I am still trying to sort out my back half 1970 Buick Skylark project (don't hate me) and I was planning to buy a S&W Chevelle kit as they are both A bodies. I had a set of Buick ralleys widened to 15x14 by Stockton wheel. They made the backspace 7 7/8. When I emailed S&W,the guy said he wasn't sure I could use my whels. I have a few feiends with 8 inch and 6 inch backspacing and was hoping some on here had an opinion and what the backspacing you are running. The only problem I see with the backspacing I have is I would have to jack the car up high to remove the wheels. This is going to be a drag car and not a street car. The suggested backspacing from them is 4 inches.Can I use a universal frame rail and still use my new rims? The width of the welded frame is also27 1/2. Any suggestions??

I run a 5 inch backspacing on my 15x14 wheels. If you have not already narrowed your rear end yet then it won't matter what backspace your wheels are. Place your tires and wheels under your car and set body at ride height. Then measure between your tires at the section width to determine frame width and measure inside of bolt flanges on the wheels to determine your rear axle width. I always set the rear frame width 2 inches narrower than the inside of the tires{ one inch clearance on each side}. Most pro street cars that sit low almost always have to have the lower shock mounts removed/ pivoted to get the tire out from under the car. Hope this helps.

I would go with the least amount of backspacing possible. This does 2 things, it makes the rear as light as possible by keeping the axles and the housing shorter, and it also keeps the housing stiffer. If your car is a 4 link or ladder bar car, there is nothing supporting the housing tube the farther out from the ladder(or 4link) bar and it is able to flex. Mine is done with S&W universal rails, at I think 28" center to center. My car has 15X15 wheels with I believe 3 1/2" back spacing with 16X32 tires. My car is low enough that I still have to jack up the car and then let the rear hang to get the tires off.

I run a 15 x 15 inch rim / 33 by 18 1/2 tires and a 4 inch BB,

This is Zachs dad posting from Team Camaro I was always told center back spacing is best.My frame rails on my 69 Camaro are 24" C/C I would measure inside the wheel wells and subtract the tire widths.Have you looked at checkered racings back half.My son and I are getting ready to tub his 70 CHevelle and I am also looking for some info on full frame jobs.I have done a few unabody cars but no full frame cars.I want to do his with no roll bar.

This is Zachs dad posting from Team Camaro I was always told center back spacing is best.My frame rails on my 69 Camaro are 24" C/C I would measure inside the wheel wells and subtract the tire widths.Have you looked at checkered racings back half.My son and I are getting ready to tub his 70 CHevelle and I am also looking for some info on full frame jobs.I have done a few unabody cars but no full frame cars.I want to do his with no roll bar.

That is true for a street driven car. Not for a drag car that will not be seeing potholes and experiencing the up and down forces on the wheels.

I am a bit bummed as I really wanted to run the wheels I paid big money to have widened. I guess I entrusted Stockton to know what they were doing.I even explained this was for a drag car and not a street car. Do you see any problems running a longer housing other than weight,as well as possible flexing. My goal is a 10.50 car as I don't need to be any faster.

The weight is an extra, I think the real issue is the rear flexing. I'll give you an example that I experienced with a stock length rear and ladder bars. My ladder bars were 28" on center with stock springs and shocks. I did have a LPW housing brace, but the brace broke due to poor quality chromoly tubes. Anyway not knowing it broke, on the next pass the driver side tire hit the 1/4 panel and sliced it all the way around. I didn't know and proceeded to run 10.52 at 126 with a tire throwing ribbons down track.

4 1/2" backspacing on a 15"x14" rim with 33.0"x19.50" tire.

David F.

It all depends on how wide your rearend is. There is no one magic backspacing number once you start modifying your car. your rearend lenght and your backspacing have to work together. Shorten your rear and decrease the backspacing.