C5 18x9.5 rims won't fit in back

I only have 275/40/18's on them and they rub up against the bump stop deal. Does every one have this problem? Can I just remove the bump stop thing and cut out the excess wheel well? Is there a spacer sold for these? I need help fast my rear tires have no tread left on them. I need these new rims and tires on fast. Thanks in Advance.

back when I had them mounted on mine I used two 3/8" spacers, but you will need longer wheel studs.

Some C5 wheels have a 65mm offset, which is excessive, and provides too much backspace, putting the back of the wheel/tire into the inner fender. The solution should be similar to the way many of us have handled the installation of the 17x11 GS offset ZR1 wheels: 1) cut corner off jounce bumper; 2) hammer inside of inner fender; 3) recenter body over axle with adjustable panhard rod.

The problem with the 65mm offset 18x9.5 is that the outer edge of the wheel remains deep in the wheel well, and doesn't have the visual impact of a correctly spaced 9.5" wide wheel. You can use "spacers" but I just don't like them on a high performance application.

What size spacers would you suggest? And where can I buy these spacers from? How awful would it look with the wheel wells hammered in?

Does anybody know where to buy wheel spacers from?

Exactly WHICH C5 rims did you get.... what year? Z06 or standard?

Are you ruling out trimming the jounce bumper bracket and hammering the inner fenders? I have pictures of both, if you need to think about it.

Do you know either the backspace or the offset? Can you just crawl under the car and estimate how much you have to move the rims away from the fender?

If you know that, we can recommend a spacer. You can buy spacers at just about any auto parts store, or in a catalog like Summit or JEG's. But for anything other than a 1/4" or 5/16" spacer, you need a very high quality piece, not the kind of thing you find in those store. There is an outfit that sells billet spacers that will work better in thicker sizes, but they are expensive. I personally don't like spacers on the back.

And, if the spacers are thick enough, you are going to need longer wheel studs as mentioned above.

I have Stock silver Y2K's and they fit with just some hammering to the inner wheel wells. I just put some undercoating back on the spot and you can hardly tell. I think the rims get close to the bump stops when the car is jacked up and the rear is hanging down, but when the car is on the ground they aren't even close to hitting.

Originally posted by Injuneer
Are you ruling out trimming the jounce bumper bracket and hammering the inner fenders? I have pictures of both, if you need to think about it.

Do you know either the backspace or the offset? Can you just crawl under the car and estimate how much you have to move the rims away from the fender?

I am not ruling out trimming PLEASE send me pics jasycZ28@hotmail.com.

These are the thick 5 spoke rims I am unsure of year. I got them off of ebay.

I don't know the backspace or the offset. The rim won't even go on the top studs because it is hitting the wheel well. If I removed the the jounce bumper bracket what effect would that have on the car. Could the wheel well hit the rear end if I don't trim it enough?

Are you actually hitting the inner fender before the wheel bottoms out on the hub? It isn't unusual for the inner diameter of the wheel to be slightly smaller than the hub diameter, and interfere with mouinting. The rear hub is 0.03" larger than the front hub, requiring on some wheels that you lightly sand the inside diameter of the wheel. Just making sure that isn't your problem.

You don't totally remove the jounce bumper bracket, you just grind off the corner that sticks out and catches on the wheel (only at "full drop", when jacked, not at normal ride height).

Grind corner off jounce bumper bracket (http://cjcfo.fbody.com/members/injuneerzz@aol.com/PhotosA/FendMas2.jpg)

How much hammering you need to do to the inner fender has a huge variation from car to car. Some people have no problem putting 17x11 GS offset ZR1 wheels in the back. I had to hammer a lot.... but when you get done you spray it with rubberized undercoating and you hardly notice it was hammered.

Hammer inner fenders (http://cjcfo.fbody.com/members/injuneerzz@aol.com/PhotosA/Drivhamr.jpg)

Inside clearances on left and right side:

Drivers side (http://cjcfo.fbody.com/members/injuneerzz@aol.com/PhotosC/TirClr2L.jpg)

Passenger side (http://cjcfo.fbody.com/members/injuneerzz@aol.com/PhotosC/TirClr1R.jpg)

C5 wheel offsets, from VETTE magazine:

YEAR-----------SIZE----------------OFFSET
STYLE------DIAM---WIDTH-----REPRO------GM
Z06----------18-------10.5--------58---------58
-------------18--------9.5--------61
-------------17--------9.5--------54----------54
-------------17--------8.5--------56

01-02-------18---------9.5--------65----------65
-------------17--------8.5--------56-----------58

00------------18-------10.5--------58
--------------18--------9.5---------65----------65
--------------17-------9.5---------56
--------------17-------8.5---------56----------58

97-99--------18--------9.5---------61----------61
--------------17--------8.5--------56----------56

Injuneer Thanks alot! By the way what did you use to grind the jounce bumper bracket? What size tire are you running?

I am going with this wheels set up soon. I have heard that it is better to buy the 275 35 18's if you can. Is that true?

Originally posted by jasycZ28
Injuneer Thanks alot! By the way what did you use to grind the jounce bumper bracket? What size tire are you running?

I have an air powered die grinder. It would take forever with a Dremel.

That is an AFS polished ZR1 replica 17x11 GS offset, with a BFG Drag Radial 315/35-17

i run 275/35 and my offset is 56mm and i have no problems with rubbing . . .the c5 make your car look real good

Injuneer would my tire size make that much of a difference?

