theory!


I think you're probably right. All else being equal, if you have good tires on those 20's you would probably see that it would do better than the other car with the stock tires.

HOWEVER, let's say that instead of 20's with 285/30-20, you had something like 18s with 285/40-18. That would most likely be even better.

ORIGINAL: Sleeper05


crazyal--while weight does have an large affect on power loss, the moment of inertia of the wheel is mass * radius^2...so the radius has an exponentially greater effect on power loss. granted, however, radii do not change much (a couple inches max), while weight might increase 2-fold with big rims.




Believe me, I understand this well. I have a Mechanical Engineering degree!

The formula you quoted has to be integrated over the entire wheel. It is not such a simple calculation in the end. Your calculation is making a lot of assumtions that aren't necissarily true, though I agree with the net conclusion.

Becasue the weight difference of the 20 is concentrated towards the outside of the wheel, it's moment of intertia is significantly higher...then again, I did't want to get into this technical of a discussion here. There's plenty of people who already don't get it and now we're dragging math into the picture....

Ok i have 20's and can say that you will notice a small loss of power but it is nothing a tune and CAI and a set of gears cannot get back plus some. If your not drag racing the car it isn't going to matter. If however you are using your car for racing mostly then stay away from 20's But if your car is used a fair weather car for weekend drives and showing at car shows then get the 20's. Or if you just want the car to look good and racing is of no concern expect once in a whiel. Then keep the stockers and race with them.

R

Richard

ORIGINAL: CrazyAl


ORIGINAL: Sleeper05


crazyal--while weight does have an large affect on power loss, the moment of inertia of the wheel is mass * radius^2...so the radius has an exponentially greater effect on power loss. granted, however, radii do not change much (a couple inches max), while weight might increase 2-fold with big rims.




Believe me, I understand this well. I have a Mechanical Engineering degree!

The formula you quoted has to be integrated over the entire wheel. It is not such a simple calculation in the end. Your calculation is making a lot of assumtions that aren't necissarily true, though I agree with the net conclusion.

Becasue the weight difference of the 20 is concentrated towards the outside of the wheel, it's moment of intertia is significantly higher...then again, I did't want to get into this technical of a discussion here. There's plenty of people who already don't get it and now we're dragging math into the picture....


sweet! 3rd yr ME here. I was assuming that the wheel was a disk that was of uniform density and thickness everywhere, and thin. im workin on my dynamics hw, so i felt obligated to post, but didn have the time to do all the math out right. lol.

the point was that you DO lose power with bigger wheels, even if they weigh the same, and the loss can be significant in many circumstances.

ORIGINAL: 05SDI

every lb you add in rotational weight is = to 4x non-rotational weight

Well, it changes with speed = inertia

I believe that you could have seen a change in the dyno numbers. But assuming the tire sizes are correct the 235/50/17 Pirelli was not the stock tire the stock tire was 235/55/17 and they were 27.1” tall. When you changed to 255/40/17 Hankooks you tire height dropped to about 25” tall. What did you change on either the dyno set up or calibration to make up for the 8% difference in the two tire sizes? (if your 235/50/17 tire size was correct then it is closer to 5% difference in tire size) Now the HP numbers you have given are within 3% and that can be the difference in either weather or a clean air filter.
Now IF you had stock 18” wheels and you mistakenly typed 235/50/17 instead of 235/50/18 and you lost HP when you bolted on a set of 17” wheels, this would be quite humorous to me!

I have always said dynos don’t win races!! They are just a tool to inform you of one aspect of how a vehicle could perform.




Sorry wrote the #'s wrong I had the stock crapellis and I put in 255/50/17 hankooks k104 if I am not mistaken. Airfilter was clean since both pulls were done 3 days apart, and the weather doesn't really change here in Puerto Rico. The tires just weigh more.

Att. Andrew

ORIGINAL: CrazyAl

now we're dragging math into the picture....


I like your sense of humor!



ORIGINAL: Sleeper05

the 20in rim will require 38.4% more power to accelerate at the same rate.


Sleeper05,

Quite simply; NO IT WILL NOT!!

You are on track with your logic, but your numbers are.. well quite... er ah... fuzzy!

For example based on your numbers;
Stock GT making 300 hp and wearing 20" rims (300hp x 61.6%) Equals the equivalent of 184.8hp! (using your numbers) Therefore a stock V6 will not only beat a GT wearing 20's in the quarter mile but will CRUSH a GT, based on those numbers! And this is NOT true as it will not happen!


