PCA SDR

I see on our TECHNICAL REFERENCE SHEET (item 1D) that "race tires" are allowed in the Improved or Modified classes ONLY.

Item 1C talks R or C compound, high performance street tires and the points to be assigned for certain DOT ratings.

I need to buy new tires and may want to get the 'baddest-most points' tire I can get and move into the IS class.

It seems like tires with DOT ratings of 50 and above have angled grooves in addition to circumference grooves and would be street tires.

If a tire is basically a slick but has 2 circumference grooves and a DOT rating below 50 (like Kuhmo V710 and Hoosiers) - is it a race tire? A street tire?

So.... what's a race tire?

Thanks.

Bill:

Race tires are NOT DOT approved, whereas the 'R' tires with the
various treadwear ratings ARE DOT approved. Race tires are
6 points, but they are not allowed in the Stock classes.

Paul.

The baddest tire you can get would probably be the Kumho 710's, but the best bang for the buck would be the Toyo RA-1's which last about 3X as long. Both are a big step up from 'street tires'. 710's may save about 3 seconds, versus 2 seconds for RA1. Your budget will guide you. Also, RA1 are 2 points, 710 are 4 points.

Thanks guys - kinda what I thought but wanted to really know.

Time to go get some 'bad' tires!

Should the 710's be shaved and heat cycled. For better grip and wear.

710's are slicks with 2 little grooves with a DOT rating. You shave tires to eliminate the movement of the tread back and forth. 710's have no tread so there is no back forth movement. They wear fast enough without taking more of the tread off by shaving them. I've never heard of anyone shaving 710's.

Along with not having any tread, the 710s start with only 4/32s rubber. Treaded competition tires, like the 700s, have 6/32s rubber and need to be shaved down to 4/32s.

The 700s are only 2 points, but if you don't shave them, you'll need plenty of Gorilla glue to repair the sections where the tread over heats and separates from the belt/cords. Bill has seen my handywork, first hand.

The 710s are definitely better than the 700s, if you can aford the extra 2 points.

While we are on the tire issue, does anyone have comments on Hoosier's. I put a pair on the rear of my car, but I'm not sure they are any better than the 710s.

Since we're all talking about the 911SC, our experience may
be of interest.

The Hoosiers are fast, but VERY tricky about wear. At WSIR,
I think they are worth a second or two over the Toyo, or
Kum-Hoe V700 Ecsta. I tried the 710 for the first time at
last Saturday's AX, so hard for me to make a direct compare.
The 710s felt fast, maybe between the Toyos or V700s and
the Hoosiers. They did feel twitchier than any of the other
tires. OTOH, The Hoosiers felt very solid, and with the most
precise turn-in. They felt like a lot more lateral grip, but
that they might not be so forgiving beyond the limits - Paul
Junior may know more about being over the limits!!

The Hoosiers seem to want a lot of camber, or maybe a lot
of pressure, and won't last nearly as long. The two of us driving
on UNSHAVED Toyos still had plenty of tread left after 6 hours
of 100+ mph stuff. The Hoosiers corded on the outside edge
after ~ 30 laps - They are faster, but OUCH! I think with better
attention to camber/air, they will last longer, and time trials
are TONS more brutal on tire wear. Your mileage may vary...

Our plan is to use the Toyos for practice, and Hoosiers for the
timed laps. At autocrosses, we'll probably just run whatever
tires we have left over!

Paul.