rear brake locking

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mukaiboston
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rear brake locking

Post by mukaiboston »

My rear wheel used to have some problems getting stuck if it was on its center stand and spun freely. Shooting some brake cleaner into where the drum/shoe is seemed to free it.

However, I recently had both tires and the rear brakes replaced. First thing I noticed when I got the bike back was that the rear brake seemed very tight. Maybe he put it like that on purpose since I've read some posts here about people keeping the rear brake lever as tight as the front one, but I prefer to have the rear brake feel a bit squishy since it's only 30% of breaking power.

Anyway, this was fine for a few days, but I went out yesterday to find my rear wheel completely locked up. I couldn't even push it. I was able to free it by adjusting the rear brake but, because they are new, the nut is mostly all the way out. I don't want to unscrew it too much and it falls off.

My friend suggested waiting a bit because the new brakes may need a chance to break in. The mechanic was also supposed to grease everything and check for corrosion if he took everything apart. I can't believe he would overlook that but I should check with the shop to figure out exactly what he saw.

Any advice for dealing with this or should I not worry about it? Also, this brake locking and dragging only occurs when the engine is cold for a few hours. Five minutes into the engine heating up, the brake problems disappear and I can actually tighten the brake up again.
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DeeDee
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Post by DeeDee »

Take it back to the shop who did the work. This is not correct. How many miles is on the scooter? Those rear brake pads last for ever.
mukaiboston
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Post by mukaiboston »

There are almost 20k miles on this scooter, but I've probably only gone about 50 so far with these brake pads.

And brake pads do wear out because I've had to tighten them all the way to the point to where the wear arrows were almost touching.
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skully93
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Post by skully93 »

I have over 18k on my scoot, and @10k on my rear brakes. They could probably use some de-glazing given how evil I am to them, but they still stop the bike.

Methinks something else is afoot.
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ucandoit
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Post by ucandoit »

When I put a new rear tire on my scooter the rear brake lining was more worn down than I expected, but still in the acceptable range, and my scooter has just 7000 miles. So, rear brake pads don't last forever.
Anyway, I "deglazed" the pads a bit with sandpaper, and cleaned things up a bit, but what I failed to do was to put a dab of grease on the two cams. I didn't know about that until I had the wheel back on. I haven't had any problems with braking but I wish I had done it right. It just takes a dab of grease, as you certainly don't want much in the brake area. I've only removed the rear wheel once so don't recall the anatomy perfectly, but that grease on the cams helps the pads move out to contact the drum and stop the scooter. I would ask Babblefish if he thinks lacking the grease may cause your brakes to lock up. I would also call the shop. Lastly, do you feel the brake cable is functioning smoothly?
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Post by mukaiboston »

Brakes work perfectly after I'm riding for like three minutes. If the bike sits a few days and then I first start out, the rear brake feels like it's grabbing. Like, I will start to pull the brake lever and then the rear brake just applies suddenly.
Also, these issues seem to happen more when it is hot out. When I picked up the scooter from the shop, it was cool and it was cool again a few days ago. That's why I didn't notice the problem then.

I'll call the shop again in a month if the brakes don't seem to correct themselves. I mean, if he just replaced both tires and the brakes, I assume he would have seen if something was off.
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charlie55
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Post by charlie55 »

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To me it sounds as if your brake actuating components (parts 13, 14, 15, and 16 in the above diagram) are sticking in the applied position and then releasing as the result of movement and vibration (and possibly frictional heating).

Applying force to part 14 via the brake cable causes it to rotate part 13, which is essentially a flat "cam" with rounded edges. This sits between the lower facing surfaces of the brake shoes and spreads them apart as it rotates. When you release the brake, the "cam" should return to its normal position (usually vertical between the shoes). This return action is caused by the lower brake spring (12) compressing the shoe bottoms against the cam.

Binding could be caused by:

- Lack of lubrication on part 13, either where it goes through the drum housing, or on the cam itself.

- A damaged cam (notched, nicked, worn out).

- Missing/broken/improperly installed brake springs.

- A binding or improperly-routed brake cable.

- Anything that impedes the free movement of part 13 between the applied and released positions.

