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Author Topic: brake pedal travel  (Read 373 times)

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Offline tow hook

brake pedal travel
« on: June 23, 2020, 02:32:14 PM »
i did a herm's dual master set up, and im starting the bleed the system. the rears did fine. still working the air out of the fronts. how much pedal travel should i have ? i have about an 1" now.

 thanks for any input :)

Online Rus Curtis

Re: brake pedal travel
« Reply #1 on: June 29, 2020, 05:22:11 PM »
Hope you got this sorted out.

My SM says "at least 1/2" free pedal travel ...."

I would think no more than an inch, the pedal doesn't have far to travel before bottoming out on the toe board. 


'54 CJ-3B "Green Gruntt"
Bantam T3-C

Offline tow hook

Re: brake pedal travel
« Reply #2 on: July 07, 2020, 02:25:06 PM »
Hope you got this sorted out.

My SM says "at least 1/2" free pedal travel ...."

I would think no more than an inch, the pedal doesn't have far to travel before bottoming out on the toe board.

i believe that i do. i used a small washer on the inside of the master. ( between the master and the bracket ) so it kicks it in just a tad, the brake rod fit much better. and i only had to push the rod in a tad to get it on the brake pedal. so yes i have about an inch of travel. just need bleed.

Offline Chuck W.

Re: brake pedal travel
« Reply #3 on: July 11, 2020, 07:37:31 PM »
Quote
and i only had to push the rod in a tad to get it on the brake pedal.
We are talking FREE TRAVEL, the amount the pedal moves BEFORE it starts to actuate the piston in the master cylinder. If you had to push the master cylinder piston in slightly before you were able to connect the push rod to the pedal, the push rod is TOO LONG and should be shortened up.  You should have about 1/2" free travel of the brake pedal BEFORE the push rod makes contact with the master cylinder piston.
« Last Edit: July 11, 2020, 07:39:09 PM by Chuck W. »

Offline tow hook

Re: brake pedal travel
« Reply #4 on: July 21, 2020, 10:28:06 AM »
Quote
and i only had to push the rod in a tad to get it on the brake pedal.
We are talking FREE TRAVEL, the amount the pedal moves BEFORE it starts to actuate the piston in the master cylinder. If you had to push the master cylinder piston in slightly before you were able to connect the push rod to the pedal, the push rod is TOO LONG and should be shortened up.  You should have about 1/2" free travel of the brake pedal BEFORE the push rod makes contact with the master cylinder piston.



oh :o ! so how does the rod stay in place ? if you have a half inch of free play....  thanks for the info i wouldn't have known that

Offline Chuck W.

Re: brake pedal travel
« Reply #5 on: July 22, 2020, 01:33:31 PM »
The push rod just fits loosely into the hole in the master cylinder piston, the rubber boot will help hold it centered. It's held to the brake pedal with a cotter pin on the other end. When you start pushing the brake pedal down, you should have about 1/2" of pedal movement BEFORE the push rod contacts the master cylinder piston and starts to move it. The master cylinder piston should be completely back against the snap ring in the bore in the rest position, and the pedal return spring should move the push rod and pedal back the additional 1/2". You may have to adjust the length of your push rod to get the required pedal free play.
Same thing happens if your brake pedal return spring is broken or missing, the weight of the pedal constantly pushing against the MC piston is enough to cause slight pressure in the system and can cause the brakes to drag.
« Last Edit: July 22, 2020, 08:44:22 PM by Chuck W. »

Offline tow hook

Re: brake pedal travel
« Reply #6 on: July 24, 2020, 11:01:46 AM »
The push rod just fits loosely into the hole in the master cylinder piston, the rubber boot will help hold it centered. It's held to the brake pedal with a cotter pin on the other end. When you start pushing the brake pedal down, you should have about 1/2" of pedal movement BEFORE the push rod contacts the master cylinder piston and starts to move it. The master cylinder piston should be completely back against the snap ring in the bore in the rest position, and the pedal return spring should move the push rod and pedal back the additional 1/2". You may have to adjust the length of your push rod to get the required pedal free play.
Same thing happens if your brake pedal return spring is broken or missing, the weight of the pedal constantly pushing against the MC piston is enough to cause slight pressure in the system and can cause the brakes to drag.

thanks that helps alot :) i don't have the rubber boot over the rod  yet, the cotter pin is in place

Offline tow hook

Re: brake pedal travel
« Reply #7 on: July 28, 2020, 11:17:18 AM »
i emailed herm, no free play, the rod should rest against the master. an the pedal should have 1" of travel

Offline Chuck W.

Re: brake pedal travel
« Reply #8 on: August 02, 2020, 01:51:52 PM »
Good luck, but I will still have to disagree. According to my 1965 Kaiser Corp. Service Manual for Jeep Universal CJ-2A, CJ-3A, CJ-3B, CJ-5 and CJ-6, page 226:

"There should always be at least 1/2" (12.7 mm.) free pedal travel before the push rod engages the master cylinder piston.
This adjustment is accomplished by shortening or lengthening of the brake master cylinder  eye bolt Fig. 227. This is done so the primary cup will clear the by-pass port when the piston is in the off position, otherwise the compensating action of the master cylinder for expansion and contraction of the fluid in the system, due to temperature changes, will be destroyed and cause the brakes to drag."


Maybe it is different with the dual master cylinder modification you have installed, but I still think you don't want any type of residual pedal pressure against the master cylinder piston.
« Last Edit: August 02, 2020, 01:59:36 PM by Chuck W. »