Merzperson

I've got some Shimano BR550 cantis on my Bruce Gordon BLT. The front brake has been nearly impossible to properly adjust since I bought the bike last year.

I can either have the brake pads at the proper position OR have the lever nice and tight, but not both at the same time. When the brake pads are in their proper position, the lever and brake cable are very loose and wiggle around freely, and I really have to jam the lever until it hits the handlebars to brake. When I tighten up the barrel adjuster to get rid of the extra slack in the cable, the brake pads are tightly gripping the rim.

The rear brake works fine. I have tried cutting some of the cable housing, tried adjusting the spring tension in the brakes, etc. but nothing seems to work. I'm beginning to think that the springs in the brakes aren't pushing out far enough; the springs stop pushing out when the pads are only 1cm or less from the rim. In the back the springs push out about twice a far as in the front brakes.

Another thing to note is that I took the bike in to a very respectable local shop for a complete overhaul after I rode the thing across the country over the summer, and they did a great job of fixing it up but the brake problem was still there when they were done.

Anybody know what I can do to fix this problem?

[EDIT] I just took apart the front brakes and noticed three little holes on the braze-ons with a little pin on the brake calipers that determines the 'effectiveness' of the springs. I tried moving the pin up one hole, but now it seems the springs are almost too tight and I'm afraid after a while the springs will snap if I leave the brake in this configuration. However, this is the most usable position so far for the brakes.

FBinNY 

Is there not a barrel cable adjuster somewhere in the system?

Merzperson

There originally was not, but I added one yesterday and it doesn't help. If I have the brakes dialed in just right (with the loose cable, like I said earlier) and I tighten the barrel adjuster to take up the slack it just tightens the brake pads down so they scrape the rim.

FBinNY 

How's the wheel alignment? Also if you disconnect the cable, do the brakes open up very wide, or is there something restricting their motion?

Is it possible the shoes are touching the inside of the fork blades?

LarDasse74

Please post some pictures of the brake, lever, and cable between them.

Some problems that might cause this: Straddle cable too low (causes mushy feeling and extra cable travel to move brakes); damaged cable housing; too short cable housing; non-standard brake levers (Standard brake levers should be able to work, V brake levers would give you the opposite problem - lots of brake movement but very little power); bad pad placement or alignment.

Merzperson

The wheel is aligned perfectly. When I disconnect the cable, before I switched the pegs the brakes opened up all the way but the springs only opened them very slightly. After I switched the pegs (described in first post edit) they open all the way with springs pushing out almost all the way until they hit the forks. In other words, nothing restricting their motion.

LarDasse74

THe springs in your brakes are capable of holding a lot of tension for a long long time and can safely use any of the three holes in the brake bosses without problem.

FBinNY 

Something is restricting their motion. It shouldn't take the maximum spring tension for them to open properly. It's probably a simple problem, but there are too many variables to cover without seeing them. Try visiting a decent shop (not the guys who say it's OK) and see what they say.

One possibility is that the bushing or post are a bit short and the brake is binding under the pressure of the mounting bolt. That's easy to check by simply loosening the two mounting bolts and seeing if they move freely.

Merzperson

Good to know, I'll use this configuration in that case. I just thought it was weird the bike shop didn't do this, but I guess they just overlooked the problem.

There is nothing restring their motion. I can physically open them with my fingers. It's just that the springs aren't opening them.

If anything the brakes have a tiny bit of wiggle room on the mounting post.

I can still post photos (just took some) if you'd be interested to see the situation.

Thank you both for your help!

bikeman715

Yes let see some photos. Have you try replacing the housing, it could have dirt in it or as said before cut to short. as far the springs go leave them in the postion it wouldn't hurt anything.

Merzperson

These pictures don't illustrate the problem (not sure how I could) but you can see if you notice anything wrong just at a glance.

AEO

I would lose the V shaped noodle the cable goes through.
It's not necessary to use that on your setup and can cause the cable to bind.

Merzperson

This is the only way I know of to have a barrel adjuster on the cable. Also, without it I'm pretty sure the housing will be too short. I'll look and see.

HillRider

Set the tension springs in the hole in the brake boss that's farthest around so as to provide the highest available spring preload. Then back off the spring tension adjusting bolts on each brake arms all the way. That will give you the highest potential spring tension but will move the close to the rims with very little spring force at that point.

Then begin to screw in the tension bolts a bit at a time to get the arms to move evenly far enough away from the rims to give the proper clearance and sufficient spring tension to retract when you let go of the brake lever.

I have these brakes on my Surly Cross Check and set them up exactly as described and they work very well.

Merzperson

Thank you HillRider, that is exactly what I have done and it seems like it will work just fine.

