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Dual pivot caliper brakes

Old 06-22-20, 07:33 PM
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Kevinx88
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Dual pivot caliper brakes

Hi. I been struggling to center my rear brake calipers. Iíve done all the possible research and still can not find a solution. Every time after I center my rear calipers, I press the brakes and the calipers get misaligned again. Further more, when I press on the rear brakes, the rear rim gets pull to the left by a few mm. After I release the brakes, the rim returns to original alignment. It seems like the cable housing is causing it to pull the brake calipers. Itís possible that the housing cable is too short. Also possible the rim is not appropriately dished but I think this is less likely the issue. One last possible culprit would be that the washer that bites into the frame is not working, therefore not able to hold the calipers position. I can apply hand pressure to make left and right adjustments to the caliper. However I have read that this should not matter. And yes I have tighten the nut a lot, to the point it is eating into the carbon frame. No matter how much, the caliper is still able to move. I have also tried using centering bolt to align the calipers, but even so, after pressing the rear brake levers, the calipers get misaligned again and pushes the rim to the left. Anyone familiar with this problem?
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Old 06-22-20, 07:42 PM
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First make sure the brake is tightly bolted to the frame.
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Old 06-22-20, 07:47 PM
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make sure the bracket & caliper is tight to frame.
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Old 06-22-20, 08:29 PM
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Yes the brake is tight onto the bike frame. It is starting to eat into the carbon fiber frame. Stupid design but this part should not have been carbon fiber as it is too soft for anything to grip onto! Could this be the problem? If so, I think my next move should be to epoxy glue the washer onto the frame.
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Old 06-22-20, 08:41 PM
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does your front brake do it to?
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Old 06-22-20, 09:12 PM
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is this Shimano? not all dual pivots are the same.

try this. Disconnect the brake cable completely from the caliper, then tighten down the caliper (if it's not already tighten). Now try to move the caliper with just finger pressure (like you did before). Does the caliper move as easily?
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Old 06-22-20, 09:23 PM
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Nobody ever says this but - if you center the pads, they will not hit the rim at the same time. Reason? The two sides have different geometries and mechanical advantages. If you center the pads, one side hits first and you will see the rim gets pushed aside as you apply more force. I align my dual pivots so the rim doesn't move. One pad (I'd have to to out and look to tell you which) is considerably closer to the rim.

Now, directly related to your question is mine. Why can't the dual pivot makers (Shimano especially) provide slots for a 10mm or 13mm brake spanner (or cone wrench) like good sidepulls have had forever? The best dual pivots I've used are as micky mouse to center as cheap sidepulls for garden variety bikes. I find my self loosening the mounting bolt, holding the brake in my hand, tightening the bolt and having to look to see if I actually improved things, Really?

Edit: read your post a little more carefully. Yup you are seeing the dual pivot push-it-over that I have never heard talked about. (I now have to watch my back. DP thugs.)

Last edited by 79pmooney; 06-22-20 at 09:27 PM.
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Old 06-22-20, 10:10 PM
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Originally Posted by Troul View Post
does your front brake do it to?
This is only happening to the rear brakes. If I recalled correctly, the rear once was working fine until I loosened the bolt holding the caliber to the frame. I did manage to get it back to center but I remember struggling as every time I squeezed the brake levers hard, it would unalign the calipers. Soft squeezes did not move the calipers off center as much, but seems like over time it just got worst. I think it may be due to the washer eating into the carbon. Look like there should have been some rough surface there previously.
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Old 06-22-20, 10:17 PM
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Originally Posted by aclinjury View Post
is this Shimano? not all dual pivots are the same.

