I am researching the additional components to complete my braking system on my 29 roadster project. There will be drums full circle on the vehicle(buick fronts, 9" rear), but would like some help in understanding the how's and why's regarding the selection of a master cylinder. Several people have said to run a 1" bore; but I ask how, does one know the proper bore size to use? I have searched for this discussion, though I cannot find such a topic. Could someone identify different Drum/ Drum brake system requirements and the different styles of master cylinders used?
I would run whatever size the original MC bore was. I don't know if it is/was a 1" bore or not. Hopefully someone in the know will post up the size for you. Good luck. Al
I can tell you with 1940 Ford front brakes and a Ford or Chevy rear end, I have run a 1967 Mustang dual reservoir MC for "drum brakes" on a lot of my model A builds and it has been just find.. I can not tell you brake system requirements or different styles.....
Here is a good thread http://www.jalopyjournal.com/forum/showthread.php?t=235235&highlight=brake+bible The Wagner or equivalent book breaks down brake systems for all makes and models. You are on the right track! Early Fords 39-48 used 1 1/16" bore MC's and 49-60 used 1". Wagner PN F73323 is Ford 67-72 Fullsize car manual 1" that works good with a 7/8" or 15/16" rear wheel cylinder. The Buick fronts were most likely 1 1/8" looking at my book also using a 1" bore MC. Hope this helps, I can look up exact year combos if needed. Trent
And in this thread is a picture of the Carquest version of the brake bible that Donzie and I auctioned off so a person knows what they are looking for. http://www.jalopyjournal.com/forum/showthread.php?t=11543&highlight=book+auction
Thanks for all of the replies. It will take me some time to review this information and consider a new question. Be back soon!
I have 1" bore on both my cars. Ford style on the coupe and Cheby style on the little truck. If you go 1" you can some day switch to front disc and use the same M/C. Or go power in the future and still use it. A 1 1/8" bore does not work well with manual brakes. IMHO a 1" M/C gives you more versitility down the line. I put residual pressure valves on my drum setup, even with the M/C on the firewall.
Alright. Now might be a good time to give some specifics on the equipment that I have gathered. My 9" came from a '72 Turino. Up front, I am doing the Buick drum swap so early model Ford stoppage there. "Tman"- thanks for the link. It seems that "Drivem" has the right terms that I want to learn more about. For example; choosing bore size, pedal leverage ratio, proportioning valve (I have read that proportioning valve is made internally in some Drum brake M/C's). Is there a formula for putting all of this together and a "ideal" brake system pressure that can be achieved? Lastly, not trying to be ugly, but I have started the project with a frame. Nothing ever existed on this thing before. I figured that the only way to learn was to jump in blindfolded at night!
4 wheel drumbrakes do not use/need a proportioning vavle except in some VERY special cases. IE very large brakes in the rear of a very light car. Never heard or seen a prop. valve built into a MC. 5-6 to 1 pedal ratio is a basic setting for manual brakes. You usually will be in the ballpark with a 1"or 1&1/16 " bore master on normal American car drum brake systems either single or dual.
Good post. I have a question. Is there a preference for firewall mounted or under floor mounting. Is one better than an other or??
If MC is mounted low, you may need residual pressure valves to keep the fluid from running back into the MC.
You just have to do the math. On my coupe I will shoot for 1247 psi. (40 ford front/9") needs a 7/8" bore with a 5:1 pedal ratio. 31" tall tire in back. A proportioning valve will help tune the brake bias. See these help full links. http://www.markwilliams.com/braketech.aspx http://outlawdiscbrakes.com/faq.html
That's the master cylinder I use to. Even used it with disc / drum combo (with a preportioning valve) and worked good to.
I'm interested in your reasoning. I'm thinking it's because the 40 front wheel cylinders are 1-1/4" or 1-3/8" in dia. I did not realize they were that large until now. I'm now re-visiting the math myself. Thanks in advance.
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