Does anyone know the ideal hot tire pressure range for the kumho ecsta XS? I believe (if I remember correctly) that the hoosier r6's are mid 40's but the kumho road race tires are around 41? But those are road race tires, and I'm using the XS's for autocross.

Thanks!

 

There is no one ideal hot pressure for each tire. It is entirely dependent on your vehicles weight, suspension, alignment, wheel size, and tire size. Someone correct me if Im wrong but the best way to figure it out is to start with a high hot pressure (40psi ish) and keep lowering until the stopwatch says you're not going any faster.

 

I ran 37-38 with great success when I ran them.

 

And check the rollover after each run. Start high and lower until you get the rollover where you want it. Then you're real close. If you need to know about rollover, read this.

 

Just looked at my brand new set of Kuhmo XS and sure enough, there is a triangle marker at the edge of the tread to gauge roll over/optimum tire pressure. Never noticed

 

This is what I found to on track, I tried running them at lower pressures and they have no sidewall feel seems like they like to run on the hot side.

For auto-x i'd start them at 35psi and bleed down to 37/38 ish as they heat up

 

Thanks for the info!

Well, I started at 39 (it was mid 50's this past sunday), tire got up to 41.5 and 41 by the end of the third run, but the tires never got hot enough to become sticky and gain grip. Surface was too cold, and they kept having problems with the timing lights, think 20 or so minutes between runs, if I was lucky. Ended up 3rd in RTR class, got beat by a Nismo 370Z and an RX8 R3. The Z was 0.5 seconds faster raw time, and the RX8 was over a second ahead, but with PAX they were both over a second ahead, both in C Stock as well. But then again, this was my second autocross with the new front swaybar and the Kumho XS tires.

 

I'm pretty sure you are running them too high I wouldn't go over 40

 

Those arrows are just there to indicate where the wear bars are. They can provide good information though. There is no simple solution for tire pressures (even a pyrometer, although it provides a lot of information) other than simple testing and trial and error.

There isn't an ideal hot pressure to shoot for unless you are very consistent with how you measure it. 38 hot in a certain ambient temp on a certain track surface may work well, but that could change as the conditions change, and a different pressure might work better.

I have found depending on the ambient temps and the surface I will be driving on, a range from 28-32 psi cold works best for me, if it is raining maybe closer to 35 cold (I would imagine starting at a higher cold pressure makes more sense for AutoX. As others has mentioned, in relatively normal conditions, 37-38 psi hot seems to be a good place to start on most non semi-slick street tires.

Just make sure you are as consistent as you can be with how you measure. If you spend a lot of time cooling the brakes, take that into consideration.

 

Really? Ok, well considering where the top of the triangle is located in relation to the tread I could see that could be an effective gauge, as the link mentioned. I never looked to see where it may coincide with the wear bars though if that’s the case. At any rate, trial and error like you say, it’s what I always go by anyhow. Obviously there is a host of variable that would dictate different ideal pressures. What it takes to utilize the full tread width/traction being the primary goal.