Brake Pedal Adjustment Ergonomics

[tmaull]

After replacing my brake booster, the resting brake pedal position has changed dramatically. I'm used to not having to take my heel off the floor and I'd like to adjust it back down to that level. Do you have to take your heel off the floor to switch from throttle to brake pedals?
-Tom

[Jameel]

There's a turnbuckle under the floor board that you can adjust to move the pedal so its where you want it. Not difficult at all. You might want to take the steering wheel off so its more comfortable to work on it.

[tmaull]

Yeah, I can adjust it fine. But curious how others have theirs adjusted.

[Undecided]

Can anyone point me to an article that explains how to adjust the brake pedal?

[911pcars]

Here's two MC actuating arms (late and early with mech. brake light switch)
The loop on the left fits onto the brake pedal arm.
The opposite end fits into the back end of the master cylinder and actuates the MC spool valve.
Notice the threaded parts; loosen lock nut, then rotate to either lengthen or shorten to adjust the pedal height/threshold of brake actuation.

On early cars with a mechanical brake light switch (second image), the large disc contacts the switch arm to close the circuit to the brake light circuit.

In your attempts to adjust the brake pedal for more convenient heel and toe operations or ???, be careful not to adjust the engagement point too low. In an emergency, you don't want to run out of space and bottom out on the floor.



(borrowed images)

Sherwood

[KTL]

Sherwood's pictures are related to pre-1977 911 cars that have non-vacuum boosted brakes. '77-up cars have a rod in the pedal assembly that leads up to the trunk where the master cylinder is mounted to the big round black vacuum booster. That booster is connected to the pedal rod via the large aluminum base that is bolted to the trunk floor.

To get access to the pedal rod, you must remove the carpet behind the pedals and then remove the floorboard behind the pedals. You can't get the carpet off the floorboard until you release the throttle pedal. Pull back on the throttle pedal to release the ball-socket rod that pops into the back of the pedal. To remove the floorboard, peel the rubber pads off the brake and clutch pedal. Once you have the pads removed and the nut at the bottom of the board, lift out the floorboard by wrestling it over the pedals. You have to fart around with the clutch and brake pedal positions a little bit to get the board holes past the pedals.

Once you have the floorboard removed, you will be able to see the brake pedal rod. It's #1 in the picture below. To adjust the length of the brake rod, loosen the nuts #4 and #5 that are adjacent to the upper clevis and lower spherical rod end. Note that the nut for the upper clevis is left hand threads. That means it ain't lefty loosey to loosen it! The reason the clevis end of the rod is left hand/reverse threads is to allow the rod to properly change length at both ends by rotating it.

Once you have the rod to the length you want it, cinch the jam nuts tight again and you're done.

[911pcars]

Hi Kevin,
Thanks for the clarification. I acknowledge there are viable 911s after '77

[KTL]

Originally Posted by 911pcars

Hi Kevin,
Thanks for the clarification. I acknowledge there are viable 911s after '77

[Undecided]

Thank you! I should have noted that I have an '88 Carrera.

[Superman]

You could set it at factory spec. Outsmarting engineers is not easy, particularly German ones.

[KTL]

Changing the pedal height isn’t a potential pitfall. I adjusted my pedal like 15 years ago to have better brake-to-throttle alignment when heel-toeing it. Makes all the difference and no ill effects all these years. Then when I sold the car, the new guy had to adjust it to his liking. He’s doing just fine now too and I talk with him most every day

No issues here with pedal travel even in the most extreme heavy braking conditions. We’re not talking about changing the placement of the pedal by several inches. It’s barely an inch and that doesn’t put the pedal linkage geometry into any sort of compromising alignment

[deguitars]

The brake pedal in my '82 has always been ridiculously high as well, to the point where it feels dangerous to me since I have to physically lift my foot up and off the throttle to get to it. And just a month ago I changed the master cylinder and had the floor board out, etc. and saw the threaded forks and never once thought to myself they were there to allow adjustment of the pedal height. Duh! Anyway, only takes ten minutes to get at this again so I'm going to adjust my pedal down as soon as I can.

cheers

[dmw]

This was the best 30 minutes I have spent in a long time. And I didn’t even have to adjust my brake light switch. Mine was a 1984 Carrera and the upper nut (#4) WAS actually lefty-loosie.

