Rear Brake Problem - Not Really Solved....

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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Re: Rear Brake Problem

Post by bratmanxj » Mon Dec 02, 2019 5:44 pm

Called Crawford today and the new brake cam & arm are on their way along with a spare set of valve cover gaskets.
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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 bratmanxj » Tue Apr 07, 2020 10:59 pm

And the saga continues.....

Back in January I put the new brake arm & cam from Cawford in the bike and used the gauge to set the shoes equal-distant from the axle. I took it for a few quick jaunts around the block over the winter and thought I had it adjusted pretty good. Now its back to the origonal problem where it feels like its "grabbing" the shoes and pulling them off the cam & stud. I've watched the Coluralado YouTube video and I feel that I have everything set up the same as his and can't for the life of me figure out my problem. The bike was great with the original silver brake shoes, and now these new gold shoes have no modulation, they just bite and lock up.
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 - Sold off to a Friend
Boats, Jets Skis and Golf Carts...other fun stuff!

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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 8:16 am



1. Arced the pads to the shoe with 180 grit sandpaper on the inside of the drum.
2. Radius the leading & trailing edge of both top and bottom shoes.
3. I made up a tool like Chaos2 posted and I believe I have them adjusted properly. The brake arm and cam are "at rest" with the fine adjuster all the way out. The clocking of the arm & cam at rest looks identical to the video. The shoe "pads" are at a 45deg diagonal to the cam, best I can tell from the photos this is correct.
4. I've done the chalk test and 90+% of both pads are making contact with with drum when testing on the center stand.
5. Everything works smoothly when the bike is on the center stand. Rev the bike up in 1st gear and apply brakes and I get a nice smooth slowdown on the rear wheel. Once I put it down on the ground and take it for a ride the 1st tap of the rear brakes and jam then won't release until I come to a stop and rock back slightly.
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 - Sold off to a Friend
Boats, Jets Skis and Golf Carts...other fun stuff!

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Re: Rear Brake Problem

Post by tgtrotter » Wed Apr 08, 2020 11:53 am

re visit your linkage ?
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Re: Rear Brake Problem

Post by Snakeoil » Wed Apr 08, 2020 12:11 pm

You say things are "at rest". I would suggest that you look at what Coluralado calls "shoes" and assure that they are flat against the brake cam. I think I'd call the "shoes" adjusting pads just to avoid confusion with the term brake shoes. If the cam is at an angle relative to the face of the adjusting pads, they you need to figure out why. Maybe your cam shaft is hanging up due to rust or something and you are still going over-center because your starting point is wrong.

And I agree with tgtrotter, you need to look at the entire system, not just the rear brake drum assembly. If your cam and pads are face to face when at rest then you need to look elsewhere. The change in thickness with the new shoes may have changed a relationship in your linkage that is causing this problem. It's a very simple system. I cannot envision a hidden problem. As a SLS brake, you only have one brake shoe with the potential to "grab". That would be the upper shoe. So, there should be a small amount of lead on the friction surface of that pad. But I really doubt this is what is happening.
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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 1:44 pm

tgtrotter wrote:
Wed Apr 08, 2020 11:53 am
re visit your linkage ?
Linkage appears to be working normal. For example, the brakes will lock at a stop sign and you can feel them dragging even after I pick my foot up off the pedal. The foot pedal returns, and you can toe-tap it and it will move up and down all while the rear drums are dragging.
Snakeoil wrote:
Wed Apr 08, 2020 12:11 pm
You say things are "at rest". I would suggest that you look at what Coluralado calls "shoes" and assure that they are flat against the brake cam. I think I'd call the "shoes" adjusting pads just to avoid confusion with the term brake shoes. If the cam is at an angle relative to the face of the adjusting pads, they you need to figure out why. Maybe your cam shaft is hanging up due to rust or something and you are still going over-center because your starting point is wrong.

