What's Wrong With These Cantis

[kbone]

I wanted to try some new cantis as my Mr. Grumpys squeal. I picked up some Forte cantis from a local Performance - 70% off because they are closing - which I believe are the Tektro CR720s.

Anyway, when I first started to install them, it seemed like the quick release side was closer to the rim. I figured the new to me wheels needed to be dished to center the wheel in the fork. Took it in to a reputable LBS and paid them to dish the wheel. Brought it home and started installing the brakes again.

The quick release side still seems closer to the rim. Further, there isn't much clearance for the pad which touches the fork. The other side has much more clearance.

I am wondering if the canti boss is bent or the fork is bent or the rims are too wide or if I am expecting to exacting tolerances.

I set it up, got it adjusted well enough, and took it for a test ride. When I brake hard there is a significant fork shudder. The pads are fairly short and cannot be cut down. The headset is tight. Do I not have enough toe-in?

Sorry for the long post. Thanks in advance for any help.

[quickfeet]

Isn’t there a spring adjustment screw on those brakes? That used to be how to center the cr720. Also don’t clamp down on the straddle cable carrier before you make those adjustments. If you do, it doesn’t matter what adjustments to the brake you make because the cable is locked in one position.

[Ken Robb]

Can you center them using adjustable spring tension?

[jtbadge]

Originally Posted by quickfeet

Isn’t there a spring adjustment screw on those brakes? That used to be how to center the cr720. Also don’t clamp down on the straddle cable carrier before you make those adjustments. If you do, it doesn’t matter what adjustments to the brake you make because the cable is locked in one position.

+1 to this.

Also:
-Not enough toe, no. Pads look parallel to the rims in that pic, or almost toed backwards.
-I tend to set up the stradle hanger lower (closer to the tire), but that's probably fine the way you have it.

[Mark McM]

Like the others said, you should try adjusting the spring tensions. The Forte cantilever brakes have a spring adjuster screw on each arm (the screws sticking out of the bottom in the middle of each arm).

Also, some cantilever bosses have multiple spring retaining holes. You might want to make sure that the springs are inserted into the same holes on each side.

Finally, make sure that there is the straddle cable is the same length on each side.

[harlond]

I can't be any help, but coincidentally, my thread "frame alignment question" addresses canti bosses that were not installed in parallel. Funny there should be two such threads on the same day.

[kbone]

I will try more toe-in. I used the rubber band method to get the toe-in set. I will switch to the zip-tie method. That said, there isn't much room in there to add toe-in without hitting the fork on the quick release side.

I am aware of the spring tensioners to center the pads - they are balanced in that regard.

The issue seems to be less clearance for the pad between fork and the rim on the quick release side. As I said, I had the rim dished. I've reversed the wheel and it is the same (rules out dishing at this point). It's almost as if the canti boss has been toed-in changing the positioning of it (pushing it back between the fork and the rim). Is there any way to measure trueness of the fork and bosses?

[harlond]

Originally Posted by kbone

I will try more toe-in. I used the rubber band method to get the toe-in set. I will switch to the zip-tie method. That said, there isn't much room in there to add toe-in without hitting the fork on the quick release side.

I am aware of the spring tensioners to center the pads - they are balanced in that regard.

The issue seems to be less clearance for the pad between fork and the rim on the quick release side. As I said, I had the rim dished. I've reversed the wheel and it is the same (rules out dishing at this point). It's almost as if the canti boss has been toed-in changing the positioning of it (pushing it back between the fork and the rim). Is there any way to measure trueness of the fork and bosses?

With the brakes off on my frame, I can see with the naked eye that the non-drive-side canti boss is misaligned. Again, not sure that's at all helpful, but offered FWIW.

[bart998]

Try sliding the cable pulley (triangle unit) across the transverse cable toward the side with more space... helps even out the tension. Just 1 or 2mm will usually do it.

[quickfeet]

Originally Posted by kbone

I am aware of the spring tensioners to center the pads - they are balanced in that regard.

Balanced doesn’t matter on those brakes you need to adjust the spring tension to straighten the brakes. They tolerances of those spring will never be equal out of the factory so those screws aren’t simply a “match them on both sides” situation. If the left pad is too close to the rim, you tighten that screw to add tension and pull it away from the rim. Do this while the straddle cable carrier is not clamped to the cable. Once everything pulls equally, tighten the straddle carrier back up.

[choke]

^^ This. You need to adjust the tension so that both pads hit the rim at the same time.

[thwart]

Originally Posted by bart998

Try sliding the cable pulley (triangle unit) across the transverse cable toward the side with more space... helps even out the tension. Just 1 or 2mm will usually do it.

This.

I'd agree with the folks who said the pads need to be toed in a bit as well. I use a piece of cardboard wedged between the pad and rim at the leading edge of the pads when I tighten them down, while the brakes are firmly applied. Easy to do on the front brakes, a little tougher on the rear because of the reach to the brake lever.

[ultraman6970]

When you put the cantis springs, there is like a hole in the fork, usually they have 3 (never seen more than 4 anyways) holes where the back spring sits, just move that to another hole till you get the brake correctly. That's the function of those holes, adjust the tension in the spring, that will fix your problem.

People and even with some some bike manufacturers they tend to put the spring in the middle hole in both sides just because of convenience not that they are adjusting the bikes to the millimeter.

JUst adjust the springs in different holes till you get it right.

Hope this helps.

[ultraman6970]

THen you have this screws that I forgot to mention before...

[ultraman6970]

THen you have this screws that I forgot to mention before... sometimes you have to use both ways to get them right. Thing I have done before.