Rear Brake Problem

Are ya having a problem with your rig? We'll try to help. Share your tech tips and experiences here. Dr. Billy Glaser, author of the "Unofficial 750 Ural Service Manual" site myural.com, is moderating this section.
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bratmanxj
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Rear Brake Problem

Post by bratmanxj » Mon Nov 18, 2019 6:49 pm

A while back I had the springs break and tear up the rear brake shoes on my '07. I've arc'd the new shoes to fit the drums, watched the rear brake setup and adjustment video over and over to get the pads set-up properly. I'm still having issue so I come to the group looking for advice:

I set up the fine adjuster on the rear brakes to have a firm, but not tight grip when using the parking brake. When I go out for a ride even the slightest push into the pedal the rear nearly locks up and the back of the bike squats. I believe there is an audible "clank" as it almost sounds like the rear shoes are getting pulled outward and jamming on the drum. Once I come to a stop (rather abruptly) I can smack the brake pedal and they free up.

I was going to take another stab at it this weekend and wonders if there were any dumb suggestions that I might be overlooking....
Thanks
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Snakeoil
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Re: Rear Brake Problem

Post by Snakeoil » Mon Nov 18, 2019 9:09 pm

It sounds like you are going over center on the brake cam. Suspect your adjustment procedure was flawed.
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Lmo
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Re: Rear Brake Problem

Post by Lmo » Mon Nov 18, 2019 9:47 pm

I second Rob's evaluation. Personally... I have no use for a parking brake (and my rig doesn't have one anyway) ... it just adds more complication to adjusting the brakes.

What's the brake shoe-to-drum clearance Rob, 0.015-0.025" ((or something like that) not critical)). This is the 'gap' between the surface of the brake shoe and the surface of the drum, when everything is at rest (allowing for inevitable high-spots on the drum). Start your adjustment from there.

Also check the 'clocking' of the rear brake cam ARM.

Might want to build yourself a Gobium Me-pi tool, it really helps out. Not hard to make, any material will work. Here's mine
My me pei tool.JPG
Look through these old discussions. VVV

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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Tue Nov 19, 2019 11:47 am

I purchased the gauge recommended in the video and set the course adjustments based on these measurements. I must have something drastically off in my math?!?
https://www.amazon.com/gp/product/B00A8 ... UTF8&psc=1

I talked with my brother in law who works at a machine shop and he can fab me up a version of the Gobium tool once I find him a 20mm ID collar. In all the times I researched how I was setting up my brakes I've not seen that tool and it's so simple.
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Re: Rear Brake Problem

Post by chaos2 » Tue Nov 19, 2019 12:32 pm

I used a cheap caliper and JB welded some copper pipe to it that had a 20mm ID. (stole the idea, Gobium?) I adjusted the brakes with the cam about 3/4 engaged, could not find any advise on that but wanted to leave some room to back it off if I had to. Good thing, the brake drums are not the same size on all my wheels.
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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Tue Nov 19, 2019 2:14 pm

chaos2 wrote:
Tue Nov 19, 2019 12:32 pm
I used a cheap caliper and JB welded some copper pipe to it that had a 20mm ID. (stole the idea, Gobium?) I adjusted the brakes with the cam about 3/4 engaged, could not find any advise on that but wanted to leave some room to back it off if I had to. Good thing, the brake drums are not the same size on all my wheels.
Yup, saw that version too but still need to find the appropriate 20mm ID pipe 1st.

So, what is the appropriate "clocking" of the arm or angle of the cam?
1999 Yamaha Royal Star Venture
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Re: Rear Brake Problem

Post by Lmo » Tue Nov 19, 2019 6:31 pm

So, what is the appropriate "clocking" of the arm or angle of the cam?
Nothing 'specific' angle-wise. You just want to make sure that when the brake pedal is fully depressed that the arm on the cam isn't too far forward.

"Mechanically speaking" the optimum force is exerted when the brake rod is perpendicular to the brake cam arm at full brake. The "fine" splines on the brake cam shaft allow for this fairly easily.

Likewise, with the brake pedal. Don't get too frustrated with the process, it definitely takes some messing around to get all these elements sync'ed up.

I start out the process with the brake shoes adjusted as close to the drums as I can get them without dragging.

Claus might have some input as well.
Lew Morris
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125/42 jets
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Re: Rear Brake Problem

Post by GHGoodwin » Tue Nov 19, 2019 7:41 pm

Try greasing the brake pedal shaft. It might be sticking.

Check the inside of the drums for burrs.

Champher the leading edge of the pads a bit with a file.
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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Wed Nov 20, 2019 10:24 am

GHGoodwin wrote:
Tue Nov 19, 2019 7:41 pm
Try greasing the brake pedal shaft. It might be sticking.