Please check your math or try and give a practical example of how drastic you are making this sound by spreading the same amount of weight 1.5” out in your example of the same weight of 2 rims, one 17” and one 20”.

05SDI

ORIGINAL: CrazyAl


ORIGINAL: 05SDI
I could confuse the issue by saying even in drag racing if I showed up with either of our cars and ran passes where the only thing I changed was rear tires, for example 215/65/16 (stock on some V6 Mustangs) and made passes with a set of 285/30/20 that the traction I would gain at the launch would never be over came by the hp I would be robbing as the car accelerates down the track!
Now this IS speculation on my part and next summer because my wife’s car isn’t banned from the track (lol) I will practice this theory!


I think you're probably right. All else being equal, if you have good tires on those 20's you would probably see that it would do better than the other car with the stock tires.

HOWEVER, let's say that instead of 20's with 285/30-20, you had something like 18s with 285/40-18. That would most likely be even better.


+1 it is all about sidewall. Like CrazyAl said most 20's are made for looks and not performance. I would say more than 90% of 20' rims are made for looks and not with performance in mind. You can find those made for performance, but if you are really looking for perfomance gains you usually go with a small tire. I would go for 17's wheels If my gt500 Brembo's didn't require 18' wheels or larger.

Att. Andrew

ORIGINAL: CrazyAl


ORIGINAL: Sleeper05


crazyal--while weight does have an large affect on power loss, the moment of inertia of the wheel is mass * radius^2...so the radius has an exponentially greater effect on power loss. granted, however, radii do not change much (a couple inches max), while weight might increase 2-fold with big rims.




Believe me, I understand this well. I have a Mechanical Engineering degree!

The formula you quoted has to be integrated over the entire wheel. It is not such a simple calculation in the end. Your calculation is making a lot of assumtions that aren't necissarily true, though I agree with the net conclusion.

Becasue the weight difference of the 20 is concentrated towards the outside of the wheel, it's moment of intertia is significantly higher...then again, I did't want to get into this technical of a discussion here. There's plenty of people who already don't get it and now we're dragging math into the picture....


I agree that it is not as simple as the calculation as presented. If you consider that the diameter of the tire/wheel combo of both setups are the same, the difference as a percentage would probably be about half of what was presented.

Increasing wheel diameter improves cornerning performance only to a certain point and then anything above that actually hurts performance. That is assuming the weights of all the wheels stay the same which they do not. This has been proven time and time again. Look at what auto-x and road racing people use. You are not going to see 20" wheels there.

For drag use, you don't want a heavy, large diameter wheel with a small sidewalled tire. You want a small, light wheel and a tire with a huge sidewall. Most people run 15 and 16 inch rims.

MASS is the enemy of performance and reciprocating mass is even worse.

On a 300 HP car, I highly doubt most people's but-o-meter is going to notice a 10 HP loss hence a lot of people's comments.

For example based on your numbers;
Stock GT making 300 hp and wearing 20" rims (300hp x 61.6%) Equals the equivalent of 184.8hp! (using your numbers)



I think he is saying that it will take 61.6% more power to turn the 20. so, if it took 10hp to turn the stock it will take 16.16hp to turn the 20.

ORIGINAL: 05SDI


ORIGINAL: CrazyAl

now we're dragging math into the picture....


I like your sense of humor!



ORIGINAL: Sleeper05

the 20in rim will require 38.4% more power to accelerate at the same rate.


Sleeper05,

Quite simply; NO IT WILL NOT!!

You are on track with your logic, but your numbers are.. well quite... er ah... fuzzy!

For example based on your numbers;
Stock GT making 300 hp and wearing 20" rims (300hp x 61.6%) Equals the equivalent of 184.8hp! (using your numbers) Therefore a stock V6 will not only beat a GT wearing 20's in the quarter mile but will CRUSH a GT, based on those numbers! And this is NOT true as it will not happen!


Please check your math or try and give a practical example of how drastic you are making this sound by spreading the same amount of weight 1.5” out in your example of the same weight of 2 rims, one 17” and one 20”.

05SDI



05SDI, i clearly stated that it would require that much more power to accelerate the RIMS at the same rate. aka, if the 17wheels have a parasitic loss of 20hp on their own, the 20s of the same weight would have a parasitic loss of 27.68hp by my number. This means essentially a loss of 7-8rwhp in that situation with those numbers, not 115! Read first, then attack.

then i went on to explain that the actual number would likely be 80%+, meaning 20*1.8 = 36=20+16...essentially being 15-20rwhp loss

:D[8D];)no offense taken tho!

