Just wanting some input. I recently got some new Michelin Pilot Super Sports(Love them!). They are 255/40/18. I know the stock pressure is 32, but I read in a white paper that had a chart saying that I should bump up 2 PSI based on the the higher load index? I'm trying out 34 right now but wondering if its the right thing. I am running around 1 degree of camber all the way around. Any thoughts?

 

Can you provide a link to this white paper? I've never heard of this "rule."

 

http://www.conti-online.com/generato...lus_sizing.pdf

Page 3

 

Actually, I made a mistake. I was looking at the wrong Yokohama as the OE tire. It is a 93Y SL. I am running a 99Y XL. I should be at stock pressure according to the paper. Either way the whole concept is a bit odd.

 

There is no real set rule for tire pressures, every tire and suspension setup will react a bit differently. Checking temps across the outside, middle and inside of the tire can give you an idea of what part is going to wear the quickest. The door jam is a good starting guide but I tend to run slightly higher at 34-36 psi on the street and with a properly setup suspension that works out pretty good for tire wear and traction. The only tip I've heard about is that for highway travel you want a couple extra PSI for less sidewall flex, less heat buildup at higher speeds, and less rolling resistance resulting in slightly better MPG.

 

I wish that they had given some explanation for the tire-pressure changes as a function of load rating. The only places where I've seen this discussed are these: (1) changes in functional load ability as a function of tire pressure [i.e., the exactly opposite relationship] and (2) suggested tire pressure changes when the car isn't using anywhere near the tire's load rating. The second of these comes close to what's going on here, but the suggestion was the exact opposite: the idea is that you can "get away" with lower pressures (for better grip) when you aren't using all of the load rating, so you can reduce pressure when you increase the tire's load rating.

My head is now hurting....

 

You dont need to change air pressure due to the change in load index.

Increasing air pressure wont increase load capabilities.

If you have a high load index. Putting it at 32psi will have a high load capabilities than OE load index