Check the inside of the drums for burrs.

Champher the leading edge of the pads a bit with a file.
Greasing the pivot shaft was on my To-Do list since I probably over-cleaned when installing the new pads.

When I found the broken spring it had chewed up the old shoes pretty bad. I did a through cleaning of the drum with some mild sandpaper to clean up the nicks.

Didn't think about the leading edge, pretty simple to do. Thank you!
1999 Yamaha Royal Star Venture
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Chinese Knock off Honda Trail 70 rescued from the in-laws shed
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Re: Rear Brake Problem

Post by Snakeoil » Wed Nov 20, 2019 10:54 am

The tool does not have to be elaborate. A piece of copper 12 or 14 ga wire with a loop to go over the axle will work. Idea is to have the shoes centered on the axle any relatively concentric. If you have young eyes or magnifying glasses, a metal scale taped to the wire will do the trick in a pinch.
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Rob
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Re: Rear Brake Problem

Post by Lokiboy » Wed Nov 20, 2019 12:39 pm

While on the center stand, tighten until the wheel is difficult to turn. Then back off two full turns. The rear provides very little stopping power and IMHO
don’t over think it or worry.

Good luck
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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Wed Nov 20, 2019 12:50 pm

Lokiboy wrote:
Wed Nov 20, 2019 12:39 pm
While on the center stand, tighten until the wheel is difficult to turn. Then back off two full turns. The rear provides very little stopping power and IMHO
don’t over think it or worry.

Good luck
And I thought I had them set up properly using this method and back it off to where I still had some parking brake, but not completely LOCKED when engaged. Then the 1st time out they'd lock on me as soon as I gave more than a light tap on the pedal while going down the road.

Edit: What has been bothering me is I'm very mechanically inclined and have set up drum brakes on a few other bikes without this much difficulty.
1999 Yamaha Royal Star Venture
2007 Ural Tourist - The Big Red Brick
Chinese Knock off Honda Trail 70 rescued from the in-laws shed
1984 Suzuki LT125 Quadrunner
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Re: Rear Brake Problem

Post by tgtrotter » Wed Nov 20, 2019 3:46 pm

Another '07 with a broken brake shoe spring.?
I've done mine twice in 30 months and the last time it felt like the spring had broke again after about 50 kms of "Baja'n". (CA off road term ) because the shoe was sticking or wouldn't release. Did not lock up tho'.

I pulled it apart and Walla, no broken spring. But in previous replacements I never lubed/greased the tiny cam or where the shoe contacted it. I did and they are releasing fine. As stated before check your foot brake arm too.

I get most of my info from myural.com and here. The shoes as far as I can tell are both the same size so you must mark them. I also have a long and very steep hill 2 blocks away so I burnish them pretty easy.

Getting the pusher to lock up I have yet to see. I can think of lots of scenarios as far as braking adjustment with the hack and weight distribution over the pusher. Best of luck.

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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Thu Nov 21, 2019 10:02 am

bratmanxj wrote:
Wed Nov 20, 2019 10:24 am
GHGoodwin wrote:
Tue Nov 19, 2019 7:41 pm
Champher the leading edge of the pads a bit with a file.
Didn't think about the leading edge, pretty simple to do. Thank you!
The more I think about this, the more I believe this might be my problem. As I said in the 1st post, you hear the "spring" noise and a clunk of the pivot points coming back to the post. I think the leading edges are grabbing the drum causing my problems.

I have my brother welding the gauge onto a 13/16" bushing I picked up. He works in a fab shop, I'd have to go barrow a welder from my buddy for 5min worth of work. I'll give it a good cleaning, greasing and buzz the front edge off the shoes and we'll see how it goes. Thank you everyone for the help on a very minor issue I just couldn't figure out.
1999 Yamaha Royal Star Venture
2007 Ural Tourist - The Big Red Brick
Chinese Knock off Honda Trail 70 rescued from the in-laws shed
1984 Suzuki LT125 Quadrunner
Boats, Jets Skis and other fun stuff.

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bratmanxj
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Re: Rear Brake Problem

Post by bratmanxj » Thu Nov 28, 2019 8:49 pm

Well, I found part of the problem....the brake cam/arm is stripped so every time I adjust the brakes to function they slip out of whack. I guess I'm making a call to Crawford for some new parts.
1999 Yamaha Royal Star Venture
2007 Ural Tourist - The Big Red Brick
Chinese Knock off Honda Trail 70 rescued from the in-laws shed
1984 Suzuki LT125 Quadrunner
Boats, Jets Skis and other fun stuff.

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