I just installed the 8.5 rear in the 68 Firebird last night and got me thinking about wheels and tires. I know that I can fit a 17x10 with 5.75 BS on a stock 8.2 rear but the 8.5 is 1" shorter overall compared to the 8.2. To figure backspacing should I add 1/2" per wheel to make up for the difference?

What's the 8.5 rear end out of?

The rear is from a 73 nova

I just installed the 8.5 rear in the 68 Firebird last night and got me thinking about wheels and tires. I know that I can fit a 17x10 with 5.75 BS on a stock 8.2 rear but the 8.5 is 1" shorter overall compared to the 8.2. To figure backspacing should I add 1/2" per wheel to make up for the difference?

Assuming everything else is the same and you want the wheels to be in the same spot as with the 8.2" rear, to compensate for a 1" shorter rear end you would want to have 1/2" less backspacing on your wheels. That would move the wheels outward by 1/2" on each side to compensate for the 1" shorter rear end.

Thanks Woody, The spring perches and shock plates are identical to the 8.2 and the rear suspension seemed to be a breeze to install.

I always thought the overall width was the same as a 1st gen 8.2. The 1" deal was in the length of yoke to center line of the axle which might require a driveshaft mod. Not sure but I think this all depends on the yoke.

From backing plate to backing plate it is exactly 1" shorter. This may be because it is a Firebird and not a Camaro. The spring mounts are the same though

Well I ran the casting numbers off of the 8.5 I have and it looks like it was from a 79 Nova and not the 73 as I was told. The distance between the spring perches is the same as the Firebird/Camaro but the overall length is 1" shorter. From the spring perch to the backing plate it is exactly 1/2" shorter than the 8.2. My concern with using this rear is that the shock plate will then be 1/2" closer to the wheel. Should I even worry about it and use it or throw it on ebay and see what I can find as far as a direct bolt in?

If you are going to use the same wheels, then the shock plate will be 1/2" closer to the wheels. If you decrease the backspacing on the wheels by 1/2", the wheels should be the same distance from the shock plate as before, assuming everything else is the same.

If you already have the wheels that want to use then you may be able to use a wheel spacer. I don't know too much about what is acceptable to use as far as wheel spacers, but in the current Popular Hotrodding, they used a 1" wheel spacer on a second gen Camaro.