Brake binding on rim

[Broadside]

This is my wife's bike and it has a problem with the brake binding on occasionally, normally every 20 miles or so.

The bike is new and it has been looked at during the 6 week freebie service, they trimmed down the cable outer as it seemed a bit long previously and we wondered if that was causing the calliper to get pushed over. The problem first occurred with the original stock brakes, so we upgraded them to Shimano 105 and the problem still occurs.

The whole calliper pivots across so that pad on the non drive side contacts the rim, so you have to get off and move the calliper back. The calliper is tightly screwed on the brake bridge, i don't want to make it any tighter incase it crushes the carbon.

I am at a loss what is wrong and the shop are confused too.

Could it be some weird faulty frame geometry? Is the wheel flexing excessively under load and pushing the calliper over? The wheel is true with no loose spokes, there is no play in the cones.

Any ideas?

 

[mrandmrspoves]

I doubt there is a major problem such as a frame fault. On dual calliper brakes there is usually a small balancing screw on the right arm (looking from behind the bike) this normally has a recessed Allen key head. This can be used to adjust the balance between the two arms and following on from making this adjustment the whole brake mechanism may need re - centering on the frame.

 

[User6179]

Had same problem , the brake cable was not fed through the frame guide correctly and was snagging because it had frayed causing the brake to stay on slightly when I braked .

 

[Broadside]

I shouldn't have said binding, they are releasing fully but something is causing the calliper to twist while riding so that you have to get off to re-centre them. I'm flummoxed by it.

 

[jonny jeez]

I shouldn't have said binding, they are releasing fully but something is causing the calliper to twist while riding so that you have to get off to re-centre them. I'm flummoxed by it.

It's new so get the shop to swap,out the caliper with anything they have and see if this helps.

If it does, get them to make a permanent swap, if it doesn't, get your money back.

 

[midlife]

By "we upgraded" do you mean the bike shop?

Shaun

 

[MattDB]

+1 for balancing screw, I messed around with mine for a while to get it right. Do you know anyone with a torque wrench, though may well not be related this was the part (callipers to frame) I most worried about over or under tensioning.

Strange that both callipers have done this though!

 

[Broadside]

By "we upgraded" do you mean the bike shop?

Shaun

Yes, the shop did it. I usually do all my own maintenance on the [cough] 9 bikes in our fleet but I'm concerned about this problem so want the shop to do all the work so they can't point at me. Specialized have already paid for a calliper upgrade so I just paid the extra to get the front calliper swapped too. Swapping out the calliper didn't help so there is something else wrong with the bike.

 

[Broadside]

+1 for balancing screw, I messed around with mine for a while to get it right. Do you know anyone with a torque wrench, though may well not be related this was the part (callipers to frame) I most worried about over or under tensioning.

Strange that both callipers have done this though!

No it's only the rear calliper, the front is fine. Or did you mean the original stock calliper and the replacement 105 unit?

 

[MattDB]

Yeah I meant the original stock and the new calliper doing exactly the same thing.

 

[boydj]

Sounds like the outer cable is still too long - the picture suggests that you could easily lose another 1cm off the outer. I'd loosen off the nut holding the brake on to see where it hangs naturally, what resistance there is to moving it and if the cable affects the movement.

 

[fossyant]

Got a cone spanner - you can slip one down next to the bridge and tweak the allignment. If not, I tend to push by hand my dual pivots to the correct position.

Make sure the callipers are well lubed - that might be your issue, no lube squirted on the pivots.

105's shouldn't do that. How old, how much wet use, and any lube squirted on the pivots, ever ?

 

[Broadside]

The bike is about 10 weeks old, the 105 calipers are a week old. They are silky smooth and not sticking but something somehow is causing the whole calliper to shift after 20-30 miles which then causes the non drive side brake to rub.

I think I'm going to try a different rear wheel on the bike to discount wheel flex or some other problem with the wheel being a factor.

 

[fossyant]

Not tight enough ! Simple

 

[Broadside]

Not tight enough ! Simple

It's done up about the same as a stem bolt so that would be about 5nm. I don't want to go over that because I don't know if the seat stay bridge is reinforced inside and could risk wrecking the frame.