13 September, 2017

Canti Post Sizing PSA

By Scott

Over the years, "standards" have changed for a lot of things. Wheel spacing for example - we went from 120, to 126, to 130/135 mm.  One of the little known changes relates to cantilever brakes. Over the years, the spacing between the posts has changed and can cause issues with folks trying to restore/upgrade an older bike with newer parts.

Canti Pass Hunter with modern spacing
The current standard for the width of the canti spacing is between 77 and 85 mm (centre to centre). On older bikes, (and by this I mean bikes made in the 70's and the 80's) it can be between 55 to 65 mm wide. This is where problems start to happen.

1984 Santana Tandem with older, narrow spacing
Modern canti brakes are designed around the new standard post width. This results in a brake that will sit higher above the post and be thicker then the older brakes. This means you can't use new brakes on older posts.

What can be done? Well not much unfortunately. As standards change, companies like Shimano and Dia Compe don't stock the classic spacing any more, and it's tough to convince our suppliers to make a small run of brakes that would work with the old standard. So the best that can be done is to use the older brakes, clean up and lubricate the pivot points, update the pads with new pads that have better compounds and use some simichrome to shine them up.

10 comments:

Anthony said...

Even more difficult is vintage spacing and trying to convert from 27" to 700c. Ahhh! I finally found a workable solution on my Trek 520, but it ain't elegant.

Joshua said...

Have any experience with the IRD Cafams? They're based on Mafacs but I have no idea if that extends to spacing.

Starmichael said...

Or of your paint isn't so great, and you're planning on a new paint or powder coating job anyways, lots of Framebuilders are more than willing and capable of removing the old posts and putting new ones on in the correct "modern" widths and for whatever wheel size you want! We do this several times a month! Mostly to convert bikes from 27 in to 700c or 650b.
While you're at it there are lots of other braze ons that can be added, bottle bosses, pump peg, rack mounts, dynamo wiring guides!

Anonymous said...


Shimano CX-70s work down to 65mm, and making thinner standoffs
looks doable.


http://cycle.shimano.co.kr/media/techdocs/content/cycle/SI/Cyclocross/SI_8K50A/SI-8K50A-001-Eng_v1_m56577569830749996.pdf

Unknown said...

Without knowing much about the nitty gritty of all of this, I've had decent luck doing things like reversing the orbital washer order on threaded brake pads, or swapping to V-brakes/mini Vs.

For changing wheel sizes, there are some products out there that are useful, like Paul Motolite v-brakes that have a wide range of adjustibility , or Cantilever Brake Post Extenders, which are fiddly bits that are pretty hard to track down but are very useful for raising or lowering the post position. The latter would be a very cool thing for VO to stock!

Scott Biggar said...

As previously noted, Shimano CX-70's (and likely the CX-50's) worked really well for me. No other modern cantilever was able to handle the combination narrow brake post + 27 > 700c conversion for me. My frame is an '83 Schwinn Voyageur and the paint is mint, so I really wanted to make it work. Note that you can modify these Shimano canti's by using threaded v-brake pads, giving you even more room on the front between post/rim.

Unknown said...

Had the same issue as Anthony with my 620. Ended up going with the cheapo Shimano Altus CT-91s off a mountain bike, with skinny kool-stop pads. And it's still a tight fit!

Dann said...

Just ran into this problem on the rear of an early 80s Kuwahara tandem. Installed CR720s up front, but vintage Shimano high profile cantis in the rear. Any idea if Shorty Ultimates work with narrower spacing?

Richard Freeman said...

I'm using Shimano BR-M550 cantilevers on a 1984 Schwinn Voyageur with 700c wheels. I had both problems - narrow spacing and wheel diameter reduction. These are some of the first cantilevers that used threaded pads, so you can run very thin V-brake pads (like the other Schwinn guy) to gain a bit more space. The arms still angle out a bit, but it doesn't look odd and they work very well.

The pad now sits at the bottom of the slot, so leverage is increased. Because of that, they are very powerful, enough to be grabby on occasion. Better than too weak, though.

bw said...

Interesting I just measured my Bridgestone XO-1 and it's 73mm c-to-c. Shimano BR550's are working fine for me with 1.75" tires, any wider than that I have to inflate the tube while it's mounted.

I can definitely see any narrower than that being a problem with the Shimano's. I did see someone successfully use the Paul Touring Cantis on a Bstone RB-T build, and I think that is similarly spaced to the XO-1 (if not narrower).