:D

Are we having fun yet!

ORIGINAL: 05SDI

:D

Are we having fun yet!


no, cuz this dynamics project is kickin my arse

Hah! I love this! Just as much fun as thermo lab!

I think it would probably be best to model a rim as about 1/3 a flat disc (representing the "spoke" area) and a hollow ring of the remaining 2/3 of the weight, for the tubular section where the tire actually sits.

But yeah, Sleeper's numbers may not be 100% accurate, the idea is solid.

Ding, Ding, Ding!!! lol

ORIGINAL: CrazyAl

Hah! I love this! Just as much fun as thermo lab!

I think it would probably be best to model a rim as about 1/3 a flat disc (representing the "spoke" area) and a hollow ring of the remaining 2/3 of the weight, for the tubular section where the tire actually sits.

But yeah, Sleeper's numbers may not be 100% accurate, the idea is solid.



Fun isn't it

If you consider two rims of the same build and tires of the same build (just different sidewall lengths) You could probably, get away with building something that represents each rim/tire setup from about inch 16 to inch 21. It should get you the difference between the two.

how bout i just take a run on the dyno, considering i just put on 20s?

jk btw, not dynoing until the exhaust goes on in 2wks

If I had an Identical set of 17s to my 20s, I would try it just for grins. I am sure mine are heavy because they where put on by the dealer before I got the car. I don't think a dyno of my car would yield the same loss as yours. Mine is a V6 (I drive a lot, 35k+ mile/year) so the powertrain only turns one wheel. lol

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.

lol! [8D]

Sleeper05 IS 100% correct in theory and logic (though I will stand by that the numbers are fuzzy lol) and ok I confess I drastically skewed his formula to chum but the fishing wasn't good!

I will also say this is about the best thread I have seen on this forum when discussing the real amount of ‘performance’ putting on a set of 20’s costs and honestly how it’ll affect our cars.

It’s weight, weight, weight, and as Sleeper05 added when that weight is mover further out on rotating mass it even more critical!
Honestly to me more then the needed HP to accelerate this mass it’s the lack of braking force that rears its ugly head….. :eek:

Btw Please don’t feel I’m switching sides, it’s just the first time on this forum I have seen the true reasons explained why most ASSUME 20’s cause performance loss. Heavy wheels and or tires (as androdz pointed out) causes performance loss!

It’s all good!
05SDI

So just for the record when I go wheel shopping, how much do the stock 17" split spokes weigh?

If I am not mistaken 22 for the rim and 28 for the tire or the other way around. It is either, can someone be more exact on this? I remember the total was 50lbs.

Att. Andrew

I'm interested in the stock weight as well. I ordered my 07' and was gonna stick some 20"s on it right after it arrived. In terms of 1/4 mile times, what would you think the time difference would be? .1, .05? Guess I'll just have to put on a supercharger to make up the power loss. Let me go tell the wife...

GrabberOrange,

LOL! Your question is legit but it makes me laugh as that is exactly my whole point!

There will be a trade off as assuming you should get better traction with running a tire with larger contact patch but with possibly more weight you will have to over come or absorb the performance loss (OMG I just typed that) when it comes to acceration rate of velocity. (you guys like that one huh)
I don’t think many can answer your question because we have no accurate measurement of IF or HOW MUCH you can launch harder therefore you will be quicker but accelerate slower as the car moves down the track! IMO the 20’s would have a greater impact to provide more of a difference in the 1/8 mile than the ¼ mile as everyone’s argument is truly accelerating rotating mass! One thing is for sure if the race never ended and with enough data we could graph this and these two lines would intersect somewhere! WHEW!

To answer what I thought was a question; Do I think 20” rims are better for drag racing then say 17” or 18”? Nope! I just don’t like generalized statements against something that are unfounded! There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!

Sometimes I just have too much fun! 05SDI

20" for looks the cons are they ride rough, less side wall give under power results in wheel spin on hard take off's
with 17's " I was 2 tenths faster 1/4 mile may have had one rotation

I had the stock 18's on my 06GT. I bought the Roush 18's which are 18x10.
Dunno what stock are 18x8 or 8.5?
I also had to get bigger wheels for them.. from stock to 275/40 18.
I couldnt find anywhere that told the weight of the Roush wheels.

I wonder how much power or acceleration I lost....?

I stare at fat women, that doesn't mean i like them.;)


ORIGINAL: slow07

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.

Any chance you could be less general?

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!

