Adjusting Brake Pedal Height

#1

I was told years ago that the height of our brake pedal was not adjustable so I never looked at the idea further. Instead I’ve always used a 1" spacer to give the pedal more height so when fully depressed it would be about the same height as the gas pedal.

Some of you, I’m sure, knew all along that the brake pedal was indeed adjustable. But for those of you like me that didn’t know, here’s how you do it.

The brake’s vac booster has a shaft that sticks thru the firewall towards the brake pedal. The shaft is fastened to the brake pedal arm via U-shaped device that is threaded on the shaft. The U-shaped device is held in place by a nut on the shaft. Thru the U-shaped device goes a pin that fastens it to the brake pedal arm. If you remove the pin and loosen the nut, you can put a few turns on the u-shaped device which will change the shaft’s effective length. Then tighten the nut against the U-shaped device.

The pin that goes thru the brake pedal arm has a clip on it’s end to hold it in place. The key to removing that pin is figuring out how the clip works. So when you attempting to remove that clip, focus less on brute forcing the damned clip (like I did) and more on figuring out how the bastard works.

The fastening point of the booster shaft on the brake pedal arm creates a 4:1 ratio. Since the shaft is prob a 1.25mm pitch thread, each turn gives you 5mm of pedal height change.

This is do-able with your seat in, but easier with the seat out.

#2

Just hit the print button and put this in my “spec e30 build” file.

Suggest that others do the same.

Thanks, Scott.

RP

#3

You say “doable with the seat in” – should I take that to mean that you are doing this adjustment with the booster mounted to the car, and reaching under the kick panel/behind the dash to do so?

I haven’t messed with anything between the brake pedal and M/C, nor have I removed the dash, hence my need for clarification.

#4

[quote=“swolfe” post=71772]You say “doable with the seat in” – should I take that to mean that you are doing this adjustment with the booster mounted to the car, and reaching under the kick panel/behind the dash to do so?
[/quote]
Yes.

I actually did it with the booster removed from the car, but I was in the middle of a booster swap. It can be done by getting down into the footwell and going at it from under the dash.

Lose the kick panel. It’s a race car.

#5

Some friendly advice; Be careful when adjusting. There is a “freeplay” spec that must be taken into consideration.

A number of years ago I had adjusted the MC freeplay on a Tilton system and spent the next few hours trying to figure out why the brakes would not disengage on track…

Guess the cause :frowning:

#6

Thanks for this Ranger. Now that you point it out I see it clearly shown in my Bentley as well.

#7

New but related question. I have finally reached the reassembly stage where I can check the pedal feel both with and without the engine running. I replaced all brake lines with stainless. The pedal is fairly firm although I haven’t done the Ranger deflection test yet. But with the motor running and vacuum on the booster the pedal travel is about six miles before the pedal reaches firmness. Is this a function of a leaking MC, the booster mechanics (I ruefully admit to never having disassembled a booster), or something else? I’m pretty frustrated as these are the worst feeling brakes I can ever recall having on a car.

#8

RRhodes, this is not really an answer to your question, but if you power bled your brakes, try an old-fashioned two man bleed before you dig any deeper.

#9

Agreed - first verify and use the Bentley method.

#10

If your brakes are light mush thru a fair amount of travel, assume air in the lines. MC movement is more characterized by higher resistance mush thru ~ an inch of travel.

A good brake bleed is kind of an art form in that different folks all all trying to get to exactly the same endstate, but each is convinced that “their solution” is the optimum way to get there.

If air gets in at the MC you’ll have to move a lot of fluid thru the system in order to clear the air out. Assume the better part of 2 liters. 600ml RR, 200ml LR, 400ml RF, 300ml LF.

When I screwed with my MC last month I tried to be tricky and push the air bubbles toward the MC, instead of pushing the air the long way thru all the hydraulics to the slaves.

After R/R the MC and putting in just a little bit of fluid, I went to each corner and compressed the slave all the way back. This moved the bubbles at the MC end of the hydraulics back into the MC. My intent was to save on brake fluid because I didn’t have a couple spare cans. It worked nicely.

My preferred way of bleeding brakes is with a pressure bleeder and “Speedbleeder” bleeder valves. Speedbleeders have a check valve in them such that you won’t get air into the system by leaving them open. So every couple of events I put a 1/2l into the pressure bleeder, hook it up to the MC and then go to each corner and bleed out a cylinder full.

Like most folks, I don’t have an assistant in my garage so any technique that helps a person do a task solo is a big help.

My first set of Speedbleeders all seemed to plug up after 3-4yrs and then would work only as conventional bleeder valves. The set I got last year is fine, but a couple yrs from now they’ll probably need to be replaced.

#11

I guess I’m not sure whether it’s light or heavy mush and the actual distance traveled. Anything over a few mm is objectionable, guess I need to pay closer attention. I use a pressure bleeder as well (my two person brake bleeding privileges were gradually revoked over a couple of decades) and have pushed about 1.2 L through the system so far. I have no objection to sending another liter after it. Thanks guys.

#12

Note that there’s one pipe going to rear that divides at the subframe. Therefore you want to push a bunch of fluid to the first rear wheel you do, but you don’t need much for the second rear wheel.

If this is already obvious, than I apologize.

#13

For those that come to this thread later, Paul is making an important point here. Don’t adjust the brake pedal nut more then a couple turns or your brakes will drag.