Do mountain bike cantilever brakes have different pull than road bike cantilever brakes?

Question

I was discussing with a friend who worked at a bike shop for 4 years about switching my mtb flat bars to drops (either a horrendously awful or great idea) and they said I would have to replace my cantilever brakes since mtb cantilevers and road bike cantilevers have different cable pull, even though they're both cantilevers.

Specifically, the traditional two-arm no-v-brake-nonsense cantilevers.

Is this true?

Answer 1

Actual cantilever brakes should have the same pull on both road and mountain bikes (which is also the same pull as a road caliper brake).

If you have V-brakes, then you would either:

1. Need to get road levers that have the pull for a V-brake (which will probably mean using a separate gear shifting system, rather than integrated brake/shifters ("brifters").

or

2. Need to replace the V-brakes with either true cantilevers or, as noted in comments, “mini V-brakes”, which would let you use standard brifters.

Answer 2

Usually cantilevers have some variability and freedom for adjustment of the pull ratio. There are two ways you can adjust the cable pull ratio:

• You can move the brake pads inwards or outwards. Some brake pads have a stud which can be freely adjusted. Others have a threaded end, but these are supplied with a large collection of washers of different sizes that can be moved to allow adjustment with small steps. Actually the washer solution might be slightly better because they allow configuring all of your brakes in an identical way.
• You can usually adjust the straddle cable or swap the link wire. Straddle cables have a free adjustment. However, straddle cables are a hazard unless used with a fender, with a cable catcher or with a slick tire. If the main cable breaks and the straddle cable falls on a non-slick tire, you WILL fly over the bars -- unless it was the rear brake, of course, in which case you won't fly over the bars. Therefore, link wire are infinitely preferrable to straddle cables. Many cantilevers are supplied with two link wires of different sizes, and you may be able to find more link wire lengths available for sale as separate items.

One problem with cantilever brakes is that the vertical rim-to-post distance and the horizontal spacing between posts is not standardized. So it may be possible that some model of cantilever brakes, used with some specified brake pad type, used with some specified washer configuration, and used with some specified link wire will perform differently on one frame or fork than on another frame or fork.

So some trial and error may be necessary. Usually you have enough freedom in adjustment that you are able to make them work well. You just need to know how to adjust them.

The main rule of thumb of adjustment is that you adjust the yoke angle. If you want to increase the mechanical advantage, you need a smaller yoke angle. This means using a shorter link wire or alternatively moving the pads closer to rim so that cable tension needs to be released and the link wire becomes more horizontal. In you want to decrease the mechanical advantage, you adjust it the other way.

As the pad wears, the pad surface moves away from the rim, so you need to increase cable tension, and all of this causes the mechanical advantage to decrease. Therefore, with cantilever brakes you should preferably use thin long pads as opposed to thick short pads, so the difference in mechanical advantage between a new and a worn pad is small. There's another consideration of pad wear too, when the pad wears the bottom surface of the pad "dives" under the rim, so with too thick pads you may need to re-adjust the pads or else you get brake failure eventually due to pad dive.

As far as I know, there's no distinction between "road" cantilevers and "MTB" cantilevers. All of them use fairly similar cable pull ratios, but all of them have a wide range of adjustability for the cable pull ratio. So unlike with V brakes where the mechanical advantage is what it is, with cantilevers you can adjust it. However, with V brakes the mechanical advantage stays the same as the pad wears, whereas with cantilevers it gradually reduces.

Also with cantilevers you not only CAN but also NEED to adjust the cable pull ratio. Frames and forks differ. No installation is identical to others.