whats the correct pressure

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whats the correct pressure

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whats the correct pressure - 9/4/2007 3:08:30 PM

ttocs

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Joined: 2/27/2006
Status: offline for 315-35ZR17's?

Post #: 1

RE: whats the correct pressure - 9/4/2007 6:17:59 PM

SVTBill

Posts: 2349
Joined: 9/17/2006
Status: offline in what car?

most mustangs require 30psi

if its a drag radial i'd be running 30 for daily driving and around 17 at the track, what kind of car you have and whats done to it plays a major roll in that factor, though

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RE: whats the correct pressure - 9/4/2007 8:30:55 PM

ttocs

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Joined: 2/27/2006
Status: offline yes I am sorry, its a 94 gt and it is not a drag radial nor get a whole lotta track time. I noticed what looked to be some wear towards the outside edge of the tire and wondered, I am pretty sure I am running 35 psi.

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Post #: 3

RE: whats the correct pressure - 9/6/2007 1:41:23 PM

ttocs

Posts: 4294
Joined: 2/27/2006
Status: offline so is 30 the magik number?

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Post #: 4

RE: whats the correct pressure - 9/6/2007 2:04:24 PM

colin@tirerack

Posts: 368
Joined: 11/1/2006
Status: offline The placard pressure (normally located in your doorjam or owners manual) would be the recommended pressure.

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RE: whats the correct pressure - 9/6/2007 2:12:12 PM

Derf00

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Joined: 2/22/2005
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quote:

ORIGINAL: colin@tirerack

The placard pressure (normally located in your doorjam or owners manual) would be the recommended pressure.

OMFG that is WRONG!
How can someone from tirerack make that statement? You're telling me my BFG KDW that are sidwall rated for 44 max psi will be fine at 32 (as recommended per my placard for my MAX 35 PSI OEM tires)? Umm..no. I'll get excessive wear on the inner and outer portion of the tire while the center tread wears less.

(sorry but I'm tired of people posting that BS) Look what happened to ford and what was it ..bridgestone? The exploders had a really low PSI on their placard and even Bridgestone said Uhhh..that's too low. So of course tires were blowing out. Tires that are too far under pressure overheat and may blow out. You also degrade handling characteristics and tread wear by underinflating.

It depends on what tire you're running. Read the sidewall and go from there (if max is 35 psi then 30-32 is ideal, if max is 44 then 35-40 is your ideal)

The placard and manual only apply to OEM tires or tires that are rated like the OEM.

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ORIGINAL: P Zero

He could strap a rocket to his ass and beat em on foot too.
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RE: whats the correct pressure - 9/6/2007 3:07:02 PM

ttocs

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Joined: 2/27/2006
Status: offline I thought that since I went to a 10.5" wide rear that it might change the pressure a little since it is wider then the stock tire.

This part of the forum is starting to scare me if you are honestly saying that no matter what wheel or tire I put on it that it should be at the number in the door?

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Post #: 7

RE: whats the correct pressure - 9/6/2007 3:17:48 PM

Derf00

Posts: 5432
Joined: 2/22/2005
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quote:

ORIGINAL: ttocs

I thought that since I went to a 10.5" wide rear that it might change the pressure a little since it is wider then the stock tire.

This part of the forum is starting to scare me if you are honestly saying that no matter what wheel or tire I put on it that it should be at the number in the door?

That wasn't me! I'm saying exactly what you are saying. It DOES matter what tire you are putting on the car. To say "follow the sticker" is total BS and I cannot believe that Tirerack (And discount) say the same friggin thing.

Perfect example. I did orignally do that when I started running BFG's. I was replacing my first set of tires at 30K on my car. Got rims and tires. OEM tires at the time stated 35Psi on the sidewall and 32 on the door. BFG stated 44psi on the sidewall. Discount did all of my rotations AND balances etc. After 10K on the new BFG's I was getting tire wear on the outer and inner edges. They said it was an alignment issue. Took it to Ford and a body and frame alignment shop. BOTH said alinment was perfect and I had the paper work to prove it. Wore out the tires by 50K miles on my car (only lasted 20k miles). Unfortuneatly KDW's don't have a tread-wear warranty so I was SOL.

After that, I did some research and when I purchased my second set of BFG's from Costco. Identical KDW's to my previous set. Also stating 44psi on the sidewall i put them at 37 Psi and kept them there. Guess what. That set lasted me to 35Kish and had a perfect wear pattern. Go figure. 40 is too bumpy for me and I'll probably get excessive center tread wear.

What's the sidewall state? If it's 40 or over take away 10% (36psi) and call it good. Unless you're at the track and want to take a few runs. Then subract 20% or even 30% of MAX psi to get a good psi for your run.

< Message edited by Derf00 -- 9/6/2007 3:20:48 PM >

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quote:

ORIGINAL: P Zero

He could strap a rocket to his ass and beat em on foot too.
-P.

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Post #: 8

RE: whats the correct pressure - 9/6/2007 4:24:38 PM

colin@tirerack

Posts: 368
Joined: 11/1/2006
Status: offline The placard pressure for an 94 GT is 30psi and the stock tire is size 225/55-16. That tire at its recommended inflation pressure carries approx 1345 lbs. Size 315/35-17 at 30 psi carries approx 1323 lbs.

The 04 GT has a front axle weight of 2364 and rear of 2072 so 315/35-17 carries more than enough weight at placard pressure.

Placard pressure is not universal. If a tire is undersized with regard to its load carrying potential its pressure needs to be increased to compensate and bring its load carrying capacity in line with OE levels. In this case it is not undersized.

The sidewall pressure only lists max inflation pressure and not recommended pressure. The max inflation pressure is also not the pressure where the tire carries is max load capacity. The max pressure has no bearing at all on the recommended pressure for a given tire.

< Message edited by colin@tirerack -- 9/6/2007 4:26:53 PM >

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Post #: 9

RE: whats the correct pressure - 9/6/2007 8:38:04 PM

ttocs

Posts: 4294
Joined: 2/27/2006
Status: offline so If I am noticing that there is wear on the outer edges, and if I remember correctly I had it set at 35 psi, I should?

I am sorry but I am a rubber moron. I have 15 yrs audio security experience and a degree in electronics but never paid attention to tires much........

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Post #: 10

RE: whats the correct pressure - 9/7/2007 4:54:10 AM

colin@tirerack

Posts: 368
Joined: 11/1/2006
Status: offline Wear (chopped or feathering) on the outer edge of the tire is normally due to a lack of rotation or alignment issues. If you have smooth wear on both edges of a tire it is due to a lack of sufficient tire pressure.

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Email: colin@tirerack.com

Phone: 877-522-8473

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Post #: 11

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