ORIGINAL: CrazyAl


ORIGINAL: 05SDI
Were in the heck did you pull those numbers from?

SO your saying someone with a good CAI & tune wearing 20" will be even in RWHP as a 100% stock GT?

I THINK NOT!

All you guys saying larger rims hurt performance; Here is your perfect example:
Do you have any proof that the GT’s with 18" rims are slower then the GT’s with 17" rims......

I THINK NOT!


A good CAI + Tune is worth 25 or so HP on average. I'd say a 10 HP loss is about right for the average set of 20's. Thus, the modded car with the 20's would still be better off than a stock GT, but by less of a margin than he otherwise would.

Go to the "other forum" (m o d u l a r f o r d s). There are numerous firsthand dyno experiences described there. The proof of the power loss is EMPIRICAL.

By the way, I HAVE weighed the OEM wheels, and they only differ by about half a pound each between 17" and 18". That's not enough to see a significant change in performance. However, I have handled and weighed some 20" wheels that were 18 lbs HEAVIER than the oem wheels. Ouch!!!!

The issue is the WEIGHT of the wheel-tire combo. Of course, there are heavy wheels in all sizes. However, the logic goes like this: The TYPICAL 20" wheel, or "Dub" if you prefer that term, is not made with performance in mind. It is designed for style. As such, weight is a very minor concern, if it is a concern at all. Thus the AVERAGE 20" wheel is significantly heavier than the OEM 17" and 18" wheels. Think about it, the average person cares about what their wheels look like. You might ask your buddies or your fellow forum members "what do you think about these wheels for my car" and then point to a picture. You see guys like Chip Foose design wheels on TV. He gets out a sketch pad and draws what he thinks looks good. That's shopping based on LOOKS. How often do you see someone shop around for wheels by asking for weights? Or even better, moment of inertia? That information is difficult to find becasue the average customer doesn't care about those specs. Consequently they are also less important for the wheel makers.

A 20" wheel is not a performance wheel, at least not on these cars. The 20 will leave you with a very thin sidewall, which in addition to making your ride uncomfortable, also greatly reduces the torsional sidewall give in the tires--and that is key to getting a good hookup on the drag strip. Take a look at what the serious drag racers are doing: They ditch the OEM wheels and they go through a lot of effort to modify the rear end so they can put on 16" or 15" wheels in the back. That lets them put some serious wrinkle-wall tires on there.

Sure, you could get your 20's with some nice, wide, grippy tires. And that might be better than stock for traction (Due to the tires and the extra width). But getting the same type of tire on 18" or 17" rims would be even better. Then you'd have the added contact area and the sticky rubber but less of the weight. The serious racers known this. That's why they run 15" Bogarts that weight half what the OEM wheels do, and give them a nice fat wrinkewall sidewall.

BUT, a lot of people don't do that becasue 20" wheels are the hot style these days. And there's nothing wrong with that. Just about everything on these cars is a compromise of one sort or another. If you like your 20's, great! More power to you. But understand that if your wheels are particularly heavy (which most 20s are) then you will loose some power becasue of it.

+1 I'm glad you said took the time to say all that. 20's don't have any sidewall and don't work as well at the track, not to mention the weight.

ORIGINAL: moosestang

Any chance you could be less general?

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!





i am guessing that these:
http://www.americanmuscle.com/black-2005-deep-dish-bullitt-wheel-20x8-5.html
with 245/35 will allow more rwhp than 17x9.5 chrome spinners with 295/50

I guess I could always throw on my stock 17" wheels when I go to the track and burn them off there. I emailed American Racing to see if they will provide me with the weight of the wheel I want (AR Rogue Black, 20 x 8.5). Does anyone know if there is a weight savings with the tire having a smaller sidewall and how the total wheel/tire weight compares?

you run 20 inch tires same horse power as someone runing 17,s runnig mickeys 2 tenths faster with mickey street radials. Look i run 20's on the street and 17 mickeys at the track and if could have put 16" rims on i would have less weight more pony on the ground

local://upfiles/52448/D5C5DB7160D94F2FB3DB4CFC3D0D6FCD.jpg

local://upfiles/52448/AD089081AAE24014B790673518C96BC6.jpg

I think it all boils down to the fact that if all things are equal (tire diameter/width/etc) except the wheel size and weight, the 17 will perform better than the 20 in the 1/4. How much better? That will depend on many things, driver, HP, gears etc. A car with 500hp and a 4.10 rear will not feel the effects as much as a 210hp car with a 3.23 rear.
I agree with 05SDI that it is not true that all 17 inch wheel/tires will outperform all 20 inch wheel/tires. A good (light & wide) 20 inch wheel/tire will most likely outperform a bad(heavy & narrow) 17 inch wheel/tire on the same car.

that is what i was trying say if all thing are the same the smaller lighter tires will out preform the larger ones

ORIGINAL: moosestang

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing


Any chance you could be less general?




