Brake wheel cylinder size

I have a qusetion about brake wheel cylinders. I have a ford 9" rear with 11 by 2 1/4" shoes, and 7/8" wheel cylinders. Now my qusetion is, would the 15/16" wheel cylinders give more stopping power then the 7/8" or would you even notice the difference, between the two. And not power brakes, I am rebuliding the rear now and putting all new parts in and replacing them anyway. Thanks for your info.

 

i personaly would just stick with the 7/8" i dont change wheel cylnder sizes unless i have to but you would be fine with the 7/8"

 

To answer your question, going from 7/8" wheel cylinders to 15/16" will increase braking power about 9%. The larger the wheel cylinder or caliper, the more force will be excerted to the drum shoes or disc pads.
Bob

 

By my calculation, the larger piston has 14.7% more surface area. I suspect this might increase the likelihood of locking up the rear end in an emergency stop. I would go to a brake shop and include their advice in your planning.

 

Last year I had to replace my 7/8 Ford rear cyls. It was for a 48 F1 rear end. Closest I could find came from a 55 Ford with the larger bore. They seem to work well, and no more leaking.

 

Thanks guy's for the info. I think I will go with the 15/16 cylinder as they are the same price, the car I'm working on is my T-Bucket with only rear brakes. I'm working now on getting all the parts for front brakes, I have the backing plates and bearing hubs for the front,I found some front drums but have been turned past specs. The front spindles are '54 chevy and every thing on the front has been chromed, so I need to get a lot of parts chromed to match.

 

I am in the exact same position. I am thinking of going with the 7/8 bores, because of the thought of more likely locking up the rears with the bigger ones, as someone noted earlier. Also, I figure the bigger bores will also move that roughly 10% much more fluid, resulting in a longer pedal throw, and I am already running a small single reservoir master.
Paintcan54, With just rear brakes, I think you are in a freer situation to go 15/16.

Anyone know why the T-Birds and station wagons had the bigger bores? They are listed as "heavy duty. Talking '57 -'64 or so.
Was it bigger shoes, drums dia, or just looking for more force?"

 

CalgaryChris,
You are right about the 14.7% increase. Math was NOT one of my better subjects! My bad.

paintcan54,
I hope you are going to install later duo-servo '48-up Ford truck/'49-up Ford car front drum brakes instead of the earlier '39-'48 Lockheed non-servos, otherwise you will have way too much rear brake.

EEZ1,
Larger wheel cylinders are used on larger or heavier vehicles that require more braking power. Engine choice also plays a role. As an example, late 60's Mustangs with small blocks usually had larger rear wheel cylinders than the big block cars, all with the same 10" brake. The reason was weight transfer, and trying to prevent early rear slide.
Bob

 

Hey guys, I am relatively new to posting. I am getting ready to add brakes to my '28 AA truck project. On the front are 56 Ford F100, I'm running a 47 Banjo Rear and need advice what brake to use on the rear, stock 47 V8, or something that is self adjusting. Any advice will be apperciated.