CX cantlever problem, need help!
10-17-13, 08:30 AM
#1
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CX cantlever problem, need help!
Hello
I have got some issues wth my brakes. I got the bike used as a first cross, maybe a bit too used but done is done.
I posted with pictures for easier explanation. I'm getting new brakes soon but need to get these old ones usable again so that I don't have to walk anywhere before new brakes arrive.
I'm all new to the bike world, but have a technical side.
Problem is brake in front pulls unevenly. Maybe because the shop set the wires up too tight, the alu thingy wont stay centered(pulls to one side), and as a result the brakes pull unevenly.
Please assist!
I have got some issues wth my brakes. I got the bike used as a first cross, maybe a bit too used but done is done.
I posted with pictures for easier explanation. I'm getting new brakes soon but need to get these old ones usable again so that I don't have to walk anywhere before new brakes arrive.
I'm all new to the bike world, but have a technical side.
Problem is brake in front pulls unevenly. Maybe because the shop set the wires up too tight, the alu thingy wont stay centered(pulls to one side), and as a result the brakes pull unevenly.
Please assist!
10-17-13, 09:05 AM
#2
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The too short cable casing has little to do with whether the canti arms move symmetrically (i think that's what you're asking about). As long as the inner cable exits the casing stop/hanger pretty well centered above the canti arms there won't be much pulling one arm more then the other. The fairly long distance between the hanger stop and the straddle cable yoke/clip further lessens any side forces acting on the arms.
More likely a cause of uneven arm movement are the spring tensions or friction within each arm's pivots. You could test this to a degree by attaching a cable to the straddle cable clip/yoke and simply pulling up and watching the arms' movements. Then move the pulling cable to one side or the other side and repeat. At some point you'll induce enough side force to have the arms move symmetrically. BY this point I would expect that the pulling up cable will be a bunch off center up by where it would otherwise be exiting the stop/hanger.
Most cantis have some form of spring tension adjustment. Many canti bosses have three spring holes for a coarse change of tension and many arms have one side with a fine tension device. Playing with these options can get very even tensions and arm movement.
Of course you want to first make sure the bosses and arm pivots are clean and well lubed. The boss bolts should not cause binding as you tighten them. I like to have the pads positioned evenly on each side, so the shaft length and angles are symmetrical. But in some cases (like when wheels are off center) I'll set one pad shaft further out of closer in to compensate.
If I were running this set up for very long I'd add housing length, maybe run the housing up over the stem to see if this is a smoother and less friction route, move the pads further out on the arms to spread the arms a bit, lengthen the straddle cable (these two points to get max leverage). Andy.
More likely a cause of uneven arm movement are the spring tensions or friction within each arm's pivots. You could test this to a degree by attaching a cable to the straddle cable clip/yoke and simply pulling up and watching the arms' movements. Then move the pulling cable to one side or the other side and repeat. At some point you'll induce enough side force to have the arms move symmetrically. BY this point I would expect that the pulling up cable will be a bunch off center up by where it would otherwise be exiting the stop/hanger.
Most cantis have some form of spring tension adjustment. Many canti bosses have three spring holes for a coarse change of tension and many arms have one side with a fine tension device. Playing with these options can get very even tensions and arm movement.
Of course you want to first make sure the bosses and arm pivots are clean and well lubed. The boss bolts should not cause binding as you tighten them. I like to have the pads positioned evenly on each side, so the shaft length and angles are symmetrical. But in some cases (like when wheels are off center) I'll set one pad shaft further out of closer in to compensate.
If I were running this set up for very long I'd add housing length, maybe run the housing up over the stem to see if this is a smoother and less friction route, move the pads further out on the arms to spread the arms a bit, lengthen the straddle cable (these two points to get max leverage). Andy.
10-17-13, 09:21 AM
#3
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The return springs have some adjustment relative to each other, (as said above)
the center stirrup can be off center to compensate for a return spring imbalance..
the brake-pad posts can also be physically off symmetry to function at the same time.
and though one shoe may precede the other in making contact with the rim,
they will still function as the balance cable pulls the second shoe in..
You have the service manual for your brakes, ?the Bike-shop may save them , they come in the box ,
but often are not put in the display tag on the sales floor.
the center stirrup can be off center to compensate for a return spring imbalance..
the brake-pad posts can also be physically off symmetry to function at the same time.
and though one shoe may precede the other in making contact with the rim,
they will still function as the balance cable pulls the second shoe in..
You have the service manual for your brakes, ?the Bike-shop may save them , they come in the box ,
but often are not put in the display tag on the sales floor.
Last edited by fietsbob; 10-17-13 at 09:26 AM.
10-17-13, 09:28 AM
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As Andrew said, the short housing isn't an issue. The wire is coming from the top and the brake is unaffected by what happens above.
The balancing springs affect how the brakes open, but have little impact on how they close. In any case, it doesn't matter how brakes close since all canti brakes are self-centering in operation. The moment one arm touches the rim and stops moving, all movement goes to the other, and after they squeeze the rim between them.
Adjust the brakes so they open nicely using the balancing screws, then when you have time, lengthen the housing a bit for a better run to the hanger. Or consider a fork crown mounted hanger, so you don't have the sharp bend at the hanger.
The balancing springs affect how the brakes open, but have little impact on how they close. In any case, it doesn't matter how brakes close since all canti brakes are self-centering in operation. The moment one arm touches the rim and stops moving, all movement goes to the other, and after they squeeze the rim between them.
Adjust the brakes so they open nicely using the balancing screws, then when you have time, lengthen the housing a bit for a better run to the hanger. Or consider a fork crown mounted hanger, so you don't have the sharp bend at the hanger.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
10-17-13, 10:28 AM
#5
Banned
And there are larger drop hangers to replace what is there..*
some mechanics set up the brakes to run the housing over the stem,
and meet the cable hanger from the other side to make a bigger smooth loop..
* sample : https://www.bikeman.com/Front_Cable_Hangers.html..
some mechanics set up the brakes to run the housing over the stem,
and meet the cable hanger from the other side to make a bigger smooth loop..
* sample : https://www.bikeman.com/Front_Cable_Hangers.html..
10-21-13, 10:38 AM
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Thanks everyone for so detailed answers. Have been able to set the brakes up better with your help, although I will be experimenting with different ideas more, the more I learn how the brakes work ..
Cheers all!
Cheers all!
