I just bought a set of used chrome ZR1's. They were sold to me as "17" x 9.5" (+56mm offset with 7.4" backspacing) 17" x 11" (+50mm offset/7.93" backspacing)"

I just put them on the car and found two issues. One, the rears seem to stick out more then I thought. I was ready to pound the wheel well to make them fit, but there is plenty of room back there. Are these 38mm offset wheels?

http://www.zmydust.com/dougsfastz/im...1's/Rears/

Also, it looks as if I have two different offsets in the front. I thought the 9.5's only came with 56mm offsets? The front passenger is perfect, tucks nicely, but the front driver sticks out like the rears. I tried to take picutres of the difference of how far the spokes come out from the brake caliper between the two wheels.

http://www.zmydust.com/dougsfastz/im...t%20Passenger/

http://www.zmydust.com/dougsfastz/im...ront%20Driver/

Anyone have an idea as too what these offsets are? Any way for me to check?

Thanks,

Doug D

 

The 17x9.5's are available in both 56mm and 38mm offset. The 17x11's are available in 50mm and 36.5mm offsets. Just looking at the pictures, it looks lke the fronts are two different offsets. I have the 56's and they look like your passenger side.

In the back, its a tough call. I believe the Camaro rear fenders may have slightly less "bulge" than the Firebird fenders. Your tires look like they are farther out than on my Formula, but its a tough call as to whether they are a 50mm offset or not.

Best thing to do is measure the actual backspace. Put the front of the tire flat on the ground. Put a steel straightedge across the extreme outer edges of the rim (be sure its not resting on the tire) and measure from the bottom of the straightedge to the surface of the wheel mounting flange (where the bolt holes are). That will answer your questions.

 

Thanks Fred, I'm glad to see you still around

The reason why I think they are 36.5's out back is because of the deep dish around the lug nuts. The 50's i believe are not as deep (on the front of the wheel).

Does that make any sense?

Doug D

 

I think that makes sense. This is my 50mm wheel. Ignore the lugs and studs because those are oversize because of the 3" long studs on the rear axles.

 

Fred, judging by the pics, my offset looks to be the 36.5mm. I'll pull all the rims off tomorrow and measure the back spacing.

Can you fill in these blanks below?

17x9.5 56mm offset = 7.4" backspace
17x9.5 38mm offset = ???" backspace
17x11 50mm offset = 7.93" backspace
17x11 36.5mm offset = ???" backspace

Doug D

 

17x9.5 38mm offset should be 6.70" backspace.

17x11 36.5 offset would be about 7.40" backspace.

 

Those rears don't look 50mm. They look like 36.5. Incidently, that is the correct offset for true Zr1s. The Grandsports are the 50mm.

 

Those look like +38mm offset to me. I bought a set of American Racing 200S wheels with that offset from a board member and they look about like yours do. Of course I forgot to ask about the offset before I bought them, but I've gotten used to the way they look and kinda like them now.