Rear Brake shoe pivot adjustment

WL series brake shoe centering - access to pivot for shoe centering

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old man emu
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Rear Brake shoe pivot adjustment

#1

Post by old man emu » Wed Jan 01, 2020 7:48 am

I'm trying to get the rear brake shoes of my WLA centred because I've just replaced them. On the test ride, I could not lock up the rear wheel. Advice given elsewhere here says that I need to centre the shoes by loosening the pivot stud and operating the brake a few times before holding the brakes locked and tightening down the nut on the pivot stud.
rear brake.png
rear brake.png (199.46 KiB) Viewed 373 times

I tried to get a spanner onto the nut of the brake shoe pivot, but was blocked by the rear stand, which was holding the rear wheel off the ground. Also the anti-rotation bracket seems to be in the way.

The manual does not make it clear if the centering of the brake shoes is done while the brake assembly is on the bench or on the bike. So which is it - bench or bike? How will simply loosening the stud get the shoes centred?



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Re: Rear Brake shoe pivot adjustment

#2

Post by svkiwi » Wed Jan 01, 2020 10:16 am

On the bike...loosening the stud allows it to 'float'. Apply the brake [jump on the pedal]...this expands the shoes out against the drum....as the stud can float, the shoes will now be positioned so as they are in full contact with the drum. With this force still applied, tighten up the stud...now the shoes are properly centred in the drum.

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Re: Rear Brake shoe pivot adjustment

#3

Post by old man emu » Thu Jan 02, 2020 4:12 am

How do you get at the nut?

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Re: Rear Brake shoe pivot adjustment

#4

Post by svkiwi » Thu Jan 02, 2020 5:48 am

Got to you, didn't I ? [bad humour]
Sure, there's not a lot of room, however, I use a 9/16 ring and open ended wrench [spanner], that I have ground the ring end down to 1/8" thick. This allows me to insert said ring end in through the gap, over the nut, and loosen said nut.You don't need/want to back the nut off too far; just enough to allow it to float. Apply brake, hold in place, tighten the nut; you can 'nip' it up using the open end of the wrench, finally tighten with the narrowed down ring end.

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Re: Rear Brake shoe pivot adjustment

#5

Post by svkiwi » Thu Jan 02, 2020 6:28 am

As an aside...I notice you mention the rear stand being in the way; when I do mine I have the bike on the side stand.

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Re: Rear Brake shoe pivot adjustment

#6

Post by old man emu » Thu Jan 02, 2020 10:02 am

Bit hard to rotate the wheel when it's on the ground. I think I'll put a jack under the frame before I raise the rear stand. Have to go find a 9/16 that I can sacrifice for the job.

Thanks for the info.

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Re: Rear Brake shoe pivot adjustment

#7

Post by svkiwi » Thu Jan 02, 2020 5:20 pm

Why do you need to rotate the wheel? No need.

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Re: Rear Brake shoe pivot adjustment

#8

Post by old man emu » Thu Jan 02, 2020 10:59 pm

'Cause that's what the book says to do.

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Re: Rear Brake shoe pivot adjustment

#9

Post by RooDog » Fri Jan 03, 2020 12:30 am

The wheel is rotated to help move the center anchor stud. Yes, ideally, simply applying the brake pedal should be enough to center the shoes, but Harleys don't always follow the ideal, so spinning the wheel helps move things along. But if it works for you, so be it....

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Re: Rear Brake shoe pivot adjustment

#10

Post by old man emu » Sat Jan 04, 2020 2:57 am

Went out and bought a $1.75, 9/16" spanner, but with the temperature at 41 Celsius, She Who Must be Obeyed has confined me inside in the air conditioning. Maybe tomorrow.

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Re: Rear Brake shoe pivot adjustment

#11

Post by old man emu » Sat Jan 11, 2020 5:59 am

The saga continues ....

After considering how to tackle the problem by operating the brakes a few times then locking down the pivot nut while the brake was on, I decised that it was a two-man job. As great as I am, I am only one man, so I decided that the next best thing would be to take the whole wheel assembly off and do the adjustment on the bench by rotating the brake assembly while the wheel remained still.

Then I remembered about arcing the shoes, so I pulled the brake assembly off. I found that most of the brake linings were glazed, which is a bit odd since the bike has only been ridden one or two hundred miles. There was no evidence of grease on the drum or any other components.