When your brakes are applied, part 14 should be at the forward limit of its range of motion. When they're released, it should be at the rear limit.

So, here's what I'd do to get handle on what's going on:

- Before your first ride of the day, grab part 14 and see if you can push forward. If not, then your brakes are already stuck in the applied position. In that case, see if you can pull it back. If you can, and if it feels "crunky", then something is indeed sticking.

- After you've ridden a while and the brake feels like it's operating normally, do the same routine with part 14. It should now be in its rearmost range and able to be pushed forward with minimal effort.

Basically, you want to see if there's a difference in the range of motion (or ease of moving through that range) when the problem is present and when it is not.

This may or may not help, but at least it's something you can check for yourself before going back to the dealer (which I would definitely recommend).
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mukaiboston
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Post by mukaiboston »

Thanks for the advice. Let me try it this weekend and I will let you know what happens.

My scooter had been sitting for two days and when I went out to use it this evening, brake operated normally. Maybe because it was cooler and not much humidity. It might be my imagination, but it seems like the weather is also affecting how the brake operates. But I had also loosened the brake on Sunday so it was not sitting in an overly tightened position.
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Post by mukaiboston »

Charlie55, you are indeed a genius.

This is exactly what is happening. I went out this evening and, sure enough, the rear wheel was locked up again. I very gently pulled part 14 towards me and it immediately clicked forward and the brake was released. I then pushed part 14 slightly and it stayed stuck in that position. So I just pulled part 14 towards me again before pulling out of my driveway.

When I got to my destination and the engine was all heated up, I pushed part 14 away from me and it did not stay in the position. It moved back into the outer position so the brake was not sticking.

I'm willing to bet there is some issue with part 13 not being greased right. My mechanic just replaced all the rear brakes and this issue was occurring before then.

Any idea on the safest way to grease part 13? Do I need to take anything apart or can I just squirt some WD-40 in there? And is that safe because I know you cannot get WD-40 on the brake pads?
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charlie55
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Post by charlie55 »

My kids would disagree about the genius part, although they do seem to think I'm getting smarter as they get older.

First off, start easy and rule out the brake cable. If you can, repeat the first test, but disconnect the cable from part 14 beforehand. While you're at it, inspect the round barrel that lies between the forks of part 14 and through which the cable runs. It may be damaged or misaligned. Also make sure that both "ears" of the fork are straight and parallel.

If that doesn't yield any clues, then I'm afraid you'll have to pull the wheel and check out the innards of the entire brake. Move part 14 back and forth by hand and watch how the cam on part 13 interacts with the shoes. If it's notchy, you'll have to disconnect it from part 14 and pull it out from the shoe side of the brake. Check the cam for wear, and also the part that sits in the hub. Make sure that it's free of gunk and do the same for the passage through the hub. If everything looks good, clean part 13 and the passage and put a bit of axle or lithium grease in the passage and on the cam itself. You don't need a lot. Re-assemble, and try that back-and-forth test by hand again.

I'm leaning towards an accumulation of old grease, brake dust, and road crud as being the culprit here; Personally, I'd tear the whole brake apart (shoes, springs and all) for a complete clean/grease job. Your shop should have taken care of all that, but it wouldn't be the first time a mechanic ever did a "quick and dirty".

As to the WD40, I would not recommend it. Even from the outside, there's a chance it could work its way onto the pads. Also, it's not really a great long-term lubricant, and you need something thicker for a rotational part like this. I use whatever axle grease I have lying around and have not had any problems.

Good luck with this, and keep us posted on your findings/results.
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mukaiboston
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Post by mukaiboston »

So just to be honest, I usually leave wheels and brakes up to the mechanic since I don't know what I'm doing really and don't want to risk damaging anything that I'm betting my life on.

How would I remove the cable? Can I just rotate the nut (the one that is used to tighten the brake) counter-clockwise until it comes off and then slide the attachment out of the fork?