try this. Disconnect the brake cable completely from the caliper, then tighten down the caliper (if it's not already tighten). Now try to move the caliper with just finger pressure (like you did before). Does the caliper move as easily?
Yes this is Shimano 105 5800. Iíll have to try moving the calipers without the cable connected, but even with the cable connected, it does take some hand pressure to move the calipers. Once calipers are moved by brake lever, the calipers move slightly over to the left side (side where the cable is at) and hold its position steady. Seems like the bolt and nuts are holding the caliper in place, but the force of the moving caliper seems to pull too strong, especially with a hard squeeze on the brake lever.
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Old 06-22-20, 10:32 PM
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Originally Posted by Kevinx88 View Post
Yes this is Shimano 105 5800. Iíll have to try moving the calipers without the cable connected, but even with the cable connected, it does take some hand pressure to move the calipers. Once calipers are moved by brake lever, the calipers move slightly over to the left side (side where the cable is at) and hold its position steady. Seems like the bolt and nuts are holding the caliper in place, but the force of the moving caliper seems to pull too strong, especially with a hard squeeze on the brake lever.
brake housing may be too short.
post a pic, these sort of post is hard to visualize without a pic
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Old 06-22-20, 10:34 PM
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Originally Posted by 79pmooney View Post
Nobody ever says this but - if you center the pads, they will not hit the rim at the same time. Reason? The two sides have different geometries and mechanical advantages. If you center the pads, one side hits first and you will see the rim gets pushed aside as you apply more force. I align my dual pivots so the rim doesn't move. One pad (I'd have to to out and look to tell you which) is considerably closer to the rim.

Now, directly related to your question is mine. Why can't the dual pivot makers (Shimano especially) provide slots for a 10mm or 13mm brake spanner (or cone wrench) like good sidepulls have had forever? The best dual pivots I've used are as micky mouse to center as cheap sidepulls for garden variety bikes. I find my self loosening the mounting bolt, holding the brake in my hand, tightening the bolt and having to look to see if I actually improved things, Really?

Edit: read your post a little more carefully. Yup you are seeing the dual pivot push-it-over that I have never heard talked about. (I now have to watch my back. DP thugs.)
Yeah, no matter how the calipers are aligned it will find a way to move and push the rim to the left, against the other side of the brake caliper. Even when the two calipers are closing in together to brake/hold the rims, the rim is slightly pushed over to the left side. I think the strong spring in addition to the carbon frame washer-rough-surface being stripped may be the culprit to this caliper push-over rim. However, I wonder if extending the cable housing at the rear can reduce the force from which the lever is pulling (cable housing does appear to be just a little short, not sure this can cause it to pull stronger). Probably will give that a try tomorrow and it how that goes.
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Old 06-23-20, 03:33 AM
  #12  
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It's tricky. I find that if you loosen the bolt, centre the brakes and then tighten the bold that action tends to pull the brakes off centre. Try and hold the callipers as you tighten to prevent this as well as starting marginally off centre to compensate. My brakes (SRAM Force) have an adjustment screw to centre them afterwards but I've found that this loosens over time so I don't bother with it any more.

They shouldn't need to be hugely tight, either - really just tight enough that it won't come undone. Normally carbon frames have a metal insert in key areas like the brake, wheel and crank mounting areas so you shouldn't be eating into the carbon.
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Old 06-23-20, 06:14 AM
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I have Bontrager Speedstop and there's a screw that adjustest the spring pressure and centers the pads.
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Old 06-23-20, 06:25 AM
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I loosen the mounting bolt, squeeze the brakes until they grip the rim, then tighten the bolt. That's usually close enough to fine adjust with the screw. I expect there are a variety of ways to set up the brakes but they shouldn't be moving after it's done. I don't think the mounting bolt even needs to be extraordinarily tight. I agree that you might check the cable housing.
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Old 06-23-20, 07:32 AM
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This Thread Should Move to Mechanics sub-forum...

...nevertheless, I'll persist.

BR-5800s are excellent calipers. Great. So, please provide a photo that shows the cable run from where it exits the rear stop or rear exit of the top tube to where it meets the caliper stop. Take one photo with the brake lever at rest, and then another with the brake lever fully squeezed. What changes?

Please also show a close-up of the mounting bolt from behind the rear bridge.

This shouldn't be as hard as you're experiencing...
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Old 06-23-20, 07:45 AM
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I just put a thin cone-wrench type spanner on the inner lock bolt and turn it slightly until the caliper is centered. That's all I have ever had to do.

