Author Topic: Canti brake play & adjustments...  (Read 720 times)

Canti brake play & adjustments...
« on: January 26, 2019, 02:00:11 pm »
I'm trying to see if I can reduce the play in the front canti brakes, which are old BR-M650 Shimano  https://si.shimano.com/#/en/search/Keyword?name=br-m650
The play is mainly 'longtudinal', i.e. the canti boss seems slightly too long, and there is >0.5mm gap, once the main bolt is tightened into the boss, between the inner washer surface and the brake arm.  The canti bosses are brazed on, non-removeable.  There is some play caused by the diameter of the boss perhaps being slightly smaller than the int diameter of the brake arm 'bush'(?)   I got hold of some slightly diff used cantis (M734) but not much better.  Is it a case of worn canti arms?

Any ideas if I can fix this?   

Also, what's the recommended boss spring hole setting for different brakes/shifters?  I use the middle hole, & shifters are 105 10sp STI.

Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Canti brake play & adjustments...
« Reply #1 on: January 26, 2019, 04:40:06 pm »
longitudinal play, by itself, rarely causes much trouble but if it is excessive then it may do. To cure that, I would suggest that you use a dished washer behind the front bolt (rather than shorten the bosses, say).  Old cantis/bosses also develop radial play and that is far more important. You can make this play practically disappear by winding a few turns of PTFE tape around the bosses before fitting the brake arm; this sounds bodge-tastic but it lasts quite a long time.

Another route you might like to go down is to use some slightly later brakes which have 'integral pivot bushings' such as BR-M520

https://si.shimano.com/pdfs/ev/EV-BR-M520_M521-1230E.pdf

In this style of brake the assembly contains a dummy boss so that the wear state of the bosses on the fork is irrelevant. However with this type of brake do not overtighten the mounting bolts; this can cause the bosses to fail since (unlike with the other style of brakes) they see a permanent tension load.


Note also that to get good braking with these brakes and your levers, you should set the arms as wide as you can and the straddle low. This may force you to use the upper hole in the boss for the spring, since the wider the arms are set, the lower the return force is going to be.   It should be easy enough to get good brakes with ST-5600 but with ST-5700 the MA of the levers is lower and you will need to set the straddle as low as you can to get anything like a reasonable brake.

cheers

Re: Canti brake play & adjustments...
« Reply #2 on: January 26, 2019, 05:36:08 pm »
Thanks Brucey.  I guess finding the right dished washer may be tricky;  I may just continuing to ignore the play as doesn't seem to negatively impact braking AFAICS - though will have a go at the PFTE tape, as have some of this.

Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Canti brake play & adjustments...
« Reply #3 on: January 27, 2019, 03:14:32 pm »
BTW if you want to make a dished washer, take a normal (but heavy section) M6 washer, sit it over the open end of a socket, and drop an M6 bolt in on top of it, with a thin-walled washer (such as one from a V-brake brake block) between. Then give the head of the M6 bolt a tap or two with a hammer. With luck you will make a washer with an appreciable dish to it, that could be used to reduce the longitudinal float in your brake arms.

cheers

Re: Canti brake play & adjustments...
« Reply #4 on: January 29, 2019, 08:26:32 pm »
I've always thought it's a bit much to expect frame manufacturers to make bosses exactly the right length for other manufacturers' brakes.  BB shells are rarely exactly 68mm wide, head tubes and seat tubes usually need reaming by the assembling mechanic, etc.

Cantis have a rather short history, btw.  Centre-pulls were de rigueur on touring bikes until the mid-1980s, when cantis came in.  Cantis took off bigtime with MTBs (for the same reason - big clearance for tyres or mudguards) but were killed off by V-brakes and then discs 15 years later.  Cantis survive on touring bikes but discs are getting in there too,  The big PITA of setting up cantis is more to do with plain-post pads than with the cabling; Tektro cantis use V-brake pads although, technically, plain-post pads allow for canti arms that are stiffer in the right direction as well as almost infinite adjustability.
Never tell me the odds.

Re: Canti brake play & adjustments...
« Reply #5 on: January 29, 2019, 08:50:15 pm »
short history? :o :o

   MAFAC cantis have been around for at least sixty years, and they weren't the first.   The boss design we still use is basically a MAFAC pattern boss, even if the spacing isn't.

cheers

Re: Canti brake play & adjustments...
« Reply #6 on: January 29, 2019, 08:52:19 pm »
Yeah, but they weren't very widespread until the 1980s.  The dual-pivot sidepull is also a fairly ancient design but barely anyone used it until the 1990s when Shimano started making them.
Never tell me the odds.

Re: Canti brake play & adjustments...
« Reply #7 on: January 29, 2019, 09:38:13 pm »
depends what you mean by 'widespread'; in halfords? -no. In cycling? -yes!

  Cantis were in common use on lightweights when I started cycling in the 1970s.  In fact they were a popular brake because the bosses could be added to a 'gappy' frame (*) which made for a  really versatile bike with good brakes.  They were de rigeur for CX, the best touring bikes, tandems, you name it.  To give you an idea, it was about as likely that you would see a Mafac CP brake as a canti in many cycling clubs at that time.