I'm not sure if I mentioned it before, but the fork only sticks if the cable is tightened. Before you posted and I discovered what was going on, I would simply walk out to my scooter and, if the wheel was stuck, loosen the nut. Then I would retighten it at my destination. The mechanic put the brakes on way tighter that I prefer so it didn't bother me. I need to experiment a bit, but it looks like a tight cable also prevents the fork from disengaging.

Also, I've had this brake issue for a while. The first time, the mechanic said I needed to loosen the brake, but I told them to look at it when I had my exhaust replaced. They fixed something and it worked for several weeks before it started sticking again. Then, when I had both tires replaced a couple weeks ago, I again told them that the brakes were sticking and they fixed something a second time. The fork doesn't seem to always stick in cool weather and the temperatures had dropped by the time I went to pick up my scooter so I didn't notice it until a couple weeks later when it got hot.

Maybe I'll just call the shop today and try to get some more information about what they greased and what they saw when they opened it up.
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charlie55
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Post by charlie55 »

Yes, that's how you would remove the cable.

Since you're not comfortable messing with the brakes, I think that you should definitely proceed with getting a shop to look into this. Drum brakes are extremely simple to work on, so any mechanic worth their salt should be able to diagnose and correct the problem in short order. And of you do go back to the same shop that did the work before, see if you can get a detailed explanation and then post it here. I'm curious as to what they did/didn't do.
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mukaiboston
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Post by mukaiboston »

So the woman who runs the shop is actually a friend of mine so I trust what she has to say on this.

She spoke with the guy who worked on my bike and said he was very thorough - checked for anything that didn't look right and greased all the parts. I specifically asked if he had regreased the parts and she said yes.

However, she also mentioned it could be the cable so I told her I would try to have a look at this myself and, if the cable seems bad, I will take it back to the shop to have it replaced.
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Post by charlie55 »

If they're saying that they did the whole nine yards on the brake job, then yeah, there's not much else it could be other than the cable (or even the brake handle mechanism itself). Lubing the cables is something that often gets overlooked, and I'm guilty of that myself. Please let us know what the final outcome is. It could be very helpful to everyone.
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mukaiboston
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Post by mukaiboston »

It's the cable. Or at least the spring that pushes agains the brake mechanism. I undid the cable like people said and part 14 was fine. I push it and it goes back to its original position.

I'm going to tell the shop what I found and they might have to order me a cable since they have none in stock. There is some issue with that spring. It's either catching on something or not expanding right.
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ME TOO!

Post by MYSCTR »

Ok, so next time you ride through north Texas, give me a yell. We got our rear wheel dragging really bad on my 170 that we had in the shop. Rides like I am dragging three more behind me. Last ride I got home and the rear wheel would not free spin on the center stand at all. Just parked it - life just gets in the way. Still have to get this figured out as I want to keep riding it 1-2 times a week.
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mukaiboston
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Post by mukaiboston »

Ugh, Scooterworks is taking forever to ship the brake cable to my shop. Ordered two weeks ago.

Any advice for what I can do in the meantime to keep this cable lubricated? The shop uses ENI grease, but it looks like this is from Belgium. I don't know where to get it in the US. There must be something else I can use on this spring.
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Post by mukaiboston »

UPDATE: Apparently the brake cable was only part of the issue. The part with the arm on it that the break cable runs through also needs to be replaced.

When charlie55 was talking about it moving back and forth, I didn't know he meant side to side, parallel with the cable. When I am facing the left side of the wheel, the arm also moves towards and away from me. When it is away from me, it pushes on the brake causing it to lock. There is too much play. The mechanic tightened it so it won't move as much but he said that part is worn out and needs replacing.
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charlie55
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Post by charlie55 »

Now that's something I never would have thought of.

And thanks for the follow-up post. A lot of folks never bother to update after their problem has been solved. Too bad because that's a lot knowledge that never gets spread around.
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mukaiboston
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Post by mukaiboston »

charlie55, this is the part you mentioned before - part 14 in the diagram. Unfortunately, part 14 is part of the entire assembly surrounding the break shoe so the whole thing needs to be replaced. Mechanic said it would be a $50 part.
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Post by DeeDee »

mukaiboston
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Post by mukaiboston »

Mechanic said that the part the lever screws into also needs replacing.
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