[Engine-Ear]

Until yesterday, I had never fit anything other than a stock 14" wheel with at most a 225mm-wide tire on the back of a '62.

Having the need to fit "rollers" to my Bonneville and only having a pair of Chevy truck steelies with 235-75-15 mounted on them, I was surprised that they fit the wheel opening.

Two observations:

1) a tire that big looks improper on a stock '62 (JMO), but more to the point of this thread,

2) there is probably a full inch of clearance at the top of the wheel opening on the RHS, but the tire almost rubs the wheel opening on the LHS.

I wouldn't have realized it without doing this, but it got me thinking...The chassis manual calls this rear end a floating rear end with no adjustments.

Having never installed a '62 diff housing myself, has anyone else observed this on his a '61 or '62?

Or, is this a just an indication of worn out control arm bushings?

[tom s]

just went out and checked mine,might be 1/8 inch less room on my drivers side than the pass side.Has someone over the years cut the inner lip?Tom

[tom s]

Sorry,had it backwards,touch tighter on the pass side.Tom

[mgarblik]

I would think worn/sagging rear springs would be the most likely cause for the difference. My car sits 1/2" lower on the driver's side. I have new springs but haven't had a chance to install them yet.

[pfilean]

My 61 is basically dead center. Space between the tire and opening lip is just enough to put a finger in the space. I'm running 15 inch Torque Thrust with 215-70 BFG. Control arm bushings have been replaced.

[AROWHED]

Body alignment to frame and control arm bushings\wear all come into play. Adjustable upper control arms are real problem solvers, allow you to adjust u-joint angle as well. For now I'd start by verifying if rear end housing is perpendicular to frame and go from there. Triangulate measurements from a spot dead center of car, that's as close to front of car as possible. A 12' long or so piece of 1/8" steel cable, bolted at the exact center point of frame under oil pan works great. You're an engine ear...you love this stuff!

[b-man]

While replacing the body to frame mounts you can shift the body over on the frame until the clearance between the body and the tires are the same on both sides.

It's not at all uncommon for the body to be 1/2" to 1" off to one side on the frame due to allowable factory tolerances. You'll certainly want to make sure all the suspension bushings have been replaced with new ones before making any body to frame adjustments.

Did exactly this on two of my '64 A-body cars, was able to pry with a long bar between the rockers and the frame to get the body precisely where I wanted it. Of course the full weight of the body wasn't on the frame at that time, I had a couple of floor jacks under the rockers (long wood 4X4s between the rockers and the jack for support) to take most of the weight off to allow shifting the body.

Absolutely essential when trying to stuff the widest meats under any full-framed car.

[Deadhead]

Get somebody to ride down the road behind you. I am behind cars all the time where the rear of the car is out of alignment like this. Let us know what you find. A lot can happen to a car in 55 years. Lord only knows the tales it could tell.

[mgarblik]

Originally Posted by mgarblik

I would think worn/sagging rear springs would be the most likely cause for the difference. My car sits 1/2" lower on the driver's side. I have new springs but haven't had a chance to install them yet.

I misunderstood the OP. You are talking side-to side tire to wheel opening lip. Carry on.

[61-63]

I've removed/replaced/switched tires on '61-'63 big Pontiacs quite a bit and the clearance on both sides has always been pretty much the same. The '63 frame over the rear axles is narrower or wider than '61/'62 (I don't remember which)
so when mounting the widest tires possible the wheels need a slightly different backspace, but the clearance has still been the same both sides.

[Engine-Ear]

Great posts, gents - I do appreciate it!

Rear springs are saggy, car has 150k on the clock with original bushings all around, and wheel openings have not been cut.

SO, I think I see where I need to begin to square things up.

[Stuart]

I've heard it more than once that 1961/1962 cars have the rear wheels offset to one side or the other. My assumption is it simply has to do with how the body was bolted down on the frame, whether that was during original assembly or later on when a car was restored. I've never actually measured any of the '61s I've owned but then again the widest tires I've ever run were 225/70-14 so the issue never came up.

[alleyCat]

My 61 Safari is tighter on the left side too. Probably near 1/4 to 1/2 inch

[Engine-Ear]

I will remember this when my GP goes back together; I suspect that the body either shifted on the frame (as bushings sagged over the years) or the body was attached on the 'edge' of assembly tolerances (or both!).

[U47]

Originally Posted by Engine-Ear

I will remember this when my GP goes back together; I suspect that the body either shifted on the frame (as bushings sagged over the years) or the body was attached on the 'edge' of assembly tolerances (or both!).

If I remember correctly, the Body / Frame bushings locate the body to the frame.

[AROWHED]

There is enough play in the bushing bolt's captive nuts inside the body to allow for body alignment..or misalignment.