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Side-pull brake woes

Old 01-28-20, 08:09 AM
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Side-pull brake woes

I'm not here just to moan. I like to think that I have a bit more talent than that.

As I'm in the protracted processes of organizing my shop and puttering along with projects, I've reached the point where I'm taking a close look at side-pull brakes, as I'm trying to fit some on one of my projects. In doing so, I'm noticing two things.

1. I have a couple sets of Weinmann calipers (and a set of Universal 68's) that have the ends of their arms severely misaligned when pressed together. I'm not talking about 2-3 mm off, they are between 1-2 centimeters off. This is the case on both the fronts and the rears. As I look closely at them, the issue appears to by with arm that gets pulled by the brake cable. I suspect they may be twisted, but there's also a bit of play in the movement, so I'm wondering if they were taken apart at some point and then re-assembled incorrectly. Is this something that others here have experienced? Was there some remedy (bending, reassembly, etc.), or are they simply toast?

2. If the above-mentioned calipers are now no better than part donors and memorabilia, Is it possible to transplant the mounting bolts from these onto one of my sets of calipers that does have proper alignment, but has recessed bolts?

Hoping that the collective wisdom here can set me straight.

Thanks,

Z
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Old 01-28-20, 08:17 AM
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I want to say the answer is yes, you can swap parts. But that seems like it would be obvious, so I feel like I'm missing something. Maybe pics would help?
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Old 01-28-20, 08:33 AM
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Need a better understanding of the alignment. How are they misaligned? is it relative to each other? I believe there is an alignment issue due to the arms being offset at the pivot point. Some calipers don't account for the offset in the design of the arm, so one pad is ahead of the other when "closed." Actually, always.
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Old 01-28-20, 08:51 AM
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Originally Posted by unterhausen View Post
I want to say the answer is yes, you can swap parts. But that seems like it would be obvious, so I feel like I'm missing something. Maybe pics would help?
My experience with assembling and disassembling brake calipers has been confined to centerpulls and cantilevers. Removing the mounting post on side-pulls is something I've never attempted, as it looks like vise-grips would be my tool of choice for removal. That doesn't give me the impression that they were intended to be serviceable.
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Old 01-28-20, 08:56 AM
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Originally Posted by SJX426 View Post
Need a better understanding of the alignment. How are they misaligned? is it relative to each other? I believe there is an alignment issue due to the arms being offset at the pivot point. Some calipers don't account for the offset in the design of the arm, so one pad is ahead of the other when "closed." Actually, always.
It is the latter. However (as in the case of the Universal calipers), I have two bicycles with the same model of caliper, and their pads are within a mm of each other when pressed together. Not so with my problem child. It looks like the arms on that set may be bent. I am guessing that correcting the bend will leave the arms even more compromised, and possibly subject to catastrophic failure.
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Old 01-28-20, 09:29 AM
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You are justified in being concerned. The Universal 61 brake calipers are cast and will break when attempting to bend them. Ask me how I know!
P1000591, on Flickr
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Old 01-28-20, 09:41 AM
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Most side pull brakes have an offset to the front arm so that the lower section of the arms are in alignment. This is primarily to put the spring retention tabs in alignment for symmetrical springs. Consequently both pads should also be in alignment. or at least close.

Edit: Here are two shots of one my Universal 68 calipers.


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Old 01-28-20, 10:08 AM
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This is helpful information.

Apparently though, I think I need to consider cannibalizing the torqued calipers to claim the pivot bolt, and to transplant it in good calipers that have recessed bolts. Not finding instructions for this process when I google "disassembling side-pull brake calipers". It there some good documentation of the steps involved? I shudder at the thought of just going at it with vise-grips.

Here are the worst of them





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Old 01-28-20, 10:37 AM
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Originally Posted by USAZorro View Post
This is helpful information.

Apparently though, I think I need to consider cannibalizing the torqued calipers to claim the pivot bolt, and to transplant it in good calipers that have recessed bolts. Not finding instructions for this process when I google "disassembling side-pull brake calipers". It there some good documentation of the steps involved? I shudder at the thought of just going at it with vise-grips...
Everything that is meant to come apart can be disassembled with traditional wrenches. This may help...
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Old 01-28-20, 10:53 AM
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Originally Posted by USAZorro View Post
It is the latter. However (as in the case of the Universal calipers), I have two bicycles with the same model of caliper, and their pads are within a mm of each other when pressed together. Not so with my problem child. It looks like the arms on that set may be bent. I am guessing that correcting the bend will leave the arms even more compromised, and possibly subject to catastrophic failure.
I haven't seen this for quite a while! My question is always, where is the misalignment? I would take them apart and inspect all the parts, that they are straight where they need to be straight, aligned to each other where it is necessary, that their pivot bores are not worn and unable to rotate true on the bolt, and of course the arms are not bent or twisted on the caliper side or on the cable pull side. Reassembling, if you tighten the pivot bolt do they seem to be better aligned? Does the alignment change when the return springs are engaged?

Sometimes it seems like elves live in our boxes of old bike parts. Usually when I take them apart I can see what was intended when the calipers were new.
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Old 01-28-20, 10:56 AM
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Just like that exploded view, disconnect the spring from the little notches, remove the nuts, slide the whole thing apart.