[KTL]

Originally Posted by dmw

This was the best 30 minutes I have spent in a long time. And I didn’t even have to adjust my brake light switch. Mine was a 1984 Carrera and the upper nut (#4) WAS actually lefty-loosie.

You are correct that the upper threads at the clevis are right-hand threads. I checked the rod I have lying around and confirmed my mistake. Sorry for my misinformation on that! It is indeed the lower rod end that has the left-hand threads (righty-loosie)

[timc]

Originally Posted by KTL

You are correct that the upper threads at the clevis are right-hand threads. I checked the rod I have lying around and confirmed my mistake. Sorry for my misinformation on that! It is indeed the lower rod end that has the left-hand threads (righty-loosie)

Same, just adjusted mine on 86 930, upper nut was standard, lower nut was reverse.

Tim

[Mocker]

You can also get a Rennline adjustable accelerator pedal. The stock plastic pedal is pretty janky, and you can adjust the Rennline pedal both in/out and side to side to suit your preference. Not cheap, but you knew that.

[Cloggie]

Don't forget there is also adjustment on the hydraulic clutch for G50 cars....if you put in an adjustable gas pedal, you should be able to get everything just the way you like it

Hardest part is talking out the floorboard.

The stock gas pedal has some adjustment as well on the pedal and usually on the engine linkage side, but it is a much bigger hassle unless you just do the pedal end.

D.

[KTL]

Just my own opinion but I think the adjustment of the brake pedal is the most critical. The throttle pedal can be adjusted a little bit but you have to ensure you’re not compromising throttle travel with respect to too little or too much. This is especially important on a 3.2/Carrera that has a full throttle microswitch on the throttle body.

The G50 clutch really has no adjustment. Here’s why:

The master cylinder installed length is supposed to be dead on at 158mm plus or minus 1mm. So there no adjustment to be had there.

The pedal travel is supposed to be 150mm plus or minus 10mm. You can only adjust the pedal at the depressed/clutch-in end via the pedal stop that is mounted in the floorboard. That stop is intended to set your travel amount and also not to over-extend the clutch master cylinder

The last adjustment area is a small eccentric linkage that is present for the purpose of ensuring preloading the assist spring in the pedal assembly. My understanding is that it’s only to be adjusted here if the pedal assembly has some slop in it due to wear. So you can use this linkage adjustment to fix a pedal that doesn’t fully return. Otherwise the only other function of this eccentric linkage is to modify pedal effort. Either adjustment of the eccentric linkage is VERY fine- one (1) to two (2) mm maximum. So there’s nothing to be had there

Lastly, the factory manual says clutch pedal vs brake pedal height should be addressed via the brake pedal adjustment (page 46-8).

So take all that for whatever it’s worth. I would not recommend messing with the G50 clutch pedal. There’s really no adjustment in it. Many years ago I messed with the eccentric linkage adjustment and I found it made things worse. So I put it back where it was originally and decided the G50 pedal is going to be where it is (I was hoping for a lower clutch engagement point, since the clutch engages VERY high in the pedal travel) whether I like it or not

[Cloggie]

Originally Posted by KTL

Just my own opinion but I think the adjustment of the brake pedal is the most critical. The throttle pedal can be adjusted a little bit but you have to ensure you’re not compromising throttle travel with respect to too little or too much. This is especially important on a 3.2/Carrera that has a full throttle microswitch on the throttle body.

The G50 clutch really has no adjustment. Here’s why:

The master cylinder installed length is supposed to be dead on at 158mm plus or minus 1mm. So there no adjustment to be had there.

Disagree with your comment about clutch adjustment.

The factory measurement for the rod that goes into the master cylinder is about right, but there is no physical reason why it cannot be adjusted enough to move the clutch pedal a fair bit.

There is a limit on one end if the rod is set too short where it will not actually actuate the slave cylinder and there is a limit on the other end where it will overextend the master cylinder.

I did some pretty heavy duty checking while my car was apart and you do have enough room in that adjustment to move the pedal perhaps 20 degrees or perhaps 30, which is what I did as I am 190 cm with very long legs.

The adjustment I used is in the one in this picture with the arrow pointing at it.



No issues in my experience, but certainly would reinforce that the recommended position is quite good for most drivers.

D

[Mocker]

The factory recommends adjusting the brake pedal to be even with the clutch pedal, without referencing the position of the throttle pedal at all? That seems wrong, doesn't it?