Bill Dearborn

I run 315/35/17 at all 4 corners. I start with cold pressures of 26 lbs front and 24 lbs rear. Hot pressures go to about 35 and 34 depending on how hard I am pushing and how much they may drop while getting back to the garage. Here is a picture of one of my Kumho 710 rear tires after two days at the Glen. From the wear pattern it looks like I may still need to drop a couple of pounds pressure in the rear. Comments....


Bill

ryan0

Looks like its wearing on the outsides.. ADD more pressure.

XPC5R

The groove in the middle usually means pressure is too low in a kumho. The stiff sidewalls keep the outer edges in contact, but not enough air pressure to maintain the shape of the contact patch under load.

Bill Dearborn

Interesting comments as I thought it was wearing in the center more than the outside since the center looks like the rubber is slightly overheated (its rippled). Before I had this happen a lot of people had been telling me I was running too high of a hot pressure and needed to drop my cold pressures down to 24/22 so the hot pressures were in the low 30s. I was a little nervous about that low of a pressure so these comments make me feel a little better about not dropping that low.

The front tires wore evenly across the tread but I was doing some throttle steering with the rears and it seemed more sensitive than other track days.

Bill

wtknght1

What's your camber settings? Suspension mods? Shock settings? How is the car handling?

Generally speaking, as long as you keep the V710s under 40 psi, you're fine.

My starting pressures (when I ran those tires) were quite low:
LF:22; RF:19; LR:15; RR:14 for a clockwise track (like Road Atlanta).

The only way to know for sure is to buy a cheap pyrometer and check your temps immediately after a hot lap. If they are too hot in the middle, lower the pressure. If it's too cold in the middle, add some. If it's hot on the outside part of the tire, you probably don't have enough camber, etc, etc, etc....

John Shiels

I never used V710 but just curious when you started that low what were the finishing hot?

wtknght1

Low 30s...upper 20s. I really didn't care as long as the pyromter showed a nice even temp spread and the car handled well. Those V710s have such a wide performance temp and pressure range, it's hard to screw them up.

ryan0

the 'ripple' is rubber build-up that isnt being rubbed off the center of the tire (cause it isnt making good contact with the ground).

all of this depends on alignment and driving style. but your pics look pretty straight forward.

Bill Dearborn

I have the pyrometer but it is hard to use if you don't have somebody to go over the pit wall and check them for you after coming into the pits. By the time I get out of the car and pull out the pyrometer the temps have changed quite a bit.

My front alignment is -1.3 and the rear is -.8 which is the most I can get. I have been running the 710s for several years and have purchased a few from Chris and this is the first time I have seen uneven tire wear on the rear tires.

Bill

ryan0

the actual temps maybe lower, but the ratio across the tire should be pretty close to when you came off track.

gkmccready

Not sure I agree, even with a probe pyro... if you're running a good amount of negative camber driving slowly to the pits to hop out and measure you're going to artificially heat the inside of the tire. And if you're not running enough camber the outside edge will cool off.

Best bet is to get a buddy [with a probe pyro] to measure your temps for you in the hot pits.

As an example, I used to jump out of the car back in my paddock spot after a session and scramble to measure temps. My front temps always looked fairly even across the tire -- but I didn't have near enough negative camber, the outside shoulder was wearing much more than the rest of the tire...

wtknght1

Correct. The only way to know for sure is with F1 style (i.e. real time) sensors, but the more practical solution is to use a buddy to get those temps as soon as come off a hot lap...with no cool down. It's not perfect, but better than waiting...

Bill Hetzel

I got to see a realtime data log, 3 sensors per tire, a couple of years ago. The temp changes in the corners were mindblowing.

Yep, cool down laps mess things up. One of the reasons is that the outer readings are closer to the sidewall which has thicker rubber and retains the heat a little longer. The center will cool faster. As said,
camber affects the readings too.
As a doulbecheck, I take the 2 outer temps and average them, then compare that to the center.

If you're by yourself, find a place in the paddock just outside the hot pit exit, jump out and take the readings. You should be able to exit the car, pull off your helmit and start taking readings in 45 seconds. This is what you have to do when you go to the track by yourself.

the blur

with that method, you'll be in the paddock changing rotors next.

wtknght1

I'll gladly trade speed, handling, proper tire wear, and race wins for a $25 rotor or two...or six.