'52 FL Front Brake adjustment

[awander]

I am trying to figure out how the adjustment of the pivot stud and the front axle sleeve is supposed to work, to center the shoes in the drum.

It seems to me that there would have to be a decent amount of clearance between the pivot stud and the hole in the brake side cover, to allow the parts to move and center up the shoes.

I'm not sure I have this clearance, my parts may be original or aftermarket. How much "slop" should there be when the axle sleeve nut, the axle nut, and the pivot stud not are loosened?

Also, how tight should the pivot stud be in the hole in the lug on the fork leg? Does that need some clearance for adjustment as well, or should it be tight?

Panhead Brakes.PNG (518.81 KiB) Viewed 1120 times

[panhead_kicker]

i had the same question a while back. do a search for 44448-48

[panhead]

Adjusting Front brake

[awander]

Thanks, guys.

SO from those links, and the other info I have found, I see that the pivot stud should have clearance in the hole in the brake side cover.

Is there also supposed to be clearance between the front axle sleeve, and the brake side cover?

And what about the holes in fork? Should the axle sleeve, and/or the pivot stud, have clearance in the holes in the fork leg?

[RooDog]

Andy, you are a machinist. Think about this from a designer's point of view.
The axle sleeve, backing plate, slider leg, axle, and wheel hub should all be concentric with just enough clearance for assembly, no?
The stud should also register securely in the slider boss. If there is any play for centering the shoes it would be between the stud and the die cast aluminum backing plate, and I don't see that happening. This is no doubt another turd from the MoCo as the rear brakes, and springer brakes, had allowances for centering the mechanical brake shoes. Having the shoes arched is probably the best way to go. But if one really wants an effective front brake, going to a disc is about the only choice, although some owner/builders have adapted a double leading drum from some import motorcycles.....
....RooDog....

[awander]

Hi Roo, yeah, from a designer's point of view, everything is concentric.....but an engineer knows that that won't be true in real life!

With the pivot stud and the axle sleeve both tight in the fork leg, the only possible movement between parts (for adjustment) would be a slight rotation of the brake side cover as related to the pivot stud.

It really seems like the hole in the fork leg for the pivot stud should be larger than the stud, maybe the same size as the hole in the brake side cover...that would allow movement of the pivot stud in any direction for alignment of the parts, and then the stud could be tightened down and hopefully hold it's position relative to the fork leg...

Wondering if I am brave enough to try it on my fork...

[RUBONE]

Hi Roo, yeah, from a designer's point of view, everything is concentric.....but an engineer knows that that won't be true in real life!

With the pivot stud and the axle sleeve both tight in the fork leg, the only possible movement between parts (for adjustment) would be a slight rotation of the brake side cover as related to the pivot stud.

It really seems like the hole in the fork leg for the pivot stud should be larger than the stud, maybe the same size as the hole in the brake side cover...that would allow movement of the pivot stud in any direction for alignment of the parts, and then the stud could be tightened down and hopefully hold it's position relative to the fork leg...

Wondering if I am brave enough to try it on my fork...

Factory backing plates are that way, however the size difference is small as there is no need for more than a slight movement to set the alignment. That is why the washer on the stud is grooved, so that once it is adjusted the grooves hole the adjustment and keep the backing plate from rotating.
The biggest issue is that the stud is a tight fit in the leg and often stuck (especially if the bike is washed frequently and with pressure) so taking the nut off does not release it. It must slide freely in the leg to allow it to slip inward enough to release the washer from the backing plate. It is a tight fit so that it doesn't shift in use, only the backing plate needs movement to adjust it.

[Mongrel505558]

Thanks to all of you for this thread. I've often looked at this mechanism and wondered how the hell it was meant to work. Apparently not very dramatically.

[RUBONE]

Thanks to all of you for this thread. I've often looked at this mechanism and wondered how the hell it was meant to work. Apparently not very dramatically.

Right on that! It is all very subtle. And if aftermarket parts come into the equation then all subtlety is removed!!

[awander]

Thanks, Robbie.

I decided butchering a fork leg wasn't a good idea, so instead I turned the shank of the pivot stud down by about 1/6" diameter.

I just put it back together, and I'll see how it works out. The humidity here is horrible, I can't work outside for more than 15 minutes without getting drenched in sweat.

[RUBONE]

Thanks, Robbie.

I decided butchering a fork leg wasn't a good idea, so instead I turned the shank of the pivot stud down by about 1/6" diameter.

I just put it back together, and I'll see how it works out. The humidity here is horrible, I can't work outside for more than 15 minutes without getting drenched in sweat.

A mistake in my estimation, but hope it helps you. As I see it now the stud can flex in the hole under braking forces.

[awander]

Yeah, you may be right about that.

But it's easy enough to replace the pivot stud if I notice any problems.

[Mongrel505558]

Thanks to all of you for this thread. I've often looked at this mechanism and wondered how the hell it was meant to work. Apparently not very dramatically.

Right on that! It is all very subtle. And if aftermarket parts come into the equation then all subtlety is removed!!

The effectiveness of my front brake is very subtle.

[awander]

Finally got 'er back on the road (my generator failed at the same time as my front brake lever broke).

The brake didn't seem to center any better with the smaller pivot stud...however, my front brake is now more than just a suggestion-I actually was able to do about 40 miles without really using the rear brake!

Not sure if this is because of what I did to the stud. I'm sure a lot of it had to do with:

-I beveled the ends of the linings
-I installed a new lever that has a much longer "seat" against the bars, so it flexes (and breaks) less when I pull it in hard
-I lubed up and installed a new brake cable
-The bike originally had the front brake lever installed with the bar clamp very close to the throttle twist grip. I moved it down the bar by 2-3 inches(closer to the steering head), so I can get a much better grip on it

But, whatever the cause, I like it!

[awander]

I had a typo in my post above-I took about 1/16" in diameter off the pivot stud ( NOT 1/6")