Why do some folk like cantilever brakes?

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pq
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Re: Why do some folk like cantilever brakes?

Postby pq » 30 Apr 2016, 7:21pm

I hate canti brakes, but reluctantly accept that they're sometimes the best option. They're a faff to set up and as the pads move towards the rim, the mechanical advantage alters the wrong way.

I have two sets. One are on a multipurpose CX/touring/winter bike. Tektro CR720s paired with Campag Ergo levers. They work fine. The other is on my shopping bike. They're awful, but good enough for shopping trips - and to be fair they're only awful because the whole bike is cobbled together from junk.

On other bikes I've got shot of cantis where I can. My tourer has downtube shifters, so I got rid of the cantis and used decent V brakes with... with... actually I forget exactly what they are, but they have the correct cable pull for V brakes. The braking is in a whole different league to any cantis I've had, including those self energising ones. If it weren't for cable pull issues, I'd replace all the cantis I have with V brakes.
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MikeDee
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Why do some folk like cantilever brakes?

Postby MikeDee » 30 Apr 2016, 7:58pm

Brucey wrote:
reohn2 wrote: .....better stoppers than the best set up canti offerings,that's the point,ie; do you want canti brakes that need a bit of fiddling with to get reasonable stopping power,or a simple set up that beats the pants off canti's?


Hmm, by ' beat the pants off' you mean

- are hideously ugly
- squeal in a whole new range of ways
- have badly engineered springs that break more often than cantis
- have off-centre cable runs that foul on stuff when you turn the steering
- have centring screws that forever need attention
- have minimal running clearance to the rim
- have a crummy sheet metal part that is only ever about ten seconds away from bending open and causing your brake to fail completely
- don't have proper strain relief on the pinch bolt so the cable frays
- have noodles that let water inside (always) and rust or start to bind as soon as you look at them
- have arms on the front brake of a typical touring bike that hit the frame if the steering swings
etc etc

if so, I know exactly what you mean.... :wink: :roll:

In fairness whatI'm driving at here is that there is no such thing as a perfect brake; what might suit some folk might not suit others so well.

MikeDee wrote:I spoke with the Santana tandems rep at a bike show recently about V brakes and STI shifters. He says they work fine with the newer type STI shifters that route the brake cables under the bar tape. The old ones with external cable routing need mini V's or Travel Agents. I just converted my touring bike from cantis to V's....


I would suggest you try such a machine before you splash out on such a setup; the cable pull of 'New Super SLR' brake levers is certainly longer than those of previous brake levers for dropped bars/STIs, but IMHO it still isn't long enough for reliable operation with full-length Vs; this setup usually gives a mushy brake lever that will come back to the bar on a single wet descent, and a running clearance that is too small for most folk.

I think such levers may pair well with mini-ish Vs that are about 90 to 95mm arm length, but not so well with arms that are 110mm long.

Obviously if the bosses are at an unusual height on the frame, various odd combinations that shouldn't normally work well can do, so always check that after a test ride.

cheers


My Tektro V brake levers pulled 9.5 mm of cable and my 10 speed Shimano STIs pulled 9 mm of cable for a similar amount of brake lever travel. I'd say that was close enough to work acceptably. I think 11 speed STI levers pull even more cable. Santana had a V brake equipped bike in a work stand at the show with STI levers. I pulled the brake lever and it wasn't even close to bottoming against the handlebars. It had a similar travel to how I set up my brakes. I should have looked more closely to see exactly what components they were running. I would agree though that a longish mini V, like 90-95 mm long may be a better match than a full 107 mm length V to a newer style STI lever.

I think Santana knows what they are doing because they sell most of their tandems with V brakes, as they do not think disc brakes are suitable for tandems. If any bike needs good brakes, it's a tandem.

Brucey
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Re: Why do some folk like cantilever brakes?

Postby Brucey » 30 Apr 2016, 9:58pm

the brake cable pull in shimano road STIs is either 'super SLR' (all pre 2008) or 'New Super SLR' (nearly all new groupsets released since 2008). Confusingly many people (including shimano) are already omitting the 'New' from the NSSLR designation with predictably confusing consequences.

