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A number of people have been speculating as to whether to observe the 30 psi tire pressure recommendation from GM, or to go higher.

Based on some testing I have done, and in the absence of more detailed data, I would have to say Do NOT go higher.

I have been running 33 psi, using first norma air, then Nittogen, and then air again, and found the following:

1. Front tire tread wear is uniform across the width of the tire (good), but

2. Rear tire tread wear is NOT uniform. MUCH more tread wear across the central part of the tread than at the edges - like almost double the wear. This indicates pressure was too high.

30 psi set with AIR as opposed to Nitrogen allows for the fact that air pressure expands aggressively with higher temperature, so the operating pressure is obviously much higher than 30 psi. NITROGEN pressure varies much less with temperature, so will likely be somewhat lower than AIR pressure once operating temperature is reched, if both start at the same pressure.

My limited testing is not enought o draw grand conclusions, but I think it's safe to say that 33 psi is too high.

Jim G
 

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On that note!!!

I have also found that 30 or even 31 PSI is sufficient for just about any High Perf vehicle. With the previous cars that I had, I always did get excellent tread wear running those tire pressures. The only tires that wore out on me fast were the Goodyear GS-C's on the T/A. They handled great, but the tread wear was nil.
Later............................................................................Tom
BTW-remember to check your tire pressure on a regular basis, and that for every
10 degree change in the outside temperature, your tire pressure will either go up 1 PSI if the temp gets hotter, or go down 1 PSI if the temperature gets colder, thats why I check my tires a least once every two weeks!!!!
 

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Molecule Size

What is the size of the nitrogen molocule compared to the "air" molecule?
 

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JOHN317 said:
What is the size of the nitrogen molocule compared to the "air" molecule?
...... versus.......:jester
 

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30 to 31 psig is about right. I tried a number a different pressures autocrosong and wound up at 30 to 31 for the best runs and best control/handling of the SSR.

I'm having a hard time digesting the difference between air and nitrogen expansion. I think it is more likely a function of the amount of water vapor in the air. Of vourse that would entail running a few calculations. Of course I'm sure my wife will understand why I'm not working on the hous ewhen I tell her I'm comparing the temperature effects of gas expansion on tire pressures.:glol
 

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I run mine at 32psi in all. Seems fine to me. Better to be over inflated than under inflated. Just never inflate them past the Max pressure on the sidewall.
 

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Watch for rear tire wear - I had kept mine in the 31 - 32 range for quite a while, and the middle section of the rears has significantly more wear than the outer sections.

Ray
 

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wheel life

Keep in mind that our aluminum wheels will pit on the inside when using air. Nitrogen is much friendlier on the aluminum.
That, and the pressure thing, is why I have just purchased a nitrogen/air purger refill station and picked up my nitrogen bottle today.

I plan on purging the air and refilling with nitrogen next week. I will probably offer this service to others for a nominal fee, once I learn how many purge/fills a bottle will accomplish.
 

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JOHN317 said:
What is the size of the nitrogen molocule compared to the "air" molecule?
Maybe this will help.....I'm no chemist:leaving ..........but I know how to put the air in:yesnod

http://www.tommcmahon.net/2004/11/fill_your_tires.html

“……….Faster-moving molecules will escape from the tire faster. Nitrogen molecules have a mass of 28.02 atomic mass units. Oxygen molecules have a mass of 32.00 atomic mass units………..”

Frank
 

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Ah!

frankmp said:
Maybe this will help.....I'm no chemist:leaving ..........but I know how to put the air in:yesnod

http://www.tommcmahon.net/2004/11/fill_your_tires.html

“……….Faster-moving molecules will escape from the tire faster. Nitrogen molecules have a mass of 28.02 atomic mass units. Oxygen molecules have a mass of 32.00 atomic mass units………..”

Frank
Someone got the point.
 

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Versus?

41chevcoe said:
...... versus.......:jester
I think that "compared to" and versus mean the same thing, at least below a latitude of 50.
 

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Old school

View attachment 8593 I guess I'm from the old school........32 to 33 in the front and 30 in the rear.....The reason......More weight up front so more air........and better wear pattern in the rear...with this combo.......but everybody to there own.....:seeya
 

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Mine just flat out rides better at 26.5 lbs..I have been meaning to get the balance checked. Still running with the factory balance job!!!:jester
 

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Assuming...

Whitewolf said:
I guess I'm from the old school........32 to 33 in the front and 30 in the rear.....The reason......More weight up front so more air........and better wear pattern in the rear...with this combo.......but everybody to there own.....:seeya
that there is more weight on the front, that might make sense. But it isn't always true, for instance; BMW always designs for a 50/50 weight distribution so front and rear tire always get the same air pressure. It is part of the handling design of the vehicle. It al depends on where the CG is.
 

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Compared To

JOHN317 said:
I think that "compared to" and versus mean the same thing, at least below a latitude of 50.
Meant the size of the molecules(dots)
......................................Compared to .......................
Yes it means the same thing either side of "50":rolleyes:
 

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Not the case with the SSR

JOHN317 said:
that there is more weight on the front, that might make sense. But it isn't always true, for instance; BMW always designs for a 50/50 weight distribution so front and rear tire always get the same air pressure. It is part of the handling design of the vehicle. It al depends on where the CG is.


I didn't think we were talking about a BMW........I thought we were talking about an SSR.........:smash.....I think somebody turned the engineers loose again......
 

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Curb Weight

Curb Weight
Front 2475
Rear 2265
 

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Weight....

41chevcoe said:
Curb Weight
Front 2475
Rear 2265


It creats a question in my mind.....so I called to make an appointment to have mine weighed......front to rear and all four corners......This inquiring mind wants to know.......I have heard all kinds of gross weights for the SSR and nobody says the same thing.....So I'll check mine......the way it is equipted....and empty of fuel.....the main thing....above all to me is the tire wear........when it is basicly even.......that's the pressure I want to use......Some of you guys really crack me up....about a thing like air pressure....air verses nitrogen..........molecules and atomic mass....:glol :glol Are these rockets were talking about.....or good tire wear on an SSR?...Everyone to there own way of thinking......am happy with mine (tire wear):lol :seeya
 
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