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]

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]

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]

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]

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]

https://www.parktool.com/assets/img/repairhelp/cantiT_002.jpg


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

[ultraman6970]

https://www.parktool.com/assets/img/repairhelp/cantiT_002.jpg



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.

https://www.parktool.com/assets/img/repairhelp/cantiT_012.jpg

[Hindmost]

Above are good suggestions for adjusting and balancing the canties. The rim still doesn't appear centered in the fork? Install the wheel flipped around and see where the rim sits. This should tell you whether you might have a wheel or fork issue.

[kbone]

Also adjusted the toe-in and straddle cable. Messed with the spring tensioners too. Lessened the shudder, but didn't resolve the core issue.

Took Hindmost's suggestion to flip the wheel again (image below). It looks more centered when flipped. Also provides more clearance on the quick release side of the cantis. What does this mean in terms of a "fork problem"?

[harlond]

Maybe it's the picture but the wheel appears to be closer to the non-drive side fork blade than to the drive-side blade.

[GScot]

Just to add to your variables, I had bad results with the brake pads on Tektro 720s with regard to shudder. Switched to Kool Stop thinline and after adjustment I was happy with brake performance. Put them on two bikes at the same time. One has never required more than maintenance, the other one can't decide which way to go on the front. After one ride the left pad will start dragging and after adjustment by the end of the next ride the right will be dragging. I've tried half adjusting but 20 to 30 miles and one pad will always be dragging. I'll probably solve the problem with some Pauls at some point.

[ultraman6970]

IMO the adjustments using the screws at the canti arms should be enough even if the fork has a problem.

If the wheel was checked at the LBS then i will say it is right at the middle spot, then the next one imo is that you have a problem in the drop outs, maybe one is longer than the other one?

If the bike doesnt pull anywhere while riding even no hands then the fork and the frame are straight, but that doesnt mean one of the drop outs is a mm off. Maybe paint is under one drop out and thats why the wheel is off center??

Seen chromed fork with this problem.

Remove the drop out and check if the axle fits flush in the drop out (both sides), if not then you found the problem.

[Hindmost]

...What does this mean in terms of a "fork problem"?...

From 3000 miles away, it sounds like your rim is slightly off center and you could have a "fork problem". Both could be very minor but somewhat irritating. As ultra mentioned a "fork problem" can mean something a little wonky in the way the axle engages the dropout.

The wheel flip test in general tells you: When the wheel is properly dished and the rim stays in the same location but off center--it's a fork problem; When the the fork is straight and the rim moves from side to side--the wheel dish is off.

[fogrider]

https://www.amazon.com/Tektro-Front-Cable-Hanger-Silver/dp/B006GHDS5A

I have given up on canti brakes! the shudder comes from the flex of the fork with the long exposed cable. the above hanger lessens the exposed cable, so less shudder.

for the same price of the hanger, I would (and did) go with mini Vs.
https://www.jensonusa.com/Tektro-926A-Mini-L-Pull-Brake-926A-Mini-L-Pull-Brake-Black?pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=CjwKCAiAyrXiBRAjEiwATI95mdxIaa1jnVC-1o9vPR7KKHz-UGuYS8mLUthOsPknulL2a4lj6Bb12RoCj74QAvD_BwE

[pdonk]

If the cantilever springs are different colors- one silver one gold they may have been inadvertently swapped. Try switching them to the other arm. May even out tension.

I know Paul's and old shimanos use this system to differentiate left from right.

[pinkshogun]

if the fork legs/wheel are straight, one of the drop outs could need a filing to get the rim centered between the legs

[Gummee]

IME if toe in doesn't fix it, try toe out. IOW the back of the pad hits 1st.

There have been a few 'problem children' over the years that had that problem.

...but... I'd say 'mini-V' before those cantis all day, every day. The mini-V removes some/most of the flex from the system so reduces chatter. Mini-Vs also actually stop you. Bout the only down side to v-brakes is mud clearance.

M

[thwart]

https://www.amazon.com/Tektro-Front-Cable-Hanger-Silver/dp/B006GHDS5A

I have given up on canti brakes! the shudder comes from the flex of the fork with the long exposed cable. the above hanger lessens the exposed cable, so less shudder.

Good point. On this bike, you are lucky enough to have a front brake hole to mount this, and it will help.

The V-brake vs canti brake debate rages on... ;)

[notsew]

https://www.amazon.com/Tektro-Front-Cable-Hanger-Silver/dp/B006GHDS5A

I have given up on canti brakes! the shudder comes from the flex of the fork with the long exposed cable. the above hanger lessens the exposed cable, so less shudder.

for the same price of the hanger, I would (and did) go with mini Vs.
https://www.jensonusa.com/Tektro-926A-Mini-L-Pull-Brake-926A-Mini-L-Pull-Brake-Black?pt_source=googleads&pt_medium=cpc&pt_campaign=shopping_us&pt_keyword=&gclid=CjwKCAiAyrXiBRAjEiwATI95mdxIaa1jnVC-1o9vPR7KKHz-UGuYS8mLUthOsPknulL2a4lj6Bb12RoCj74QAvD_BwE

Agree, your underlying problems is that the brakes are canti-"they work great when you set them up correctly"-lever. Mini-Vs 4 life

[jc031699]

One of your pads (right) is installed at a substantial angle to the brake arm which is holding it, compared to the left one. It’s visible from the front view pics. This is in the direction perpendicular to what you would set for toe in. That seems to be the main difference between the two sides.

If it’s tight either way you can get more clearance by using v brake shoes with thinline pads. Some CR720’s were sold with those so it works.

Also, as others said squealing should be adjusted with toe in.

If you are getting shuddering on the front, you may need a fork mounted cable hanger instead of stem or steerer mounted. Tektro has those.


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