Shimano have some very clear recommendations for their brakes and levers; IIRC they run

SSLR levers are compatible with zero V brakes (mini or otherwise) and
NSSLR levers are compatible with their Mini-Vs (which are 90mm arm length) but not full Vs.

If your tektro levers pulled 9.5mm of cable they were not V-brake levers; V brake levers (for full Vs) pull more like 25mm of cable.

BTW the danger with running full Vs with road levers is not that you can pull the lever back to bar when you are fiddling with a machine on a display stand, it is that in the real world you will get half-way down a wet alp and [b] then[b] the lever comes back to the bar..... :roll: NB as per my earlier comment, not all frames have the bosses the same height, and a few mm makes a big difference here; don't jump to conclusions without obtaining accurate measurements.

cheers
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reohn2
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Re: Why do some folk like cantilever brakes?

Postby reohn2 » 30 Apr 2016, 10:42pm

Brucey wrote:
I'm a materials scientist,

I knew that :wink:
but I was happily sorting my cantis out when I was a callow yoof, (and knew less than half of nothing about anything). They are not complicated things at all; by contrast sorting out indexed gears etc is far more difficult and fiddly work, which seemingly in no way deters people from the mechanical abominations of modern gearing.... :wink: :roll:

cheers

The difference is index gears generally once set up (after initial settling of cables)tend not to need looking at,whereas brake pads are wearing down all the time,more so in winter or wet weather,so need attention and need pads changing again more frequently in bad/wet weather.

I'll leave it at that as I feel I've made my point,we don't agree,so we'll have to agree to differ :)
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MikeDee
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Re: Why do some folk like cantilever brakes?

Postby MikeDee » 30 Apr 2016, 11:09pm

I'm a bit confused about changing the MA of a canti brake by changing the length (height above the tire) of the straddle wire. This is not the same as changing lever ratios, pulley sizes, or gear ratios. If the straddle wire is not 90 degrees to the brake arm when the brakes are engaged, a portion of the force is wasted in trying to stretch the brake arm instead of providing useful torque about the brake arm pivot.

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Sweep
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Re: Why do some folk like cantilever brakes?

Postby Sweep » 1 May 2016, 5:25am

MikeDee wrote:
I think Santana knows what they are doing because they sell most of their tandems with V brakes, as they do not think disc brakes are suitable for tandems. .

Can I ask why? An open honest question.
Sweep

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531colin
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Re: Why do some folk like cantilever brakes?

Postby 531colin » 1 May 2016, 6:53am

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Last edited by 531colin on 2 May 2016, 6:13pm, edited 3 times in total.

Brucey
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Re: Why do some folk like cantilever brakes?

Postby Brucey » 1 May 2016, 7:24am

re the change in MA of cantis as the brake blocks wear;

if you use cartridge shoes the inserts will each wear about 2mm before they should be replaced. I would say that this ought only degrade the MA of a canti by 5-10% or so in most cases (even if you just use a barrel adjuster on the main cable), which ought not be critical.

I guess it could be more than that if you start out with a narrow profile canti and you set it up badly to start with, or use much thicker brake blocks (without suitable adjustments), but there is surely no need for any of that, is there?

Regarding power; I have several sets of cantis that would cheerfully chuck me over the handlebars if I were to pull the lever more than normal. I don't usually see a need for more power than that; also, these brakes modulate well too. They also don't squeal, stick out too far or suffer any of the other 'issues' that some folk claim are inherent. To achieve brakes that work like this merely takes a little care when selecting parts and setting them up. The idea that to do this is terribly difficult, and/or you are somehow must inevitably accept a markedly inferior brake when you have cantis is simply not correct IME.

cheers
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bainbridge
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Re: Why do some folk like cantilever brakes?

Postby bainbridge » 1 May 2016, 10:50am

From a touring perspective cantis are better than disc because you don't need disc specific racks etc.

V brakes IMO are much easier to set up, but once cantis have been fitted and adjusted they're fine.

My 2015 Cinelli Hobootleg has 'stuck with cantis for simple, reliable braking'. After a very muddy, rainy tour in March they're fine.

