I am going to get rims and want 17's instead of my factory 16's. Im not sure what I can fit on my Iroc. I know that the front and rear are two different offsets, but not sure what the offsets are. I would like to go to 17X9, or even 10. I am getting American Racing Torque Thrust II's. Has anyone put 17's on there Iroc that can give me some insight into this matter?
thanks,

 

I had 17x9.5's on my '89 Formula with 5.5 inches of backspacing (as I remember, I've got the numbers at home) with a 275/40-17 tire. They fit just fine. I can verify the backspacing tonight and post it.

 

alright let me know. I assume the the fomula's had two different offsets two. Im really clueless on the whole thing. Could you explain to me what backspacing and offsets really are.
thanks

 

Offset is the distance from the rims "center". On a 9" wide rim, if the "pad" where the rim mounts to the vehicle was exactly in the center of the wheel (front to rear), it would be "0" offset and 4.5" of back spacing. Offset is measured from the centerline of the rim (think "the center of the tire"), back spacing is measured by laying a straight edge (yardstick?) across the rear of the rim (not up on the buldge of the tire) and measuring to the "pad" where the holes for the lug nuts are (where it mounts to the car). So, offset is negative or positive depending on which way the offset is (1 inch and -1 inch are 2 inches apart, not the same thing), and back spacing is always a positive number.

Did that make sense?

Yup, you can use a 17x9.5 rim with 5.5 inches of backspacing and a 275/40-17 tire.

Yes, the Formula had different offset wheels. But the rims listed above do fit just fine. Here is my '89 on centerline 17x9.5 "Galaxy" rims with 275/40-17's.

Hope that helps.

http://home.columbus.rr.com/trackbir...to_album_3.htm

 

Thanks for the help, your explanation was very understandable. BTW your car looks great, I know what size rims Im getting now.

 

Glad to help. I just wish I still owned that car.....

 

Hey I have some 17x9 rims for sale, they have 0 offset and 5 1/2 back spacing. check out my sig for more info.

 

sorry man but no thanks, I hae my heart set on torque thrust II's

 

Correct me if I'm wrong, but 0 offset on a 9" wide rim is 4.5 inches of backspacing, is it not? I think that 5.5 inches of backspacing would be about 25 mm of offset.

Just checking.

 

I could be wrong , but I just got the offset off the net and and it said the 17x9s have 0mm offset. And I messured the back spacing today.