This is a strange one for you guys out there. My friend bought an 84 Olds 98. The car is mint. The guy he bought it from threw in a set of Olds rally wheels. My friend had them painted, mounted new red walls on them and then finds out they have a 4.75" bolt pattern and his car is a 5". Theyre 15" just the wrong bold pattern. Now hes trying to figure out a way of using them. Anyone have any ideas ? He was thinking about having the rotors and axles drilled for the smaller pattern. (I think hes nuts but I told him I'd ask)
5" to 4.75" conversion question
- Thread starter Mike
- Start date
If the front rotors are 12” (11.86”) rotors, then you can buy a pair of Camaro rotors from a 1989 to 1992 1LE or heavy duty (HD) Camaro. Stock Camaro rotors are 10.5” just like the g-bodies. The 1LE rotors are the same rotors as the 12” rotors on a b-body (caprice, olds 98, etc.) but with the 4.75 bolt pattern. You will not be able to find these in a junk yard, so you will have to buy new. Measure the brakes on the Olds 98 first before you buy. They may be 11” rotors, but I don’t think they had the 5x5 inch bolt pattern on the 11” rotors.
For the rear drums, look into the 1973 to 1977 gm a-bodies (regal, Malibu, chevelle, cutlass, grand prix) for the 11”x2” drums. Make sure that is the same drum you have on the Oldsmobile 98.
The differential on the olds 98 should be an 8.5”. The axle shaft length should be 30 3/8” and have a 28 spline count. From that same a-body that you pulled the drum brakes you should be able to use the axle shafts which have a length of 30 7/16”. It is only a 1/16” of a difference and should not matter once everything is bolted together. Some A-bodies from 1973 to 1977 came with bolt in axle shafts instead of c clip (most were c-clip). The Olds 98 should use the c-clip axle shafts instead of the bolt in axle shafts.
For the rear drums, look into the 1973 to 1977 gm a-bodies (regal, Malibu, chevelle, cutlass, grand prix) for the 11”x2” drums. Make sure that is the same drum you have on the Oldsmobile 98.
The differential on the olds 98 should be an 8.5”. The axle shaft length should be 30 3/8” and have a 28 spline count. From that same a-body that you pulled the drum brakes you should be able to use the axle shafts which have a length of 30 7/16”. It is only a 1/16” of a difference and should not matter once everything is bolted together. Some A-bodies from 1973 to 1977 came with bolt in axle shafts instead of c clip (most were c-clip). The Olds 98 should use the c-clip axle shafts instead of the bolt in axle shafts.
To me it's not worth the hassle of swapping shafts / drums and re-drilling the rotors just so you can use a $ 100 set of wheels. Peel the tires off and find some new wheels to mount them on or just sell them complete and buy a new set. The 5 on 5 pattern is plentiful and used on many GM cars ( bbody ), trucks, and vans for many years.
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