I need to replace the rear wheel cylinders on my '60 Comet wagon which came with the smaller "sedan" drums/cylinders...not the larger "wagon" brakes. Would installing the larger "wagon" cylinders give me better braking?....or would it be pointless since I still have the smaller "sedan" drums?
Changing to a larger diam. wheel cyl. will give more force to push out the brake shoes. More diam. = more area = more force.
Short version is the early wagons came with the smaller brakes and in order to keep it on the road, I replaced the drums with the same smaller ones. Otherwise, to change to the bigger drums, I would have had to change out the rear axles or wheel bolts at the very least. It just would have been more time and money involved. Now, though, I need to replace the wheel cylinders and figured that if I could get "bolt on" better braking, why not?
Just be sure to give it a throrough test, including downhill and wet panic braking. You don't want a surprise when it rains. There could be an issue with the physical strength of the drum. Could bigger wheel cylinders actually crack a drum? I dunno. New, uncut, US made drums could be a bonus.
i actually tried this on a vw. the rears do lock first but only when i stomped on it. for regular street driving... they were ok..didn't fell much difference unless i slammed on the brakes.
Hey Chad, Being that you have a single pot reservoir wouldnt you got even pressure to all the wheel cylinders no matter what? I would say put a proportioning valve in it but that obviously wouldnt do you any good in your case, I would say you would be ok, just make sure everythings adjusted really good.
As a whole the only problem I see is capasity, The larger cyl will require the preasure transfer of fluid from resivor to cylinders, Larger cly more fluid more fluid lower brake pedal. I dont think you will notice. Cal
I would keep an eye on the shoes after you have had the car on the road for a while. I did the exact same thing on my car (not the same car but a drum brake rear setup). I replaced my orginal stock 11 dia drums with smaller 10" drums because they came with the entire new, more modern, rear end I installed in the car. The one thing I changed on a hunch was I used the brake cylinders from the old larger 11" brake system. They happen to be a larger bore than the stock cylinders for the new rear end brake system. In answer to your question, you will get better braking. I did. But if I hit the brakes just a bit too hard I would end up going through the windshield. The brakes ended up being very touchy and the brake shoes wore down really fast. So inspect them to make sure they don't get worn down to to the rivets way sooner than you would expect. Don't ask me how I know. I have a power master cylinder that might exaggerate the premature wear. If you have a manual master cylinder it might not cause a problem. It's possible the later wagons had bigger front cylinders than the rear cylinders. That is how they are on my stock Merc drum brake. That is how the front brakes stop harder than the backs.
[ The brakes ended up being very touchy and the brake shoes wore down really fast. So inspect them to make sure they don't get worn down to to the rivets way sooner than you would expect. Don't ask me how I know. I have a power master cylinder that might exaggerate the premature wear. If you have a manual master cylinder it might not cause a problem. maybe you need bigger return springs
Good idea, they might not have been pulling back from the drums. After I finally got those rear drums off, I removed the oversize cyinders and installed the smaller stock size brake cylinders. That eliminated the touchy brakes and so far it seems I am getting longer life out of the brake shoes.
I am going off of what the engineers did the following year. They switched to the larger bore cylinders and deeper drums. I just won't have the deeper drums. I am not sure how it equates, but they only went 1/16" larger on the bore.
I believe the engineers went to deeper drums to make use of the extra pushing force of the larger cylinders. Now with deeper drums there is more contact area. On the stock version of my car, the front cylinders are slightly larger bore than the back cylinders. My front drums are deeper than the back drums. Good luck with the swap.
Engineers that designed it using sliderules and REC tables, spoken like a true restorer. I worked in engineering for a couple decades.... "smarter" than the engineers isn't necessarily a tall order. I had a similar discussions with a local named David North who is a retired GM designer Pontiac, Buick, Olds 1960's - 1990's, and stories abound of how many times the engineers thought it "worked out great on paper". Traffic conditions and highway speeds require better brakes than the 50's technology of my hardtop. I'm taking advantage of what I can reasonably afford, using a proportioning valve to balance the all drum brake, wilwood manual dual remote master in my 52 Pontiac, I've sized up the rear wheel cyl from 7/8" to 1" and similarly sized up the front. Future plans call for a disk setup as cash allows. s.
I went up an 1/8" on the rears of my OT 86 Buick Grand National. It was mainly to help holding it on the starting line at the track (foot braking). It help out on the launch and I never noticed a difference on the street.
I am no brake expert. but I'd say it wont work well, because you are introducing too much force on too smaller area of brake shoe. Seems the designers increased cylinder diameter and shoe size accodingly. However a proportioning valve fitted to the rear line only should help fine tune those rear brakes if it dont work out so good. Report back so we know how it worked out. Good luck and thanks for sharing.
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