AO

The programming is not hard. I can do that pretty fast. It's knowing the limits both inboard and outboard. If you look at the rear suspension, the further you move away from the hub, the more inboard room you have, so that also play into consideration.

FlyingDog

Take known fitting combinations and calculate how much room you have. Jim page has 305s front and rear without flaring. Marc Thomas posted how it's done with wheel size and offset. That should be a good start to knowing what fits.

AO

Here, I think I found it. Thanks to 928org.uk

Vilhuer

Few more pics:

AO

Okay... I'm now just looking at those pictures. I guess these are based on factory wheels. We need to come up with limits. I may need to do a little survey at SITM....

drnick

id keep it to rim size only for simplicity as tyre diameter varies greatly with different manufacturers. i think the rears will be the same for all model years excepting the GTS and barring spacers... and the fronts the same before 86.5 and then again after??

FlyingDog

You would have to account for tire sizes. You could use generic calculations of their size like the Miata tire size calculator. For wheel well sizes you'd have unrolled front, rolled front, unrolled rear, rolled rear, GTS rear and any variation between pre-S, S, and S4+ suspension dimensions. I think stock ride height could be a safe assumption.

marton

our Australian colleagues have done a lot of work on this topic
http://www.landsharkoz.com/tt/ttwheels.htm

Marton

F451

Wow, that is awesome. I wish I had found that a few mths ago when I was struggling to figure out this very same thing. I had a folder full of printouts on 928 wheel and tire fitment and was considering trying to tie it all together in one spreadsheet, but then I ended up buying a set of Cup 1's from a lister - so I knew they would fit, and then life happened, and I never got around to it.

1981 Shark

If you can get this information down in something like a spreadsheet format, I for one would like that.
I promise I'll donate to the shrine if you do!

I'd like to know what will work and what won't in an aftermarket wheel when the time comes. Trying to figure offsets out has made my brain hurt thusfar...

greg928GTS

Andrew, I'm thinking the same thing. 5-spoke, no twist, 18".

I just want someone to tell me what to use!

The aussie info is good from what I've read. They talk about not going less than 55mm ET on the fronts or there may be handling problems. So it's not just what will fit under the fender.

piccardo

In the morning I am going to try to draw something that is clear. I will just have to find some dimentions for the suspension components so that I can determine the arc that the wheel travels on in reference to the fender lip.This will give us an absolute dimension without spacers or offsets.

Bill Ball

I and others have not found less that 55 to present any problems up front with handling. The loss of scrub angle is supposed to cause wandering and tramlining. I put 17x7.5 with 50mm ET and found no such problems at all. The car handles better than with the stock 16s. Now, 8, 9 or 10 inch wide with 50 up front will present some rub issues.

atb

Someone recently posted this link, pretty helpful:

http://www.1010tire.com/WheelOffsetCalculator.asp

Ispeed

After re-reading the OZ pdf, I am thinking my 8x17 et70 front wheels could use a 5mm spacer to get back to 65mm offset. I thought I had an ideal front wheel, but now not so. Hmmmmmph.......