Light wt. Rubber

[jwerion]

I was reading a thread a few weeks back and it stated that some tires are lighter than others. I have 10 & 12 X 18 wheels and would like to know who makes lighter wt. tires for track use but still has good racing qualities.

[Grady Clay]

Right on!

The lighter the better. This reduces un-sprung weight and rotating mass at relatively low cost compared to the alternatives. What does it cost to reduce the un-sprung weight $/lb other than tires?
The other part of the equation is the grip. Not all tires are created with equal grip.

I like using Goodyear racing slicks at DE events, even when it put me in the highest classes with a street 911. Lots of grip, grip maintained at higher temperatures, very predictable, and exceedingly light weight.
The disadvantage trade-offs are they are absolutely not suitable for the street, even driving to and from the track, and short life (you can spend a set per day at $1000 per set.) The suspension set-up should be different compared to DOT track tires.

SO, what is the weight/grip ratio of the suitable DOT track tires? Can some post the mass of the various tires and sizes? It is difficult to measure the rotational inertia so we should leave that for another day

Best,
Grady

[jwerion]

Grady thanks I will look into getting some goodyears. Any one else have #Wts. on tires of other brands.

[Grady Clay]

There is a HUGE difference between DOT track tires and track-only race tires. Be aware.

Our local official Goodyear Race Tire supplier is George Ibbotson, Road Racing Services, Inc. in South Denver (Santa Fe & Dartmouth, sorta) 303-789-5427.

Are you going to the Second Creek DE this weekend?
I’m going to try and be out there some of this week. Let me know your plans.

Best,
Grady
gradyclay@hotmail.com

[jwerion]

Grady, No I will not be there this weekend. I plan on being very active next year. Justin

[RaceProEngineer]

Justin,

A little elaboration on Grady's most accurate evaluation -

Without knowing wheel/tire sizes, we can not provide exact weights, but can give you a couple "ballpark" ideas. Let us assume a tire size of 245-45-16, as an example.

Obviously, regular 40,000 mile, steel-belted radial, street tires are going to be very heavy, and unsuited for track work EXCEPT in the rain. Our Dunlop S-8000s weigh in at 26 pounds each.

DOT Track tires, within their own category, vary significantly in weight. At one extreme, the Michelin Pilot Sport Cups tip the scales at 23 pounds. At the other, Hoosier R3S03s are 19 pounds. Goodyear GS/CS are right in the middle at about 21-22. It should also be noted that, although these are all NOMINALLY the exact same size, their contact patches are drastically different, and their fit under the fenders is equally varied!

Getting to Grady's suggestions, Hoosier does not typically publish weight figures for the slicks, because weight will vary depending upon rubber compound. Goodyear simply takes an average weight of all their slick compounds in a given size, so for the comparable diameter and section width, their slicks show 16.5 pounds.

Obviously, your reason for posing the question was reduction of unsprung weight and rotational mass. As Grady points out, that is only part of the track-tire equation. When we evaluate race rubber (for dry conditions) we look to weight, contact-patch size, fitment to fender and wheel (naturally), side-wall stiffness, ultimate grip, consistancy in behavior, feedback to cockpit, overall diameter to help with gearing; THEN, longevity, cost, suspension setting requirements.

There is a lot to consider, but Grady has simplified it for you: If you have no restrictions against running Goodyear or Hoosier slicks, they provide the very best grip with the very lowest weight. For a 911, get the widest which will fit under your rear fenders, then a size or two narrower for the fronts.

Tire pressures and suspension settings (particularly camber) will be critical with slicks.

We hope this helps,
Ed LoPresti
RacePro Engineering

[jwerion]

Ed thanks for the onfo its very helpfull