Brake Pedal Travel Suggestions

[crashr]

Hi Folks,

This weekend I replaced my old master brake cylinder as the cars braking was pretty spungy and I couldn't lock up the brakes. The job was a bit of a PITA but after the install and bleeding process (with Mocal Power Bleeder) I flushed the system with ATE Racing Blue, and the brakes are rock solid and lock up when needed.

I have two questions however that I would like to clarify:

1) how much free travel should I experience from the (1975 non-boosted brakes) brake pedal before I start to feel them engage. Just moving the pedal by hand it feels like there is a fair bit of play (about an inch or more) before I start to feel resistance in the pedal. I know the Haines manual mentions that you should only have 1mm of play before the piston in the MC becomes engaged. So does it sound like I need to lengthen the rod that inserts into the master cylinder? When braking it feels like I push the pedal in about 30% before I get any real braking effect. I know the other problem is sometimes that the caliper pistons are retracted into the caliper too far, however I tried to do the suggested fix for this last year when I was trying to diangose my brake problem, so I dont' think the caliper piston travel is the issue.

2) When I do lock up the brakes, (going about 80km/hr to full hard stop) the car has a tendancy to slide its backend about 30-40 degrees clockwise. Does this mean one of my brakes is locking up before the others. From the marks on the ground it looked as though my driver side was locking up but my passenger wasn't. Just looking for ideas of what I should be looking at to get a more equal braking effect.

Best Regards,

[pete3799]

Have your calipers been rebuilt?
If not that may be why you couldn't lock them up before the M/C replacement.

[crashr]

Yes I repbuilt them before I replaed the master cylinder.

[Jerome74911S]

The amount of brake pedal travel you describe is identical to my '74, so I'm interested in this question. After 30% travel the pedal is hard and braking works fine.


Jerome

[crashr]

Hi Jerome,

I wonder if we can get any other 74-77 owners to chime in on the feel of their brake pedal.

[Jerome74911S]

I hope so. There are a few round up here in CA.

[Eagledriver]

Yes you need to lengthen the pushrod. The new MC is probably slightly different than the old one. The rod has a lock nut on it and a threaded portion you turn to adjust the length. Lengthen it until you have only a small amount of slack before the rod hits the piston. Some people use this adjustment to make the pedal height where they want it for proper heal toe down shifting.

-Andy

[ab54666]

I need to do this on mine as have a similar 'pedal'.

Reading the manuals it talks of a 1mm gap/clearance with the end float - how do you test/check this?

[harrisracing]

I rebuilt all 4 of my calipers and my 77 car stops VERY well and has a VERY solid pedal now. Stock booster and all and it's powered.

I had another guy drive my car and he gave his opinion that my brakes are as sensitive as any 911 he's driven...I guess compliments to my caliper rebuilding Skillz as my car had 2 TOTALLY frozen ones from sitting up for YEARS before I started on it.

Patrick

[crashr]

In reference to the 1mm/gap, thats what I was wondering. I am wondering if you can bend a 1mm feeler guage into that spot.

[ab54666]

Mine's a later model (1987 3.2)

Looking back at the haynes manual, the supplements at the back show the adjustment of the brake operating rod.

It states;

"With the engine off, manually operate the brake pedal. There should be 0.394in (10mm) free play"

I'll try that in the morning.