Cantilever Conundrum

4 different cantis – vintage to modern- Mafac Criterium; Shimano BR-AT50; Dia Compe 960; Shimano BR-R550

An upcoming bike build will need cantilever brakes.  The frame is new (more on that later), but vintage cantis would not be inappropriate for the project.  As I am not a fan of V-brakes for road bikes, I am exploring the many cantilever options which are available for a frame with canti braze-ons.

Modern cantilever brake options include Paul’s, shown above, as well as other models from Shimano, Dia Compe, Velo-Orange, Avid, and Tektro..  With all these alternatives, it can be hard to determine the best set of cantilevers for a given application.

Shimano BR-R550 with integrated springs

Beautiful Dia Compe 960 Cantis – in as new condition.

But before that a primer on cantilever brakes was in order.  While there are many factors to consider, one of the important ones involves whether you want your springs integrated into the brake or not.  Newer cantilevers, such as the Shimano’s shown in the top photo, have integrated springs that allow for separate spring tension adjustment on each caliper.  Older cantis, such as the Dia Compe’s in the lower photo above have external springs.  The only way to adjust spring tension on older cantis is to mount the spring into a different hole on the canti brake boss (some bosses have 3 separate holes to allow for this).  Or, the spring can be modified with “strong arm” force by changing its shape.

Fortunately, the bike I am working on has 3 hole canti bosses, so I can take the time to evaluate vintage vs. modern caliper options.

1940’s Mafac Cantilever boss

If you have a newer bike and you want to change your cantilever bosses, you can unscrew them from the frame and add a different plate or a different length stud.  Paragon Machine Works is a good resource for sourcing canti studs and plates.

Meanwhile, one has to wonder about the shape and angle of the caliper arms.  It would seem logical to conclude that the arms with the widest angle would have the most mechanical advantage.

But apparently one must think again.  Low profile cantilever brakes can have as much mechanical advantage as calipers with a more extreme angle.  Why?  It all depends on the position of the straddle cable, according to Sheldon Brown.

I experienced this when setting up Tektro canti’s on my 1987 Panasonic commuter bike.  I had to position  the straddle cable very low, but in doing so I found that the brake performed quite well.  The rule of thumb is to not set the yoke below the bottom of the fork crown.  While the angle of the straddle cable looks extreme, the brakes work just fine.

The Mafac cantilevers in my collection are the lightest weight calipers among the group.  Their springs are external of course,  but with the 3 hole option on the frame’s canti bosses, I am leaning toward installing them.  We’ll see!

15 thoughts on “Cantilever Conundrum

    • Oops – forgot abut Compass’ offering. They offer a beautiful and lightweight set which is a copy of the original Rene Herse design. Spendy at over $300 for a set – but possibly worth it?

  1. It’s not the position of the straddle cable that makes the difference.

    The applied force is either increased or decreased, depending on the distance from the fulcrum (the point or support on which a lever pivots) to the load, and from the fulcrum to the effort.

    In the case of cantilever bicycle brakes, the fulcrum point is the brake pad.
    The longer the arm length from the fulcrum (brake pad), to the cable point (the effort), the greater the pressure that can be applied to the pad. The shorter the length, the less pressure.

    Also – a shorter length from the fulcrum (brake pad) to the load (the boss) will increase the braking pressure. The longer the length, the less pressure.

    • Excellent points! Modern cantis have toe in adjustment built in to the design, although they tend to be significantly heavier than their vintage counterparts. With the pad as the fulcrum, brake squeal can be an issue, so toe-in adjustment is important.

  2. I should also state that the angle of the straddle cable makes a big difference. The shorter the cable, the better the braking.
    The reason for this is because the shorter the cable, the greater the force is applied towards the rim (sideways pressure). If cable is too long, much of the force is going in an upwards direction, instead of sideways.

  3. Hi Nola … one other thing to consider about cantis … my issue I wrote to you about last summer:
    With respect to my 1988 (or so) Bianchi Advantage. I had removed the front reflector bracket and reflector many years ago , not knowing how critical the bracket is for protecting the front tire / wheel from the cantilever front brake transverse cable in the event of a main cable break (see Sheldon Brown’s discussion at : ) . When the main brake cable broke, it caused the upside “V” transverse cable to get snagged on the front tire , essentially bringing the wheel to an immediate freeze. I went up and over, and even with a helmet on (thank goodness), I had facial fractures , lacerations, and road rash (I’ll be OK with time). So, be sure to cover a front tire using a canti with a fender or reflector bracket !

    • Bob – thanks for pointing out this important safety warning: cantis need either a fender or a reflector bracket between the straddle cable and the tire. Otherwise: disaster could strike, and this is why V-Brakes came into being.

  4. Another set worth considering are the shimano cx50 or the discontinued cx70. With their adjustable spacer system it is possible to use a new brake set on the narrow spacing of a vintage frame. I went to them on my fuji touring bike, the old vintage brakes just don’t have enough arm for leverage.

  5. So now it’s May 2019. What did you finally decide to use, and how has it worked out?

  6. Hi just to say I had a trekking bike with v brakes that needed the front replacing drove me mad setting them up then sold that and bought a retro trek/ jazz /voltage with cantilevers so easy to set up and the pads can be set at different angles very easily

  7. Hi there,

    i found this post really informative and fascinating!

    I am currently building a Japanese ALPS bike from the 70s that has Mafac bosses so before reading your article I thought I could get away by installing modern Dia-Compe Gran Compe 999 Cantilevers. Now I realise there is not enough tension so I was wondering can I modify theirs springs to bring in the missing tension?

    I noticed that in your article you mention: “the spring can be modified with “strong arm” force by changing its shape.” Are there any resources available that demostrate how this is done?

    Or am I completely out of context here and I should instead by some MAFAC cantis to solve the issue?

    Any feedback you might have would be highly appreciated!

    Thanks and continue the good work!

    • Thanks for your comment. Those 999s do not have a spring adjustment so you would need to change the shape of the spring that sits over the canti boss. I don’t know if there are any videos on how to do this but I would probably use pliers or a vice grip. If there is another spring behind the arms it’s possible that could be modified as well. Or just buy a different set. The old Shimano cantis from the 80s are pretty good.

  8. Howdy, I just wanted to write that I found this post pretty helpful. I can share what has worked for me with a particular bike.

    I picked up a mid-late 80s Gazelle Randonneur Trophy and have updated it with new parts as a sport touring / rando bike. It has canti bosses but with pretty narrow spacing, by “modern standards”: 55mm front, 65mm rear. As I’m doing a mostly new-parts-on-old-frame build, I opted to try the Shimano BR-CX50 cross cantilevers which I found great an another bike, plus they are only 35 EUR a pair here (Germany). I find the post slots are low enough to line up the brake pads but the smallest spacer included with the set (~14-15mm) is too long for the narrow front to allow straight shoe contact. I was also putting on SKS Longboard fenders at the same time and noticed the hard plastic spacers included with the set are ~7mm thick and the same diameter, so they worked in a pinch: one plastic spacer inside the brake slot and one outside give the right length for the short brake post bolt.

    This setup works very well so far and gives me straight pad contact, although I plan to find replacement metal spacers as I don’t trust the plastic in this location for the long term… perhaps larger stainless steel nuts. The braking is *very* good so far IMO.

    I know, I know, the tradition post with a side nut is more adjustable for this situation but I like these particular brakes as I find them much easier to adjust and they are pretty light. I’m lazy and I like the “set and forget” aspect of these.

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