Nope! I'm thinking I did a pretty good job of dumb-ing that one up just right! lol

Hey nice looking car even if it is only sportin 18's! j/k but I do like your car!


OK I got one more example;

Even heavy 20"s will not affect acceleration and handling as much as having one or two of our fat beer drinkin buddies climb in and wants us to show them “what it’ll do"? Last week just before I put our car away for the winter I had to have had 350lbs of passengers in the back seats, I had just topped off with fuel so there was an easy 400 pounds over the rear end I wasn't used to! I about missed a slow 90 degree corner because I thought I was going to break the rear end loose and go around the corner but unbelievably hooked up from weight in the rear and the front just washed out “whoa crap!” After some brakes and steering input, and I got heading where I wanted, I looked at my back buddies and said that they'd have to go on a diet before we tried this again! Not 5 miles later, I drag the rear as I SLOWLY rolled over a speed bump! The rest of this story will be continued in another thread as I have questions…..
05SDI

ok so i think im going to be sticking with either 18s or 17s bc i dont plan on getting any power adders any time soon. thanx for the help guys.

Your guessing? It doesn't even say how much those weigh. I'm guessing that a 17 inch rim with a tire of 30 diameter or more will result in less rwhp, but probably hook at hell of a lot better than any 245/35/20 will.

This is insane! Anyone with 20's who wants to race?

ORIGINAL: Sleeper05


ORIGINAL: moosestang

Any chance you could be less general?

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!





i am guessing that these:
http://www.americanmuscle.com/black-2005-deep-dish-bullitt-wheel-20x8-5.html
with 245/35 will allow more rwhp than 17x9.5 chrome spinners with 295/50

ORIGINAL: moosestang

I stare at fat women, that doesn't mean i like them.;)


ORIGINAL: slow07

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.





moosestang is trying to crack jokes. Everyone watch out. I can tell the difference between a good stare, and a WTF stare.

I found out today that the 20" wheels I am going to buy are about 35 lbs. I'm waiting to see how much the tires weigh to see how much the total will be. Anyone out there that has 17" or 18" stock wheels wanna pull one off and throw it on the scale for us?

I weighed my 17's on the bathroom scale and it was exactly 50lbs with the stock pirelli's.

ORIGINAL: GrabberOrange07

I found out today that the 20" wheels I am going to buy are about 35 lbs. I'm waiting to see how much the tires weigh to see how much the total will be. Anyone out there that has 17" or 18" stock wheels wanna pull one off and throw it on the scale for us?

I stare at the fool running 24's on his cutlass in my town, but I don't think he knows it's a "Your a dumbass" stare.

Looks similar to this guys gay mobile.
http://www.cardomain.com/ride/588895

When you see something out of place it's only natural to stare at it.

ORIGINAL: slow07


ORIGINAL: moosestang

I stare at fat women, that doesn't mean i like them.;)


ORIGINAL: slow07

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.





moosestang is trying to crack jokes. Everyone watch out. I can tell the difference between a good stare, and a WTF stare.

The OEM wheels weigh about 22 lbs, for those of you that wanted to compare. That may not be perfect as it was a "bathroom scale" measurement. Needless to say, that's just the wheel, itself, tire not included.

I remember a Mustang comparo back when the '05 GT and Saleen w/ 325 hp were in the same article. The stock GT was .1 or .2 tenths quicker in the 0-60 times. I thought this was strange! Paying all that money and 25 extra horsies and getting beat in both the 0-60 and 1/4 mile. Well, the Saleen had the 20" rims. The GT had the 17" rims. If you're performance minded and you don't have a blower, the 20's are not for you. If you're all about looks, AND THERE'S NOTHING WRONG WITH THAT, then strap on the 20's and enjoy. I'm somewhere in between the two.

http://i79.photobucket.com/albums/j151/pitpup/Q_Complete/Back_In_Black_005.jpg

That is lighter than I thought, so my tires must weigh around 28lbs.

Most 20's i've looked at weight around 36lbs so my comparison between having a one piece aluminum is probably pretty close. So if you want 20's and still want to hang with a GT without 20's just get yourself a 1 piece shaft and hope the other guy doesn't have one.