Question: What could have caused the lining to glaze after such a short distance traveled, and no harsh braking carried out?

So I got out my rotary tool and used a mini-cylinder sander to remove the glaze and expose fresh linings. Yes the linings are NOS from the War, and No, I didn't wear a dust mask. They say it takes twenty or so years for asbestosis to develop. Other things will have caught up to me by then. I also used the sanding cylinder to clean the brake drum surface and to make a slight cross-hatch pattern on it.

I put the assembly back into the drum and tested the linings for contact with the drum. All OK. So I did the rotating the brake shoe assembly process and was finally beginning to tighten the pivot nut when I saw that the brake assembly could move in a circular path, so that the pivot could move back and forth in its slot. I decided the set the pivot in the middle of its back and forth run and lock it down there.

Question: Is that what is meant by centering the pivot?

I also noticed that the the grooves that the grooves of the rectangular washer engage with were either a bit warn, or clogged with chrome plating. So I ran a fine file along the grooves to remove the chrome.

So now the wheel is ready to go back on. All I need is a helper, willing or not, to lift the wheel into the frame. Then I can go test it (on a back street).

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Re: Rear Brake shoe pivot adjustment

#12

Post by RUBONE » Sat Jan 11, 2020 6:57 am

Question: Is that what is meant by centering the pivot?
No that is not. Centering the pivot means when the shoes are in full contact with the drum the location of the pivot can be wherever it ends up with pressure on the shoes. It has nothing to do with the slot dimensions. You are missing the point of all this. Did you arc the shoes? That is step one. Did you relieve the leading edges? Only when everything has been done for maximum contact do you center the shoes, or rather , allow the shoes to center themselves at which point the pivot is locked down. None of it is a two man job.

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Re: Rear Brake shoe pivot adjustment

#13

Post by Andygears » Sat Jan 11, 2020 4:22 pm

While I know little about WL’s, the principals are similar to all drum brakes. One point I did not see mentioned is the eccentricity of the drum surface around the wheel bearings. I know on big twins, with star hubs, it is not a given that bolting a drum to a hub will yield a perfectly concentric inner drum surface due to the small purchase area of the mounting. In fact unbolting the drum from the hub, turning 180 degrees and reattaching may yield a much better concentric drum surface or worse. With that in mind, turning the rear wheel in 90 degree increments, then applying the brake may find multiple places for tightening the pivot if the drum is eccentric to bearings for whatever reason. So I would start by assembling the rear wheel, without brake backing plate & shoes, with axle tightened down and check concentricity of the inner drum surface with a dial indicator or simple pointer. This will also reveal out of round condition which will have to be corrected by boring the drum. Obtaining a concentric inner drum surface will make all subsequent adjustments easier, and may be the cause of your glazing of low mileage shoes because they were dragging on the eccentric drum slightly.

My two cents
Andygears

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Re: Rear Brake shoe pivot adjustment

#14

Post by RooDog » Sun Jan 12, 2020 12:08 am

Thee are five mounting bolts, the drum may only be indexed in 70* increments, so a 180* repositioning is out of the question. Jesus Cee Riste, how complicated can this get????
....RooDog....

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Re: Rear Brake shoe pivot adjustment

#15

Post by old man emu » Sun Jan 12, 2020 3:12 am

I examined the contact between the shoe surface and the drum wall when the brake was applied. There were no gaps. I filed across the leading and trailing edges of the linings the create a slope of about 25 - 30 degrees (estimate by eyesight, but nothing like 45 degrees).

I had the pivot nut loose before I rotated the brake assembly and then fully engaged the brake shoes using the brake lever. When the brake shoes were fully engaged, I tightened down the nut. It just so happens that when it was ready to tighten the nut, the pivot stud was in the middle of the slot.

The "two man job" arose from the method of keeping the wheel on the bike and rolling the bike along the floor before applying the foot brake before tightening the nut. You can't readily keep the brake applied and reach the nut at the same time.

What is annoying me the most is that the brakes were working fine before I decided to replace the somewhat worn linings while the bike was undergoing a major overhaul.

Tomorrow I'll have everything back together and go for a test run.

Thanks for your inputs.

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