c4cruiser

I have been running 17x9.5" wheels (38mm offset) and 275/40-17 A6's on my '87 autocross car and I'll be in the market for new tires for next year. I would like to go up to an 18" wheel (OK with my associations rules) mostly so I can get a 200 treadwear tire which seem to be cheaper than A6's or A7's. There isn't very much I have found in 275/40-17" sizes in anything close to a 200 rating.

But one problem is that I haven't found any 18" wheels that have a 38m offset. I have seen wheels with anywhere from a 52 to 58mm offset but I would most likely have to run adapters or spacers. The car has ARP 3" wheel studs. OE Wheel has some 18" wheels that are close but I had heard these wheels are pretty heavy.

Ideas? Comments?

jesup16

17" tires in 200 treadwear are pretty much capped at 255/40/17. I would only consider the RE71R's and RivalS's. The Toyo Proxes R1R's are available in 275/40/17, but probably wouldn't even be as fast as a 255 RE71R/RivalS.

What is the size you are considering in 18"?
Are you capped at 9.5" width for fitment?
What class are you running and what's allowed if its a "local" class that isn't using SCCA regulations?

Here's my recommendation (in order of cost, lowest to highest).

Option 1: Keep you wheels and run a 255/40/17 RE71R or RivalS (I like the RE71R's). A 255 fits nicely on a 9.5.

Option 2: Buy some manufactured light weight wheels like OEM Speedlines, Alcoas, enkei, etc. Then buy some spacers and tires to fit. There's nothing wrong with a QUALITY spacer.

Option 3: Order some custom wheels e.g. CCW in 18" and buy tires.

talon95

Well C6Z front wheels are 18x9.5" with a 40mm offset. Maybe you could run 4 of those?? I think bolt pattern and bore size are the same for all C4-C6 (and probably C7).

Oh and I tried both 255/17 and 275/18 Rival S' on 9.5" wheels this year. 275 is definitely faster.

c4cruiser

Just found that out today about the front C6Z wheels! I would expect those front wheels will work on the early C4's. GM has been at the 5x4.75"/5x120.6mm bolt circle for a long time but I think there were some bore size differences over the years so I'll have to double check that.

In our autocross association, I can run any wheel/tire combo in my class with no limitation on treadwear rating. I'm also looking at the BFG g-Force R1-S slick as it's not as costly as the A7.

93Rubie

Don't over look the C5 Wagon wheels I picked up 4 of those in 18X9.5 for cheap and they are fairly light since they are factory. I put some Eibach spacers on and the bolt up no issues. The offset is +50mm, my 17" OEM is 56+, I took advantage of the SCCA +/- 7mm rule so they are pushed to the corners for sure. Should fit on the earlier C4's.

Lost Luggage

If your looking to go wide Im selling my old autox setup that was on my C4..

https://www.corvetteforum.com/forums...-17-tires.html

mcguirjf

Ah the anticipation for spring and the next autocross season to arrive.

I'm in the process of assembling my 89 Z51 now and looking for wheels and tires.

The only 275/40r17 tire is Toyo R1R with not so good reviews.

I have spent the last two days reading and searching for a great setup for B-Street domination and returning the C4 to SCCA Victory Lane!

Wheel Options
97-04 Rear or 05-13 front = 18X9.5 with 57mm offset
06-13 Z06 front or C6 GS front = 18X9.5 with 40mm offset
A wheel spacer is needed for the 40mm, but rule book states that it is permissible to bring overall wheel within offset limits using spacers. 16mm difference = .630" Summit sells a .625" spacer from BAER or a 15mm spacer from Eibach.

I did find a set of 6 (2 front and 4 rear on CL) but the rears were 10.5 and that's a no go. Make sure the rear C5 wheels you check out are 9.5 as there were two width options.

Unfortunately everyone who sells their rims as run a staggered setup on their corvettes.

Aftermarket 18X9.5 with 56mm offset RIMS
Motegi Racing MR120 is a very nice wheel, but appears to be sold out or less than 4 available per finish option.

Sport Muscle ZR is available, but not sure "I'm feeling it".

Tires are plentiful in the 275/35R18 size, but on a little more pricey side. I am personally eyeing the DZII Star Specs. 283/each I would be using these as both Autox and DD. As long as I get 30k miles out of them, I'm happy.

Lost Luggage - very nice tire and wheels for sale. If I could run them in B-Street, they would be mine.

93Rubie

My comments in RED and below.

Your goals and reality are completely lopsided. Not trying to be a jerk just being honest. Being competitive in a C4 on street tires in a pretty tough class...yeah your not getting 30K miles or going to be super competitive unless your one heck of a driver. I'd say my prepped C4 is at least .5 slower than a C5 on the same course. I'm honestly not sure my 2010 MX5 Miata is not JUST as fast on an auto-x course.

I'm not the worlds best driver by any imagination but better than most. That and I know C4's, great cars and I love mine but just too old at this point to be truly competitive. It might be at the local level but even then....iffy.

mcguirjf

Here is the website I went by for measurements.

http://www.corvettecentral.com/wheel-offset/

I guess the red flag should have been with the 18x9.5 rim offset being called out as 54mm.

The majority of sites I visited stated a factory spec for 1989 as 17x9.5 and 56mm offset 5x4.75 bolt pattern

Too much false information out on the net that really misleads and drives me nuts!

Any quality wheel information sites?

MatthewMiller

If you can run anything, then slicks are the only real competitive choice. That obviously means you have to change them at the event site and have a set of street tires/wheels and tire trailer. If you have to use DOT tires, then Hoosiers are the only bet. Ditto though about not driving them on the street. If you want to drive on your race tires, at least to events and back, then the best choices are RE71Rs or RivalSs. Just don't expect to compete with anyone on Hoosiers or slicks.

Assuming you go the 200tw route, yes you must get 18" wheels. There are no good 17" options. I am in the same boat here, as all my wheels are 17". I would bypass any compromise and go directly to 18x11 wheels, which allow you to run 315 RivalS tires with no rubbing and no poking out of the fenders on a stock C4. This is the easy option, and I will almost surely be doing the same thing (for CAM-S). The harder and more expensive - but tempting - option is 18x12 or 18x13 with flares at all four corners, and 335 RivalSs. Flares and those extra-wide wheels would also let you run 335front/345rear A7s should you choose to go that route. As I said, I am tempted; but it will be so easy to push the "easy button" and just get 18x11s.

As far as wheel choices, the aftermarket has dozens in all price ranges. Another "easy button" choice is Forgestar cf5 or the lighter f14 in 18x11. They are cheap, light, and strong, and can be had in many color options.

93Rubie

Best thing to do is look at the wheel itself either in person or via pics. They stamp the sizes and offset on the wheels.

In 17" you really don't have any GOOD options for tires in the full width for a 9.5" wheel. You HAVE to go to 18" wheels.

Tomswheels

I have a set of 18x11 +40 offset Forgestar F14s absolutely like new if that helps, $1100 shipped.

Rob31

http://www.ebay.com/itm/191575181787?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AITPlus 40mm

Nokones

Don't settle for something that is not what you want or something that may not fit. Forget the take-off wheels and the hand-me-downs. Get exactly what you need. Call Forgeline. They will make a wheel exactly to your spec. Then I would be putting the BFG Rival S 275-35-18 on your brand new bitching set of Forgelines. You might be able to get the 315s on a wheel with the right width and backspacing. Your competitors will be jealous. You only live once, do what is best. You'll be glad that you did and not regret what you should of done.