Master Cylinders

[John_Bitting]

What size master cylinders should I be running with 4 piston wilwood superlite calipers? I am currently running a 7/8 and 1" but it does not stop it at all. I dont know if its the new pad/rotors or not enough master cylinder. Thank you in advance.

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[dezertdude]

how longs your brake pedal?

[DSRacing]

Are they CNC masters? I have the exact same set-up on my 7s Ranger. It was trial and error for me to find the right balance between pedal pressure and stopping ability. I started with two 3/4" bore MC's which were on the truck originally. I increased the bore size and lenghtened the brake pedal about three inches to find the right balance. Your truck is a lot heavier than mine so you may have to increase the bore sizes. Call whoever made the MCs and give them the following info.

Current bore size

Number and diameter of caliper pistons

Weight of your vehicle

They should be able to tell you the correct size of the MC you'll need.

[partybarge_pilot]

What size pistons were in those calipers? Still have the P/N's?

[John_Bitting]

I think the back is 1.5" and the front is 1.75". The pedal is 16" long.

[sickrick]

3/4" Is what I would run. Remember the smaller the M/C bore size the more PSI you can get. It will increase pedal travel.

What is the pedal ratio?

I have used the 3/4m/c with a 6.25 pedal ratio on the same calipers and they worked well.

[ShaneR]

John, does it stop after you pump it or just doesn't stop well at all? You might need a pressure residual valve to hold the pads tight to the rotor or you have to pump the brake pedal 1 time to get the pads close the the rotor. With most disk brakes setups you will run either a 2 or 4 lbs valve.

[John_Bitting]

it does not stop very good at all, backing off the trailer fully pressed down it will still roll down the ramp. I have the gold valves I think they are 4lbs. Sickrick, Nestor at Newline suggested smaller also. Everyone else has said 1 1/8. Bigger might not be better in this case.

[DailyPedal]

it does not stop very good at all, backing off the trailer fully pressed down it will still roll down the ramp.

I am thinking you have more issues than cyl size...

[partybarge_pilot]

Run the 3/4's

Normally you stager them I.E 3/4 in front and 7/8 in back to keep the ballance correct. But you have a lot better wieght ballance than a truck so the same size MC's will work.