(*) Which was most frames built in the UK since the mid 1950s.  The fashion for close-clearance racing frames was pretty new; IIRC campag didn't start to make their piccolo brake until the early 1970s, and in fact side pulls of any kind only became popular for racing since ~1969 when the (standard reach) campag brake was first introduced.  Before then it was mainly CPs, dodgy universals, or cantis.  If you bought a dedicated racing frame of continental design it might have a brake drop of ~57mm (and mafac CPs probably), but most UK-built frames had bigger clearances than that.  Many secondhand (as well as new) 'lightweight' road frames used the longest reach centre-pull or side pull brakes  to reach to 27" rims; all pretty poor.  If you wanted to run sprints and tubs you needed to find another 4mm brake drop and this meant that the brakes were guaranteed to be extra-feeble.  If you started out with a used frame (that didn't have canti bosses on it already) it made lots of sense to have canti bosses put on it when it was being resprayed; lots of my chums did exactly that.

CLB used their own boss design but Mafac was most popular and this became the one that was copied and used by the Japanese.  I dunno when (say) Dia Compe started to make cantis (they had been making brakes since the 1930s and had been involved with Weinmann since the 1960s) but the first mass-produced MTBs (eg the spesh stumpjumper) used Mafac cantis because they were the best (and most popular) then available.


five different models of MAFAC canti, circa 1964


Jacques Anquetil, ~1957





Of course cantis had been popular well before MAFAC even existed; for example since 1929 the Resilion cantilever brake had been used on quality machines in the UK, and was arguably one of the first really good bicycle brakes of any kind.


1949 Resilion brakes


cheers

Re: Canti brake play & adjustments...
« Reply #8 on: January 30, 2019, 09:30:01 am »
I'm thinking of mainstream British tourers like the Dawes Galaxy, Holdsworth Mistral and Raleigh Royal.  These had centre-pulls well into the 80s (all the 1983 catalogues for these bikes show CP brakes).

I remember a university friend proudly showing us his tourer with cantilever brakes in 1989.  They were considered pretty exotic just before the MTB boom.

Never tell me the odds.

Re: Canti brake play & adjustments...
« Reply #9 on: January 30, 2019, 09:47:27 am »
OOI how would I get on with a swap to XT V-brakes vs the cantis?  Would they be compatible with these canti bosses, and the 105 shifter/levers.  Edit.  I see one needs a 'travel adjuster'...
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Canti brake play & adjustments...
« Reply #10 on: January 30, 2019, 10:48:15 am »
There are special V-brake drop bar levers made but they are a bit kludgey.  I had some Dia-Compe 287V levers and they were nasty.  Travel Agents are ok if you can cope with the extra maintenance.

If you use standard levers you have to set the pads so close to the rim that they rub on climbs.  Powerful, though!
Never tell me the odds.

Re: Canti brake play & adjustments...
« Reply #11 on: January 30, 2019, 10:51:01 am »


The straddle angle in that photo shows quite well that traditional wide-profile cantilevers aren't fussy about cable geometry!
Never tell me the odds.

Re: Canti brake play & adjustments...
« Reply #12 on: January 30, 2019, 11:11:04 am »
There are special V-brake drop bar levers made but they are a bit kludgey.  I had some Dia-Compe 287V levers and they were nasty.  Travel Agents are ok if you can cope with the extra maintenance.

If you use standard levers you have to set the pads so close to the rim that they rub on climbs.  Powerful, though!

Thanks.   Will stick to cantis.  Also noticed that the travel adjusters (SJS) are the same £ as the XT v-brakes themselves.
Destroying rainforest for economic gain is like burning a Renaissance painting to cook a meal.  EOW.

Re: Canti brake play & adjustments...
« Reply #13 on: January 30, 2019, 12:07:19 pm »
you could probably  run short mini-Vs with ST-5700 (even then it depends on the exact boss height as to how good it really is)  but with ST-5600 you are best off sticking to cantis.


Re cantis; yes there were not OTP touring bikes from the big makers with cantis until the 1980s. But there were (literally) hundreds of frame builders who served club cyclists at that time, many of whom wouldn't have thought to buy an OTP bike anyway. Why on earth would you? The likes of Raleigh, dawes etc didn't offer anything terribly appealing; eg in 1977 the best Dawes would offer would be a galaxy with 531PG main tubes and no-name forks and stays; a bit of a plodder really. The super galaxy was introduced in the late 70s and was a much nicer bike but it wasn't a very good load lugger at first  because they had mostly specced lighter gauge 531DB tubes.  This may have spurred the introduction of 531ST, who knows; but Dawes also went a bit mental for a while; for at least one year in the early 1980s  the standard galaxy came with side pull brakes which were long and flexy. They were completely unsuitable for loaded touring.

cheers

Re: Canti brake play & adjustments...
« Reply #14 on: January 30, 2019, 11:13:41 pm »

The straddle angle in that photo shows quite well that traditional wide-profile cantilevers aren't fussy about cable geometry!

yes indeed.  There is a better picture (in colour) here

http://veterancycleclublibrary.org.uk/ncl/pics/Simplex%20Dupont%20Delrin%20article%201985%20(V-CC%20Library).pdf

of the same bike. I  they are Mafac 'driver' brakes (rather than 'criterium' ones) -and I have not ever used a set of those brakes so I don't know for sure-  but it looks like the vertical separation of the boss from the brake block might be less than 25mm, which would tend to improve the brake MA even though the arms are pretty short.

Also in the link above is a description of why simplex used 'engineering polymers' in their RDs.  Some folk blame them for simplex's demise, but I note that shimano are busy tromping off down the same path; more and more of their RDs contain plastic parts and have all the same problems as you might expect with a fifty-year old simplex.... ::-). I guess the main difference is that with modern chains and sprockets the shift load is lower. Doesn't stop the blessed things going in the spokes though.....

cheers