Hot track pressures for Kumho Ecsta V700's

[Jack Olsen]

I've run my Yokos bare, finally. Should I be shooting for 40 psi, hot, with these new Kumho's?

[Chuck Moreland]

Depends. I've seen people run ECSTA V700 from mid 20s to as high as 40 hot.

You can't really go by others experience because they have a different car, different size tires, etc. You need to use a pyrometer to determine the best temps for you.

Here is a piece on reading tire temps, and it talks directly about pressure:

http://www.elephantracing.com/techtopic/tiretemp.htm

[cstreit]

Jack,

Kumho's have a higher spring rate than many tires and tend to run better a bit softer. My numbers are from Victoracers, but the other Kumhos seem to be about the same as far as this goes.

I run them 29F/31R hot in my car @ 2000 lbs

Newer/heavier cars seem to do better with them getting closer to upper 30's.

I have changed the pressure up and down and found that the lower pressures stick about the same as going up a few pounds, but that the tires wear rate increases dramatically. Also, at the higher pressures, the Kumho's seem to "go away" quicker.

I researched this a few months ago based on samples I got from other cars, and it seems like hot pressures follow a linear scale based on car weight...

A good starting point seems to be if you start at 30 psi for a 2000lb car, then add 1 psi for evert hundred pounds over.

In other words,

2000# car is about 30 psi
2100# car is abou 31 psi
3500# car about 35psi

A pyrometer will help, but this should give you a ballpark starting point.

[Jack Olsen]

You mean 35psi for a 2500 pound car, right?

[Jack Olsen]

35 psi seemed to do the trick. Two pounds higher made me 1.5-2 seconds slower. I didn't try 33, though.

[campbellcj]

Very interesting. I just got a set of these to slap on my 914 track car. I ran A008'S, Victoracers and Hoosiers previously (on other cars); this is my first set of Ecsta's.

I will take some tire temps, but thanks for the tip to probably not start off running them at 40psi hot as is commonly done with Hoosiers etc.

How many psi did you guys pick up between cold & hot on a recent Fall track day? Do they seem to behave as you'd expect (i.e. like other tires) in that respect?

[Lothar]

Jack,

What cold pressure did you use woth your Yokos? What does your car weigh and how much neg camber do you run?

[Jack Olsen]

Lothar, on the track, I'd start the A032R's with 21/23, looking for a peak pressure of only 30 psi. Normally, this would mean bleeding a lot more air out as the day went on.

On the street, I'd run much more pressure.

My car weighs 2430 pounds dry, and I have 2 degrees negative in front and either 2.5 or 3 (can't remember right now) in back.

Chris, I started at 28/30, and then bled off air after each session. My tire temps were very hot, though. I imagine this is partly because they were new, full-tread tires. I got some readings of over 200 degrees.

But as I said, when I added more air, I'd kill myself out there for lap times that were 2-3 seconds off my previous session.

[cstreit]

Jack,

Did you try the lower pressures then? You see what I mean?

My tires would feel great untill they got hot at higher pressures, then they would just get greasy and slippery.

Last year when I started running with Kumho's I just kept dropping them...

My tires increased about 10 lbs in the summer 7-8 in the fall, so I actually started out at like 19/21 which freaked me out the first time I tested them cold after dropping pressures, but hey, it works,,

[Lothar]

Jack,

Are the lower pressures to address the spring rate contributed by sidewall or to increase the contact patch?