what Bore master cylinder

[tooslow]

I am running manual brakes with 13 Baer disks up front and 11.75 Wilwoods out back. I want to upgrade my Autozone manual master cylinder. Its a dual reservoir. I have a proportioning valve-adjustable I use for the rear brakes. All work well but i do not trust the Autozone Master cylinder?
When you look at aftermarket master cylinders you can purchase them in various bore sizes. 7/8. 1inch ect....
How do I determine what bore size to buy? The bigger the bore the more power i have and is it that simple?

 

[70Duster440]

The bigger the bore, the more effort is required for braking. Personally, for a manual brake setup I'd want 1.03" or smaller (for stock calipers). A 1.125" requires a lot of leg. They often publish the bore size on OEM replacements. It's all relative to caliper bore displacement too. You may want to just try what you have and see how it feels.

If you need to change MC's, Dr. Diff can set you up with an MP aluminum one with adaptor for a pretty decent price. He can provide valuable advice on the subject too.

 

[tooslow]

The bigger the bore, the more effort is required for braking. Personally, for a manual brake setup I'd want 1.03" or smaller (for stock calipers). A 1.125" requires a lot of leg. They often publish the bore size on OEM replacements. It's all relative to caliper bore displacement too. You may want to just try what you have and see how it feels.

If you need to change MC's, Dr. Diff can set you up with an MP aluminum one with adaptor for a pretty decent price. He can provide valuable advice on the subject too.

Really NICE DUSTER! I had a duster with a 440 DUSTER and a 5.13 gear a long time ago...BOY was it fun but hard on back tires......

I will go to DR, DIFF and get it from him

 

[Johnny Dart]

Increasing the bore size will increase the pedal effort,and the required movement of the brake pedal to do the same "braking" will decrease.
Bigger bore = harder pedal,less movement required.

You go to larger mc bore sizes to compensate for increased volume required with bigger caliper pistons,wheel cylinders,ie bigger brakes like you have. Those bigger calipers have
more clamping capability, but also take more fluid volume to operate.

So yes,in your case a bigger bore is not only better,but necessary.
I would talk to Baer or Wilwood, and see what they recommend for their brakes.
I would think a 15/16" to 1" bore would do the trick.
JD

 

[tooslow]

Increasing the bore size will increase the pedal effort,and the required movement of the brake pedal to do the same "braking" will decrease.
Bigger bore = harder pedal,less movement required.

You go to larger mc bore sizes to compensate for increased volume required with bigger caliper pistons,wheel cylinders,ie bigger brakes like you have. Those bigger calipers have
more clamping capability, but also take more fluid volume to operate.

So yes,in your case a bigger bore is not only better,but necessary.
I would talk to Baer or Wilwood, and see what they recommend for their brakes.
I would think a 15/16" to 1" bore would do the trick.
JD

Thanks, I assumed it would be the opposite, Bigger bore less effort, but now i understand... I woulld like less pedal travel so definately interested in a bigger bore size.

 

[tooslow]

The stock 15/16 unit feels pretty good but would like less pedal travel so maybe i will move up to the next size larger. i would stick with the autozone Rem but worried it will fail on abuse

A dual reservoir is dual piston correct??

 

[Johnny Dart]

Doesnt sound like you are staying stock look,so if I were you I would go to the light weight Mopar Alum mc.
This is the one I installed on my 65. You will need the 2 to 4 adapter for it.
This one is a 1 1/32" bore. Stops real nice. Got a new mc with adapter for $100.00.
Also used the stock push rod with it. Simple bolt on install.

 

[tooslow]

Thanks Johhnydart, I aprecciate the picture and nice Dart!

 

[70Duster440]

Doesnt sound like you are staying stock look,so if I were you I would go to the light weight Mopar Alum mc.
This is the one I installed on my 65. You will need the 2 to 4 adapter for it.
This one is a 1 1/32" bore. Stops real nice. Got a new mc with adapter for $100.00.
Also used the stock push rod with it. Simple bolt on install.

That's the 1.03" MC I mentioned that Doctor Diff can supply you with (including adapter). It will increase pedal effort from the 15/16" you have now - probably by quite a bit. That's what I run. So now, we've come full circle.