Lemming

I've been thinking about doing either the Carrera GT or GTR conversion on my 924S trackcar. However, in doing that, the increase in car width is going to look very strange with me runnning 7x15 phonedials. That got me thinking that I could use 2" spacers to push the wheels out and at the same time provide greater stability.

What are the pros and cons of using spacers and widening the stance?

Geo

Adding spacers will increase your scrub radius. I cannot remember the impact off the top of my head, but I remember this is something I'd rather avoid. I'm sure someone can fill in the blanks on this before I can get home and consult my references.

IIRC this will be a little bit harder on bearings as well.

JCP911S

If you don;t increase tire surface, the performance improvement will probably be negligible...

Spacers reduce the strength of the wheel/hub assembly and put increased load on the bearings... most people do not consider them safe for track... (BTW... this does not mean "shims" a few 1/8ths of an inch used to fine tune the back-spacing)

Lemming

That is true, but it is also true that these cars came from the factory with very little negative camber. By running more negative camber on my car (-3.5 F/-2.5 R), I believe that I have reduced scrub radius. Thus, wouldn't adding spacers bring it back in line with the factory specs? The question is, how much spacing to increase.

M758

Tim,
Easist thing is this...

Put 944 width body parts on the car. That will get you wider, but at the same time I don't think you need a "951 widebody" type car given your power levels.

So that make things easy... Get early offest wheels and they will fit in to standard 944 body width.

In front get 944 fenders (steel or FG) and in the rear do Carrera GT or GTS flares. Should look good that way.

BTW most 944 Turbo widebodies look a bit too wide and with ONLY 202 RWHP I think you would be suffining from too much drag an be slower.

Lemming

Correct, I likely go 2 inches wider in front (944) and rear fender flares in back. The reason I thought about spacers instead of early offset is that I already have three sets of late offset phonedials.

M758

Well early offset 15x7 wheels (cookies or phones go for about $200 a set). So 3 sets runs about $600. Less than a set fo RA-1's.

You can probably sell of teh late offset Phonies to a spec race for that same $200 a set. Net cost is zero. (other than tire mounting & shipping)

Cory M

A large scrub radius increases the amount of steering effort required by the driver. The scrub radius also serves as a moment arm acting through the tire contact patch and inducing bending stresses on suspension components.

(diagram from Racecar Vehicle Dynamics by Milliken and Miilliken)

924RACR

Like the Pontiac Grand Prix commercials - Wider is Better. Do it. Get the cookies, as mentioned - very cheap way to do it. I wouldn't be too worried about suspension loads until you're running new Hoosiers.

Remember, all you're doing is duplicating the 944 setup at that point. And you should be servicing your bearings regularly anyway, on a track car.

With the wider bodywork, you can even add a bit of spacer with the cookies to really get the most out of it.

Yes, you can encounter a bit more steering effort. You'll get the same effect with more camber. Who cares? How often do you have to parallel-park your racecar? Don't you have power steering anyway?

I've run cookies with stock bodywork in the past, but now I'm running 6" spiderwebs (orig rims, per ITB rules) with spacers... IIRC 7mm up front, I think about 30mm worth of spacer in the back (stock plus 14 or 7's...).

Lemming

No, I've converted to a manual rack and I doubt very much that I will run Hoosiers since I'm building this to run in DOT R tire classes. I'm trying the new Avon Tech R's (225/45s) this weekend at Barber.

Geo

In addition to the additional steering effort, something fuzzy in my memory says there are other negative effects. IIRC those negative effects are not deal breakers, but something to think about.

That said, just duplicating a 944 set-up I'm sure would be no big deal. Going for a true wide body might have some real trade-offs.

Geo

Oh, I the more I think about it, the more I think it has to do with caster and some weight jacking. I'll look it up in my references when I get home.

924RACR

OK, but Hoosiers are DOT R's...

Lemming

I learn something new everyday

gbaker

You're only fuzzy because you missed your annual ARRC fix.