Cantilever upgrade

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iandusud
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Re: Cantilever upgrade

Post by iandusud »

rogerzilla wrote: 21 Sep 2022, 9:42pm
The problem with V-brakes and drop bar levers is well known. There are special levers with more cable pull, but they are not great.
I'm using Tiagra 4700 levers on one of our tandems with a full length linear pull brake on the front and it works very well (believe me I wouldn't use this set if it didn't work well as we tour well loaded and tackle some very steep descents notably in the Yorkshire Dales).

On our other "hack" tandem we have full length linear pull brakes coupled to Tektro RL520 levers, which are specifically designed for linear pull brakes, and again these work very well.
mattheus
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Location: Western Europe

Re: Cantilever upgrade

Post by mattheus »

<lurker post - I want to try a really good front canti on one of my bikes before I make final "new bike" decisions ... Carry on folks ... >
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531colin
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Re: Cantilever upgrade

Post by 531colin »

iandusud wrote: 22 Sep 2022, 9:31am
rogerzilla wrote: 21 Sep 2022, 9:42pm
The problem with V-brakes and drop bar levers is well known. There are special levers with more cable pull, but they are not great.
I'm using Tiagra 4700 levers on one of our tandems with a full length linear pull brake on the front and it works very well (believe me I wouldn't use this set if it didn't work well as we tour well loaded and tackle some very steep descents notably in the Yorkshire Dales).

On our other "hack" tandem we have full length linear pull brakes coupled to Tektro RL520 levers, which are specifically designed for linear pull brakes, and again these work very well.

If you can use full-size Vee brakes, this is the best way forward.
Two things govern whether or not your existing lever(s) will work full size vees.......the obvious one is how much cable the lever pulls, and I think the current (NSSLR?) levers pull more cable than the old ones. The less obvious one is the exact placement of the bosses on the frame/forks. If the pad is at the bottom of the slot, the brake will have a greater mechanical advantage and require more cable pull than if the pad is at the top of the slot. The slot is a significant proportion of the length of the arm (a sixth? an eighth?) so the effect is noticeable. Choose a brake with big chunky stiff arms.....skinny weedy arms flex and give brake squeal and "lost motion".

Mini vees are a lot less faff than cantis, in the general run of events.
For mini vees, Tektro RX 6 are good and not silly money....again, stiff brake arms ("U" section, as I recall) so you don't get too much flexing and lost motion. Use a noodle with an adjuster so you can back the adjuster off and get the wheel out https://spacycles.co.uk/m7b0s101p3530/S ... h-Adjuster

Cantilevers with horizontal arms have a fixed mechanical advantage, this being the ratio of the distance from the pivot to the straddle wire attachment and the distance from the pivot to the brake pad.....so again, the precise height of the canti. studs governs the mechanical advantage of the brake on any particular bike.

"low profile" cantis with the arms almost vertical can be set up to give a good mechanical advantage, but the snag is they are "regressive" in action. ....you pull the lever, the straddle wire goes up and as the straddle wire goes up the mechanical advantage drops like a stone.....so you get a high mechanical advantage (MA) as the pad approaches the rim, and a low MA when the pad is in contact with the rim.....and what you want is the exact opposite.....the pads to move quickly (low MA) approaching the rim, and a high MA for the actual braking. Low profile cantis work much worse as the pads wear, specially if you take up the wear by adjusting the main cable. ....because that raises the straddle cable

The best canti. compromise is a mid profile brake. CX 70 were good and after-market pads fitted. My recollection is it requires a bit of fettling to get aftermarket pads to fit CX 50.
How to set them up is here viewtopic.php?t=57410
Philip_Rogers
Posts: 51
Joined: 22 Sep 2007, 9:17pm

Re: Cantilever upgrade

Post by Philip_Rogers »

Norman H wrote: 22 Sep 2022, 8:04am What brake levers are you using?

What cable hanger are you using on the front brake ?

When I fitted Shimano STIs to one of my my bikes the performance of the CR720 brakes was sub optimal when braking from the hoods. The new levers were Dura Ace 9 X 3 and the previous levers were Tektro BL 340. The performance was markedly improved when I fitted a fork crown mounted up-hanger in place of the previous head set hanger. Head set hangers can introduce a lot of cable friction if the outer cable is bent sharply where it emerges from the bar tape. The extra friction will rob you of a lot mechanical advantage. An up-hanger allows for a much better cable route.

Cantilever brakes are much more susceptible to cable friction than linear pull brakes because of the greater cable tension required.

Edit to add: I should just say that the drop in performance when braking from the hoods with the Dura Ace levers was due entirely to the ergonomics of the levers.
Thanks Norman.

