Question: smaller front vs rear tires?, what's the rationale? Options

[nine14cats]

Here's a question that for no particular reason I ask...other than I want to know! I'm sure this board has plenty of suspension guru's... (IMG:style_emoticons/default/biggrin.gif)

Question: What is the reason for a smaller size front tire/wheel than the rear? Particularly on race cars? On my street 911, or even race 911's, it's usually real big meats in the back and much smaller in the front, even with fiberglass fenders that can house larger tires up front. On my race only 911, I run the same size slicks all the way around, as do many 914's.

Most track cars seem to run bigger tires in the back, front engine, mid-engine, or rear engine.

Why?

I look forward to the education! (IMG:style_emoticons/default/tongue.gif)

Thanks,

Bill P.

P.S. We were sitting around last night wrenching on the race car and this came up....nobody had a decent answer... (IMG:style_emoticons/default/rolleyes.gif)

[Demick]

2 general reasons you might want big tires on the rear: weight in back and/or lotsa power.

911's have their weight biased toward the rear, so they need to have more tire in the rear to keep the back end from coming around in the turns.

Any car with lots of power (and rear wheel drive) will want larger rear tires in the rear to be able to transmit the power to the ground without breaking the rear end loose.

A front engine/FWD car will not need bigger tires in the rear. A front engine/RWD lower power car will not need bigger tires in the rear.

Mid-engine cars are well balanced to start with, so generally, the same size tires all around will keep the car balanced UNLESS you have enough horsepower to warrant larger tires in the rear.

This is all very very general, and there are always lots of exceptions.

Demick
'74 2.0