Wheel back spacing

[Blown353]

I've fit several wheels on 68-72 A-bodies for friends; assuming a stock width rear end, 6" or 6.25" backspace out back puts the wheel just about perfectly centered in the wheel well. 6" works well with factory drums, and 6.25" works well with discs out back because of the added thickness over the axle flange for the rotor hat. Anything smaller than 17" and you will run into interference issues with the lower shock mount.

9.5 wide with 5.5 backspace up front is just about right for stock spindles; if you are running B-body spindles you would probably be better off with 5.75" backspacing as the B-body spindles increase the track width by about 3/8" per side over the stock spindles.

I have fit 10" wide wheels on the front of a '70 using 5.625" backspace on stock spindles, but I had to replace the inner fender to fender bolts right at the wheelwell lip with button head allen bolts to keep the tires from rubbing when the suspension compressed. A very close fit.

Again, your mileage may vary and you really need to measure your car... factory tolerances weren't that great, plus there may be collision repairs and/or the body may be shifted on the frame a bit.

Troy

[hectore3]

Blown353,

You stated that you have fitted a number of 68-72 A-bodies for wheels. How any 64-67 A-bodies?

[Blown353]

Originally Posted by hectore3

Blown353,

You stated that you have fitted a number of 68-72 A-bodies for wheels. How any 64-67 A-bodies?

I've also done a 66 and a 67 Chevelle; both had B-body spindles up front and both received 17 x 8 x 4.75 backspace up front and 17 x 9.5 x 5.5 backspace out back; tires were 255/45/17 and 285/40/17. No clearance issues on either car during "normal" driving but if going up a very angled driveway the inside of the tire sidewall out back would very lightly rub the inner wheelwell on the 66 & 67 with the 285 out back. Nothing bad, but *very slight* rubbing. No rubbing at all during normal driving including hard turns, but just a bit of contact if taking a very "angled" approach into steep driveways and parking lots. Much better to rub the smooth inner wheelwell than the outer wheel lip, which can be sharp and cut the sidewall or worse yet have the tire "grab" and bend the lip and crack paint. Regardless, I still like to slightly trim and then roll the rear wheelwell lip.

I haven't done any wheel/tire fitups on 64-65 cars, but I do know they're the most "cramped" of all. 73-77's are GIGANTIC, 68-72's are pretty darn generous for room, 66-67's aren't bad but more limited in back than the 68-72 cars, and from what I've seen it would be kind of hard to fit "big" meats in a 64-65 car, but I have not measured any as close as I have the 66-77 cars.

Now that I think about it I also worked on a 66 GTO Convertible; however the owner wanted to use IROC wheels (16 x 8 x 4.75" backspace I think) and IIRC I had to extend the front fender braces to "push" the front fender lips out some to keep the tire from grabbing at about 1/2 steering travel. This was a Pontiac-only issue due to the shape of the front wheelwell and the size of the tire used-- I don't remember the size of the tire exactly but I remember them being rather tall, about 28". A smaller tire wouldn't have had the problem and the extended fender braces were a necessity... it wasn't my car and I couldn't talk him into fixing it "right."

Troy

[USAZR1]

Originally Posted by Blown353

I have fit 10" wide wheels on the front of a '70 using 5.625" backspace on stock spindles, but I had to replace the inner fender to fender bolts right at the wheelwell lip with button head allen bolts to keep the tires from rubbing when the suspension compressed. A very close fit.

Again, your mileage may vary and you really need to measure your car... factory tolerances weren't that great, plus there may be collision repairs and/or the body may be shifted on the frame a bit.

Troy

You just answered a question I've often wondered about.
If a 10" wheel will fit the front of a 68-72 with only 5 5/8" backspace,you can increase it to 5.75" safely with stock A-arms and 6" with tubular arms.
On a 66-67 A-body,17x9.5's w/5.75" backspace will fit with 275/40 tires on the front and 17x10's w/5.75" backspace & 285/40's on the rear.
On a 64-65 A-body,a 17x9.5 rear w/5 7/8" backspace and 285/40 tire will fit.
These are just a few of my experiences.

[Blown353]

The 10's up front are a very tight squeeze Clint. The wheels the guy had were 5.5" backspace and had a fairly thick pad, so I ended up cutting the mounting pad down some to eek out the last bit of fender lip clearance. Could have taken a bit more but I didn't want to cut more than I had to off the wheel.

One issue to mention is the front tire rubbing the frame and sway bar during a tight turn; my current combo of 255/45/17 on 17 x 8 x 4.75 backspace have very, very minor rubbing issues at full lock, the sidewall of the front tire will just barely kiss the sway bar at full lock. More backspace would make this problem more pronounced. Part of the problem on my car is I'm running GW control arms so the spindle can pivot more before the hard-stop on the spindle contacts the A-arm, and I'm also running a DSE600 steering box with no travel limiters, so I have quite a bit of steering throw at my disposal even with the less than favorable steering ratio of the B-body spindles.

Sometime later this year I'm going to re-do my suspension again; probably going with ATS spindles/Howe Tall BJs and may try to re-use my GW uppers to save a few bucks. I'm really wanting to fit 17 x 10 or 18 x 10's all the way around with identical backspace so I can rotate the wheels/tires for wear (I have a tendency to rapidly "lose" tread on the rears and cone the fronts... LOL) Right now the magic 8-ball seems to think 10" width with 5.75" backspace will work nicely on all 4 corners but without the new spindles and brakes I don't know if that will work or not. I can always fall back on 9 or 9.5" up front and 11" out back, or 9.5" all around if need be.

Troy