Power brake pedal rod question

[gregbr]

I'm adding a power brake booster to my 67 4wd drum/drum setup. The problem is that the adjustable rod from the booster linkage to the pedal is about an inch short (will not adjust out enough). Are there 2 different rods or do I have to change the pedal also?? I did this on my 70 GMC and just welded 2 together to make it longer. Thanks

[krue]

I used an adjustable rod on my 70 GMC and it worked fine.

[Low69CST]

We've built 2 trucks and had the same problem on both. One truck we had a rod made on the other bought a custom master cylinder/booster that came with a cut to length rod. If you figure it out i'd like to know what the fix is.

[HugrOrang71]

A friend of mine just converted his '69 to power with a late 70's setup and had the same issue. I cut the rod in half and sleeved it with steel pipe. I measured the length to the pedal and built it to be slightly shorter than the actual length so that he would be able to adjust it for fine tuning.

[screamin_c102]

I had the same issue on Screamin' I just lengthened mine with some tool steel and kept it adjustable , worked out fine

[72GMC51]

I had the same problem on my 72 GMC, also the brake pedal arm does not reach the stop bumper on the front of the dash? I went to a salvage yard and purchased a complete set up (pedal assembly, brackets etc.) from a power brake truck installed it and had the same problem, I ended up with three rods all of them are to short. It seems like the position of the pivot assembly in the truck must be different I have never had a non power brake and power brake truck next to each other to measure but it would be nice to know what the differences is.
JC

[gregbr]

I'm glad I'm not the only one. I just welded the one together for my second truck to be done with it. All the threads that talk about converting to power brakes and NOBODY has mentioned this until now?? And it seems most us have had the same problem.

[Bob Moore]

What causes the problem? Lets see if we can't figure this out. Is it 3/4T or 1/2T that causes the problem? Drum to disc? Must be something we are using that is wrong vs those that get it right.

[PICKMUP]

OK, guys...here's what I think the problem is: There is no problem! The pb pedal location is NOT supposed to come back up to the rubber bumper.
Take a look at the pedal location on an original pb truck...the pedal hangs down an inch or so. That is how it is designed. It doesn't need any cutting/welding/adjusting. You just need to make sure you don't extend it so far that it is pre-loading the mc. There should be a little free play so brakes release completely.
Remember, the travel of the pedal into a booster is a lot less than the travel of the pedal directly into a mc.

[HugrOrang71]

I agree with what you're saying about the distance from the pedal to the rubber stop, and the pedal- rod geometry and not extending it so far that it holds pressure on the master cylinder.

In my example, he was using a 78 4wd booster and bracket on a 69 2wd cab. With everything bolted into place, the rod was about 1 1/4" short which meant that it was only about 2" off the floor at the pedal itself. There wasn't enough travel for the brakes to function properly and the brake light switch wasn't contacted. We determined the pedal height by measuring my power setup and some measurements with his manual master cylinder and rod. I also had him compare his pedal ratio to mine. This kept the pedal off the stop, allowed the brake switch to function and most importantly, gave plenty of travel for the brakes to work.

[pjmoreland]

I had this same problem on a 67 that I installed a power brake booster in from a 70 about 8 years ago. I've always wondered what the cause of this was. I lengthened the shaft too far so that the brake pedal contacted the rubber stop. My brakes wouldn't release completely.

[Rod]

Your all using the correct era brake booster and brackets with the adjustable rod to the brake pedal... right?

[gregbr]

Yes, I have the same setup in both trucks. I didn't know the pedal was supposed to be an inch away from the rubber stop. I lengthened the rod enough to make it just touch the rubber when adjusted. Oh well, at least I wasn't alone on this one. Thanks guys!!!