hello everyone, i have a question for you. i just recently puchesed some olds rims for my 75 cutlass supreme and they only fit the front of my car. the rims have a bolt pattern of 4"5/8s, and my rear end has a bolt pattern of 4" 3/4s. what can i do to get these rims to fit? my rear end is a 12 bolt, posi, with 3.08 rear gears, and from what i was told it came out of a 68 olds delta 88. any help would be greatly appreciated. thanks

 

A '60s through '70s A-body will have a 4¾" bolt pattern.

A '60s through '70s B-body will have a 5" bolt pattern
(except for the '77-'84 non-diesel, non-wagon Deltas).

This is one of the reasons to use caution when swapping parts between model series.


There are two possible ways to use your wheels on that car:

1. Change the axle shafts.
   I have no idea how easy or hard it would be to find shafts that length with the smaller bolt pattern, but I would imagine you could have them made up if worst came to worst.
   "Monzaz" on this forum would be able to tell you.
2. Use adapters.
   This is not recommended, as it is not entirely safe, and it will space the wheels outboard, which you may not be able to afford, as you already have a full-size rear under there.

The short answer is that you can't do it without a bunch of extra work.

- Eric

 

The easiest thing to do would be to take your existing rear axle shafts and brake drums to a machine shop and have them drilled for the smaller pattern. Get the shop to install new wheel studs for you while they are at it.
Brian

 

I've never seen that done. Good idea.

Leaves you the option of going back to the 5" pattern later, too.

Do you lose any strength that way?

- Eric

 

Eric, this is a fairly common modifiction in the street rod market since people are always using differentials from various vehicles. 9" Fords are commonly used under many vehicles so the rear axles get drilled for a Chevy pattern for example if the differential is in a Chevy with front disc rotors with a Chevy Pattern. Even the Jeep market does a lot of this as I think the later model 8.8 Ford differentials with disc brakes are a popular swap into some Jeeps. I'm sure the extra set of holes could cause a loss of strength but for most vehicles, it's not an issue. If someone had a blown engine making 1000 hp, then new axles would be better and for more reasons than just the extra set of holes.
Brian

 

Excellent. Thanks!

I'm not a street rod guy so I didn't know about that one.

Always learnin'.

- Eric

 

First, you are measuring wrong. There is no such thing as a 4 5/8" bolt pattern. The dimension is the diameter of a circle that passes through the lugs. With five lugs, you don't measure from lug to lug, you measure the circle diameter, which is an imaginary point on the far side of the pattern. That's why they sell those plastic lug pattern gauges at swap meets.

In any case, EVERY Cutlass (and GM A/G body) built between 1964 and 1988 model years uses a 4 3/4" bolt circle, and every one of them had the same pattern at both ends of the car. If yours are different, someone swapped the axle.