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.
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whipple HO SC,FRPP springs, Pypes mid mufflers, Che adj. LCA, hurst, 4.10's, 1 piece DS, spec stg 2 clutch. Accel coils 12.52@117.6mph so far with a 2.01 60 ft time(pre shaft, coils, clutch).
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Joined: 7/27/2006 From: Chicago (South Loop) Status: offline
quote:
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...
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-john
2006 ford mustang gt coupe 5spd black on black, shaker 1000, IUP, 3.55 gears 100% stock!!! 13.498 in the 1/4
2003 s/c debadged pwp rsx-s 265whp/186wtq = ~302hp sold 7/25/06
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.
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Black 2006 GT Coupe Dynatech LT headers & X; Borla catback C&L CAI; 93 oct tune Full BMR, Spohn & Steeda suspension D-Specs; Alum driveshaft Second Skin Audio damping; Infinity spkrs; Goodyear Eagle F1 255F/295R - FR500 wheels
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
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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.
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.
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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
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05 gt: 12.54 @ 324rwhp/337rwtq Goodies on the way.
PR Manager for Automotive Dezignz MECP Installer and Mobile Product Specialist Mechanical/Manufacturing Engineer.
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
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…..
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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....
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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)
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Black Bullitt Motorsports 20X8.5/20X10;FRPP Stingers; BBK LTs & O/R X; FRPP Drop Springs;FRPP 4.10 Gears;FRPP Hurst STS;C&L CAI/SCT XCal-II Anne-Marie
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.
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Black 2006 GT Coupe Dynatech LT headers & X; Borla catback C&L CAI; 93 oct tune Full BMR, Spohn & Steeda suspension D-Specs; Alum driveshaft Second Skin Audio damping; Infinity spkrs; Goodyear Eagle F1 255F/295R - FR500 wheels
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!
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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!
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I slept in a Holiday Inn Express so I am posting here with confidence! Currently own 5 Mustangs: 06 Saleen 281S/C Vert clone; 06 V6 Pony Package vert; 67 GTA; 69 302 w/4 speed; 69 351 auto.
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.
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05 gt: 12.54 @ 324rwhp/337rwtq Goodies on the way.
PR Manager for Automotive Dezignz MECP Installer and Mobile Product Specialist Mechanical/Manufacturing Engineer.
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.
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Black 2006 GT Coupe Dynatech LT headers & X; Borla catback C&L CAI; 93 oct tune Full BMR, Spohn & Steeda suspension D-Specs; Alum driveshaft Second Skin Audio damping; Infinity spkrs; Goodyear Eagle F1 255F/295R - FR500 wheels
Printable Version
Power loss with 20's? - 
RE: Power loss with 20's? - 
Anne-Marie
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)
