Background: When I got my '96 CE it had C5 Z06 wheels on it and bad tires. I replaced the tires, which were rather stupidly expensive. After 1-1/2 seasons of driving and a half dozen autocross events the fronts are shot again. They were old date coded Toy Proxes from eBay, so I got what I paid for.
Long story short while I like the look of the wide rear tires, because the car is a daily driver I would like to go to a square setup that I can rotate, with a readily available tire size. The obvious answer is 17x9.5 56 offset rims like the Z51 cars came with and 265/40-17 tires. But that tire size doesn't seem all that common now either.
There is a dizzying array of posts on wheel/tire/size/offset that I did try to sort through, but some of it is a bit dated. Sorry if this has been hashed to death, but there's a lot of knowledge on here so thanks for your thoughts.
I like the look of the original A molds or something similar, and it seems that one can probably get wheels and tires for not much more than replacing the tires in the C5 Z06 sizes.

 

My '94 Z07 has 17x9.5 wheels on all 4 corners and 275/40R17 tires which are still widely available. If you look at the TireRack and other places you only find them showing the staggered setup of the base cars for late C4s. Get around this by selecting a 1990 Corvette as they used the same square setup.

 

Not sure where this is coming from. Corvettes with 17x9.5 use 275/40ZR-17.

Here's a really good reference for c4 wheels and tires Mirrock Corvette

 

Thanks for the replies and the link, not sure where I got the wrong tire size.......will the 17x11 rears fit all the way around?

 

I believe that there are several guys who run 11" wide wheels on all 4 corners for auto cross but I'm not aware of anyone who does it for street driving.
My 95 is also a Z07 and so came with 9.5" wheels and 275x40x17 on all 4 corners. That's plenty wide for the street.

 

I took my car to a hill climb a few weeks ago. In the afternoon groups I a black C4 and by the lettering saw that he runs SCCA Solo CAM-S. In speaking with him I found that he uses 315/35R17 on 11" wheels for autocross. I wish he had them on the car for the hill climb as I was curious to see how they fit.

 

FWIW, I know from owning both an ‘88& an’89 Z51 cars that they are 275x40-17 on all corners.

 

As noted, 275/40/17 is the size to use on 17x9.5 wheels. However, you mentioned autocross events, and so...
Yes they sure will. Regardless of diameter, you want 50mm offset at all four corners. And you can then run up to 315-width tires at all four corners. There's no reason you can't run these on the street, too. I often do. Whether you want 17s with 315/35/17 tires or 18s with 315/30/18 tires depends on what class(es) you enter. If you're in CAM-S for SCCA, you need to go with 18s because all the good UTQG 200tw tires are 18s (BFG Rival S or Yokohama AO52 when it becomes legal, or sort of the Falken 615+ but it's a step behind in grip/speed). Or you could even go with 19x11 and run the 305/30/19 Bridgeston RE71, which is the other good tire (and there is a Rival S in that size now, too). IMO 19s look a little out of proportion on C4s because the cars are so much smaller than modern cars, but that's just an appearance thing.

If you run most NCCC classes, or SCCA's B Street Prepared, you can run Hoosier A7s, and you can use 17s with 315/35/17 tires if you want. However, while those tires are DOT-legal (I have no idea how!), they have zero tread and they wear out with heat cycles, so you don't actually want to drive them on the street at all. Toyo has an r888r in that size, too, which is probably a little more streetable (but not really a street tire).

Moving to the "street-tire-that-also-works-for-autocrossing" side of things, you could look at the Continental ExtremeContact Sport in a few sizes. They make a 275/40/17 that would go on 17x9.5. For 18s, you could go with 275/35/18 on wheels from 9-11" wide, or the 295/35/18 on 10-11" wheels. I'd try that if you can find two more 18x10.5 Z06 wheels and run them square. These tires are basically as fast as Michelin PSS in the dry, and are the reigning king of wet/cold-weather tires where Hoosier rain tires aren't allowed. They are also very nice street tires. I'd say on a typical autocross course they are 1-1.5 seconds off the times you'd get on Rival S or RE71R tires. And they won't break the bank. So this is a great plan if you aren't super-competitive in the autocross events.

PS - Here's a better look at my 18x11 and 315/30/18 setup:



And countersteering some oversteer:

 

Wow, thanks for the detailed reply, you've definitely given me some options to consider. As far as being "super competitive" I'm not. I have just gotten started with a few events. Honestly I think I could be quicker around a tight AX course in my winter beater Mazda 3 than the Vette. Anyway, right now it is just for fun. My local club is very laid back and they put me in B stock (probably because they know I'm not going to be at the top of the class). There's an experienced wheel-to-wheel racer who is routinely !4! seconds quicker than me which is like an eternity in a 40 second event.

 

If that experienced racer guy is on Rival S or RE71R tires, then he may be gaining 2 seconds on you just due to tires. They make that much difference - tires are always the most important equipment upgrade! If he's in BS in something like a BMW M1 or Porsche Cayman/Boxter, then he may have a second just in the car. So your driving may not be as far off his benchmark as you think.

That said, given your "just for fun" mission statement, I'd go with the Continental EC Sport for now. They'll be good for daily driving except in snow/ice, great in the rain, and significantly faster than what you've been running in the dry. If things get more serious, then you may eventually get a second set of wheels and tires just for competition, and then you can get a size and model that's ideal for whatever class you choose at that point. If you have two 17x9.5 sawblade wheels right now, then you could go the cheap route and just get two more in that width and use 275/40/17 Continentals. Then save up for mods and/or race tires later.

 

Excellent tips in this thread!

How do factory 9.5” Saw Blades compare in weight to other 17x9.5” factory offerings?

Not many readily available lightweight 17x9.5 aftermarket offerings without breaking the budget it seems

 

I haven't weighed them bare, but sawblades are fairly heavy for their size. But so are the other factory options (salad shooters and A-molds). I think among C4 factory wheels, the weight is not a distinguishing factor: just get what you like at a price you like.

 

In an 2008 VW R32 i swapped out the factory 18s for a set of Team Dynamics 17s that were about 7 lbs lighter per wheel and the difference was felt every time I drove the car.

Will have to take some weights when the tires come off

 

I second Mathewmiller's suggestion to get 2 more rear C5 Z06 wheels and run 315's on all 4 corners. That's what I do with mine. You might need to use some small spacers on the front so you don't rub at full lock. But since you already have 2 rear C5 Z06 wheels that should be really easy for you to check.

As far as weight the 17×9.5 C5 Z06 wheels weigh 19lbs each. and the 18x 10.5 C5 Z06 wheels weigh 21lbs each.
My stock 88' 17x9.5 salad shooter wheels weighed about 25lbs each, I imagine the saw blades are similar in weight.