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Cantilever brake will not return
#1
Ok, I've watched the video and I've even read the book (Zinn & The Art Of Mountain Bike Maintenance) but I still don't get it....

I had a puncture in my front tyre, so I took the wheel off and fixed it. Easy.
But for some reason the cantilever brake is now not functioning correctly..
I've checked the wheel alignment and that it is seated in the forks properly so it's not that. I've adjusted the brake lever to ensure that is ok....

The problem is that when I test the brake using the lever, I can see the brakes closing correctly onto the rim of the wheel but when I release the lever, only one side of the brake arm actually moves away from the rim thereby leaving the other in contact with the wheel rim.....

Could anyone shed some light on this for me please and tell me what I'm either doing wrong, or simply not done.... I'm really hoping that this will be an easy fix and I will have a 'Eureka' moment once it's explained but at the moment, I just don't get it.....
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#2
Hi duffmann,
Welcome to the forums! Just wanted to asked do you have the v looking cable ends on the correct swing arms?
Good maintenance to your Bike, can make it like the wheels are, true and smooth!
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#3
(05-02-2011, 02:27 PM)Bill Wrote:  Hi duffmann,
Welcome to the forums! Just wanted to asked do you have the v looking cable ends on the correct swing arms?

Bill,

I'm not sure... However, they are the original and came with the bike so it is not anything unusual. I've included a photo if it helps...?
Thanks,

duffman[attachment=2304]
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#4
Hi Duffman;

Cabling looks fine.

Usually there is a spring around each pivot that pushes each arm away from the rim. They usually have little adjustment screws to very the force on each arm individually. After making sure that both arms move freely with the cable disconnected, play with the return spring force. Typically; I start with by reducing the force on the arm that is moving freely, and then if I can't go far enough, but increasing the force on the one that is not returning.

Occasionally these springs break, your LBS will have replacements.
Nigel
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#5
(05-02-2011, 04:24 PM)nfmisso Wrote:  Hi Duffman;

Cabling looks fine.

Usually there is a spring around each pivot that pushes each arm away from the rim. They usually have little adjustment screws to very the force on each arm individually. After making sure that both arms move freely with the cable disconnected, play with the return spring force. Typically; I start with by reducing the force on the arm that is moving freely, and then if I can't go far enough, but increasing the force on the one that is not returning.

Occasionally these springs break, your LBS will have replacements.

Nigel,

Thanks for the info; the only issue I have with that is that there is only one little adjustment screw on one side of the arms - typically, the one that is returning correctly! Will adjusting this then affect the other too?
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#6
Possibly corrosion on the pivot.
Unhook the cable and try both sides by hand, should move freely and equally, if not, remove the stiff side completely by undoing the allen head screw and gently pulling off, observe the spring position as you do so. Clean up the pivot arm and bush with fine sand paper and reinstall with a little grease.
To adjust, slacken off adjusting screws both sides, then retighten until you have the desired movement, make sure you have tension on both screws or you may lose one.
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#7
Hi duffman. From the pic, it appears that your spring-housing is broken. It's the grey, plastic piece between the arm and the fork. Shimano had a problem on these brakes for a year or two back in the '90s.

And guess what... I have a few! Follow this http://forums.bicycletutor.com/thread-2845.html and look at the part 10 pictures down. Look like the one?
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#8
Further thoughts on this. This type of brake with the separate and fixed length of cable on the right in the pic, required a special tool, a plastic template, that held the arms in position while the left side cable, the run of wire from the brake lever, was locked into the pinch bolt.
Tricky to use and different templates were needed to suit different lengths of fixed cable and most users rapidly changed to a standard hook and bridge wire.
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#9
(05-04-2011, 05:14 PM)trevgbb Wrote:  Further thoughts on this. This type of brake with the separate and fixed length of cable on the right in the pic, required a special tool, a plastic template, that held the arms in position while the left side cable, the run of wire from the brake lever, was locked into the pinch bolt.
Tricky to use and different templates were needed to suit different lengths of fixed cable and most users rapidly changed to a standard hook and bridge wire.

Amazon has "Z-type" aka "Z link" links from several manufacturers in different lengths. If you use a little bit of care, they will last a very long time. Our tandem has them.
Nigel
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#10
Not to knock anyone elses ideas but... dudes... look at the pic of Duffs spring retainer on the right side in the pic that was posted! Compare it to the other side. See how it is WAY BIGGER? It is split! It is no longer keeping the return spring at proper tension. No amount of swapping pin holes can fix that. Sorry. Been there - done that - no T Shirt.

If I am wrong, it will not be the first time. But I would bet a dollar or a donut on it! That silver RockShox fork looks like a Quad and those are CT-60 brakes, I think. Maybe CT-40s. It was a long time ago but, I haven't completely lost it, yet. Have I? Smile

The tire looks like a Tioga Psycho K. Did I win??? Wink
Wheelies don't pop themselves. (from a QBP fortune cookie)
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#11
hey robAR,

sorry you never got a reply to your post verifying that you are right since you most definitely are!! so common with those altus's
-freedom on a bicycle
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#12
Thank you for your acknowledgment, Duffbaker! Wink I was doubting myself for 3 months! The tire is a Tioga Psycho. Isn't it? Huh? Please?

I got your PM and I do still have those. I'll reply soon.

Rob
Wheelies don't pop themselves. (from a QBP fortune cookie)
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