daniell

For decades I have not been able to balance the brakes. This is my third set of brakes. I have tried everything that I can think of. The cable does not pull in a straight line. Why, I don't know. Perhaps the frame is out of alignment.

JohnDThompson 

What do you mean by "balancing" the brakes? Is one pad closer to the rim than the other? Sheldon Brown offers some advice:

https://www.sheldonbrown.com/canti-trad.html

ClydeClydeson

Make sure the axle is fully seated in the dropouts. It looks like the tire is not centred in the fork, and this makes it almost impossible to adjust brakes properly. Also, next time you take your wheel out and put it back in, the brakes will be out of adjustment again. If the axle is fully seated in the dropouts then you can replicate the position perfectly every time.

One other thing to look out for is the conical springs on your quick release skewer - if one of the springs is on backwards it will jam between the fork's dropout and the axle and throw everything out of whack. The larger end of those springs must be pointed away from the centre of the bike on both sides of the axle..

mack_turtle

one or both of the sides of that brake should have a small screw with a philips head to adjust spring tension. on a lot of those older Shimano canti brakes, the spring is housed in a plastic sleeve and those sleeves get brittle and crack with time. if your plastic bit is cracked, you'll need to replace the springs, if you can find them. a whole new brake set should be cheap and easy to source though.

daniell

Believe me, I tried to improve matter by turning the screw. The spring is not broken. This is my third set of brakes with this problem. The rear wheel has the same problem.

Bill Kapaun

Turn the bars more and it'll look like the tire is touching the fork.
You just can't tell unless it's a straight, head on shot.

andrewclaus

The brake shoe shown isn't installed correctly--the post should be perpendicular to the rim. The other side may not be symmetrical, and doesn't appear to be from what little shows in the photo. In fact, it looks like the left caliper is at a different angle to the wheel. I'd remove the brake shoes, get the calipers centered by adjusting spring tension as mentioned, then reinstall the shoes correctly and symmetrically.

The yoke angle looks a little high. See Sheldon Brown's article on cantilever geometry. A few millimeters makes a difference.

daniell

Another View

dsbrantjr

Ditch that hard-to-impossible to adjust link wire arrangement and use a straddle cable and cable carrier instead; I like the Problem Solvers Wide Cable Carrier but they seem to be getting hard to find. You balance the brakes by moving the straddle cable. You will need to have something to catch the straddle cable if the main brake cable comes loose, to avoid it catching in the tire, but that could be something like a reflector bracket or zip tie.
Extra points for installing a fork crown-mounted cable stop to get rid of the root cause of brake shudder.

cyccommute 

Yup. The Link Wire was another Shimano misstep. Why do we keep thinking that they are a great company?

I prefer Paul Cantilevers and Moon Units but most people balk at the cost. Too bad, they are excellent brakes. But ditching the link wire will go a long way toward easier adjustment.

daniell

I was thinking of changing the cable but had one concern. If the main cable breaks, the wheel could lock up.

mack_turtle

Part of your problem might be that the cable is not installed on the link wire correctly.

if several brakes do the same thing, the common denominator is: the mechanic. Look up BASIC instructions about how to adjust older canti brakes like that.
Is the housing on the right side of the brake (your right, while sitting on the bike) the EXACT same length as the fixed-lwngth end of the link wire?

daniell

On my wife's bike I have no such problem. Also, I tried different positions in the yolk.

dsbrantjr

Read my post: "You will need to have something to catch the straddle cable if the main brake cable comes loose, to avoid it catching in the tire, but that could be something like a reflector bracket or zip tie." Problem solved.
The link wire was a solution to a minor problem (straddle wire catching) which introduced other problems (crappy adjustability).

mack_turtle

There are 100 reasons why the brake is off. I can see from your photo that the link wire is not attached correctly. I would start there.
your dropouts could be misaligned, the brake posts could be bent, wheel not centered in the dropouts, the axle is bent, the frame/fork out of alignment, etc. It sounds like this is beyond your powers and you need to spend a lot of time inspecting it or take it to a professional.

​​​​​​I've worked on HUNDREDS of older bikes with those exact same brakes and on almost every single one, the plastic sleeve that holds the spring in place was damaged from old age.

Ross200

The link wires come in several different lengths. The right length and the proper color coded Shimano setup tool generally gets you close in a short time unless there are problems not related to the brake itself.

cyccommute 

I’ve used cantilever brakes with straddle cables since I bought a Miyata touring bike in 1983. I’ve used them on mountain bikes since I started doing that in 1984. I’ve even had them on shocks. I have had at least one cantilever bike in my stable since then and often many more...I currently have 3 of them. I’ve ridden thousands, no, tens of thousands of miles on with cantilever brakes and I’ve never had the main cable break. I haven’t heard of a single person ever having one fail. I’m sure someone will come along with a tale of woe but it’s a very rare occurrence. If you are worried about it, you can mount a reflector on the fork that will catch the staddle cable if it ever does fail.

dabac

Well, for starters, your left brake pad shows a lot more exposed post than the right one.

daniell

Please explain how I would use a zip tie.
Thanks

dabac

While aestethically annoying, as long as both pads clear the rim when the brake isn’t engaged, this is not a functional problem.
Pinch force will be automatically distributed evenly between sides when the brakes are engaged anyhow.
The return springs are fairly weak. I generally unhook cable, lube brake bosses etc generously and make sure both arms are moving freely before trying anything else.
Unless there is something blindingly obvious going on.

Geepig

I have used a super short fender/mudguard as a cable catcher.

dsbrantjr

I loop a zip tie around my fork-mounted cable hanger and make it long enough for the brakes to function properly but short enough to keep the cable from fouling the tire. You could use a loop of string of appropriate length going around a stem- or headset-mounted hanger and the cable.

daniell

I must admit that I never had a problem stopping.

daniell

I just measured the alignment of the frame. I put a string around the head tube and attached to the dropouts. There was about 3/4 cm of difference between the sides. Is this significant? Can this be affecting my inability to balance the brakes?

dabac

If the frame isn’t symmetrical, it’ll be impossible to set the brakes symmetrically as well.
But you should still be able to set the brakes where you want them: