Wheel & Tire Rotational Inertia Spreadsheet

[Paul]

http://se30.dyndns.org:8080/SVX/rot_inertia.html

[Redwood]

Re: Wheel & Tire Rotational Inertia Spreadsheet

Ow, my head hurts from math.

[Fair!]

Re: Wheel & Tire Rotational Inertia Spreadsheet

That calculation is great, in theory. Should help you choose lightest theoretical wheel/tire package. In practice, other factors usually take precedence over these values, namely: Cost and Tire Availability.

Say you wanted to run a 265mm tire on an E36 M3 in STU class (a real example). There's no 17" ST tire available in that size, so your choices dwindle down to Yokohama Advan in 265/18. The available tire is only made 18" diameter, so you're stuck with one wheel choice: 18" diameter. Costs go up radically over the 17" ST tire available for this car, namely the 255/40/17 Falken. Not to mention the added diameter rubs worse and the entire 18" package... yep ... weighs more. So rotational inertia does factor into these equations.

On a "real race car" costs are less of an obstacle and almost all cars in a given class migrate to one or two tire/wheel packages, usually limited by rules, chassis limitations or available tire diameters/widths. These tend to be in the lightest practical package, too.

At the solo2 level, those real world limitations of cost and tire availability sway choices much more than rotational inertia. Just my 2 cents.

[Paul]

Re: Wheel & Tire Rotational Inertia Spreadsheet

Totally agree Terry, cost and fitment will be our determening factors. Just thought it was interesting info.