mx-5

What do you guys run with these tires on the street and for autocrossing? Thanks.

ooyahhh

Higher pressure reduces traction and increases responsiveness so correct pressure depends on your priorities.

Rule of thumb: cold starting point. vehicle weight/100 +2 psi. If vehicle is unbalanced add 2 psi to heavy end. Then adjust for over/underteer.

Cold vs hot, I've had pressures increase 8-10 psi after one autocross lap. I usually have to air down between runs. I've even found the sunny side raise 2-3 lbs over the shady side when parked.

I like just enough to keep the tire from rolling over. Try marking the sidewall with soap or chalk. If your rubbing the soap or chalk off on the sidewall above the tread increase pressure. Once you find your optimum pressure start each run about 2-3 lbs lower depending on track lenght. You'll be back to optimum by the first few turns and probably over pressured by the end of the run. Since a couple of lbs can change the the way a car handles an 8 lb change from the start and end of the run can result in a completely different car at the end than you started with. Have you noticed more people spin out in the later runs and in the later part of the track. Remember to check and record your pressure before each run and make notes at the end of each run.

If you don't want to fiddle with all that try reducing pressure by 5 lbs (32/30) just before your first run. After the first run your pressure should be up for the second and third run.

coasTTal

I would seriously think you would be rolling over the sidewalls with that low of pressure. I would much rather start high, and go down.

Chalk is a good way to check the sidewall. Borrow an infrared temp. gun if you can and get good tire reads across the treads.

See the url for a good synopis on handling.<ul><li><a href="http://www.wprince.com/CARSETUPGUIDE.htm">http://www.wprince.com/CARSETUPGUIDE.htm</a</li></ul>

ooyahhh

Re: your right I was just giving a lazy man's alternative. He won't be at 32 very long.

ooyahhh

I've seen guys use those tire pyrometers. Although they are a good tool for racing ovals and road courses I question their value in autocrossing where you only have 3 50-80 second runs. By the time you fine tune for a given track on a given day the event is over. Extreme temperature changes occur very rapidly. I've seen tires blister after two runs. Outside edges almost always run hotter. I doubt that any tire would hold up for 30 or 40 continuous autocross laps without turning into a pile of grease.

Here's some more info:

http://www.turnfast.com/tech_handling/handling_pressure.lasso<ul><li><a href="http://www.turnfast.com/tech_handling/handling_pressure.lasso">http://www.turnfast.com/tech_handling/handling_pressure.lasso</a</li></ul>

MaxHedrm

...not so useful. Especially when competing @ SCCA Solo 2 type events where there are 3 heats, 2 runs per heat &amp; you only run in 2 of them. Often your runs are 30+ minutes apart &amp; the 2nd &amp; 3rd run could be even further apart if you run in the 1st &amp; 3rd heats.

ooyahhh

Re: I didn't know that. Here in San Diego there 's so many cars you get 3 runs B to B 1 heat