JIMC

What is Roll-Out and how is it determined and how is it used???
We are having a trophy race next weekend and are going to run a foam tire class along with rubber tire class.
I want to give the foam tire class a try with my TC4.
I have a setup on the car that requires a 57mm tire and will be running an EA Motorsports Monster stock and have a 100 tooth 64 pitch spur, currently .
Thanks
Jim Crider
Team crider Racing

Brian McGreevy

iTrader: (10)

Jim,

Rollout is Tire Circumference (diameter x pi) divided by final drive ratio.

I typically measure my rollout in inches, so a 57 mm tire is ~2.25" (divide by 25.4)

So for you it'd be (2.25 x 3.14...) / ([100/pinion] x 2.5)

Basically you have to use rollout when your tire diameter changes due to wear or cutting the tires down more. You have to make sure you stay within a +/- .01". So if your target rollout is .95", a .94 or .96 will be ok, but once you exceed that, you'll have to readjust gearing or tire size. Rule of thumb: one tooth on the pinion is equal to .03" for rollout. So if you had a .95" rollout and went up a tooth, you'd have a .98" rollout.

JIMC

HEY BTW
We are having the trophy race this coming weekend.
Sat. from 2:00 till 6:00ish will be sedan practice and sat evening will be MINI Cooper racing.
Sun. will be sedan racing, rubber tire and foam tire classes. 3 heats and a main..
Scotty Ernst and his crew, Boomer, MukLuk, pete Dorn and a couple others are coming down. I heard Eli Ezrow might be coming over. He came over last weekend for our Big oval race .
If your interested you can go to allensrccars.com for more info

Brian McGreevy

iTrader: (10)

Jim,

Springfield is a bit far for me, I'm in the northeast Chicago suburbs. If you're ever up this way, check out RSJ Raceways, www.rsjraceways.com .

If you talk to Eli tell him hi from me.