I am looking into getting some 17” wheels for my car but need some help on understanding backspacing and offset. I know I want 17x8 in the front and 17x9.5 in the back but am unsure of the offsets I need to have the wheels stick out the same amount on the front and back. I found the data for the offset for the
ROH ZS 17x8.5 and 17x9.5 wheels, which I know fit and are staggered properly and used it to do some
estimates. Since I know that the backspacing for the wheels I am looking at is not of concern I am mainly
interested on how the offset will effect how much of the rims width is placed on the frontside of the mounting point (how far it sticks out).

Here is what I came up with for the ROH ZS wheels.
Front – offset -7mm -- (8.5/2)-7/25.4 = 3.97” on the backside and 4.53” frontside
Back -- offset +5mm – (9.5/2) +5/25.4 = 4.95” on the backside and 4.55” frontside

Since I know the ROH ZS wheels fit, the rear wheels were easy to pick since they come in a very similar set up.
Back – 17x9.5 with a +6mm offset, which gives 4.99” on the backside and 4.51” on the frontside.

However, the front wheels are another story, especially since I want to use a Baer track kit.
Front – 17x8 with a -12mm offset, which gives 3.53” on the backside and 4.47” on the frontside.
-- 17x8 with a 0mm offset, which gives 4” on the backside and 4” on the frontside.

Initially, the -12mm offset wheels looked like what I wanted because they would stick out the same as the rear. However, then read on the boards that the Baer track kit increases the front track width by 0.4” making the wheels stick out 0.4” more than they would normally. Therefore, I think I want the wheels with zero offset, because once I get the brakes they will stick out 4.4” from the mounting surface. This is fairly close to the rears and leaves the ability to use a 1/8” spacer if caliper clearance is an issue.

Now what I really need to know is if my reasoning and wheel selection is correct. Also, anyone with the Baer Track kit, how far out does it move the wheels. Also, I heard that they will not work with billit aluminum wheels and I was just wondering if this was true and if it can be alleviated by using a small spacer.

Thank you very much for any advice you guys can give me. By the way I am looking at these wheels.

 

Doesn't anyone know about wheel fitment? I really need help,
because I think I understand it, but am not completely sure. I am
sorry for the length of the first post and would really appreciate
any help with this matter.

 

standard offset use on our cars for 17 x 8" rims is 4.5" backspacing.
17 x 9.5" rims use a 5.5" backspacing

Those figures are used for front or rear/ the industry does not recognize the different offsets of Camaro front & rears and apply the above figures for backspacing that will work.

if you want the front rim sitting outboard slightly more then use longer wheelstuds and a 1/4" spacer.

I run Iroc rims on mine that are 4 rears ( Not 2 fronts and 2 rears). I use 12 x 1.5 x 2 1/2" long ARP wheelstuds and 1/4' spacers on Both front and rear hubs. The front spacer alone brings the tires equal but I like the rear bumped out a bit more as well- looks great and corners great.

 

The ROH ZS's are 17x8.5, not 17x8. My 18's are 18x8 front with 4.5" backspacing and 18x9.5 rear with 5.5" backspacing (just like AFGT said, those are the correct specs for those widths). I will be running a Baer front track system with a set of ROH ZS's (17x8.5 front 17x9.5 rear) on my 90 RS pretty soon here. I think you're right that the front will stick out a little more than the rears, but the fronts should still have no problem clearing the wheelwells (even when lowered). I don't care about the looks too much so I'm just gonna run it like that.

 

one piece or two piece rotor?

going with the two piece and dimensions stay stock.

go with single piece and you'll need to figure in a 1/4" of outward movement.

 

Thanks alot you guys. The 17x8 fronts do have a 4.5" backspacing and the 17x9.5 rears have a 5.5".