Rear Axle offset for 12 bolt stock rear?

[g356gear]

Hey guys,
I am trying to figure out a rear brake set up for my 69 Camaro. Rear is a totally stock 12 bolt Posi with stock c-clips and I need to know rear axle offset in order to order the brakes. Does anyone have any experience with this? Thanks.

[Apogee]

2.81"...same as the 10-bolt w/c-clips. Some housings' flanges are welded on wonky, so your mileage may vary.

Tobin
KORE3

[g356gear]

Wilwood specifies a 2.75" offset. Why the difference?

[Apogee]

I don't know, but the early 10/12-bolt housings are typically 2.81" and the late model housings are 2.77". I just checked Wilwood's website and it shows 2.81" being the standard...where is it that Wilwood specifies a 2.75" brake offset dimension? What are you referring to?

You could always measure your rear end just to be absolutely certain of what you have.

Tobin
KORE3

[Skip Fix]

Mine is around 2.80 but had new ends with taper bearings welded on.

[g356gear]

This was the reply from Wilwood. I have no idea which direction to go....

"There are two popular kits for your application, and the only difference is the offset. Kit 140-7141-D has a 2.81" offset, and kit 140-7149-D has a 2.75" offset. Otherwise, both kits are 12.2" in diameter with black calipers, drilled rotors, and the Parking Brake Kit."

Could the different offsets be to allow for different wheel applications? I spoke with Frank at Prodigy and he recommended a completely different part # 140-9315 for staggered shocks on a stock 12 bolt with C Clips and 2.75" offset. The 140-9315 is listed as 68-81 Camaro. The others are listed as Chevy 12 bolt.....maybe the staggered shocks is the determining factor here. You would think a Wilwood rep would know what they are selling.



SKU: 140-9315
140-9315 FDL P/S Park Brake Kit
1968-81 Camaro 12 Bolt 2.75” offset

SKU: 140-7141
140-7141 FDL P/S Park Brake Kit
Chevy 12 Bolt w/ C-Clips

SKU: 140-7149
140-7149 FDL P/S Park Brake Kit
GM C-Clip 12 Bolt-2.75” Offset

[thedude327]

I was looking at the wilwood kit too and the best reason I could come up with is that there were some slight discrepencies during manufacturing of the 12 bolt rears. It is probably critical on the wilwood kit beacause it incorperates a drum with the rotor for the parking brake setup and the distance needs to be correct for the drum portion of the rotor to slide all the way over the parking brake shoes. Also the wilwood kit uses 1/2-20 thread size wheel studs which means that you have to drill out your axles and fit larger studs in them or buy new aftermarket axles with the 1/2" wheel studs installed to make it work properly.

Paul