V-Brake - Not enough spacer washers

[eddieboo]

Hello

I am replacing my rear cantilever brakes with Vs.

As the rear wheel is not perfectly centred between the frame (due to the gear cogs) the brake on the chain side does not reach the rim. Even with both sets of spacer washers on the pad side of the bracket, they're a good 5mm short.

Is this normal and can I just space out the pad with any washers I can find?

Thank you

[DaveM]

I think you have two separate problems.
First, the rim should be centered in the frame even though there is gears on one side. That means that either the wheel just isn't tightened down centered (easy fix) or the wheel isn't "dished" properly (more complex fix). I would try playing with the axle bolts a little to see if you can get the wheel to center better. Usually you pull the axle all the way back into the gear side drop out and tighten it. Then try to get the wheel to center and tighten the left side bolt to lock it in position.

On the brakes, I'm not 100% sure without a picture to see what you mean, but I don't think you want to put all the washers on the pad side. If these are pairs of concave and convex washers, a pair is supposed to go on each side so you can adjust the angle of the pad. Once you get the pads adjusted so that they hit the rim straight on, then you adjust the brakes so you get an even gap on each side when you release the brakes (I think this gap is what you mean when you say the brake isn't reaching the rim?)

To adjust centering, there is usually a little bolt or screw that sticks out of the side of the v-brake arm near the bottom by the pivot. Tighten/loosening these will move both brakes from side to side by adjusting the spring tension and should let you center the brakes.

But see if you can figure out the wheel before you adjust the brakes to fit the wheel being in the wrong place. Let us know if I'm misinterpreting your problem.

[Bill]

Dave,
This is more of a question, can Cantilever be replaced with V-Brakes? I thought the geometry was different in the bosses?


Thanks ,
Bill

[DaveM]

(05-07-2010, 11:19 PM)Bill Wrote:  Cantilever be replaced with V-Brakes? I thought the geometry was different in the bosses?

There's normally no difference on the frame/fork. So you can put vbrakes on a frame built for cantis and vice versa. But technically cantilever and vbrake brake levers are not compatible. The amount of cable pulled by the lever is different. Intermixing will work, but you may end up with very mushy feeling brakes or excessively stiff ones.

[Joe_W]

Incompatible are the Mafac-style centre-pulls, even if they are some kind of cantilever brake. As for "normal" Cantis vs. V-brakes: no worries ('cept for the levers)

[Bill]

Ok that is great information to know. Thank you both. Joe when you say Mafac are you meaning the RollerCam style? As the RollerCam does not accept the Cantilever or the V-Brakes bosses. Just didn't know about the Cantis and V's interchanging. Levers definitely not huh. Cool.


Again thanks I didn't know that,
Bill

[DaveM]

(05-09-2010, 05:52 AM)Joe_W Wrote:  Incompatible are the Mafac-style centre-pulls, even if they are some kind of cantilever brake.

Joe, I've several people refer to old Mafac brakes as "cantilevers" but all the ones I've seen have a single central mounting bolt like a normal caliper. I know they sort of look like cantilevers because of the two pivots. But is there really some that are cantilevers or is this just a terminology issue? My solid knowledge base doesn't go back as far as some...
thanks

[Joe_W]

From this thread: http://forums.bikeride.com/thread-957.html
http://www.thebicyclingguitarist.net/graphics/schwinn/200310/20031003-front-brake-m.jpg

And of course:
http://www.sheldonbrown.com/harris/mafac.html

I have them on my Peugeot (crossified road bike), they perform... mediocre under wet conditions, though the salmon coloured KoolStop pads help a little

[Bill]

I have a pair of those in a box in my shop.

[Joe_W]

I'd like to get rid of mine, but I cannot mount another brake on the frame, the bosses are in the "wrong" place and there is also no break bridge in the rear... so I'm stuck with those and the break levers and thus the old shifters. Would like to get STIs for cross duathlons, sucks to suddenly realize you are in the wrong gear but cannot reach down to the shifters 'cause of the terrain. To be honest, I think I'll get a (halfway) decent cyclocross bike next (with fender eyelets and disc break tabs, good luck finding those...)

[DaveM]

Joe, don't mean to flog this issue, but I'm still confused by what you describe. Everything you link to describes these as "caliper" brakes that mount to the fork crown or rear brake bridge. Are there Mafacs that are true "cantilevers" that mount to bosses attached to the fork legs or seat stays?

Also, I'm pretty sure modern road brake levers (and STI levers) will work with both old calipers and cantilever brakes. I thought the only thing they're not compatible with is v-brakes. So maybe you could make the switch to STI levers?

[Joe_W]

Grrr... ok, I just realized that the Mafacs on Sheldon Brown's description have some sort of back plate. Mine don't, see pic.

[Bill]

Nice brakes !