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Discussion Starter #1
I’m just wondering how everyone decides what PSI to run on the street if you don’t run stock-size wheels/tires. My ‘88 has the pressure on the sticker in the door jamb for 15” tires (225/60/15). I’m running the stock ‘88 Saleen wheels (16x7.5 front/16x8.5 rear) with Dunlop SP Sport 5000’s (225/50/ZR16 all around).

I found this tire pressure calculator. Granted it’s supposed to be optimal for AutoX and what I really want to know is what to run on the street. Anyways, according to it (assuming weight=3200 lbs., lateral g’s=0.75, and weight distribution= 60% front, 40% rear) I should be running 51 PSI in the front and 34 PSI rear?!?!

Can this be right? :confused:
 

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I'm running American Racing rims on new Bridgestone RE940, Z-rated radials. If the tire says 35 lbs., I run 32 to 33 lbs. A Mustang's smoothness of ride was never a consideration anyway.
 

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Discussion Starter #4
KUcurt said:
If the tire says 35 lbs., I run 32 to 33 lbs.
Do you mean what the tire says as MAX PSI? Because mine says 51 PSI, maximum, so maybe I should be running up around there? I thought there had to be a more scientific way of determining the PSI, not just "a few less than what's on the sidewall".

...smoothness of ride was never a consideration anyway.
And obviously I'm concerned with performance, not comfort, or I'd be in a Buick like my wife :eek:
 

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Discussion Starter #5
I can't believe there isn't a more scientific answer to this?!?!

So everyone here just runs a few PSI less than the max as it reads on the sidewall? If mine reads 51PSI should I just run 45PSI or around there (for street use)?
 

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Depends on the type of driving you do. If your in for the handling aspect you want maximum contact patch, and minimal sidewall deflection. So I would doubt you would run maximum tire pressure as that tends to force the center of the tire to buldge (drag racers like this on front runners as it decreases rolling resistance).

THe best way to find out what your optimum tire pressure is is take some white paint, and paint a stripe across the tire. Then go out and "agressivly" run the car. If the paint is wore only out of the center of the tire, the pressure is too high. If its only off the edge its way to low.

In most cases the wider the profile on the same weight vehicle results in a lower pressure to maximise contact patch. The larger the surface area of the tire the more prone they are to center crowning.
 
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