Backspacing for 17x11 wheels on a 1985?
03-31-2008, 08:07 PM
#1
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Backspacing for 17x11 wheels on a 1985?
Sorry guys I did a search but couldn't find anything. I am getting ready to buy a set of torq thrust II's for my 1985. The 17x9.5 for the fronts are stock. I am going to have the 17x11 for the rear special cut because they are not a stock item. In order to do this I have to order them with the correct backspacing. My options are between 3" and 8" and is done in 1/4" incraments. I want to make sure they will fit. I am going to be running 315/35/17 on the rears. Any help will be greatly appreciated.
03-31-2008, 08:30 PM
#3
Safety Car
I agree, 36mm. Thought I'm not positive. If you're buying from someone who knows Vettes, they probably know. I got a set of wheels from Tomz Wheels, and I just told them the year, size and style I wanted.
03-31-2008, 08:42 PM
#4
A "real" ZR1 11" wheel with 36mm offset fits well on '87 and earlier cars. Here's a quick chart but ignore the information you're not concerned with. You want to look at what they refer to as a "low offset". They're back spacing is pretty accurate. For your fronts I believe if you're doing 9.5's you'll want I believe the 38mm offsets. I haven't measured mine for some time but I've got several GM ZR1 wheels and also GS wheels. These offsets in the chart look correct!
http://www.skulte.com/adapterfaq.html
Most after market wheel manufacturers rather deal with "backspacing" as it much easier for the customer to determine fitment. If you need a physical measurement to confirm let me know and I can do it tomorrow evening!
http://www.skulte.com/adapterfaq.html
Most after market wheel manufacturers rather deal with "backspacing" as it much easier for the customer to determine fitment. If you need a physical measurement to confirm let me know and I can do it tomorrow evening!
Last edited by WVZR-1; 03-31-2008 at 08:55 PM.
03-31-2008, 10:27 PM
#5
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Correct offset for 17x11s is 36.5mm, or 7.93" backspacing, so go with the 8" and you'll be good.
03-31-2008, 10:47 PM
#6
Race Director
I agree the backspacing is much deeper than the original 36mm listed. 36mm is the offset (from wheel center). I was thinking 7.75" was stock backspacing, but Vader is probably right.
The only thing I'd add is this... Look at how your existing wheels fit inside the rear wheel wells. It was my opinion that they were set in just a little -- esp compared to fronts. (Specifically, I measured them as 3/4" too far in). To make them fit flush with the edge of the car, consider 7" - 7 1/4" backspacing (3/4" less than stock). Less backspacing will move the wheels out.
Backspacing has a direct correlation. 1/2" less backspacing will move the wheel (tire) out 1/2".
gp
btw: You won't have any problem rubbing if you decrease the backspacing. And, you might want to mix the backspacing -- making it less for the rears.
The only thing I'd add is this... Look at how your existing wheels fit inside the rear wheel wells. It was my opinion that they were set in just a little -- esp compared to fronts. (Specifically, I measured them as 3/4" too far in). To make them fit flush with the edge of the car, consider 7" - 7 1/4" backspacing (3/4" less than stock). Less backspacing will move the wheels out.
Backspacing has a direct correlation. 1/2" less backspacing will move the wheel (tire) out 1/2".
gp
btw: You won't have any problem rubbing if you decrease the backspacing. And, you might want to mix the backspacing -- making it less for the rears.
Last edited by GREGGPENN; 03-31-2008 at 10:52 PM.
