I bought a 1986 930 that has been modified, it also came with 18" hollow turbo twist wheels, I think they were from a 2001 turbo, sizes are:
Front 225x40x18, Rear 295x30x18 with the stock potenzas.

Is this a decent wheel / tire to go with in terms of handling? Looking to autocross and track the car occasionally.

 

You certainly will have more tire choices than if you had 15's or 16's.

 

That is a good point. I was concerned that it might be a bit too much wheel for that car. Being a manual rack too, I was afraid turn in, would not be as sharp. I guess I will try them out; get a good feel for it. This car is a 1986 930, it has an Instant G 3.6 Conversion, G50 trans, 22mm front and 29 mm rear, ride height adjustable rear trailing arms. Tarrett sway bars front and rear, turbo tie rod ends, strut tower brace, lowered, corner balanced, aligned, etc - all by Instant G. However, it does not seem to handle as crisply as my old 87 911 did which had similar components but 17" wheels. That car was setup by someone else though. This new to me 930 may need a tweak or two on the suspension. I'm not sure. Still getting a feel for it! Thanks all.

 

I'm no expert, but check with the Turbo forum... sounds like this car had significant mods. First, 86 and 2001 turbos had different wheel offsets. Indicates a hub change. Also, I believe putting a G50 into an 86 requires changes to the tub and rear suspension.

Don't know who Instant G is, but if this kind of work can change suspension geometry.

I'd have a really good specialist check your bushings and alignment, and also make sure the tires are not worn.

86 turbo should handle better than an 87 Carrara.

 

Yes, he had to do extensive surgery. He does this upgrade often though. http://www.instant-g.com/
That is a good idea, I'll do that. There's a possibility that there may be some cars on that forum similar to mine. My original engine had a few issues and I didn't like that stock transmission that's why I ended up doing a 3.6 upgrade. Thanks for the input, I appreciate it.

 

So the PO swapped a turbo 3.3 for a 3.6?

 

Correct. It was bought as a rolling chassis (no motor). He had a 3.6 already built so it went into the 930 along with a g50 and a bunch of other suspension upgrades. Then...the wheels and tires got included.

 

Don't you mean less tire choices with 15s or 16s?

 

both statements above are correct.... they say the same thing