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| | | | Joined: Jun 2005 Posts: 1,002 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 1,002 | I want to mount a dual master cylinder on the firewall of my '41 3/4 ton (It had one there when I got it).
I understand I need one with 1.25" bore for my drum/drum application. But I don't see any vendor listing them. All of the 1.25" ones listed are for disc/drum.
So, do I just go with that and use a residual valve on the front, or am I missing something?
Thank you.
~ Victor 1941 3/4-Ton Pickup (in process). Read about it in the DITY Gallery1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD 1957 3100 - moved on 1959 C4500 Short Bus "Magic Bus" - moved on 1959 G3800 1 Ton Dually "Chief" - moved on 1958 C4400 Viking "Thor" ~ moved on to fellow Bolter | | | | | Joined: Feb 2004 Posts: 29,851 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,851 | You will need residual valves on front and rear brakes for a drum/drum system. The pressure is necessary to keep the wheel cylinder cups expanded to avoid air being drawn into the wheel cylinders. The main difference in disc/drum and drum/drum master cylinders is the size of the reservoir chambers. The reservoir for a disc brake caliper is bigger because the volume of the caliper bore is larger, requiring more reserve as the pads wear and the pistons move forward to take up the space. On a dual drum system, there's no need for the extra reservoir volume, but it doesn't hurt for it to be there. Racing parts places like Summit or JEGS should have the external residual pressure valves you need.
Jerry
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| | | | | Joined: Nov 2005 Posts: 6,100 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,100 | Hy VEW, if your brake system is from the 1953 to 59 truck as we figured in your other post, then a master cylinder with a 1 1/8" bore would be sufficient. Your F.L.A.P.S. should be able to get you Raybestos p/n MC36246 which is a drum/drum master cylinder and would require no external residual pressure valves, hope that helps. | | | | | Joined: Jun 2005 Posts: 1,002 'Bolter | | 'Bolter Joined: Jun 2005 Posts: 1,002 | Thanks Jerry and 3B.
I guess I was getting it confused with my 1.5 ton trucks. I went out and looked at the one on Doughboy, which is a 3/4 ton frame, and it does have an original 1 1/8" diameter MC on it.
I guess I'm all set. All I need to do is get the MC, booster, brake shoes, cylinders and hoses and I'm good to go.... I mean stop.
Thanks again for all your help!
~ Victor 1941 3/4-Ton Pickup (in process). Read about it in the DITY Gallery1955 Grumman Kurbside "Doughboy" 235/3 on tree w/ OD 1957 3100 - moved on 1959 C4500 Short Bus "Magic Bus" - moved on 1959 G3800 1 Ton Dually "Chief" - moved on 1958 C4400 Viking "Thor" ~ moved on to fellow Bolter | | | | | Joined: Feb 2000 Posts: 5,228 'Bolter | | 'Bolter Joined: Feb 2000 Posts: 5,228 | No need for the residual valves if you are mounting on the firewall. Gravity will take care of that for you. | | |
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