ORIGINAL: CrazyAl

The OEM wheels weigh about 22 lbs, for those of you that wanted to compare. That may not be perfect as it was a "bathroom scale" measurement. Needless to say, that's just the wheel, itself, tire not included.

Why are you starting crap with me? Are you that bored, or just that much of an ass? All I know is that I get a lot of thumbs up and compliments. Nobody cares if you think they look out of place. This thead is not about opinions of how they look. I only mentioned getting looks, because that is the only change that I noticed after putting them on. Since you think the car only looks good with a retro look, did you grind your calipers to fit 15" Cragers and white letter tires? If you don't like the way 20s look, start your own thread instead of hijacking one just so you can tell us.

ORIGINAL: moosestang

I stare at the fool running 24's on his cutlass in my town, but I don't think he knows it's a "Your a dumbass" stare.

Looks similar to this guys gay mobile.
http://www.cardomain.com/ride/588895

When you see something out of place it's only natural to stare at it.

ORIGINAL: slow07


ORIGINAL: moosestang

I stare at fat women, that doesn't mean i like them.;)


ORIGINAL: slow07

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.





moosestang is trying to crack jokes. Everyone watch out. I can tell the difference between a good stare, and a WTF stare.

Moosestang, thanks for your tire weigh in. Anyone out there with 20"s on wanna weigh their tire/wheel combo??

ORIGINAL: GrabberOrange07

Anyone out there with 20"s on wanna weigh their tire/wheel combo??


I will be rotating my tires this weekend and I will throw one on the scale.

Ummm, maybe you forgot that you told me to shut up a few posts back. I'm also bored and i'm an ass.

ORIGINAL: slow07

Why are you starting crap with me? Are you that bored, or just that much of an ass? All I know is that I get a lot of thumbs up and compliments. Nobody cares if you think they look out of place. This thead is not about opinions of how they look. I only mentioned getting looks, because that is the only change that I noticed after putting them on. Since you think the car only looks good with a retro look, did you grind your calipers to fit 15" Cragers and white letter tires? If you don't like the way 20s look, start your own thread instead of hijacking one just so you can tell us.

ORIGINAL: moosestang

I stare at the fool running 24's on his cutlass in my town, but I don't think he knows it's a "Your a dumbass" stare.

Looks similar to this guys gay mobile.
http://www.cardomain.com/ride/588895

When you see something out of place it's only natural to stare at it.

ORIGINAL: slow07


ORIGINAL: moosestang

I stare at fat women, that doesn't mean i like them.;)


ORIGINAL: slow07

I changed from 18" fanblades to 20" wheels with nearly stock size tires (I don't remember the size, and the car is not with me). Anyway my arm scale nor my buttdyno could tell a noticeable difference. However, my eye-attention meter could tell a big difference. I can't go anywhere without people starring at the car.





moosestang is trying to crack jokes. Everyone watch out. I can tell the difference between a good stare, and a WTF stare.

Nitto Tire emailed me today to tell me that their 255/35ZR20 tires weigh 29.5 lbs. I guess the entire wheel/tire package I'm looking at will weigh in at 64.5 lbs. Anyone out there with 18's wanna tell us what your wheel combos weigh? Maybe our engineers can chime back in with HP loss data now.

grabber orange, i have 20-10s and 20-8/5s, 275/35/rears 245/35 fronts my rear rim weight is 28lbs rears and fronts 26lbs. its the tires that make a huge difference, some tires weigh almost 3 to 4lbs more than others!! maybe a 4 to 5hp difference nothing to lose sleep over, plus if you drive primaraly on the street you will never tell the difference(if you have power adders of course):D all in all do what makes you feel good

I weighed 235/55/20's on my bathroom scale and got 66.2 lbs. I weighed it three times to make sure I was seeing it right. Its a little heavier than I thought it would be but I should have expected that because the dealership put them on before the car was purchased.


If you get lonny2's front rims and the nitto tires you could have a 55.5lb combo. hmmmmmm maybe I should change.

ORIGINAL: moosestang

Your guessing? It doesn't even say how much those weigh. I'm guessing that a 17 inch rim with a tire of 30 diameter or more will result in less rwhp, but probably hook at hell of a lot better than any 245/35/20 will.

This is insane! Anyone with 20's who wants to race?

ORIGINAL: Sleeper05


ORIGINAL: moosestang

Any chance you could be less general?

