danswofford

Just to keep you forum addicts entertained I thought I'd let you guys read my tire.

In one of Carrol Smith's books he stated that he didn't like tire pyrometers because the readings were inaccurate because of the heat loss or tranfer between the time the car was in a corner and stopping to get read. Smith says that he perfers to read the tires but unfortunatly does not go past that teaser in his book. I've got a pyrometer but I don't use it much, I've gotten in the habit of visually inspecting my tires and trying to figure out what is going on by the grain patterns. I don't have any answers, just jump in with your comments.

So the first picture is the left rear 315 Kumho after some hot laps at Thunderhill (counter clockwise) the left side is the outside of the car. Camber is -1.5 about 1/8 toe in. The pictures are pretty clear, but what does not show well is that the outside of the tire is darker and scuffed in harder. The inside of the tire has plenty of tire chunks smeared over the tire but the tire itself seems pretty smooth and clean. I start cold at 28 (on a cold day) and they heat up to low 30s.


This is the outside of the same tire.



This is the inside of the same tire.

C6400hp

Looks to me like you need about double the negative camber you currently have.

trumper Z06

Dan,

Try adding a little air. Most of us run Kuhmo's at ~ 36/38 psi Hot, with the heavy Corvettes. Just stay below 40 psi., and you will be fine.

Are you sliding the tires in the corner? As I recall from his book, the outside (small graining) looks fine... discoloration is due to heat.

Sidney004

Did you get any accurate pressure readings when the tires were hot? What sort of laptimes were you running?

danswofford

That is my take too; all four tires look more or less like the rear pictured. I'm -2.1 front, - 1.5 rear. I'm maxed out without camber plates which are on my next mod list.

danswofford

I don't take tire temps often and didn't that day. I was running about 2:05s (over the top of 5) at Thunderhill

danswofford

Nice 4 wheel drifts through 3,4,5 at Thunderhill probably generating some heat. Looks to me like most of the grip is comming from the outside 4 inches of the tire. In the middle of the tire the grain goes away and the inside is mostly devoid of grain, it is smooth tire covered with chunks. I can imagine, from your post, that more tire pressure could bring the middle of the tire into play. And I'm thinking that more negative camber could bring the inside of the tire to the party.

Sidney004

The tires are getting a pretty good workout running 2:05's. I have noticed the band of discoloration on my 710's in more or less the same place. I believe(of course I could be wrong) this comes about from a difference of temperature the tire is seeing, not necessarily overheating; the greater temperature coming about from greater loading at that part of the tire.
My startegy is to monitor hot tire pressures immediately after coming in. Although the surface tire temps may drop off pretty quickly and be inaccurate, the pressure buildup from a twenty minute session don't drop off that quickly and is repeatable. I think changing cold pressures based on grain pattern without monitoring the hot pressures is iffy. On the V710's, I would shot for hot pressures of 36 ft, 34 rear and bleed down on each tire until they equalize. I think that dropping pressure will allow the middle of the tire to work harder during cornering because it will be more compliant.

ZR1 MK

Tire temps are important. Its the basis for adjusting tire pressure and alignment. The tire temp gets reduced over time as mentioned from a fast lap to pit or padock, but assuming the entire surface gets reduced the same or close to the same is what matters. Its the difference between the three areas that is key, not the actual temp.
My tires have the same approx 2 inch dark area on the outer edge. I used a larger sway bar on the front and it helped considerably, but with heavy street cars, theres nothing we can do.

Tom03Z06

It definitely looks like you need more air. You are really wearing the outside corner of the tire, when a load is placed on it from the outside you are essentially moving the tire carcass inward lifting the inside of the tire and not making proper contact. I’m running 38lbs hot on my 710’s. IMHO

davidfarmer

I don't know, looks to me like you've got a ton of pickup on the inside, and I'd trust chord tire-temps any day over reading a tire with pickup.

Chord temps can tell you if the pressure is right lickety split (front that is). Rears are never accurate due to tire spin.

Maybe Carrol can work his magic for you, but I'll stick to temps and pressures.

danswofford

I'm with you. I'm going to start taking and recording tire temps.

The tires look to me like they are grinding off rubber on the outside 3" and then just rolling it to the inside of the tire, pickup as you call it.