mstateglfr 

I use cantis, love em, and currently have em on my touring and gravel bikes. I've used dozens of different brands and models from diacompe, shimano and SunTour.

one thing that's always confused me was why did the right side of some sets have a washer that the spring pin would lock into instead of using the post mount pin holes.

what is the history behind it?
what is the benefit?

i am referring to the hex shaped washer in the pics below. That is then held with friction...just seems odd when there are holes on the stud mounts for the pins.

Fat Tire Trader 

Its for balancing the spring tension between each side of the brake.

mstateglfr 

would placing the pin in the middle(of 3) holes in the mount not balance tension? Both sides would be in the same location so there would be balance...right?

The Golden Boy 

Depending on how worn or not worn your springs are.

With those brakes you can set the "start" position anywhere you wish it to be- and you can tighten the spring tension to however you wish it to be.

Other cantis are dependent on where the holes are and hope the springs match each other (or you have enough adjustment to match) or force you to bend the spring with your fingers...

In reality- Shimano's solution of having one side have adjustment makes a whole lot of sense- No it's not infinitely adjustable, but you have the ability to match the other spring.

With the DiaCompe/Suntour infinite adjustment- once you figure it out- it's easy and it totally makes sense. Until then, it looks outrageously complicated.

The Golden Boy 

Just because...



Grail Brakes by Dave The Golden Boy, on Flickr

mstateglfr 

The ones in the pic are SunTour and that's mostly what I use- the varying levels of XC(t/e/m). Only 1 side is infinitely adjustable, but you mention that is Shimano's set up.
maybe I misunderstood your comment.


regardless- I love the setup of the SunTour cantis as all I have used, regardless if year or model, were easy to set up.

follow up question- why not have both sides be infinitely adjustable and attach to the frame or fork with friction?

The Golden Boy 

The only ones with the "friction" attachment that I've used that I'm sure of- have been the champagne colored XC Pros. Those are definitely infinitely adjustable on both sides.

The MC-70 Shimano XT brakes had no provision for evening the spring tension- so it would be like the DC brakes of the time- bend the springs with your hand- but by the time the M-732 brakes were out- (perhaps an earlier version as well) had the spring tension adjustment on the right side brake (pictured the M-732 and MT-62 brakes)- but there was no adjustment for the left side brake.




M732MT62Bottom by Dave The Golden Boy, on Flickr



M732M62Front by Dave The Golden Boy, on Flickr


As far as the Suntour brakes... the Roller Cams I have also have that 13mm collar- but I don't recall if they mount to pins on the boss.


1987 Schwinn High Sierra by Dave The Golden Boy, on Flickr


As opposed to the XC Pro brakes which tighten wherever you tighten the Allen center screw- and the spring tension was controlled by the 13mm collar.



Superbe Pro Brakes by Dave The Golden Boy, on Flickr