I have Ultegra 9-speed STI 'washing line- levers. The front hanger is at the top of the headset, set in above the first 10mm spacer. The rear hanger is in the frame tig welded between the two seat stays.
Philip_Rogers
Posts: 51
Joined: 22 Sep 2007, 9:17pm

Re: Cantilever upgrade

Post by Philip_Rogers »

531colin wrote: 22 Sep 2022, 10:38am
iandusud wrote: 22 Sep 2022, 9:31am
rogerzilla wrote: 21 Sep 2022, 9:42pm
The problem with V-brakes and drop bar levers is well known. There are special levers with more cable pull, but they are not great.
I'm using Tiagra 4700 levers on one of our tandems with a full length linear pull brake on the front and it works very well (believe me I wouldn't use this set if it didn't work well as we tour well loaded and tackle some very steep descents notably in the Yorkshire Dales).

On our other "hack" tandem we have full length linear pull brakes coupled to Tektro RL520 levers, which are specifically designed for linear pull brakes, and again these work very well.

If you can use full-size Vee brakes, this is the best way forward.
Two things govern whether or not your existing lever(s) will work full size vees.......the obvious one is how much cable the lever pulls, and I think the current (NSSLR?) levers pull more cable than the old ones. The less obvious one is the exact placement of the bosses on the frame/forks. If the pad is at the bottom of the slot, the brake will have a greater mechanical advantage and require more cable pull than if the pad is at the top of the slot. The slot is a significant proportion of the length of the arm (a sixth? an eighth?) so the effect is noticeable. Choose a brake with big chunky stiff arms.....skinny weedy arms flex and give brake squeal and "lost motion".

Mini vees are a lot less faff than cantis, in the general run of events.
For mini vees, Tektro RX 6 are good and not silly money....again, stiff brake arms ("U" section, as I recall) so you don't get too much flexing and lost motion. Use a noodle with an adjuster so you can back the adjuster off and get the wheel out https://spacycles.co.uk/m7b0s101p3530/S ... h-Adjuster

Cantilevers with horizontal arms have a fixed mechanical advantage, this being the ratio of the distance from the pivot to the straddle wire attachment and the distance from the pivot to the brake pad.....so again, the precise height of the canti. studs governs the mechanical advantage of the brake on any particular bike.

"low profile" cantis with the arms almost vertical can be set up to give a good mechanical advantage, but the snag is they are "regressive" in action. ....you pull the lever, the straddle wire goes up and as the straddle wire goes up the mechanical advantage drops like a stone.....so you get a high mechanical advantage (MA) as the pad approaches the rim, and a low MA when the pad is in contact with the rim.....and what you want is the exact opposite.....the pads to move quickly (low MA) approaching the rim, and a high MA for the actual braking. Low profile cantis work much worse as the pads wear, specially if you take up the wear by adjusting the main cable. ....because that raises the straddle cable

The best canti. compromise is a mid profile brake. CX 70 were good and after-market pads fitted. My recollection is it requires a bit of fettling to get aftermarket pads to fit CX 50.
How to set them up is here viewtopic.php?t=57410
Thanks Colin. There's a lot to look into here. I'll have a look at the pad position in the slot first as that may be a quick win if I can set them a bit lower. Does anyone have a better suggestion than KoolStop Dual compound pads? Someone mentioned SwissStop green to me but they look to be discontinued for the fitting CR720s take.
deejayen
Posts: 48
Joined: 1 Apr 2011, 1:56pm

Re: Cantilever upgrade

Post by deejayen »

I've used SwissStop Green pads for years, and they're absolutely brilliant.

I think the current SwissStop offering for aluminium rims is the BXP model.

I'm just about to try Koolstop Salmon on one of my bikes.
Philip_Rogers
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Joined: 22 Sep 2007, 9:17pm

Re: Cantilever upgrade

Post by Philip_Rogers »

deejayen wrote: 22 Sep 2022, 12:25pm I've used SwissStop Green pads for years, and they're absolutely brilliant.

I think the current SwissStop offering for aluminium rims is the BXP model.

***Thanks, unfortunately SwissStop don't appear to do these in the CR720 fitting (v-brake)
www.swissstop.com/brakepads/rimbrakes/

I'm just about to try Koolstop Salmon on one of my bikes.
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531colin
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Location: North Yorkshire

Re: Cantilever upgrade

Post by 531colin »

I don't think you will get anywhere moving the pads on your existing cantis......you can't alter the pivot to rim distance.
With "washing line" levers, I would go straight to Tektro RX 6 mini vees and Koolstop salmon....the original pads are pants!
Norman H
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Joined: 31 Jul 2011, 4:39pm

Re: Cantilever upgrade

Post by Norman H »

I don't think that braking from the hoods is ever as effective as braking from the drops and for me some STI levers exacerbate the problem. If the brakes themselves are less than perfectly set up then performance can drop to the point where it becomes an issue.

