Stock Rear end width?
 

What's the tolerance here? 1/8' , 1/2", 1" , rules say.... distance between backing plates cannot be changed.

I have looked under a lot of cars the last year or so and, well I will just leave it at that.

The question is....I am supposed to measure in at 56" and I have a housing here that's 55", what would you do?

Re: Stock Rear end width?
 

As you said, the rules state that the distance between the backing plates can't be changed from stock (assuming we're talking a stocker). Later it states that a replacement rear end can be widened or narrowed to obtain that original distance. You can't bolt something on to do that so it's would be a machine shop task.

As for looking under other peoples cars, you need to make your own decisions as to whether to follow the rules or not.

Dale

Re: Stock Rear end width?
 

Bill… Now that 4 wheel disc brakes are allowed, the BP-BP measurements seem to have fallen away. Most fit the tire to the wheel housing and choose rim offset to work. This allows a lower closer to "Stock" ride height. Read deep into the rule (real deep). MB.

Re: Stock Rear end width?
 

Pretty much sums up tech's attitude with this.
What can be gained? Loss of a few pounds?
8-10 " wheels only come with few offset options.
Special made wheels with a bunch of offset would be really noticeable on ,say a 69 Camaro, wouldn't they be?