And I agree with tgtrotter, you need to look at the entire system, not just the rear brake drum assembly. If your cam and pads are face to face when at rest then you need to look elsewhere. The change in thickness with the new shoes may have changed a relationship in your linkage that is causing this problem. It's a very simple system. I cannot envision a hidden problem. As a SLS brake, you only have one brake shoe with the potential to "grab". That would be the upper shoe. So, there should be a small amount of lead on the friction surface of that pad. But I really doubt this is what is happening.
I originally had the pad square with the cam, and in the last few days rotated them to be at a 45deg to the cam as you stated. I'm still getting the same hang-up. The cam is brand new and greased with high-temp moly as of 2 months ago, but I will be completely dissembling again to re-grease the next time I'm in there. With the wheel off I'm getting maybe 20 deg rotation of the cam before the brake pedal bottoms out, no where near a 90 deg rotation of the cam. I assume your "over-center" is referring to the pads riding over the end of the elliptical cam?

I may have been thinking of the Leading vs Following shoe backwards. I'll make sure the top-forward edge of friction material is clearly beveled. As I noted in my original post, I'm not a dummy when it comes to working on cars & motors so I'm just getting so frustrated that something this simple is being so difficult. Other than arcing the pads, is there any other type of "break in" required for the pads?
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 - Sold off to a Friend
Boats, Jets Skis and Golf Carts...other fun stuff!

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Re: Rear Brake Problem

Post by S 854 » Wed Apr 08, 2020 3:06 pm

With the brake rod nut not installed... how much play do you have on the actuator rod before the brake pads engage the drum? Shouldn’t be much more than an inch of arc or so...

When you have everything assembled and ready to ride... what is the angle between the brake rod and the brake cam actuator arm?

As you apply the brake... the arm and rod should just be getting to a 90 degree angle (that’s where yer gonna get the best leverage for maximum braking).
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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 3:21 pm

S 854 wrote:
Wed Apr 08, 2020 3:06 pm
With the brake rod nut not installed... how much play do you have on the actuator rod before the brake pads engage the drum? Shouldn’t be much more than an inch of arc or so...

When you have everything assembled and ready to ride... what is the angle between the brake rod and the brake cam actuator arm?

As you apply the brake... the arm and rod should just be getting to a 90 degree angle (that’s where yer gonna get the best leverage for maximum braking).
With the wheel off and the fine adjuster nut slacked off the arm is about 30 deg. towards the rear from vertical (about what is shown in the video I posted). I have the arm set in the cam so that there is virtually no rod left to adjust out when the fine adjuster nut goes slack.

With the wheel installed and the fine adjuster taking up the slack the arm is about 10 deg. towards the rear from vertical. With the parking brake set (just as a reference for brakes applied) I'm vertical or ever so slightly forward of vertical.

Now that you say this, should the arm never go PAST vertical? Is this what SnakeOil was referring to by cam-over?
1999 Yamaha Royal Star Venture
2007 Ural Tourist - The Big Red Brick
Chinese Knock off Honda Trail 70 rescued from the in-laws shed
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Re: Rear Brake Problem

Post by S 854 » Wed Apr 08, 2020 4:24 pm

bratmanxj wrote:
Wed Apr 08, 2020 3:21 pm


Now that you say this, should the arm never go PAST vertical? Is this what SnakeOil was referring to by cam-over?
Two different things... cam-over would occur inside the brake drum... if you removed your brake assembly from the bike and began rotating the arm eventually the brake shoes would be forced apart to their maximum as the cam pushes as far as it can... then, as you continue to rotate the arm, the shoes would begin coming back together... at that point, when the shoes begin closing together, that would be a cam-over...

