Martin S.

After going through three sets of Kuhmos 17" Victoracer tires (I mean by a set, when 1 tire goes bad, I replace all 4, in 6 events at the Streets of Willow, it came to me that this could not be right. Kuhmos have a reputation for longevity, why the apparent to me, excessive wear?

Tire Rack referred me to Kuhmo Technical in Ohio. The chap I spoke to was Rudy.

According to Rudy, here is the deal for maximum track tire life:
1. Initial pressure should be 32 front, 34 rear,
2. Don’t bleed them down after a session,
3. The heat across the tire should be 160 to 180 degrees F., with no more than a 20 degree delta,*
4. When the tires show signs of wear, flip them around, mount them inside out,
5. Shave the tires…they will actually last longer. The recommend depth for race track applications is 4/32s,
6. Dial some camber into the car, 2 to 2 ½ degrees negative.**

* If they run too hot, perhaps some sort of alignment is in order, more camber! I didn't get this info from Rudy...it was a somewhat brief phone call.

** I don’t think I can get this much camber out of my stock 993 struts, and I don’t know if I want to drive on the street with this much camber. Perhaps the camber should be dialed in just before driving to the track, no trailer for PoBoy Racing. If the camber will provide better tire performance, it could/would be worth it to dial in some extra camber before a track day, and dial it out after, $$$$ though. But who ever said racing was cheap. One final note, I used to drive my SC on the street with –2 ½ rear and -1 ½ front, no problems to speak of. I didn’t drive in wet weather where cars with lots of camber are supposed to be spooky to drive.

My 993 has -1*10' front and -1*25' rear, with + 2.5' toe front and 1.0 kinematic toe in the rear.

Hank Cohn

schacht993:

I am assuming that an event is at least 2 days long and that each event is at least 3 hours worth of driving with about 8 individual runs per event. Is that about right? If yes, then would say that if you are getting 6 hours and 16 heat cycles out of a $500 set of tires, you are living right – real right. That is excellent tire wear. I have a hard time believing the pressure numbers, however.

I have run Kumhos for practice tires because they seem to do well with the same suspension settings that Hoosiers like. If you are using regular old compressed air then they should grow 7-9 PSI when hot and I have found that I like the feel of the tire at 35 PSI hot. Anything more and my car feels like it’s skating across the surface of the track. A lot of that feeling is personal preference and you may like the way your car handles with higher pressure.

I think Kumhos are a reliable tire with very predictable manners. I have also found them to consistently be 1.5 to 2 seconds slower than Hoosiers. That is pretty awesome for a tire that cost 45% less than Hoosiers.

Above are my experiences and opinions. I would like to hear what others have found.

Hank Cohn

JJayB

Martin, I ran Kuhmos on a 944T and 993tt (before 18'' R tires were available). Unless they have changed compounds, I found they like a lot of heat. I spoke to their tire engineer, when the tires felt greasy, he told me to run 46-48 psi HOT. Bingo,they really worked. Tires did go away at 190 F. I confiremed this with several race teams who ran endurance with Firebirds and Cameros.

I agree with Hank, there at least a second slower than the Hoosiers, but at half the price you can drive to the track and have a reliable tire.

Your camber settings are very conservative, for the Streets of Willow. Another 1/2 degree all around will make a hugh difference. As far tire wear, Firestone Firehawks, will give you about half a season,
downside is...there 5 seconds slower than Vogue premium white walls.

See you at the Chanteclair, DJ buys this month.

PS: DJ, give Martin your e-mail. He's found a loop hle in the rules.

DJ

Yes, I'm buying this month guys, just name the day.

Also, Jim, Martin described to me what he found in the rule book as an "opportunity", not a "loophole".