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!





i am guessing that these:
http://www.americanmuscle.com/black-2005-deep-dish-bullitt-wheel-20x8-5.html
with 245/35 will allow more rwhp than 17x9.5 chrome spinners with 295/50


I wish you lived in Texas, I'm actually curious to see if my new 295's (20's though) slowed me down or sped me up (in terms on hooking/times, not dyno numbers). 295s vs 235 but 18" vs 20".

well dotsonian if you read mmff they weighed stock 18' with 255 45's and that combo weighed 55 lbs, the stock wheels no matter what size have some weight to them. factory makes them heavy and strong! now let me see v6 , chrome wheels, bathroom scale,,,,, hmmmmmm[:@] buy the way i used a ups scale to weigh my wheels.

I have 17's and i'm willing to bet those tires will slow you down.

ORIGINAL: BlackoutStang


ORIGINAL: moosestang

Your guessing? It doesn't even say how much those weigh. I'm guessing that a 17 inch rim with a tire of 30 diameter or more will result in less rwhp, but probably hook at hell of a lot better than any 245/35/20 will.

This is insane! Anyone with 20's who wants to race?

ORIGINAL: Sleeper05


ORIGINAL: moosestang

Any chance you could be less general?

ORIGINAL: 05SDI

There are some 20” rim/tire combos that OUT PERFORMS some 17” rim/tire combos in drag racing and that is why I choose to fight this battle!





i am guessing that these:
http://www.americanmuscle.com/black-2005-deep-dish-bullitt-wheel-20x8-5.html
with 245/35 will allow more rwhp than 17x9.5 chrome spinners with 295/50


I wish you lived in Texas, I'm actually curious to see if my new 295's (20's though) slowed me down or sped me up (in terms on hooking/times, not dyno numbers). 295s vs 235 but 18" vs 20".

come on guys really,they put 20's on porsches,ferrari's,lambo's, just to name a few. i have yet to race(and i dont like to street race) a car that can beat me on my 20's including other gt's. all in all 17's 18' 19' 20's who care's , as long as your happy with what you have;)

ORIGINAL: lonny2

come on guys really, ... all in all 17's 18' 19' 20's who care's , as long as your happy with what you have;)



Amen!

THE END

Well, lonny2
Just so you know, my hmmmmm was intended to be shown as a pause for self thought, not sarcasm. My reference to your front rims was that if a person wanted light rims they could use the kind you have and end up with a 20 inch tire wheel combo that would have no increase in weight from the stock configuration. Your rims are a good example of 20's, mine on the other hand are a not good for performance.

I am happy with what I have and probably would change to lighter rims but I feel that I would upset the person that gave me the car as a birthday gift. I definately do not want to do that.

BTW, my bathroom scale is certified for medical use and regularly checked for accuracy. Just as the ones at most medical clinics are.

my apologies then , at least this last post it seemed more sincere than the last one,the last one was worded like sarcasm.

i ran 13.56 @ 101.78 yesterday with 20s, a system, full tank, spare tire, and a 30mph headwind. i cant say that the 20s themselves hurt me too much there.

20's Hurt you performance because:
1. There is less sidewall to actually bend during launches so that the tire doesn't put all the power in one woop to the ground but a more progressive (Look at a dragster wheel, the rim turns almost 1/2 way before the tire starts moving)
2. Most 20's are made for looks and not performance thus they tend to weight more which this in turn means more rotational weight and approx 1lb rotational = 4lb regular weight
3. Since they have less sidewall and tend to weight more and have a bigger radius that means the weight is more concentrated farther from the center of the wheel which this in turns makes it harder to turn.

I am trying to get a friend of mine to our local dyno to prove the actual hp loss on stock 17's vs 20's. Of course I am gonna weight his 20's so you guys get an idea of the 20's weight.

Att. Andrew

ORIGINAL: androdz

20's Hurt you performance because:
1. There is less sidewall to actually bend during launches so that the tire doesn't put all the power in one woop to the ground but a more progressive (Look at a dragster wheel, the rim turns almost 1/2 way before the tire starts moving)
2. Most 20's are made for looks and not performance thus they tend to weight more which this in turn means more rotational weight and approx 1lb rotational = 4lb regular weight
3. Since they have less sidewall and tend to weight more and have a bigger radius that means the weight is more concentrated farther from the center of the wheel which this in turns makes it harder to turn.

I am trying to get a friend of mine to our local dyno to prove the actual hp loss on stock 17's vs 20's. Of course I am gonna weight his 20's so you guys get an idea of the 20's weight.

