I have been running street tires. After being consistently trashed by the competition using race rubber, I have bought a set of Kumho V710's in hopes of leveling the field. I could use some cold starting pressures for 115/40/16's. I am running on asphalt this weekend. Thanks for any help.
(JD)

 

if its autocross, then bump it high... i ran 38/36 on the exact same size and seems to give me plenty of rotation and grip... but my courses are shorter, so i'd try 35/33 to begin with and see how much pressure goes up...

on the track though i tone it down to 32 all around

 

I've been running 43 front, 50-56 in the rear depending on how the car is rotating.

 

James, the 43 & 50-56 psi would be cold starting pressures, correct? Don't mean to be stupid here, but I am not use to running race tires.
(JD)

 

I run 45f/55 rear. That's not only cold pressures, but also hot pressures. bleed the pressures down after every run.

Also, if you have more than one driver, buy a garden sprayer and spray the V710s down with water between runs. V710s stick best when temps are near ambient.

Per

 

Thanks all for the advice. Now it's off to slay the evil wicked Volkswagens & Honda's .
(JD)

 

What Per said. Good luck this weekend. Don't forget the sprayer.

 

45/55???? isnt the idea to run the front harder so the car'd rotate better?

also, as per the sidewall of my 215/40, max pressure allowable is 50psi... is it really safe to go above that?

 

In auto cross you can't believe everything you read on the sidewall. We are checking the pressures after each run and setting them back to the target pressure. The car will rotate with more or less pressure. I happen to like more in the rear with the 710's. With the Avon Tech RA's I run less in the rear. The bottom line is you need to tune the tires to the way you drive. Add or decrease pressure until the rear comes around on you then go the opposite direction a couple psi. This should give you optimal rotation.

 

Every tire has an ideal pressure window where it yields the most traction. Once you've determined what that window is, you can choose to overshoot it or undershoot it to reduce traction. Most people choose to overshoot it to save wear on the sidewalls. I think this is why Per is running more pressure in the rear....to reduce traction and free up the rear.

 

We have a 2006 JCW MCS with camber plates and 215/40-16 V710's-we run 45 psi in front and 65 psi in back and are getting great results. I agree with Per, spray your tires with water between runs if running two drivers. I also give the intercooler a spritz but am not sure if it helps at all.

 

higher rear pressure makes the rear sidewalls more rigid, making their breakaway characteristics more consistent. Plus, since your tire's deflection is a part of the entire wheel rate of the suspension, you're stiffening up the rear's rate, helping keep the front hooked up.

Autocrossers are weird :-)

Per

 

WOW 45/55!!! Sheesh, that's a lot higher than what most have been running. How much should surface affect PSI?? In our region we have the slickest of all asphalt (like driving on ice) and on the other hand, the grippiest tire destroying concrete of Wendover.

 

How does Wendover compare to Atwater?

 

I ran like 42/32 asphalt and 45/35 concrete on mine, but I'd take Per's advice over mine

 

I would tend to agree that higher pressures work better on concrete and slightly lower pressures for asphalt. This has been my experience in the past with street tires. Tomorrow I will get to try my V 710's on asphalt (if it doesn't rain).

 

Post race update: WOW!! My times have improved almost 3 to 4 seconds, and now am running extremely competitive times. I went from 4th to 1st place in my class & 7th overall in this event! The weather was hot (93dgF) on dry asphalt. The tire pressures, as recommended (45f/55r) produced a almost neutral handling. I think if I had bumped the rear psi up a slight bit, I would have had more rotation. On such a hot day, the use of water spray on the tires between runs did seem to help. I can't help but think that these tires really have no place in the "stock" class though. I am just glad I could afford them because many "stock" competitors use them and leave the conventional street tire people in the dust. Again, thanks to all for the advice.

 

Oh jeez, don't bring that up too many times. There's enough heat concerning that on the SCCA Solo boards as it is!

To sum up your experience:

"He has sipped of the R-compound, and it was good."


Eddie
New England SCCA Solo2 Novice Chief
G-Stock Homeboy

 

me running 38/36 was no longer effective last time.... could also be me.... i cant blame the tire.. going to try 45/55 at the coming autox on the 30th here... since im not in the running for that one... might as well toy around with it

o yeah. for those who run track days with v710s, what pressures you guys running on track days? im running 30 all around.. is it too low? because my inside is not on even worn at all.... especially noticeable in the back where im strangely, running close to 3 degrees negative camber... still cant quite figure out why

one last question (sorry, again, very ot), but the little holes are the wear markers right?

 

Why do you say your pressures were no longer effective?

one last question (sorry, again, very ot), but the little holes are the wear markers right? Yes

 

it was hot out last time around... VERY hot.... i ran 38/36, but seems the car's understeering... the sidewalls are rolling over a bit too according to some of the pictures ive seen... also, the tires arent hooking up as much as i liked

 

Go with 43 / 56 and spray them down after every run. You want them warm to the touch but not hot.