HELP-ZR1-Style Wheel Fit Problem '95

[compyelc4]

Can someone give me some advice? Right now I'm pretty confused and ticked.

Just received a set of new-in-box (Ebay) ZR1-style chrome wheels for my bone stock '95. Somewhere on this site I read that 9-1/2 x 17's front and rear will fit my '95 Vette just fine. Right now I'm running the stock 8-1/2 x 17 front pinwheels (with stock Goodyears) and stock 9-1/2 x 17 rear pinwheels with new KUHMO 712 ECSTA SUPRA'S.

Prior to having my new KUHMO 712 ECSTA SUPRA tires mounted on the two new front wheels, I thought I'd mount a new wheel on the front end to see how it fits. To my horror I find that the outside edge of the new wheels protrude about 1/2-3/4" outside the top edge of the wheel well. When I mount the new KUHMO's (stock size) I think the outside edge of the tire will protrude another 1/2"! I believe my stock pinwheels are 56mm offset. Those that I bought are indicated on the boxes as 56mm offset.

Can someone tell me what gives, or how to measure these wheels to see if the offset, width and diameter are correct? I am really bummed at this point, not knowing if I'm stuck with at least two wheels that don't fit.

 

[c4cruiser]

A 56mm offset is correct for 88-96 cars. a 9.5"x17 wheel is the correct size for later C4's with the optional Z07 suspensions and thsi wheel should fit your car. Installed, the wheel should be flush with the outer edge of the wheelwell. The edge of the tread may stick out beyond the lip of the wheel but some tires have a different treadwidth even though the tire size is the same.

For 84-87 cars, the offset was 38mm a difference of 17mm or about 3/4". Here's how to measure offset: http://www.tirerack.com/wheels/tech/offset.htm
Backspacing is defined as the measurement from the inside of the rim edge to the edge of the mounting face or pad and is expressed in inches.

Measure the offset as described to find out if you go the correct wheels. ZR-1 style wheels are made by a number of companies for 84-87 cars as well as 88-96 cars. What company sold you the wheels?

 

[Ken]

[font=Arial, Helvetica, adobe-helvetica, Arial Narrow]TIRES AND WHEELS (STANDARD):​

• [/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Tire size:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] P255/45ZR-17 (front), P285/40ZR-17 (rear)[/font]
  
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Tire type:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] High speed steel belted radial Eagle 50ZR Goodyear, unidirectional and asymetrical[/font]
  
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Tire inflation front:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 35 psi (coupe), 30 psi (conv)[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]
• Tire inflation rear:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 35 psi (coupe), 30 psi (conv)[/font]
• [font=Arial, Helvetica, adobe-helvetica, Arial Narrow][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Revolutions per mile at 45 mph:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 497 (P255), 499 (P285)[/font][/font]
• [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Wheel type and material:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] Left-right aluminum alloy road wheels with specific vent design[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]
• Wheel rim size:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 17" x 8.5" (front); 17" x 9.5" (rear), left/right specific[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Wheel offset:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 1.97"[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Attachment type:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] Stud[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Attachment circle diameter:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 4.75"[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Attachment number and size:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] 5 hex nuts, one anti-theft; M12x1.5-6H[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Spare tire and wheel:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] T155/70D-17, 17" x 4" wheel[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Spare tire storage position and location:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] Horizontal under fuel tank[/font]

[font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​

[/font]

[font=Arial, Helvetica, adobe-helvetica, Arial Narrow]TIRES AND WHEELS (OPTIONAL):​

• [/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Tire size: [/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]P315/35ZR-17 (rear ZR-1)[/font]
• [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Tire type:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow] High speed steel belted radial Eagle 35ZR unidirectional, Goodyear (rear ZR-1)[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Wheel type and material: Left-right a[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]luminum alloy road wheels with specific vent design[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Wheel rim size: [/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]17" x 11" left-right specific, 1.41 offset (rear ZR-1)[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]
• Tire size: [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]P275/40ZR-17 (front ZR-1, front and rear Z07)[/font]
  [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]​
• Tire type:[/font][font=Arial, Helvetica, adobe-helvetica, Arial Narrow]High speed steel belted radial Eagle 40ZR Goodyear[/font]
• [font=Arial, Helvetica, adobe-helvetica, Arial Narrow]Wheel rim size: 17" x 9.5" (front ZR-1, front and rear Z07)[/font][/font]

 

[compyelc4]

c4cruiser,

Purchased wheels from KS&L Corp., Raleigh, N.C. They have as nice a finish as ANY I've seen on MANY of my vette friend's vettes.

I went to the offset site you noted. Yes, I looked at that same site a few days' ago. Thanks. By my measurements, the offset on these wheels is between 56-58mm, and I know I could be off by 2mm easily! I checked the wheel width, inside lip to inside lip. It is 9-1/2" as advertised.