Att. Andrew




I agree with some of what you are saying about weight and sidewall flex but the radius on the tires will remain the same. Thats why you have a small sidewall. I think the weight thing plays an important roll in performance and the fact the 20" combo does weigh much more than 17's or 18's does rob power but so does a full tank of fuel and passengers. Just have to pick your battles.

The extra weight could slow you down but you just have to decide if you want to look good or take a little power hit ..... if your going to run it at the track every w.e. i wouldnt put 20s on but if your just an occasional dragger then go ahead and slap them on it wont be a huge difference

my 20" wheels & tire combo weighs 11 lbs more per wheel, I know because a friend loaned me his stock wheel & tires when I took one of mine in to the chrome shop for replating. While we had the 1st wheel off we weighed it and found the difference - don't remember the exact weight, just that the 20's were 11 lbs heavier[:o]
Don't care though, this isn't a racecar, its a streetrod that is as much about looks as performance and just plain old old fashion streetfun:D

A vehicle will change speeds (and direction) faster with 1 flywheel rather than 5 flywheels.

ORIGINAL: GrabberOrange07


ORIGINAL: androdz

20's Hurt you performance because:
1. There is less sidewall to actually bend during launches so that the tire doesn't put all the power in one woop to the ground but a more progressive (Look at a dragster wheel, the rim turns almost 1/2 way before the tire starts moving)
2. Most 20's are made for looks and not performance thus they tend to weight more which this in turn means more rotational weight and approx 1lb rotational = 4lb regular weight
3. Since they have less sidewall and tend to weight more and have a bigger radius that means the weight is more concentrated farther from the center of the wheel which this in turns makes it harder to turn.

I am trying to get a friend of mine to our local dyno to prove the actual hp loss on stock 17's vs 20's. Of course I am gonna weight his 20's so you guys get an idea of the 20's weight.

Att. Andrew




I agree with some of what you are saying about weight and sidewall flex but the radius on the tires will remain the same. Thats why you have a small sidewall. I think the weight thing plays an important roll in performance and the fact the 20" combo does weigh much more than 17's or 18's does rob power but so does a full tank of fuel and passengers. Just have to pick your battles.


We are talking about power loss on 20's were do passengers and full tank comes into play? Also Norty erm.... You ok over there??

Att. Andrew

ORIGINAL: GrabberOrange07


I think the weight thing plays an important roll in performance and the fact the 20" combo does weigh much more than 17's or 18's does rob power but so does a full tank of fuel and passengers. Just have to pick your battles.


It's not the same kind of weight. The engine doesn't have to turn the fuel tank or your passengers.

ORIGINAL: moosestang


ORIGINAL: GrabberOrange07


I think the weight thing plays an important roll in performance and the fact the 20" combo does weigh much more than 17's or 18's does rob power but so does a full tank of fuel and passengers. Just have to pick your battles.


It's not the same kind of weight. The engine doesn't have to turn the fuel tank or your passengers.



the increase in gravitational weight is minimally significant, tho present. you are right that the rotational weight increase is what the main issue is with bigger wheels.

ORIGINAL: GrabberOrange07

I agree with some of what you are saying about weight and sidewall flex but the radius on the tires will remain the same. Thats why you have a small sidewall. I think the weight thing plays an important roll in performance and the fact the 20" combo does weigh much more than 17's or 18's does rob power but so does a full tank of fuel and passengers. Just have to pick your battles.


He's not talking about the radius of the tire where it contacts the road. He's talking about the radius of the wheel itself.

Wheel weight isn't the whole story. The real problem is the INERTIA of the wheel. Inertia is calculated by integrating mass times radius over the entire wheel. Remember calculus class back in school?

Anyway, the point is that if you have two rotating objects of identical weight, but one of them is larger in diameter than the other one, the one with larger diameter has more inertia. This is a classic phyics demonstration that you might have seen in school: a larger hollow ring has more inertia than a solid disc, even though both weigh the same.

In other words, suppose you had two wheels, both of which weigh exactly 25 lbs on a scale. Their designs are identical except for the diameter: one of them is an 18" wheel and the other is a 20" wheel. The 20" wheel has more inertia becasue it has a larger radius, despite the fact that their weights are identical. More inertia = bad for performance.

Not only do most 20s weigh more than the smaller wheels, but they also carry the bulk of that weight at a larger radius than their smaller counterparts. Thus even if the 20" wheel weighs the same as the smaller wheel, it's inertia will still be higher simply becasue it is larger.