what MC is everyone using

[72EB]

Wanted to know what master cylinder everyone is using with front disc and drum rear with NO booster ? thanks, jim

 

[Broncobowsher]

When I ran that combo the hot setup was supposed to be the F250 camper special 1¼" bore. It was the worst thing I had ever done. Pedal was rock hard, no stroke. It stopped but took massive effort. Dropped down to 1-1/8" Mustang SVO, better. 1" is stock, but I found 15/16" before I went to hydroboost.

The smaller bore reduces effort but increases stroke. Good pads and lines kept the stroke short even with the smaller bore master cylinder. Never came close to the floor.

 

[Apogee]

Which "front disc" brakes are you running? Ford or Chevy? Standard calipers or calipers with the larger pistons? The master cylinder is the "master" and the caliper is the "slave", so the ratio in their respective areas is what matters. Factor in pedal ratio, pad compound and system compliance and you've got yourself a brake system.

For manual brakes with the base level Ford or Chevy calipers (Ø2.88" and Ø2.94" pistons respectively), I would run a Ø15/16" bore master cylinder with a decent "FF" rated brake pad and preferably braided stainless soft lines instead of rubber anywhere. That should result in a very safe and drivable setup IMO.

If you run the larger bore calipers, then you should increase the MC bore size accordingly.

 

[SHX669]

Our '76 with factory front disk and rear drums and non power assist stops real well with the Factory MC for a '76 - with front disk and rear drums and no power assist.

 

[Apogee]

FWIW, changing the bore size from Ø1" to Ø15/16" or Ø1-1/16" equates to about an 11% difference with respect to pressure and volume. Obviously, the smaller the bore, the higher the pressure and the lower the volumetric output, and then the opposite for a larger bore.

 

[spap]

X2 on what SHX said
Had a 76 first bronco no booster and stock master cylinder, did good.
I think the truck actually had a fire and the people I bought it from actually just left it off

 

[jckkys]

I've run my '77 with the booster doing nothing. No vacuum hose after the diaphragm perforated. Sure it still stops. But I didn't want to keep it that way.

 

[nvrstuk]

Like Broncobowsher I tried the "hot setup" 23+ yrs ago... the camper special 1.25" bore. That lasted about a month. In fact, I finally moved it out to the barn this summer when rearranging all the stuff in my shop... I should have thrown it away 20+ yrs ago.

I went thru 7 different brake systems in the last 25 yrs since I went disc and I'm looking to change again... I don't want HB anymore. Works great, don't want the complexity.

Got a buddy running stock '74 EB with discs up front and stock rear drums and it takes a HARD push to stop.

Caliper size makes a huge difference. You need to design a system, not just stick an mc on the firewall and see how it works... I did that a couple times! lol

 

[Madgyver]

stock replacement for a 77 with no power booster, discs front, drums back

 

[nvrstuk]

Mad...that's what my buddy runs... hard pedal.

 

[nvrstuk]

I read this somewhere a month or so ago when I was looking for the calculations to run a single pedal/dual mc manual brake combination system... well, here it is, I accidentally ran across it tonight.

Just trying to show how much more leg pressure is going to be needed from a .75 bore mc to a 1.00 bore mc a lot more than we can imagine. 77.7% MORE pedal force to operate a 1.00" bore mc than a .75" bore. That is a lot of pedal force.

This is from Mark Williams brake tech page:

" Slack comes from two factors: retracted pistons must be moved back out, and misalignment caused by deflection in the axle and housing mis-alignment. One of the most common misconceptions is that a larger master cylinder will create more pressure. While a larger master cylinder creates a larger displacement, it takes more force to create the same pressure as a smaller bore. While a larger master cylinder will take up system slack with less pedal stroke, it will take more force to create the same system pressure. The result after adding the larger master cylinder is a harder pedal which needs much more pedal pressure to create the same amount of braking force. For instance, moving from a 3/4" master cylinder to a 1" requires 77.7% more force on the push rod."