I have a low profile wrench that works perfectly to get at the nut in the "N" position in the illustration. Hold steady and remove the cone/acorn nut.
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Old 01-28-20, 10:57 AM
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Thanks. Part "D" is what concerns me. What tool is used to insert/extract it?

Also, I suspect something(s) is/are missing in the stack of parts between 'E' and 'P'.
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Old 01-28-20, 10:59 AM
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Did you check the brake block mounts? are the mounting studs in the same location fore and aft?
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Old 01-28-20, 11:02 AM
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Originally Posted by USAZorro View Post
Thanks. Part "D" is what concerns me. What tool is used to insert/extract it?

Also, I suspect something(s) is/are missing in the stack of parts between 'E' and 'P'.
Once you remove those two nuts, it pulls right out the back of the assembly. The whole post with both threaded sections is one piece.
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Old 01-28-20, 11:19 AM
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Originally Posted by BFisher View Post
Once you remove those two nuts, it pulls right out the back of the assembly. The whole post with both threaded sections is one piece.

ok - cool. I think the Weinmanns that I have (not quite as off kilter as these, have a post that is secured by a recessed bolt in the front part of the caliper. If I can get these sorted though, I may not have to explore transplanting the external bolts for recessed ones.

Thanks to all!
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Old 01-28-20, 11:51 AM
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Originally Posted by USAZorro View Post
Thanks. Part "D" is what concerns me. What tool is used to insert/extract it?

Also, I suspect something(s) is/are missing in the stack of parts between 'E' and 'P'.
Based on Tmar's photo as well as the exploded assembly diagram, I would disengage the spring ends from the caliper arms first. Then hold the unthreaded shaft of "D" with a small locked Vise-grip or the similar Craftsman version. I have a long nose narrow-jaw one I bought for adjusting old Brooks tensioners. The latched Vise-grip needs either a muscular assistant (cats not recommended) or a real or improvised bench vise. Take careful note of the play between the two arms and if they are able to rock on the shafts of "D". Then unscrew both nuts without losing them or the washers. When you separate the two arms from each other, don't lose any of the washers, or the ones on the interface between the second arm and "D". Those will be really important to re-assembling without play or binding.
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Old 01-28-20, 12:15 PM
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I would also measure the thickness of F, H, and L. Since there is an offset, I would put the thin one in the H position, if there is a difference. Lubing them slightly would also be a good idea.
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Old 01-28-20, 12:31 PM
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If the problem is one brake pad rubbing the rim, or contacting the rim before the other, I've used a kludge on my Suntour GPX and Dia-Compe BRS 500 brakes -- at least until I had the patience to reset the mounting bolts to center the arms.

I just wrap a zip tie once or twice around the cable housing, then wrap that around the handlebar/stem, and tighten the zip tie lock just enough to pull the arms into more equal positioning. A small Velcro strap can do the same thing and is more readily adjustable.

I used that trick for several months before I finally got around the resetting the mounting bolt on the brakes so they'd open/close evenly.

Similar issue on the rear brakes. The cable housing would creep a bit inside the frame-mounted guides. So I could either tug the cable housing back into place, or use a zip tie to keep it in place.

Cutting the brake cable housing to the perfect length also seems to help, but it's a PITA to get that length perfect, and I discovered with some bargain priced cable housing the housing would compress when new and it took awhile to finally take a set where I didn't continued to compress and effectively shorten. (Note to self: Don't by cheap cable housing.)
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Old 01-28-20, 12:58 PM
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Originally Posted by USAZorro View Post
Thanks. Part "D" is what concerns me. What tool is used to insert/extract it?

Also, I suspect something(s) is/are missing in the stack of parts between 'E' and 'P'.
If you're talking about the spring retention flange on the brake centre bolt, it's not meant to be removed. Consider it integral to the centre bolt. In some cases it's an separate piece that is pressed onto the bolt using an interference fit but in other cases it's part of the billet that is forged or turned to manufacture the centre bolt.

It doesn't look there is anything missing from the diagram.
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Old 01-28-20, 01:11 PM
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Originally Posted by T-Mar View Post
...

It doesn't look there is anything missing from the diagram.
Thanks. I meant that I suspect my brake caliper is missing something.
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Old 01-28-20, 01:26 PM
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Confirmed: there's nothing missing from the diagram.
All three brass washers are identical.
Tools req'd: Flat bladed screwdriver to disengage and re-engage spring, 8mm & 11mm wrenches or sockets.
Disassembly time: 1 minute, 15.23 seconds
Assembly and adjust time: 1 minute, 28.02 seconds
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Old 01-28-20, 01:57 PM
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^^^^ Exactly this. Easy peasy. No vice grips needed.
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Old 01-28-20, 03:13 PM
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Looks like it's all here, save one washer on the nut end - which I wouldn't think should affect the function.




Looking closer at the front half of the caliper, I think I see what the problem is:




Appears substantially warped. Toast?
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Old 01-28-20, 03:24 PM
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Might be. Don't know if Universal sidepulls differed, but I had the same experience as SJX426 when I tried to straighten a Uni. centerpull once. Part was cast, and so snapped right off.
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Old 01-29-20, 08:25 AM
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Originally Posted by USAZorro View Post
Looks like it's all here, save one washer on the nut end - which I wouldn't think should affect the function.




Looking closer at the front half of the caliper, I think I see what the problem is:




Appears substantially warped. Toast?
There ya go!
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