The angle of the arm in relation to the brake rod affects how much pressure is applied... it’s fine to go past 90 degrees... you would get much less leverage if your arm was canted forward say 45 degrees
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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 4:52 pm

S 854 wrote:
Wed Apr 08, 2020 4:24 pm
Two different things... cam-over would occur inside the brake drum... if you removed your brake assembly from the bike and began rotating the arm eventually the brake shoes would be forced apart to their maximum as the cam pushes as far as it can... then, as you continue to rotate the arm, the shoes would begin coming back together... at that point, when the shoes begin closing together, that would be a cam-over...

The angle of the arm in relation to the brake rod affects how much pressure is applied... it’s fine to go past 90 degrees... you would get much less leverage if your arm was canted forward say 45 degrees
The problems of the internet and how somethings written vs interpreted. I'm a Civil Engineer with a STRONG background in Mechanical, again this shouldn't be rocket science and I feel that I'm somehow overlooking something so stupid. SnakeOils "cam over" is exactly what I thought it was and I am no where near that point in the movement of the lifting cam on the brake shoe pads.

My only real idea is that the leading edge is "biting" somehow and I need to eliminate that. I took my air grinder with a sanding pad and radius all the edges on the friction material, I'll give it another quick lick. I'll take some sand paper to the drum and make sure there are no burs. I'll go through the whole linkage again and grease it front to back. I'll report back in a few days.

Thank you all for chiming in....
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 - Sold off to a Friend
Boats, Jets Skis and Golf Carts...other fun stuff!

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Re: Rear Brake Problem

Post by S 854 » Wed Apr 08, 2020 5:43 pm

Another thing about the internet is: we as prospective helpers have no idea who we’re talking to, what their background is or how mechanically inclined they might be... sometimes we’re interpreted as “talking down” to someone as we try to make things as clear as we can...
:oops:
One more (simple) thing... have you greased the brake cam where it goes through the backing plate?

As you said... it’s not rocket science... once you find the issue yer gonna give yourself a big face-palm...
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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 8:13 pm

Yes, I used a high temp molly on where the cam passes through the plate when I installed the new parts back in January. Actually getting in there to grease it back in December is when I noticed the booger splines were on the old part was half my battle.

At this point, I feel like I should be talked down to like I'm a 5th grader that can't figure out something that should be so simple!
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2007 Ural Tourist - The Big Red Brick
Chinese Knock off Honda Trail 70 rescued from the in-laws shed
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Re: Rear Brake Problem

Post by Snakeoil » Wed Apr 08, 2020 8:50 pm

Something that might not be obvious but is simple is the width of the new shoes. Any chance they are hanging up on the sides.

I know that your old shoes were damaged, but suspect they will still work for testing purposes. Put them back in and see if the problem persists. If not, it is something with the new shoes. If the problem persists, it ain't the new shoes.

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Re: Rear Brake Problem

Post by bratmanxj » Wed Apr 08, 2020 9:28 pm

Snakeoil wrote:
Wed Apr 08, 2020 8:50 pm
I spent my career as an ME. We build bombs. You build targets. :wink:
Nope, I build places for those targets to go? My largest client is a major metropolitan cemetery system. 54 properties; 50+ miles of roads, sewers & burial mounds. On a positive note, its a sorta recession-proof gig.
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 - Sold off to a Friend
Boats, Jets Skis and Golf Carts...other fun stuff!

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Re: Rear Brake Problem

Post by Snakeoil » Thu Apr 09, 2020 12:14 pm

bratmanxj wrote:
Wed Apr 08, 2020 9:28 pm
Snakeoil wrote:
Wed Apr 08, 2020 8:50 pm
I spent my career as an ME. We build bombs. You build targets. :wink:
Nope, I build places for those targets to go? My largest client is a major metropolitan cemetery system. 54 properties; 50+ miles of roads, sewers & burial mounds. On a positive note, its a sorta recession-proof gig.
And the customers never complain.
Regards,
Rob
Proud member of the Peanut Gallery
2000 Ural Tourist
40 Pilots, 122 Mains
Before you say something stupid, always ask yourself, "What would Harpo say?".

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