I am currently running 245/40R17 tires on my 17X8 wheels but at the las autocross event I seemed to have more tire roll than I need even when my tires were aired up to 40 psi. I am looking for best width/ratio for cornering. Would it be benificial for me to use a narrower tire?

 

Wide vs Narrow Tires - Technical Discussion - Autocross.US Forums
Wide vs Narrow Tires - Technical Discussion - Autocross.US Forums

Check this out this might help you make a decision

 

What I got from that is wider is better lol.

 

yes wider is better, a 245 should be good for you to track your car or maybe use a 235 and also dont put 40psi in the tires because the more air you put in the less traction you'll have especially when you start generating more heat. id say drop em down to about 25-28psi

 

If I understand the dynamics correctly lower pressure is better for grip because the contact patch is larger. However I don't think I would want to autocross with 25 psi as the tires will roll completely over onto the sidewall. The lower pressure is good for accelerating but I don't think it's good for going around a sharp corner. I may be mistaken though. 40 psi is the pressure I have my tires at when they are warmed up to temperature and just for autocross. It is not cold tire pressure. I only have 30 psi cold tire pressure for daily driving.

 

That why track tires have strong walls on them

 

oh ok well then how bout this, what for tire are you running?

 

I'm trying to learn here I've just been faced with some contradictory information. I originally asked John Powell what he would recommend for autocross and he said to shoot for 38-40 psi when the tires are heated. Now I never did any chalk or anything so this has been my most reliable information to go off of. Now you are recommending I go the complete opposite direction and reduce tire pressure to around 26.5 psi. At the last event it seemed I had enough tire roll in at least one corner to get over onto the sidewall because I could see marks there. To reduce tire pressure from 40 to 25 psi seems like it would make the tire roll even worse. I don't know that for sure though.

I'm running Michelin Pilot Super Sports.

 

Street tires being used at autocross yes, you should air up because street tires have relatively soft sidewalls. If you pickup autocross tires like Potenza RE-71R or Hankook RS-3 then the sidewalls are much harder and designed to be run lower.

For your MPSS tires higher is probably a better bet, but it's something you should feel out at the track. If you need more grip drop pressure, more responsiveness then add pressure. It's a compromise with a street tire.

 

Potenza RE-71R sounds like they are the best candidate for my next set of tires. For the time being I am on the MPSS until they wear out. With the RE-71R would you really drop clear down below 30 psi ? Wish I had somewhere close like a skid pad or something where I could go mess around with it a bit. I'm just so novice at this point I really don't know where to start.

 

I wouldn't suggest them for a daily street tire unless you have all kinds of money for your tire budget and don't see much rain. I haven't actually run mine yet but the guys that do usually run around stock pressures. You can always go to autocross and see what the fast guys on RE-71R tires are setting their pressures at relative to their OEM tire inflation.

 

There we go now that I know what for tire your running it can help some people out lol. Running the street tire like the Michelin you have air up because the side walls aren't as strong. So if you go with an actual track tire then you'll be able to air down since the sidewalks are much stronger. So what Powell told you yes that's correct and he has loads of experience in auto cross because that's all he does lol.

 

Lower tire pressure add slight negative camber to front wheels.

 

I wouldn't do anymore than 245/40/17 on a 17x8, I have that sized BFG Rival on my 17x8 and it's really the max I'd ever recommend.

That said, I do have a pair of Yoko AD08's in 255/40/17 on the rear and they're just too wide for that rim lol.

 

235 or 245 would be fine hankook rs3 ftw!

 

Kinda random but what happened to the Nitto Nt05 craze? I remember people swearing up and down about them.