The other problem, if using more recent Shimano STIs, is that the mechanical advantage (MA) of modern STI levers is not a good match for the MA of old style cantilever brakes. As a general rule pre 2008 levers should be OK but later models will underperform with most cantilever brakes. The only exception that I am aware of are the CX 50 and CX 70 cyclocross cantilevers which I believe are designed to be a perfect match for Shimano's NSSLR levers. By happy coincidence Sora ST-R3030 9 X 3 NSSLR shifters paired with either of the above callipers would make an ideal setup for anyone wishing to have STI shifting on a 9 speed tourer. CX 50/70 brakes also work very well with older levers.

Incidentally another way to compensate for poor braking from the hoods is to fit cross top levers. Tektro's own cross top levers work very well with CR 720 brakes.
mattheus
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Re: Cantilever upgrade

Post by mattheus »

Norman H wrote: 23 Sep 2022, 11:51am Incidentally another way to compensate for poor braking from the hoods is to fit cross top levers. Tektro's own cross top levers work very well with CR 720 brakes.
Interesting. I've only used those levers when testing the ones we fitted to my partner's bike (she asked!).

Personally I would rather have my hands at full width when braking in an emergency. Hence mostly riding on the hoods in traffic.
slowster
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Re: Cantilever upgrade

Post by slowster »

1. OP, I suggest you post some photographs of your bike showing the brakes and their set up from front and side angles. Although they are not sensitive to straddle height, there may be some other aspect of their set up affecting their performance, which photographs may help to identify.

2. CJ has used the same combination of Tektro CR720 brakes and 9 speed STI levers on his touring bike, which suggests that they are quite able to provide good braking.

3. Regarding this comment:
Philip_Rogers wrote: 21 Sep 2022, 2:05pm I now also have a Birdy for commuting which has Deore hydraulic brakes, these are so much better esp in the wet.
I am doubtful of how useful a comparison that is. On a small wheeled folding bike I would not ride as fast downhill as on a large wheeled tourer.
scragend
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Joined: 13 Oct 2020, 7:16pm

Re: Cantilever upgrade

Post by scragend »

Philip_Rogers wrote: 21 Sep 2022, 4:20pm
GideonReade wrote: 21 Sep 2022, 3:38pm Why not go to mini vees instead? I put these on the front of my 1980s tourer, and they work well and are a bunch less hassle.
That is another option. The frame is set up with hangers for canti cables so might look odd with them empty. I like the look less but that's secondary to the bike stopping downhill in the rain!
I picked up an immaculate Cheviot second hand earlier this year (for an absolute steal), which had the same brakes as yours. When I test rode the bike I thought the brakes were absolute rubbish, but the rest of the bike was so good that I couldn't turn it down.

I've swapped the brakes for Tektro RX-6 mini-Vs, which took quite a bit of fiddling to set up but work OK now. The back one could do with a bit more fiddling (particularly in terms of the cable routing from the end of the top tube to the brake), but generally they are fine. There is the added bonus that the horizontal cantis would have fouled my fork bags, but the mini-Vs don't.

The bike does, as you say, now have empty cable hangers, but that doesn't bother me at all.
Philip_Rogers
Posts: 51
Joined: 22 Sep 2007, 9:17pm

Re: Cantilever upgrade

Post by Philip_Rogers »

scragend wrote: 23 Sep 2022, 3:27pm
Philip_Rogers wrote: 21 Sep 2022, 4:20pm
GideonReade wrote: 21 Sep 2022, 3:38pm

I picked up an immaculate Cheviot second hand earlier this year (for an absolute steal), which had the same brakes as yours. When I test rode the bike I thought the brakes were absolute rubbish, but the rest of the bike was so good that I couldn't turn it down.

That’s another reason for reviewing the brakes. I was all set to look at Cyclescheme for a new disc brake tourer but I can see that quality rim brake tourers are not fetching much money second hand so I appreciate mine wouldn’t go for much.
rogerzilla
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Joined: 9 Jun 2008, 8:06pm

Re: Cantilever upgrade

Post by rogerzilla »

I tried normal Vs with standard drop bar levers (Shimano BL-400 or something) years ago. They stop the bike just fine, better than cantis, but they are a bad idea because the pads have to be set very close to the rim to avoid running out of lever travel. This means, even with a perfectly true wheel, you get brake rub on climbs. This is particularly annoying in the wet because you can hear it. I gave up after a week and went back to cantis.
gregoryoftours
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Joined: 22 May 2011, 7:14pm

Re: Cantilever upgrade

Post by gregoryoftours »

I'd agree with using mini vs. For myself I'd even go full length v brakes. I'm one of the people who has had very good experience with the latter setup, despite it being an official 'no no'. Maybe it depends on the stiffness of your frame/wheels, but I've never had any trouble with brake rub, nor the lever bottoming out against the bar.
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