However, now I notice another (less important) thing. When I have everything adjusted correctly, both pads an even distance from the rim, I will pull the brake lever and one pad will move to the rim and the other will stay put until the first hits the rim. It doesn't seem to make a very big difference in a practical situation, but I wouldn't want to be on a big tour and find out it's wearing one pad and not the other. Any ideas?

HillRider

Play around with the spring tension bolts on both arms. Tighten the one that moves too soon and loosen the sluggish one a little at a time. You should be able to achieve a balanced tension that lets the arms contract and retract in unison.

operator

That tells you that the boss probably needs to be faced, and is probably why you needed to increase the spring tension on the arms itself. Do this test.

1) Disconnect the cable so it doesn't interfere with the arms moving
2) manually push the arms towards the rim - they should both spring back equally with a moderate amount of force
3) If either of them does not, undo the bolt that holds the arm until it does

If 3) is sucessful then you got a problem with the bosses.

Also, both of those brakes only need to have the spring set in the middle position. Needing more spring tension that that usually indicates a problem, either cable and housing or that something is binding.

Merzperson

HillRider, that did the trick, thanks again.

I've never had to deal with cantilever brakes before this bike, so I thank all you guys for teaching me what you have, I appreciate it.

[EDIT] Operator - didn't see your post before reply, I think my bosses are fine though. The tension just needed to be balanced between the arms like HillRider said.

TimeTravel_0

from the picture:

looks like your quick-release is open on the brake levers
looks like the link-wire is resting on the fender / is too low / not a 90* angle
ditch the noodle -- less bends, the better.
and the housed cable coming from the link-wire should be flush with the cable anchor bolt.
are the convex/concave washers symmetrical?

if you cant get this figured out, find a bike shop in portland that regularly deals with cross and touring bikes. they should be familiar with the BR550s and cantis in general.

HillRider

looks like your quick-release is open on the brake levers
How can you tell from that picture? Even so, that wouldn't make the lever come too close to the bars, it would just increase the reach to the lever.

looks like the link-wire is resting on the fender / is too low / not a 90* angle
The length of the link wire with these brakes is fixed by Shimano.

ditch the noodle -- less bends, the better.
Agree with the noodle being unneeded but it currently contains the only adjusting barrel. A cable hanger with a built-in adjuster would be better.

and the housed cable coming from the link-wire should be flush with the cable anchor bolt.
Right, that sets the symmetry of the link wire.

are the convex/concave washers symmetrical?
Yes, they are.

TimeTravel_0

How can you tell from that picture? Even so, that wouldn't make the lever come too close to the bars, it would just increase the reach to the lever.

the brake lever looks open to me (notice the angle of the lever relative to the hood -- I have the same levers and thats what they look like when the quick release is open)...if my eyes are not deceiving me, this would create slack in the system. I could be wrong though about it being open...

The length of the link wire with these brakes is fixed by Shimano.

the link wire needs to come up just slightly, I think, to get off the fender and create a 90* angle. this has nothing to do with the length of the link wire itself.

HillRider

Actually if the cable tension and pad clearance were set with the lever qr open, it would increase the lever's available travel and allow more pad clearance without the lever hitting the bars. What you would lose is the qr function.

From the picture, I can't tell if the link is actually sitting on the fender or just above it. On my Cross Check with these same brakes and Planet Bike fenders, I had to file the front fender's hanger bracket to lower the fenders enough to clear the link wire. Actually, as the brake is applied, the link wire will approach a 90° angle which is ideal for this type of brake so it will get better, not worse.

As an aside, Shimano does provide two link wires with these brakes and the "F" wire is a bit longer for use on wide rims and/or widely spaced fork legs. Using the F-link would give the OP more fender clearance and a colser approach to the 90° wire orientation if he wishes.

TimeTravel_0

just looks like if he made the cable flush with the anchor bolt it would be raised.

I thought the different link-wires for front and rear..?

HillRider

Not according to Shimano's installation sheet. The brakes come in boxes marked "front" and "rear" but both show the "E" (shorter) link wire installed.

In fact the instruction sheet doesn't even mention the longer "F" wire at all and the only way to tell what it's for is to hold it up the the E-wire and compare lengths. I used the E-wire for both brakes and set up and adjustment were pretty straight-forward.

fietsbob

Revert back to a cable hanger and transverse cable , which would let You
make the length of the cross-over cable an adjustment, rather than a parts purchase.

That one looks too short..
You probably don't need the noodle on the housing stop,
under the headset nut, since there is a tall stem on there..

I believe there are multiple lengths of those Shimano link wire scheme [QBP probably stocks them all]

Wider spacing of brake bosses appears to over stretch the out of the box ones .

All else fails Ask Bruce..