UrbanKnight

Ok,
I tested a set of Kuhmo V710's today for my first race tire experience. My first run on cold tires obviously doesn't give me great times. Fortunatley, with the local corvette club, we do a total of 14 runs in one day, and it was broken into 1 run, 3 runs, then 4 runs, lunch, then 3 runs, then 4 runs.

My 1st run, and my 1st run after lunch has cold tires, so I lose time. Now when running 12-14 sessions, not a game changer, but on the SCCA events, we only get 3-4 runs, so I want to maximize the time on all runs if possible... I assume the answer to the pros is probably tire warmers, but how about us weekend warriors? Not sure we have much area available to go get them warm before our first run....

My Kuhmos are 50% worn, so ultimately, i will get different tires eventually. Is there a better "cold tire for low run count autox?

Thanks

FYI, Shaved 2.5 seconds off my personal best with these tires... Love the feeling of sticky tires....

Also add- I'm running 18x11 and 18x13's on a 2011 GS

mountainbiker2

Hoosiers A6's will be your best choice. Your first run will be so much better then Kumho V710's.

Steve A.

UrbanKnight

Thank you Steve.
Can those reading this also recommend some tire pressures as well?

I'm running 18x11 with 305's in the front, and -8x13 rears with 345's

Thanks

UrbanKnight

Running 30/28 hot pressures on the Kuhmos and seem ok...once tires are warm.
What pressures are the A6 guys running, as I think thats my next set of tires

Thanks

Solofast

You really need to get a tire pyrometer and learn how to use it if you are going to go to sticky tires. You won't get the best performance out of your tires if you don't, and you will shorten the life of A6's drastically if you run them too low.

You said the tires were "half worn'. Were they second hand, and if they were how were they used? They very likely could have a number of heat cycles on them, and on V710's, as they get older, you have to get more heat into them to get them to work. As they get really old, they will still work, but you've got to get them pretty hot or they will be greasy. Newer V710's are better on early runs than older ones.

In any SCCA event the first run for the first driver is a throwaway on R compound tires. That's why serious folks always have a 2 driver car. The tires get hotter faster, and stay hotter, and by the second run of the first driver, the tires are fully up to temperature. Tire warmers are not legal in SCCA autocross. You can use blankets or covers to keep the heat in, but electrical or other means of heating tires is verboten..

In order to get more heat into the tires you need to start your first run of a heat at least a couple of pounds lower than your normal pressures. That is even more important when it is cold outside. If the tires don't get any grip, they won't distort. If they don't distort they won't make any heat, won't make any grip and you'll never get there if it's pretty cold. It's a vicious cycle, so if you want to get some heat into the tires you need to start a bit lower and then, as you make runs and the grip starts to come in, the pressures will come up and you can bleed off the pressure. You can't go out and drive the first run like a gorilla since the tires are a bit softer and you will roll them over like crazy if you do. But since the first run is a throwaway anyway, you want to go out and drive hard to generate some heat, but when you feel the tires giving up and rolling over back of and use the first run as a heat generator and to get to know the course better.

That said, the pressures you are running seem a bit high. We ran 28/24 on a C5Z on Hoosiers, and when I ran V710's I was lower than I was on Hoosiers, so I am thinking you were too high in pressures to start with. V710's will also tolerate a bit lower pressures without damage. Run A6's too low and you can ruin a set in a half a dozen runs.

UrbanKnight

Thanks Solofast, I am only on my second non novice SCCA event, so I have a lot to learn..

the tires were 4 heat cycles or so old(I think one of the cycle was a 20 minute track session if memory serves. I currently have them at the wear bars after 2 events (one event was 14 runs), I don't know about tire temps and properly measuring them yet, I am just going off what the local solo pro, who is also on 710's was running...

I agree that maybe the pressures are a bit high as Im not seeing much wear ont he outside edge of the tire (I haven't got into marking them yet, but I figure that would help me tell). After 2 runs, they hold me at my current driving level really well, with very predictable handling. Agree on the 2 driver concept, although Im on a relative island right now, and only one other car even runs in the SS class usually for the SCCA stuff I do, the corvette club, I kind of follow the pack there and my times are very respectable there (we run the same course at the corvette club, so its great to guage my progress, what works and what doesn't, and I run with them once a month (the 12-14 runs a day...so i can experiment a lot...)

I do constantly monitor the pressure in the race tires and bleed it off as the temps go up and the pressure climbs currently.

Edit to add- Im generally the only one in my class at the local SCCA, and I'm not worried about being top shelf yet, Im still working a lot on me the driver too, so I am trying to get down all the basics..

l98tpi

I start out with 30frnt/26rear with Hoosier A's and sometimes will let air after 2nd run if necessary. It depends on outside temps and the course material; type of asphalt or concrete. And after each run I look at the tires to see how far they have rolled over. Optimum is for them to roll over to the where the tread meets the sidewall, usually marked by a triangle.

JRL

28F/24R when I ran stock C5Z06 in SS Class on A6's.