JeffOYB

I'm used to easily swapping 27" for 700c with vintage sidepull brakes. they always seem to have enough brake pad slot to just lower them down a bit and presto. A friend just bought an older 27" wheel bike w canti's. I glanced at it thinking about the handy switcheroo and got nowhere. I don't see an easy way to drop them a half inch or whatever so that the pads can reach the new lower rims. are canti's often limited like this? less tolerant for this swap? like do some canti's have slots or something w the pads higher up w room to slide down. these brakes don't seem to have any slot at all. any adjust involves pivoting the pad. which seems like i'd end up w a bad braking angle. and maybe my pad wouldn't have a long enough post anyway. or am i missing something obvious? this is for an early 80's Trek 520 tour bike, tiny frame. thanks!

fietsbob

Have your favorite framebuilder Move the posts down .. remove & replace .

I'd suggest bosses on the center line of the fork blades rather than offset to the inside ,
which was common on older forks..

good time to add fittings too..

then repaint


Unless you find pad height adjustable brake calipers

you must move the pads even closer to the pivot bolt axis.. not upward,








....

JeffOYB

ah ahahaha ... i need a 5 minute low dollar fix. cheap vintage bike. awesome bike. but no re-doing anything or painting. all time will be a *bad* time to add or change anything framewise or paintwise to this bike.

so... "unless you find" doesn't give me the critical factor of availability. ...so: is there a readily available canti w height adjust pads that i can nab cheap? i'd only want to use comparable parts. our co-op has a big box of brakes -- prolly some common vintage cantis in there. if i'm likely to find something that'll work, i'll dig. if not, i won't.

...just like many common sidepulls can be used. this wd be a done-deal already if it had sidepulls. i'm wondering if there's an equally handy canti option ... or if it is known that canti's don't readily work for this conversion. if you know, please say! like, i can tell anyone that w common sidepulls the 27>700 works a charm. that's where i can help someone. can someone help me w my canti variant? ... i hope this gives a sense of what i'm after, info wise. thanks!

fietsbob

stick with 27" rim wheels then.. or bolt on center pull or side pull brakes ..

leave the canti posts in place,

they're below the rim & wont interfere with a brake mounted from above


radial discrepancy after all is 4mm , 315 vs 311.






.....

JeffOYB

is this your way of saying "i am familiar w the range of common old cantis and none have height adjust"???

fietsbob

you have the CoOp parts bin not me..

my made for 700c old forks have 65mm spread between posts

already a significant angle on the Mafac style posts ,,

was not an issue with on center posts on the old AlAn ...


the 4mm discrepancy upward.. makes it worse ... Pauls moto light V brakes could adjust downward..

Cheap Bodge? just use the hole in the fork crown and bolt on another brake type ..

Bill Kapaun

I have 1 bike with 27" wheels.
I can use a 700c on the rear but not the front.
The ANSWER IS- YMMV.

dedhed

It's his way of saying, "I'll give you expensive solutions to simple problems, especially if you go to the LBS".

https://velo-orange.blogspot.com/201...ake-reach.html

https://www.amazon.com/Tektro-BR2007.../dp/B00NHPJCBI

fietsbob

MTB boom saw pad height adjustable cantilever calipers and frames with such variation on post location ,
loose tolerances,
they took advantage of that and needed the range..

in 1974, I bought Mafac Cantilever brakes, for a touring bike frame project,

and used the wheels , to show me where the bosses were to be brazed on..

Bike still works..






....

jlaw

The items shown below are a BMX component - they lower the posts 16mm - might work on your 520 - suggest you ask the company before buying. And, the spring on your existing canti's may or may not work with the 3 hole set-up.

https://www.boxcomponents.com/Box-Tw...Post-Extenders

The Tektro CR720 canti brakes might also work as suggested previously, but you should measure the distance between the posts before buying and inquire with Tektro. I have a 1984 Trek 620 and the spacing on the front posts is approx. 60mm - very close. Once mounted the Tektro pads might be too close together to work with this spacing - not sure.

JeffOYB

cool -- thx.

tektro -- who knows we might have a set in the big box. good to know there's a reasonable canti w slot for pad post. (cute that those brakes cost less than the extenders.)

also maybe switch to sidepull if need be

jlaw

Might be more than you want to get into - but you could also source vintage cantis that would work with narrow spacing and have the nec. downward adjustment. Some possibilities were discussed in this thread - about the 3/4 point - look for this picture:

Shimano m732 ($$$) or mt-62($) might work.

The Golden Boy is a knowledge source for this type of thing.

https://www.bikeforums.net/classic-v...0-project.html

jlaw

Or, the Shimano CT91 is cheap - $8/set at Jenson - and looks like they might provide the nec. clearance with narrow posts. The arm design is different than many vintage cantis and this might effect leverage/performance - might need different brake levers.

Sometimes updating a vintage bike with new components involves trial and error.

brian3069

You might find something helpful here.

https://www.google.com/search?q=bike...w=1440&bih=687

fietsbob

NB # 10 (previously offered in another thread) is for 406 (r=203) to 451 (r=225.5) wheel changes, ... 2_20" wheel sizes.

BMX frames have often used U brakes. , only more recently V type..







...