(Crampy Veloce, but looks the same as any other dual-pivot I have seen.)
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Old 06-23-20, 07:36 PM
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Test
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Old 06-23-20, 10:34 PM
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Hello and thank you everyone for being really helpful in this time of uncertainty. I think gluing the washers onto the frame would have been a major mistakeóthis would cause the cables to pull off from the frame that the calipers are bolted onto. Thankfully I didnít go that route. The problem has been resolved. The reason it once worked and was center is probably because it was tightly screwed in place with good friction, but this probably caused unnecessary stress to the frame part holding the bolt and overtime just stripped the roughage area where the washer is attached to. The solution was a longer cable housing. Just increasing this cable length by an inch fixed the problem. The bolt does not need to be tighten much to keep calipers in place as one of the earlier posters mentioned. Once in place, squeezing levers does not change position nor push the rim over. I could not post pictures because I have less than ten post. I could not respond sooner because posting is limited to 5 a day. Thank you all and happy cycling!
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Old 06-24-20, 06:39 PM
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Originally Posted by 79pmooney View Post
Nobody ever says this but - if you center the pads, they will not hit the rim at the same time. Reason? The two sides have different geometries and mechanical advantages. If you center the pads, one side hits first and you will see the rim gets pushed aside as you apply more force. I align my dual pivots so the rim doesn't move. One pad (I'd have to to out and look to tell you which) is considerably closer to the rim.
Originally Posted by Kevinx88 View Post
Yes this is Shimano 105 5800.
Actually the 5800 caliper has the SLR-EV design.


The pivot points are symmetrical. I have 2 105 R7000 calipers, and you should have absolutely no problem getting these things centered and hitting the rim at the same time. I agree, though, that typical dual pivot designs are absolute garbage.

Please upload a video clip to youtube or something. This is probably like a 2-minute diagnosis that we're agonizing over.

So there are a couple of things that can cause your problem, and a loose mounting bolt, believe it or not, isn't one of them. You could have "too short" housing. This could also just mean you need to pull some slack into the housing near the caliper because the housing has slipped into the frame. If that's not it, then make sure the brake shoes are at the same level on the arms. If they are... then this is a longshot, but try adjusting the small centering bolt. But my bet is that it's a housing issue.

EDIT: I can't believe I missed the second page. My bad. I think it didn't load on the desktop site with its newfangled autoloader. Great that it worked out, though.

Last edited by smashndash; 06-24-20 at 06:42 PM.
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Old 06-24-20, 07:19 PM
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Originally Posted by smashndash View Post
Actually the 5800 caliper has the SLR-EV design.

The pivot points are symmetrical. I have 2 105 R7000 calipers, and you should have absolutely no problem getting these things centered and hitting the rim at the same time. I agree, though, that typical dual pivot designs are absolute garbage.

Please upload a video clip to youtube or something. This is probably like a 2-minute diagnosis that we're agonizing over.

So there are a couple of things that can cause your problem, and a loose mounting bolt, believe it or not, isn't one of them. You could have "too short" housing. This could also just mean you need to pull some slack into the housing near the caliper because the housing has slipped into the frame. If that's not it, then make sure the brake shoes are at the same level on the arms. If they are... then this is a longshot, but try adjusting the small centering bolt. But my bet is that it's a housing issue.

EDIT: I can't believe I missed the second page. My bad. I think it didn't load on the desktop site with its newfangled autoloader. Great that it worked out, though.
Yup, you wouldíve won that bet. It wasnít extremely obvious that the brake housing were too shortóit really look like it was just at the correct distance and correct angle going into the caliper cable holder. Lucky shot but it worked! Thank you for chiming in to help.
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Old 06-24-20, 09:10 PM
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Originally Posted by Kevinx88 View Post
Yup, you would’ve won that bet. It wasn’t extremely obvious that the brake housing were too short—it really look like it was just at the correct distance and correct angle going into the caliper cable holder. Lucky shot but it worked! Thank you for chiming in to help.
Unfortunately, that is a side effect of side-pull brake designs. If the housing is the "perfect length" when the brake is not engaged, it will be too short when the brake is engaged. I'm sure you know that now. But the result is that the housing always needs to have a bit of "slack" in it. I put that in quotes because housing is rigid. The housing is always pushing on the caliper. And that's the only reason SLR-EV calipers need the mounting bolt to be tight - besides keeping your brake from flying off.


I believe center-pull designs don't suffer from that problem.
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Old 06-24-20, 09:31 PM
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i didnt see what the OP did there.
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Old 06-25-20, 06:33 PM
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Dual pivot, like single pivot were not stupid designs, but you need to know what you're doing like anything else, so I got some videos for you to watch that should clarify what others are telling you; see:
https://www.bing.com/videos/search?q...tail&FORM=VIRE

https://www.bing.com/videos/search?q...tail&FORM=VIRE

read this: Centering Dual Pivot Brake Calipers the Right Way ? Killa?s Garage
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