I'm getting ready to mount my new wheels. I need help in determining the best offset. I'm just about to get my wheel/hub centric adapters made up. The wheels are made by ACE and model is the "slick". They are a mix between a C6 and C5 Z06 style wheel. They are 18x9.5 on all four corners. The tires 255/45/18 are identical in height and width to a 255/60/15 size. I weighed the wheel at 22lbs and the tire at 27lbs. My goal is to have the combo sit slightly in board as I'm planning on lowering the car. As you can see the body isn't back on so I need help from the guys/girls on here who have 9.5" wide wheels installed. I have been reading up on the subject with the search feature on here. I think a 5 1/4" back spacing would be ideal but I'm not sure if that will work up front. I have no problem with having to move the E-brake cable. Will I need a shorter rear spring? It looks like I might not due to the fact I'm using a 18" wheel. I don't have offset trailing arms and read that they aren't required with this combo. Most guys that run this width of wheel are using the slightly wider tires then what I have ....275/40/18. I understand that you can run with as much as a 5 1/2" backspacing. My main concern is the front backspacing. I'm getting conflicting advice when I do a search on the subject. It seems that most elect to use a 8" wide wheel instead. I'll decide what thickness adapter I need based on my 53mm offset wheel and the backspacing depth. If I decide to go with 5 1/4" back spacing then the correct thickness for the adapter will be 2.087". If I decide that 5" is best then the adapter will need to be 2.337". Most aftermarket (newer style Vette wheels) have a 57mmm offset. Some "low offset wheels" made for the 84/87 Vettes have only 40mm offsets. I know of a couple of guys on here that are using 2 1/2" adapters for the 57mm offset wheels. That would give you a back spacing of just under 5". There tires seem to be close to the lip though and I'd like it slighty in board. So am I correct in thinking that a 5 1/4 back spacing will be better for me. Any help would be much appreciated.

 

on the rear with the same size tire I did not need to get a shorter spring. It clears although only by 1/2" or so. I had to use 2-3/4" spacers to do that, sorry I don't know the offset off hand. Could look later if no one chimes in on this. I had t trim a corner of the e-brake cable mount but didn't have to move it, just round it off.

 

When you tried the rears with the 2 1/2" spacer what was the outcome if you don't mind I ask? Would they have fit if you moved the E-brake cable/bracket and used a shorter spring?

 

On one side it was the spring and on the other side it was the ebrake cable. It was just too close for me, about 1/4" clearance, maybe a little less. If I used a shorter spring and moved the bracket they would have worked. The spring was just too big a task at that point for me to tackle, money and time wise.

 

I had 17x9.5 with 275/40 on back ,stock t/a ebrake moved and 2.5 adapter on my 73 ,and it just barely cleared the swaybar,
up front 17x9.5 275s also 2.5 adapters and seemed to work.

Now have 18x10 on back with 5.75 bs should have done the 5.25bs,cause it barely rubbed the seat belt reinforcement bracket up in the fenderwell and had to use a 1/4 spacer. and had to lose the swaybar.
up front 18x8 with 4.75bs which works.Good luck.

 

I bolted 18x9.5 C5 Z06 wheels on using 2.75" adapters. After I modified my sway bar, I went down to 2.5" adapters. My e brake bracket was already mounted out of the way. I could go in another 1/4", but I plan on bolting on 18x 10.5" wheels with 295/35-18 tires on soon.
Bee Jay

 

Was there any interference with the rear spring Bee Jay? In the front....could I go in a little farther or were you pushing the limit with that?
Thanks for all your help guys.....please keep it coming.

 

With 18 and 19" wheels, the spring should fit up inside the wheel.
Bee Jay

 

Can I go in a little farther than you at the front wheels Bee Jay without any interference or rubbing? I'd like to go in another 1/4" if possible. This would give me 5 1/4" offset front and rear. From my calculations you have about 5" offset front and rear now.

 

I'll have to check when I get home. I drove one of the red cars today.
Bee Jay

 

ttt

 

ttt

 

OK, sorry about that. With 17" wheels, you don't have another 1/4" clearance to go further inside. The ends of the tie rods will hit the wheels. I think 18" would clear though.
Bee Jay