Another benefit is that a couple of friends can't believe I bought a bike for over a grand fitted with cantilever brakes. They equate an expensive bike with disc brakes so hopefully the thieves do too :)

reohn2
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Re: Why do some folk like cantilever brakes?

Postby reohn2 » 1 May 2016, 11:05am

bainbridge wrote:From a touring perspective cantis are better than disc because you don't need disc specific racks etc.......


I don't see how that's a disadvantage,once the rack's fitted there's no difference,just buy the correct rack.
Also it doesn't apply to disc brakes fitted within the chain/seat stay triangle.
That said we have two bikes with the disc callipers outside the triangle and both bikes have been fitted with modified racks that only needed a little bending of the left side rack leg,a longer bolt and suitable(20mm) spacers.Though if I'm honest I think I'd prefer a disc specific rack if I were doing any heavy touring on those two bikes.
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Brucey
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Re: Why do some folk like cantilever brakes?

Postby Brucey » 1 May 2016, 11:35am

re disc specific racks; if you need one, there's less choice of racks, and many of the ones I have seen are structurally compromised, in that they have some kind of bending/cantilevering going on at the bottom, that wouldn't occur with a non-disc rack.

I suspect that if you carry a heavy load on such a rack, the rack, the mounting bolts, and/or the frame itself may be more at risk of damage in the long run. I've seen lots of racks break over the years, and the kinds of breakage I have seen would certainly have been 'helped' by the loadings seen in many disc racks.

It may just be a question of choosing carefully, but then again the rack manufacturer can't know about every frameset and vice-versa; it seems likely that there are both good and bad combinations that are possible, and telling the difference mayn't be that easy.

cheers
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reohn2
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Re: Why do some folk like cantilever brakes?

Postby reohn2 » 1 May 2016, 12:00pm

One of the bikes in question:-
Image

Which TBF isn't a touring specific bike,but 20mm ain't the end of the world for spacing off a rack for light and occasional two pannier with a racktop bag(12kg) load.

Now if we wish to carry(sorry) this to the next level,most touring bikes manage with 5mm dia bolts holding the rack in place when they'd benefit from 6mm dia from a fatigue POV.

The overwhelming number disc equipped touring bikes have the calliper tucked neatly out of the way between the seat and chain stays where a disc specific rack isn't required.
So it follows that anyone doing any amount of loaded touring would give their racks and fittings a serious coat of thinking about,no?

EDIT:- there's also the option of high tensile bolts,though I've never checked their availability or cost.
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pq
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Re: Why do some folk like cantilever brakes?

Postby pq » 1 May 2016, 2:27pm

I suspect Santana's dislike of disc brakes has more to do with heat dissipation than pannier racks. A fully loaded tandem with 2 less than svelte adults on board on (say) an Alpine descent would produce more heat than even the biggest rotor could cope with. Rims overheat too of course, but there's a lot more metal to go at.
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Bmblbzzz
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Re: Why do some folk like cantilever brakes?

Postby Bmblbzzz » 1 May 2016, 2:44pm

Bmblbzzz wrote:I don't have an engineering, physics or maths background, so I had only a vague understanding of mechanical advantage. I looked it up and found I was right (vaguely at least) and also found the three classes of levers.
http://www.uark.edu/depts/aeedhp/agscience/simpmach.htm
Don't know why, but that was the first thing that google found me, and I can understand it so there it is!

Would I be right in thinking that whereas cantis and calipers are Class 1 levers, Vs are Class 2?

Nobody else is sure either?

reohn2
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Re: Why do some folk like cantilever brakes?

Postby reohn2 » 1 May 2016, 3:49pm

pq wrote:I suspect Santana's dislike of disc brakes has more to do with heat dissipation than pannier racks. A fully loaded tandem with 2 less than svelte adults on board on (say) an Alpine descent would produce more heat than even the biggest rotor could cope with. Rims overheat too of course, but there's a lot more metal to go at.


I'd agree with that,you can't drag discs or rims FTM,on a tandem.
Only an Arai drum or similar,will dissipate the heat on loonnnngggg descents,and keep coming back for more.
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