I have the '98 18x9.5 C5 wheels on the back of my car. I cut about 3/4-1" of the jounce spacer(metal and all), I did it with my Dremel and it took a long time. I also beat the inner fender in a few places. I tried a spacer and the lug nut would only grab a few threads. I think the studs would have to be changed.

So which combo doesn't require mods to the fenders - LOL. I assume 56 mm offset and the 275/40/18 would fit w/o mods at this point? (94Z)

i got those same C5 Y2K Rep. with the 65mm offset, I hate them. I have had nothing but problems...i have pounded the inner fender to hell, totally cut off the bump stop, and the car still rubs when going over bumps at 40+ mph, drives me nuts.

EDIT: heh sorry, didnt notice it was a two year old thread lol.

THANKS for the reply - I still never bought wheels ; )

Is the majority of the problem that they are 65mm offset or that they are 18" wheels in general? Most of them I am looking at are 18" with a 56mm offset rather than 65mm.

Any help would be appreciated.

no its the 65mm offset, it just sits to deep into the wheel well, with modest tires youc an make it work...but if you need to get anythign wider your screwed....you can forget about 300s

Got it - I'll make sure to go with something less than the 65mm offset - sounded like guys with the 56mm didn't have any issues. I don't mind the grinding part, but I'm not about to start beating the hell out of the inner fenders on that car ;)

THANKS Again!

you wont have any problems with the 56mm offset on the 9.5" wheels, i have the 18x9.5 Z06 wheels on my car with the 56mm offset and they fit perfect with a 285/35/18 :) no grinding or hammering and havent rubbed once, oh but one thing you have a 94 right? youll have to do what injuneer mentioned about grinding the inner hub to make it fit. i did on mine, but the shop i bought the wheels from did it on some machine and made it perfect for no extra charge. but anyhow good luck picking out a set of wheels!

Thanks for the info - much appreciated.

sorry for bringing up an old thread, but I was looking into those wheels and I called the guy that sells them, he said he's sold about 3000 of those wheels since 2000 and he hasnt had a problem, and that most ppl fit them in camaros and birds....

let me guess O.E wheels? hes a liar, told me the same thing and i sure as hell complained.

so how did you make it work?

what about the ppl that have the z06? they are 56mm offset but 10.5 in wide...

that means that from where the wheel sits its 10.5/2+56/25.4 inside and 10.5/2-56/25.4 outside so you have 7.45Inches inside and 3.05 outside

for the 18" 9.5 wide with 65mm offset you have 9.5/2+65/25.4 inside and 9.5/2-65/25.4 outside.... so 7.31 inside and 2.19 outside...

the Z06 wheel with 56mm offset actually sits further in than the C5 with 65mm...

I'm confused

the 18x8.5 65 will fit with 240 45 tires if you jack it by the pumpkin....but it will rub when you go over bumps, i had to grind and hamm in my bump stops and then ahd to majorly hammer in the side walls when i got wider tires that actually fit the rim.

so it will definitely not fit with a 275/35 tire?
does everyone with the z06 rims have this problem as well?

i have a 275 tire...I made it fit....but i still rub on bumps.

so is it hard to make them fit? what do I need to do?

im thinking about buying longer wheel studs and high quality spacers...I really hate to use a spacer...but its that or or new wheels.

its weird cuz they have 18x9.5 with 54mm offset they sell them, just no in that package

call them and ask them to sell them to you in that way. Also, mine seem to be very ehavy...I don't think their really aluminum

what about the ppl that have the z06? they are 56mm offset but 10.5 in wide...

that means that from where the wheel sits its 10.5/2+56/25.4 inside and 10.5/2-56/25.4 outside so you have 7.45Inches inside and 3.05 outside

for the 18" 9.5 wide with 65mm offset you have 9.5/2+65/25.4 inside and 9.5/2-65/25.4 outside.... so 7.31 inside and 2.19 outside...

the Z06 wheel with 56mm offset actually sits further in than the C5 with 65mm...

I'm confused
You may have the wrong dimension for the C5 Z06 wheel.... according to a table of wheel sizes in VETTE magazine, the C5 Z06 wheels are 10.5" wide, 58mm offset.

And, you're ignoring the width if the flange that holds the tire on the rim. Wheel width is measured where the tire beads seat, not at the outside edge. You need to add about 0.45" - 0.50" to each side for that.

10.5" + (2 x 0.45") = 11.40"

58 / 25.4 = 2.28"

Backspace = (11.40 / 2) + 2.28 = 5.95 + 2.28 = 7.98"

A 7.98" backspace puts the inside edge of the tire against the inner fender. Those of us running the 17x11 50mm ZR1 wheels, with 7.93" backspace, generally have to hammer the fenders.

For the 9.5" wide wheel with 65mm offset:

9.5" + (2 x 0.45") = 10.4"

65 / 25.4 = 2.56"

Backspace = (10.4 / 2) + 2.56" = 5.20 + 2.56 = 7.76"

That backpsace gives you almost 1/4" more clearance for the inner edge of the tire. It will look "sunk" into the wheel well. But with a reasonable size tire, should clear.

And the 56mm offset on the 9.5" wide wheels solves all the problems, giving you only a 7.40" backspace.

Oh, I see, thanks.