okay, I know my race pressures, but I'm doing a new type of tire for auto-xing this weekend and I need some advice.

Tire: Kumho V700 Victoracer (shaved)
Car: 90 CRX racecar
Weight: 1970lbs
Temp: mid 60's

I know optimum hot pressure for Kumhos is 35psi. Do I just set them to that cold? I don't have the ultra-stiff springs in the rear of my car, so I guess I should up the pressure in them even more for something as tight as an auto-x.

Could some of the die hard auto-xers shed some light on this? Thanks!

Matt

 

When i was running my saturn, i was using the V700's - 205/50/15's all the way around and a a weight of around 2250lbs. They liked to be set around 36-38psi front, and 34-40 psi rear. I found that setting them to the desired pressure cold and then bleeding off and/or retaining air in the tire to gain the desired handling characteristics was best. You may be able to get away with lower pressures since you have a lighter car. Increasing the rear tire pressure (running 36/36 or 36/38) helped the car rotate somewhat better. On the autoX course, i've seen alot of CRX's on V700's with the tendency to snap oversteer as well, so 36/33 might be a good start.

Ryan

 

I ran my kumhos at 38F/45R. This was on a Type R, so it is quite a it heavier. But I ran the back at higher pressure to help induce more rotation. Some say run the rears higher others say lower. This seemed to work for me.

Usually you'll set the pressures with cold tires and if they warm up, bleed out the air so you maintain the inital pressure.

Overall, I think most autoxers run higher pressures than what you would run on a road course.

 

Higher initial pressure... but the end result is the same.

 

Absolutely, because the tires don't get as hot, so the pressures don't go up as high. At VIR, I was running these pressures cold:

FL: 28 FR: 29

RL: 30 RR: 31

I try to get them all at around 35 hot. That is why I was thinking that for an auto-x I might be best off starting all of them around 33 or so. I don't think that I will see the kind of temp variation from front to rear that I see on a roadcourse. With the nature of an auto-x though, I thought I might want the rears a bit higher to help increase rotation.

Matt

 

I ran my new Kumho's a little lower than that, but am still experimenting myself. I ran 33 front and 32 rear on my 5th gen SM car. I was getting good wear without going over the edge of the tire. I know a national champ in our area in a stock class civic who said he was running closer to what the posted pressures are something like 42/35, front/rear. I do like the tires so far, they got better as the day went on. good luck

Dan
27 Street Mod