Canti brake mechanical advantage?
#1
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Canti brake mechanical advantage?
Which Canti brake geometry has the best mechanical advantage when used with road levers, low profile or conventional geometry?
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#3
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The short profile cantis have a narrower range of acceptable straddle height and vary mechanic advantage more during their travel (unfortunately decreasing in MA as you get deeper into the lever), but have shorter arms and in most cases will feel more powerful. They also will interfere less with racks/fenders/panniers less if that's relevant, and also can be nice to have more tucked in on the rear for mounts/dismounts during cross racing. Medium (truly long is pretty much extinct) cantis are less sensitive to straddle height. Both work fine with road levers.
https://www.sheldonbrown.com/cantilever-geometry.html is a pretty good lay guide. I had an article that laid out the physics of cantis in insane/academic detail but can't find it right now.
For practical advise, try to get cantis that use threaded linear pull style pads--they're way easier to set up than older smooth post pads, even though both work totally fine in the end.
There's a lot of advise that creating a 90 degree straddle angle leads to highest MA, but really pretty much the lower the straddle wire, the higher MA in all real world scenarios.
https://www.sheldonbrown.com/cantilever-geometry.html is a pretty good lay guide. I had an article that laid out the physics of cantis in insane/academic detail but can't find it right now.
For practical advise, try to get cantis that use threaded linear pull style pads--they're way easier to set up than older smooth post pads, even though both work totally fine in the end.
There's a lot of advise that creating a 90 degree straddle angle leads to highest MA, but really pretty much the lower the straddle wire, the higher MA in all real world scenarios.
#5
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A pretty common combo is medium in front and short in the rear, for reasons of dismounting/rack/pannier clearance on the rear. This is what I run on my CX bike (Tektro CR720 in front, Oryx in rear) which I am happy (but not crazily so) with.
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This is generally true (lower straddle cable = higher mechanical advantage) for most low- and medium-profile cantilevers, because they need to be pulled in, towards each other, for best brake force. This isn't true for the traditional designs like the CR520/CR720, old MAFACs, etc. With these, because the cable attachment on the cantilever brake arm is so low (below the pivot, actually), they need to be pulled up to achieve the best brake force. With these, the longer straddle cables work better.
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#7
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The answer to OP's question is less than clear and there is much disagreement. The two best cantis ever, IMO, would be Campagnolo Record O.R. (1992-1995) and the current production Rene Herse. Which have completely different geometry. The basic inexpensive and still available Shimano CX50 was used by many cyclocross pros right up until the sponsors just would not have it. That brake has little in common with the other two above. Paul Components sells cantis with widely differing geometries and all of them are more than good enough. I would suggest try the CX50 at the very modest price and see what you think. The different brakes are not all the same and user expectations and requirements are all over the place.
#8
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This is good advice. I have Tektro CR510s on my Trek 750, and use Avid 20R pads in them. This is working very well for me -- these liner pull pads are strong and quiet, and very easy to setup and adjust in these cantilever brakes.
This is generally true (lower straddle cable = higher mechanical advantage) for most low- and medium-profile cantilevers, because they need to be pulled in, towards each other, for best brake force. This isn't true for the traditional designs like the CR520/CR720, old MAFACs, etc. With these, because the cable attachment on the cantilever brake arm is so low (below the pivot, actually), they need to be pulled up to achieve the best brake force. With these, the longer straddle cables work better.
This is generally true (lower straddle cable = higher mechanical advantage) for most low- and medium-profile cantilevers, because they need to be pulled in, towards each other, for best brake force. This isn't true for the traditional designs like the CR520/CR720, old MAFACs, etc. With these, because the cable attachment on the cantilever brake arm is so low (below the pivot, actually), they need to be pulled up to achieve the best brake force. With these, the longer straddle cables work better.
#9
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The CR720s work really well with short-pull road style brifters and feel identical at the levers to road calipers. In general these wide profile cantilevers work much much better than medium or low profile cantis. I see the person above me called them "medium profile" and it's true there are other ones with with even a wider profile but the 720s are wide enough to work well. The only reason to not always use wide profile cantis which have so much more mechanical leverage is the unfortunate fact they stick out far, can interfere with panniers if you have racks, and worst of all they might hit your heels if you have large feet and ride a smaller frame size, or they might scratch your legs as you dismount. If you can run wide on both front and back though do it because wide cantis work and feel great. I would call the CX50 medium-profile cantis. Low profile cantis are hell on earth with short-pull brake levers, don't go there, there's isn't enough leverage and your hands will never be strong enough.
Last edited by Clem von Jones; 09-23-19 at 12:37 PM.
#10
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The CR720s work really well with short-pull road style brifters and feel identical at the levers to road calipers. In general these wide profile cantilevers work much much better than medium or low profile cantis. I see the person above me called them "medium profile" and it's true there are other ones with with even a wider profile but the 720s are wide enough to work well. The only reason to not always use wide profile cantis which have so much more mechanical leverage is the unfortunate fact they stick out far, can interfere with panniers if you have racks, and worst of all they might hit your heels if you have large feet and ride a smaller frame size, or they might scratch your legs as you dismount. If you can run wide on both front and back though do it because wide cantis work and feel great. I would call the CX50 medium-profile cantis. Low profile cantis are hell on earth with short-pull brake levers, don't go there, there's isn't enough leverage and your hands will never be strong enough.
I've had the opposite experience with short cantis. The best setup I rode was probably some Shorty Ultimates. You do absolutely need to set the straddle low with short cantis--their MA curve varies much more wildly with straddle height. Short cantis have the disadvantage of a more regressive MA curve, but have the advantage of having shorter arms that will, all things being equal, be less flexible.