Dual pivot brake not springing back

Kbrook

Über Member
when I tighten the bolt that holds the caliper to the frame. If I have it loose it springs back but when I tighten it at all it stops the brake releasing. It's got me puzzled, any ideas?
 
Do you have a picture of the brake caliper ? It sounds as though there is something missing to prevent them from binding .
 
There’s a centring adjustment screw, either a grub screw, in the side of the calliper arm, or a screw on the bridge of the calliper at the top. Screw that all the way in, then all the way out, to make sure it’s not sticking, then pull the lever a couple of times. I had a similar issue recently, and this sorted it out
 

Ian H

I am an ancient randonneur, & I stop often for tea
Location
East Devon
Try tightening it with the brake applied (use your hand, or you can get a '3rd-hand' tool to clamp it shut).
 
OP
K

Kbrook

Über Member
How tight should that nut that holds the spring be? If I tighten that up it also stops the arm springing back?
 

Dogtrousers

Kilometre nibbler
Check that the cable is running freely through the outer. I once did something stupid (just the once? you say) and somehow kinked the cable so it was sticking inside the outer. My hands were strong enough to pull the brake on, but the brake spring wasn't strong enough to pull the jammed cable back.

Edit. I've just read your post properly and I don't think this is relevant. I'll leave it here as a monument to my stupidity.
 
The centering screw is the black Philips head screw to the side of the bridge at the top of the calliper in the first picture. That’s the issue. Give it a spray with some GT85 or something similar, then screw it in and out to unstick the calliper.
 

fossyant

Ride It Like You Stole It!
Location
South Manchester
How tight should that nut that holds the spring be? If I tighten that up it also stops the arm springing back?
Not too tight - enough to take out play - that's what's causing the brake to get too tight - As you are turning the allen bolt, that nut is also tightening up. It's why I've always used a cone spanner, even on dual pivots as it's easier to centre the brake doing it that way - never bothered with the little screw.
 
Location
Loch side.
Those brakes run on thrust bearings. This is a circle of bearing balls enclosed in a flat nylon or metal "washer" in such a way that the balls protrude both side of the "washer". The proper word for that washer is retainer, but "washer" describes what it looks like. Either side of that bearing is an arm from the caliper and that entire assembly is held in position by the nut on the brake mounting bolt. That's the nut that, in your first photo, sits immediately right of the black aluminium arm. If that is too tight, or, very loose, to start off with, the extra force applied when mounting the tubular nut compresses the bearing and prevents it from moving freely.

I would disassemble the brake, (after getting a feel for the current tightness of the bearing) clean and grease the bearing, re-assemble it and play with the adjustment.

https://images.app.goo.gl/7LMERoQkt7bGrV2y9

and here

https://images.app.goo.gl/oMdir7ZVqpREmV9N7
 

Paulus

Started young, and still going.
Location
Barnet,
Do the calipers spring back when squeezed when they are off the bike? If so I would agree with Fossyant that you are doing the calipers up too tight on the bridge or fork crown. Also, if they are not centred correctly only one side will release.
 
Location
Loch side.
Do the calipers spring back when squeezed when they are off the bike? If so I would agree with Fossyant that you are doing the calipers up too tight on the bridge or fork crown. Also, if they are not centred correctly only one side will release.
The tightness of the mount should not influence the tightness of the pivot bearing. Visualise this as a short threaded rod with three adjacent nuts screwed onto it. By tightening any of the end nuts against the middle one (without the middle one turning), nothing happens to the tension between the middle one and the opposite one that's not being turned.
 

Shearwater Missile

Über Member
Location
Heart of Suffolk
The tightness of the mount should not influence the tightness of the pivot bearing. Visualise this as a short threaded rod with three adjacent nuts screwed onto it. By tightening any of the end nuts against the middle one (without the middle one turning), nothing happens to the tension between the middle one and the opposite one that's not being turned.
I had a similar problem on my rear caliper which had me stumped. What it turned out to be was....... If you look at the photo on the right you will see that the end of the spring runs into a collar, on mine that is made of plastic and the spring was binding in the collar, it is supposed to move freely. I noticed that the spring on yours looks a little rusty so would actually make it worse. If it has been OK and only just started to play up then that might me the answer. If so, I`d remove the spring and lightly sand the end, lubricate and refit. Hope this helps.
 
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