3.3TT Rear tire pressure

[itguy61]

Has anyone here experimented with rear tire pressure? I just bought the car with 12K miles on it and when they measure the rear tires the center was at the wear bar and the edge had 4-5/32nd's left. Said it looked like over inflation. The door label says 36psi rear cold. Makes me wonder if this is too high and causes the rear tires to have excessive center wear?

These tires are not inexpensive so it would be nice to be able to get more wear out of them if by chance the listed pressures are too high.

TC

 

[ShannonC]

The previous owner probably ran pressure too high.

 

[PMB]

Tires are worn out after 12k miles though? Sound like the previous owner probably did a bit more than just run the pressure high.

 

[brancky3]

Tires are worn out after 12k miles though? Sound like the previous owner probably did a bit more than just run the pressure high.

If they're the stock summer tires then 12k is pretty decent.

 

[MisterMac]

I am guessing these are the summer 19 inch tires on a GT. The wheels/tires are staggered and not rotatable, thus the life expectancy is cut in half.

You wouldn't have been able to drive them for much more anyway, even if they hadn't been overinflated by the previous owner.

 

[itguy61]

If the majority of owners get center wear faster than outer edge wear running 36 psi cold then that would tell me the cold 36 psi is too high to achieve optimal tire wear. At that point the owner has to make the decision to either run them at that pressure and replace tires earlier due to center wear or disregard that recommendation and find a pressure a bit lower to mitigate this without negatively affecting handling and/or safety. Ugh!

 

[MisterMac]

If the majority of owners get center wear faster than outer edge wear running 36 psi cold then that would tell me the cold 36 psi is too high to achieve optimal tire wear. At that point the owner has to make the decision to either run them at that pressure and replace tires earlier due to center wear or disregard that recommendation and find a pressure a bit lower to mitigate this without negatively affecting handling and/or safety. Ugh!

That, "If" simply isn't going to happen. Proper inflation for the stock tires is perfectly in alignment to the weight of the car and the load rating of the tire.

The previous owner clearly ran the tires at a higher psi than 36. The laws of physics guarantee it.

 

[Dochidalgo]

My friendship with an expert tire and wheel engineer from NHTSA who, like me, owned a Trans am with RWD, recommended in the Pontiac Firebird model forum, to inflate the front tires 2 psi more than the rear tires. This is because the front tires supported more weight of the engine and transmission than the rear tires and these should have the entire tread in uniform contact on the pavement for better traction.

 

[MerlintheMad]

The tires come inflated well over 50 psi. If the previous driver kept everything where s/he found it, there is your answer. Anything above the recommended 36 psi is going to trend toward higher center wear. But there is a sweet spot, where tire rigidity, handling and wear all balance. And where I now take my wheel/tire questions (Wheel Werks in SLC), they look at the psi rating inside the door and if it says above 40 psi they inflate to that: but everything less than 40 psi rated gets inflated to 40 psi. So now I am riding on 40 psi all around, year round.

 

[MisterMac]

The tires come inflated well over 50 psi. If the previous driver kept everything where s/he found it, there is your answer. Anything above the recommended 36 psi is going to trend toward higher center wear. But there is a sweet spot, where tire rigidity, handling and wear all balance. And where I now take my wheel/tire questions (Wheel Werks in SLC), they look at the psi rating inside the door and if it says above 40 psi they inflate to that: but everything less than 40 psi rated gets inflated to 40 psi. So now I am riding on 40 psi all around, year round.

Very good point, Merlin. It wouldn't take very long at 50 psi to wear out the center of the tires.

 

[itguy61]

40 PSI may be too much, I guess you will see if you get center wear.

 

[Ozstung]

38 front 40 rear on a gt(2) 11,000km- very little wear so far. Mind you i drive it like i owe money on it lol.

 

[app_master]

38 front 40 rear on a gt(2) 11,000km- very little wear so far. Mind you i drive it like i owe money on it lol.

Cold? ... what do you see when warm?

 

[ShannonC]

Cold? ... what do you see when warm?

I used the same settings on our Hunter run on Sunday when ambient temperature was 30°C. Fronts went to 41 and rears 44.

 

[app_master]

I used the same settings on our Hunter run on Sunday when ambient temperature was 30°C. Fronts went to 41 and rears 44.

Cool, thanks. Have been running with the placard at 36/39 ... so will try those now. Always preferred a slightly higher tire pressure, for whatever reasons (initial feel, economy, stiffness, etc) it feels good to me.

 

[Ozstung]

Cold? ... what do you see when warm?

Funny you mentioned that i put those pressures in cold the fronts went up to 39 & 40 and the backs rose to 42 and 43.

 

[RUFFSTUFF]

Ha right now mine are 47 cold all 4... Oh well.

 

[Ozstung]

Ha right now mine are 47 cold all 4... Oh well.

That sounds a fair to high, I know they come out of the factory at around 50psi. But then on the 19'' they recommend 36 fronts and 38 rears down here.

 

[RUFFSTUFF]

I'll have to look at my Tire and Loading sticker... and see what the max pressure is on my tires. I usually go with the tire spec over the door sticker.

 

[itguy61]

I would not go with the tire spec as that is the maximum pressure the tire will safely hold. One size tire may go on several different vehicles with different weights and characteristics that require the pressure to be adjusted to the vehicle. I don't know where the mis-conception that the pressure listed on the sidewall of the tire is what should be run on every vehicle comes from. I say this from knowledge gained working in the tire business for five years.