SOT: Implications of reducing tire diameter?

[Grover]

This is SOT because it's not related to my 02, rather our Lemons racer 280ZX. But hopefully its just a useful tire question so nobody will get upset its in the General Discussion forum??...

The spec tires on the car are balloons: 195-70-14's. However, for the race we want to run either Falken Azenis 615's or Dunlop Star Spec's as they seem to be the best tires in the acceptable wear rating. However, my preference has been to get some stock ZX 15" rims, but the only of the above tires that are 15's will give me a diameter of just over 23", which is quite a bit less than the stock tire diameter of 24.74". What, if anything, is the significant impact of reducing tire diameter like this? Is it a bad idea? And if so, why?

Thanks in advance.

[eastsidebimmer]

Take a look at this site for the exact Revs Per Mile, etc.

http://www.1010tires.com/tiresizecalculator.asp

[TobyB]

Since my experience is from a 2002, here's an on- topic reply:

I've run tires as big as 23x10 and as small as 23x6 or 20x7.

The single biggest factor in setup is how the tire works on the rim.

A 185 vs a 205 vs a 225 on a 6 inch rim... well, let's say that the

static camber needed varies as much as 5 degrees.

Once you get that dialled, the difference is incremental- going up to a certain

point, you'll reap increased tire life, both in laps before it overheats and in

laps before it wears out. At a certain point, you plateau in life, as in, it's

never really going to wear out. But somewhere before that, you start

to suffer reduced top speeds, as tire drag becomes a factor. So there's

a point where what you make up in the corner from increased stick you pay back on the straights in reduced top speed- and that can hurt early,

because often the end of a straight's where you're going to put a pass on

an inexperienced driver.

Other than that, it's not a really big deal. The increase in handling you get

from a shorter sidewall's a much bigger benefit than the loss in rubber at the circumference of the tire.- at least until you go below a 50 series...

I'd do it. I HAVE done it, and liked it much more than the tall, floppy sidewall.

Suspension adjustments are easier. Tire wear goes down. Car responsiveness

goes up. You can use softer spring and shock settings, since the internal

spring rate of the tire's higher...

t