65superrocket

I'm attempting to order some wheel cylinders as I will be redoing the entire brake system on my 1965 olds Delta 88 4 door hard top. I plan on keeping the drum set up. I see that both the police package and non police package wheel cylinders are available. Are they interchangable? Other than the size of the bore what's the difference. My car has the small, 1 25/32" O.D first design front wheel hub grease cap if that's any help. What did the drum brake police package brakes consist of, as I thought all Olds big car drum brakes were the same from 1959-to the late1960's. Thanks.

joe_padavano

Installing wheel cylinders with a larger bore will increase brake force for a given pedal force, but at the expense of pedal travel due to the increased fluid volume.

jensenracing77

if the wheel cylinder had a biger bore size wouldn't the master cylinder have a larger bore size also when they were from the factory?

aliensatemybuick

I THINK that the 65-up B-body cop cars cars got the Ninety-Eight (i.e. C-body) rear brakes (backing plates, drums, etc). Not sure what implications there are for the wheel cylinders however.

joe_padavano

Not necessarily. This is hydraulics 101. For a given line pressure, a larger slave cylinder produces a larger force. Similarly, for a given pedal pressure, a smaller master cylinder produces a higher line pressure (which also produces a larger force at the slave cylinder). Keep in mind, however, that this is like a lever. You're trading mechanical advantage for more travel. Since the larger bore slave (wheel) cylinders require more volume (and thus more brake fluid) for the same stroke, the master cylinder needs to travel further if the bore on it is not increased. Unfortunately, increasing the bore of the master will negate the benefits of increasing the bore of the slave. That's the system design tradeoff.

65superrocket

Rockauto shows a common 1" bore for the rear cylinder for the police and non police brakes, and a front bore of 1-3/16" for the police brakes, and
1-1/8" for the non police brakes.

65superrocket

They also list a slightly smaller 7/8" bore size for the police package master cylinder, and a larger 1" bore size for the non police master cylinder.

joe_padavano

Interesting. That will increase brake force even more.

65superrocket

Another question: Olds used two different drum, bearing and grease cap sizes in 65' on the big 88's, with the left front grease cap driving the speedo with a built in nylon shaft. My car has the small 1 3/4" grease caps and I guess bearings as well. Would this impact using the police spec. master and wheel cylinders?