Gernby

I have searched for this, and created a thread in the Tire & Wheel Forum, but there weren't any responses.

I want to see what pressures other autocrossers are using in their 16" Kumho Victoracers. I have been to a couple autocrosses on them, and found that 32 PSI at all 4 corners works better than 35 PSI, but I am curious is 32 is optimum, or if I should try less than 32, or stagger the front and back. When I ran 35 PSI, I couldn't get the rear end to stick worth a crap. I don't want to spend the rest of the season searching for the right pressures.

The pressures that I am referring to are COLD (before my 1st run). If I start at 32 PSI, the pressures are probably closer to 37 PSI after the 1st or 2nd run.

jzr

The hot pressures are much more relevant than cold. Are you checking pressures between runs?

Tire Rack has some good, relevant information.

For a given car/driver setup, the optimum pressure will vary depending on surface, ambient temperature, time between runs, etc. Since there is no one right answer, just keep playing around with pressures to see what works best for you. The hardcore folks keep a log book noting all relevant information (car setup and condition, environment, times they ran, how the car felt), and use that for later analysis and adjustment.

I seem to recall 38f/36r (hot) working well for me. YMMV

jguerdat

Hot temps are only relevant if you're running in heats and/or multiple drivers running closely together. Our typical event has plenty of time between runs for tires to return to near ambient, making the cold temps more important (get as much grip out of the hole as possible since 60 seconds later, yer done).

I've done some experimenting and have stuck with 34-36 front, 30-32 rear. I tried 50 front, 44(ish) rear based on a comment of a year or so ago from folks that used an Evolution school to play around and found my times to be identical although I thought the car was a bit looser with the higher pressures. I think I still need to do some more work to be more consistent but it's also obvious that I need to tune my driving since backing off the gas when the rear is loose causes, ahh, INTERESTING behavior...

Gernby

Thanks for the replys thus far. I should also mention that my last alignment was to the OEM specs.

DSF_S2k

I usually run 36~38 PSI front / 32~30 Rear (cold). I have messed around with the tire pressures and have found that the above pressure seem to work best for me. That's not to say that they won't work for the next driver, but they seem to suit my driving style. One thing to note here is that the pressures should absolutely not work!!! Usually, if the car is oversteering (the S2000) you should decrease your pressure in the front and increase the pressure in the back (causing understeer to balance the car), however this seems to make matters worse for the S2000. Applying the exact opposite of what your supposed to do seems to work for me (and other autocrosses just simply scratch their heads when asked what my tire pressures are ) Now, this is with the stock setup (stock swaybar), I think that getting a bigger swaybar (rollbar) will actually help with the oversteer condition when running V700's. Hope this helps out.


Dale

Mrsideways

As much as I dislike driving on hoosiers they seem to be the "Hot ticket". I'm just hoping I don't Finish DFL on the Kumho's. However in our limited testing and never with new rear tires this is what we came up with.
35 (cold) Front
32 (cold) Rear

37 (hot) Front
34.5 (hot) Rear

Cheers
Ian

autoxEX

Good tread, I've been wanting to hear what pressures ppl have been running as well. I am running on a non-ideal alignment at the moment (fixing this to Euro specs on Monday hopefully), but here are my pressures that I have felt comfortable with:

~36-37 F (hot)
~32 R (hot)

With this setup, my car feels pretty balanced with a good controlable oversteer, with the stock front bar. Why is there such dramatic differences not only in tire pressures, but having higher pressures in the fronts than the rear and vice versa?

Gernby

[QUOTE]Originally posted by autoxEX
[B]Good tread, I've been wanting to hear what pressures ppl have been running as well.

Cooperman

I have tried many different combinations and found the weather to be an important factor as well.For hot weather 80-95f with low humidity 36 front 30 rear with high humdity 38 front 32 rear.
If the temperatures are in the range of 50 - 75f try 32-34 front and 28-30 rear.

sfphinkterMC

AutoEX,

the "reason" for the disparity in fr/rr pressures is because that is the pressure you have found in that particular tire, at those ambient conditions that generates an amount of lateral acceleration in the front and back to yield the desired handling balance u find most useful(pleasing,fastest,predictable,balanced, or whatever). absolute tire pressure is not in itself meaningful unless u know at what pressure in those conditions yields highest grip, and then go up OR down from that to DECREASE grip in either front or back to create desired overall lateral G and handling balance and other characteristics(turn in, rolling resistance, temp control, etc.).