Bear with me on what follows......You said the outside edge of the wheel should be "even" with the outside edge of wheel well? By my calculations I figured the outside edge of the wheel would be about 5/8" INSIDE the wheelwell and the KUHMO tire would then be about 3/8" INSIDE the well. Here's how I got that! The outside of my stock front passenger wheel (8-1/2") with about 1/4" Goodyear GSC overhanging the wheel (the KUHMO will overhang about the same) sits about 1-1/8" inside the wheelwell. Going to a wheel that is 1" wider (1/2" wider both inside and outside) should result in my KUHMO's riding inside the well by 3/8" (1-1/8" minus 1/2"). Aren't I figuring this right? I just remeasured how far the NEW wheel sticks out of the center outside edge of the well. It is exactly 1/2". With new tire mounted I'm going to be looking at 3/4" overhang! Something has got to be wrong.

 

[Hib Halverson]

I don't understand how this problem could exist, given the data posted but, I'd double check everything. The offset of both the 8.5x17 and 9.5x17 is 56mm. I'd compare the two wheels and double check that the offset of both is the same. If they are the same, the wheels will fit the car.

If you're going to change your tire sizes to 275/45ZR17 all the way around, be advised that, at the limit, the car's handling qualities may change slightly.

 

[compyelc4]

Ok. I'm going to try to attach a picture of the mess.

Wheel Image0020.JPG

 

[compyelc4]

Let's try that2004_1004Image0020+.JPG picture again.

 

[compyelc4]

I found out why the wheel sticks out so much! One of the three wheels had the wrong offset, and guess which one I installed first? The wheel was sticking out so much because the offset is actually 38mm. The box was identified as 56mm.

All my measurements pointed to a 56mm because I was measuring a wheel from the second box because that was easier than taking the measurements on the car. When I finally DID pull the wheel off and compare the offset to the other three wheels, I found the problem immediately.

Of course if I had put a 56mm on first, I then would have taken the car up to get the new tires mounted and I would REALLY have been screwed then. I would probably have had them remove all the tires they just put on, and mount them back on the old wheels. That would have cost me a little extra. There's no way I am going to drive with three ZR1's and one pinwheel.

I guess I'm going to have to wait for my exchange. Will probably be snowing here by the time I get the new wheels and tires back on.

Thanks for all your help guys. You were all right on.

 

[Rain]

glad to hear thats what it was..
Almost thought I was going to be in the same boat when mine get ordered..

Thanks
Rain

 

[c4cruiser]

c4cruiser,

Purchased wheels from KS&L Corp., Raleigh, N.C. They have as nice a finish as ANY I've seen on MANY of my vette friend's vettes.

I went to the offset site you noted. Yes, I looked at that same site a few days' ago. Thanks. By my measurements, the offset on these wheels is between 56-58mm, and I know I could be off by 2mm easily! I checked the wheel width, inside lip to inside lip. It is 9-1/2" as advertised.

Bear with me on what follows......You said the outside edge of the wheel should be "even" with the outside edge of wheel well? By my calculations I figured the outside edge of the wheel would be about 5/8" INSIDE the wheelwell and the KUHMO tire would then be about 3/8" INSIDE the well. Here's how I got that! The outside of my stock front passenger wheel (8-1/2") with about 1/4" Goodyear GSC overhanging the wheel (the KUHMO will overhang about the same) sits about 1-1/8" inside the wheelwell. Going to a wheel that is 1" wider (1/2" wider both inside and outside) should result in my KUHMO's riding inside the well by 3/8" (1-1/8" minus 1/2"). Aren't I figuring this right? I just remeasured how far the NEW wheel sticks out of the center outside edge of the well. It is exactly 1/2". With new tire mounted I'm going to be looking at 3/4" overhang! Something has got to be wrong.

One thing different about Corvettes compared to steel cars is that you may not get an exact mirror image of how one wheel sits in relation to the fenderwell for opposite sides. The fiberglass (SMC panels) may not necessarily be the same as you would expect in a stamped steel fender panel.

For example, on my 87 coupe, which has never been wrecked, the left rear wheel is even with the edge of the wheelwell at the top. On the right side, the wheel is inboard about an inch!! The wheels are AFS Wheels in the ZR-1 design and no matter which of the 4 wheels I install, they sit the same way. There is also a chance that the body may not be exactly true when the fender panels are installed.

On my 92 vert, both rear wheels appear to be in the same position in relation to the top of the fender well, but the right front wheel is further out than the left front. This is probably due to the hood not being exactly true or the mounting brackets are off slightly.

 

[JohnyH]

Very unlucky to pick the ONE that's the wrong offset! But at least you figured it out. I have 9.5 on the front and 11's on the rear, with the right offset there should be NO problem!!

Blame the shipper!