Was it comon to have the front brakes smaller then the back brakes with 4 wheel drums? Mine are 11 inch on the back and 9.5 inch on the front. I am not really thrilled with the single brake cylinder set up is it an easy change to a double cylinder? One more Question for the night any idea what rear gear this might have it really seems to be rappin at 75 miles per hour but it will do 120 miles per hour also (only once so far) not sure it would do 120 all day long but she would do 75 all day long and I got 22 mpg doing it with the 2 bbl Ultra High Comp. 425 what a great cruzer this car is I love it. I use 91 oct. should I use Lead Sub. with the High Comp. engine? It never has knocked and runs better every day I've put 2000 miles on her so far and get great looks and thumbs up when I drive her in town once I get the paint done she will really get the looks. (oridginally White with Red Int.) Going Red with Red Int. It's a 2008 Buick custom Red my Parents have it on there new Lucern and it is stunning. Thanks for all the INFO and for reading about an old car lover who just got a new toy to play with. Wife's gone car is here to STAY!!! WEBBISH

 

Welcome to the website. I believe it was common to have larger drums in the back. I am not sure how you can change to a dual chamber master cylinder. If you are good at fabrication it might not be that difficult. Your rear gears are probably around 2.73. The best way to tell is to get under the car and see if there is a tag on the rear end.

Now post some pics.

 

I believe the standard rear gear in a non AC car was 3:23 and AC cars had a 3:08....Its troublesome to install a dual master cylinder as the problem I had was that the dual master cylinder lines came out on the wrong side and there was a problem with the lines hitting the wheel housing. I went with a 67 master cylinder but maybe if I researched options it would have went easier. You would also need a different proportioning valve. I drove a 66 Delta for about 8 years straight, never had a problem stopping with the single reservoir master cylinder but you want to make sure all rubber lines are new. They rot and can snap.

 

If this is a Dynamic or Delta 88, someone has put Jetstar 88 front brakes on it. Likewise if it is a Jetstar 88, someone has switched the rear end out from under it and installed one from a Dynamic/Delta/Starfire. My guess is you also have 4-3/4" bolt pattern front wheels, and 5" on the back.

ALL Dynamic/Delta/Starfire had 11" brakes front and rear, 2.5" wide shoes in front and 2" in back. Jetstar 88s shared the small brakes with Cutlass and Chevrolets.

 

Rocketraider is correct. The front brakes do most of the stopping, so they would normally be larger. As noted, on the full size cars, the drum diameters were the same front and back, but the width of the lining was different (larger on the front).

The J88s got the A-body 9.5 x 2.5 front drums and the 9.5 x 2 rear drums. All other B/C body Olds cars got the 11 x 2.5 fronts and 11 x 2 rears. As noted, someone changed one end or the other in the last 40+ years.