Lilo Tapia

hey everyone hope everyone is doing well.
just picked up a 97 z28 lt1 6 speed .
i bought 2003 c5 rims 17x8.5 fronts and 18x9.5 rear will these bolt right on my car or do i need modification?
also witch tire size would be best for them. thank you everyone[IMG][GALLERY=media, 28309]20170909_142717 by z28lilo posted Sep 12, 2017 at 11:03 AM[/GALLERY][/IMG]

Injuneer

Are the wheels real C5's, or aftermarket replicas? If replicas, you have to post the "offset" of the wheels, to determine if the wheels (rear wheels in particular) need spacers.

Stock 2001-2002 C5 wheels:

Front - 17x8.5" 58mm offset
Rear - 18x9.5" 65mm offset

It's the large positive offsets the push the wheels inward, deep in the wheel well. In the back you will have a tight clearance between the inside edge of the tire and the inner fender, but shouldn't rub. Replicas are often made with smaller positive offsets (45-55mm) to fit the 4th Gen F-Body better.

As far as tire's, what size do you have on the car now? The originals were either 235/55-16 (26.1" outside diameter) or 245/50-16 (25.7" diameter). Check the tire tag on the driver's door. You need to match the original tire diameter as closely as possible, or you may have to have to have the PCM programmed for the new tire to keep the speedometer/odometer correct. Not a big deal, since your other post indicated you want to switch to 3.73 gears. That will require a PCM reprogram.

For tire's, 245/45-17 front; 285/35-18 rear is about as close as you can get to a 25.7" outside diameter.

Lilo Tapia

Thanks for all that info. There original 2003 c5 rims I do not have the wheels on the car yet i still need to buy the tires this weekend . I was also told i needed 1.50 inch spacers to clear the rear is that true?

Injuneer

2003 dimensions are the same as 2001-2002. I'll check the spacer, but that sounds even wider than what is required for the C6 19x10" 79mm offset wheels. Those require 1.25" spacers. You shouldn't need anything like 1.5".

I'm on an iPad right now. I'll check the spacers using the offset/backspace calculation spreadsheet on my PC tomorrow.

Lilo Tapia

Awesome that's a huge help thank you.
18x9.5 rear 56 + offset
17x8.5 fronts 54 + ofsett
Says on the box.

Injuneer

Then those are not OEM C5 wheels.

Here's where the STOCK 8.0" wide, 55mm offset wheels sit:

Front Space (distance the wheel sticks out from the face of the hub)=2.33"
Back Space = 6.67"


For your NEW FRONT WHEEL at 8.5" wide 54mm offset:

Front Space =2.62" - The outside edge of the new wheel will be moved outward 0.29"
Back Space = 6.88" - The inside edge of the new wheel will sit 0.21" deeper in the wheel well


For your NEW REAR WHEELS at 9.5" wide 56mm offset:

Front Space =3.05" - The outside edge of the new wheel will be moved outward 0.79"
Back Space = 7.45" - The inside edge of the new wheel will sit 0.71" deeper in the wheel well

Bottom line - they will bolt directly on, no spacer required.

You could move the rear wheels out about 1/2" and still have the edge of the tire under the fender, looking straight down. But I would put the wheels with tires mounted on the car and see how they look BEFORE buying a spacer.



For comparison, in the first photo, all 4 wheels are 9.5" wide w/ 49mm offset

Front Space = 3.32"
Back Space = 7.18"




In the second photo, the fronts are 9.5" wide w/ 56mm offset

Front Space = 3.05"
Back Space = 7.45"

The rear wheels are 11.0" wide w/ 50mm offset

Front Space = 4.03"
Back Space = 7.97"