I am currently running a 1.125" bore 2-bolt master cylinder with front 11-3/4" brakes and rear 10" drums. I pretty much hate it, I've had it on there for quite a while and am not too happy with the effort required. I'd like to go down to a 1.032" master and an aftermarket proportioning valve.

I would like to run rear discs in the near future and want to make sure I won't regret making the swap.

What master are you running and is it with disc/disc or disc/drum?

Thanks!

Which bore master cylinder? single choice
	1.032"
	1.125"
Votes accepted starting: 10/19/14 09:48 AM
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Which brake type combination single choice
	Disc/Disc - Manual
	Disc/Drum - Manual
Votes accepted starting: 10/19/14 09:48 AM
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I have the same setup you do in a Duster with a 15/16" master cylinder from Dr. Diff. Had a 1 1/32 before and it's a lot better. That's what I would suggest.

I was looking for the correct 1" bore m/c for my big block A body. The particular unit is pretty much unobtainable. Got with the Ramman. He set me up with a unit that had a 11/16" bore which is pretty close. I've since found the correct numbers correct unit which he's restoring so I won't be needing the one he setup for me.

What calipers do you have? If OE, what is their piston diameter?

I'm using wilwood dynapro's (way stiffer than dynalites of any flavor) with a late model Mopar 1-1/16 M/C and I find the pedal effort to be just about right. This is in a '65 A body, which sets up the next question.

What is the ratio of your pedal?

This is going somewhere, so please bear with me.

If you have the room for the additional pedal travel, go with a 15/16".

15/16" here.

Thanks for the input. Does anyone have a part number for the 15/16" bore? I haven't been able to find that in the 2-bolt flavor.

Also, do all of the aluminum 2-bolt masters have a provision for the manual pushrod grommet?

Without knowing the caliper piston area and pedal ratio it is impossible to choose the m/c size. Or suggest one.

I also use the Dr. Diff 15/16" MC with "manual" disc (OE 11-3/4") up front and 11" OE drums in the rear.

Disk/Disk

7/8 piston

6-1 pedal

It's time for the brake math spreadsheet.

http://3gduster.com/brakes.html

I've got an updated version available should anyone want it.

Goody, it is possible to over engineer things. I sometimes have a hard time knowing when to stop "making it better."

What I posted is a very basic spreadsheet that I cobbled together late one night. As I stated above, I have an updated version available that does have units of measure listed. However, I do not have admin access to that link so I can't change it.

The spreadsheet won't win any Formula 1 races (especially with friction as 1) but it'll be more than enough for a car on the street.