V710 pressures?

[C. Ludwig]

I've been meaning to call Kumho and pick their brains but...

What are the recommended hot pressures for the V710? Tirerack said 35psi cold but that's of little use to me. Thanks!

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Chris Ludwig
08 ITS RX7 CenDiv

[slackerjay]

the 710 pressures are ideal around 32psi HOT

~jay

[Daryl DeArman]

One of the cars I crewed for was an ('88 Rx7) we ran the 710's, both the original and newer lots. We found much higher pressures to be the fastest.

We were at 40-42 HOT.

I'd start around 35 cold, utilizing the same balance split front/rear that you currently use. If you are happy with the balance, increase all pressures 1 psi and see if you are faster or slower. If you are slower go back the other way...if you are slower again then your starting point was probably really close to ideal.

When you are testing like this, there is little value in running numerous laps as fuel loads will change, futher don't put more laps on the tires than you need to find out if it is better/worse.

Whatever direction makes you faster keep going that direction until you start to slow down. Back up a step or two and then see how they behave at those pressures over longer runs.

You may find that while a lower (say 32 HOT) and a higher (say 42 HOT) pressure might arrive at the same lap times. One setting may be more comfortable. Some drivers may want something a little less nervous feeling, while others may want something more responsive.

Too many variables and tradeoffs between ultimate grip, rolling resistance, feedback, alignment and spring rates for me to give you a concrete answer.

35 Cold is a safe starting point...test, test, test.

[JohnRW]

A good head-start on all that testing is always appreciated...and Jay (above) is both a racer (SS & IT...and pretty damn good, too) and one of the Kumho Tire Reps who wanders the country doing trackside tire support, in a big-ass tractor-trailer marked "Kumho".

Jay - you gonna race the Nelson Nat'l in May ? See you there, prolly.

JW

[ShelbyRacer]

My personal experience also shows low pressures work very well, when looking at many different factors. Of course, my driver is not always a "known quantity" so take it for what it's worth. Keep in mind we also run a relatively wide wheel for the tire-a 205/50 on a 15x7 wheel. Narrow wheel/wide tire combos are known for liking higher pressures...

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Matt Green
"Ain't nothin' improved about Improved Touring..."

[Fastfred92]

We tried the first 710's on a heavy fwd car... they needed 30 f and 36 r cold to get 40 - 42 hot

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Fred Alphin
#92 Hankook tire SSB VW GTI VR6
BMW 325i ITS ( 2006 ? )

[slackerjay]

it is a good idea to test and see how your car is with various temps, however we have found that 32 psi is ideal with 180 temps across the tire. with these temps the tire will not fall off as fast and will last longer. this is not to say higher temps are bad...40 hot can work great too depending on your setup, car weight, track temp, etc..test test test

john..thanks for the kind words, you make me feel all warm and fuzzy inside. not sure if i'll be there...alot of ALMS testing going on at the moment..and my new car is yet to be finished. been on the road alot so keep your fingers crossed.

~jay

[C. Ludwig]

Thanks. Unfortunately our first "test" was the regional at Gateway where ambient temps were in the 35* range. We saw 80* tire temps all around except for the right rear which upon total abuse reached all of 140*. I liked the tires though and they gripped well for no more temp than we could get in them.

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Chris Ludwig
08 ITS RX7 CenDiv

[Eagle7]

Originally posted by C. Ludwig:
...except for the right rear which upon total abuse reached all of 140*.

Do you think the exhaust contributed to the RR temps? I've been consistently unable to get sensible temp readings from my RR, and assumed the exhaust was a factor.


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Marty Doane
ITS RX-7 #13
CenDiv WMR

[C. Ludwig]

No. I think the car being very loose around a left turn track had everything to do with it. My temps are usually fairly square.

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Chris Ludwig
08 ITS RX7 CenDiv