renyay

I'm converting a MTB (built for 26" wheels) to 650b wheels. I've read that the conversion can work smoothly and that there are some fairly highly adjustable canti breaks out there which will line up with the larger wheel. The best article I've read on this is here:
https://velo-orange.blogspot.com/2011...t-to-650b.html
Anyway, the Tektro 720's mentioned in the article aren't working for me at all. I'm using some old dia comp breaks that are passable, but I know I can find better.
Should I spend the money on Avid Tri-Align brakes, or something similar? I know Onza made similar breaks, does anyone have experience with any other canti's like these? Can you move the pads up pretty high, and if you do does it compromise break power?
Any advice for something more modern I should try?
Thanks!
(And please keep negative opinions about this conversion to yourself... I'm not interested )

FastJake

Moving up the pads on canti brakes 12.5mm will certainly reduce braking performance due to the greatly reduced mechanical advantage. Perhaps some long reach caliper brakes?

For fun I once ran 650c wheels on a MTB with the stock cantis but that was only a 6mm difference. After deciding I didn't like 23mm tires on a MTB I stripped the wheelset down for the hubs as originally planned

Seriously though, I see absolutely nothing to be gained by running 12mm larger rims. There is a good selection of 26" tires already, the slightly larger rims won't change anything but your braking performance, if you can get it to work at all.

Six jours

I don't know of any light, supple, wide 26" tires. There are several in 650b.

B-R-A-K-E-S.

Pads are a very significant part of brake performance. If your current brakes aren't stopping well, the problem can often be addressed with new pads rather than new brakes.

dsbrantjr

Try these https://problemsolversbike.com/produc..._cable_carrier and some Kool Stop Salmon pads (the Tektro ones are not so hot) with your Tektro CR-720s. Adjust the straddle cable as low as possible and see how they work, I think you might be pleasantly surprised.

renyay

Seriously Though: "(And please keep negative opinions about this conversion to yourself... I'm not interested )"

I'm really not interested in explaining all of the issues I have with frame sizing, my very short legs, and my reasons for thinking this would make a great touring bike. I really just want some functional advice about what breaks offer high adjust-ability.

renyay

I will look into this. Though the current pads on the tektro cr720's barley touch the rims at all. I can't imagine that changing the hanger/pads woud change this.

At the moment I'm using vintage ritchey pads which are really beefy and have worked great on other set ups. My brakes are Dia Comp 998 canti's.

FastJake

Nothing wrong with using a MTB for touring, they can make great touring bikes. I wasn't expressing negative opinions, just simple facts. The bike will fit you exactly the same no matter what wheel size you use. The slightly larger rims won't change anything except your brakes. If you have a valid reason to run a different rim size that's fine, but given all the strange questions people ask I am always curious as to the reason behind it. Often times people try to do things that just don't make sense, whether or not they realize it.

pierce

there's plenty of lighter 26" road tires in slicks/semislicks, for instance Vittoria Randonneur Pro's come in 40-559 (26x1.5"), and are a 120 thread/inch tire. Schwalbe Marathon Racers come in 40- and 47-559 (26x1.5 and x1.75) and are a light strong tire. There's even a Schwalbe Durano HS399 in 28-559 (26x1.10) which runs 85-115psi and is a 260 gram tire, also available as a 35-559 (26x1.35)

renyay

You should check out the link to the VO blog entry I included initially. Aside from being able to run supple/high pressure tires, I find climbing with 650b's to feel much easier. My legs are really short, I dislike 700c's because I like to run fat tires and that combo creates a large overall diameter which makes climbing very difficult; it also causes toe overlap on the smaller frames that fit me. Of course climbing is easier w/ 26's, but they feel too small for touring with a moderately wide slick tire. 650b really is a great size for a touring bike, or a commuter. Sure, the overall diameters end up being similar with fat MTB tires on a 26, or 650b's and a 38 - 42cm touring tire, but the difference in the actual ride quality, especially long term tour riding, is huge.

I guess in a nutshell, it's about being able to climb more easily, and feeling like I have better performance than 26" tires with slicks will give on surface streets. Small folks and women end up having all kinds of issues with traditional bike sizing and I am no exception. I apologize if I sounded rude, i just don't like having to explain all of this every time I have a question or am interested in doing something non-conventional which will make riding easier for me.

renyay

Ya, these are probably the way I'm gonna end up going.
If I can though I want to use canti breaks because they will work with the break levers/inline levers I already have.
Those motobmx breaks are linear pull. In the end, they will prob be the best bet, I'll just have to get linear pull drop levers.

Six jours

Those are horrible tires compared to things like Pari-Motos and Hetres.

Of course, many folks are not interested in things like Pari-Motos and Hetres, in which case there truly is no reason to go to 650b.

Mr. Fly

Built with the same carcass as the excellent Grand Bois tires, the Compass 26" tires are similarly excellent but expensive.

pierce

he said touring on a mountain bike frame.

btw, Panaracer has 32-559 Paselas, too.


regardless of how he manages to get a cantilever brake to reach 1/2" higher, the fact remains that with the same size 'drive arm', he now has around 33% less leverage on the pads, since the standard cantilever brakes are about 1" from the pivot to the rim, and his 650B tires will be more like 1.5" from the pivot to the rim. effectively this means he needs a super-short-pull brake lever to get the same pad force as standard brakes. think anti-vbrake.

I suppose the ultimate solution would be to take off the brake bosses, and braze on new ones 1/2" higher .... its actually a lot easier than I thought it was going to be, I enlisted the help of a friend of mine who has extensive brazing and silver soldering experience. To prep, I wire wheeled off the paint for a couple inches where the bosses go, and I used a couple round files to shape the new bosses to fit the frame tubes. My brazing/machinist friend made a jig (basically just a strip of aluminum with two holes drilled that we bolted the two bosses onto to hold them parallel), we c-clamped the frame to a jury-rigged stand of 2x4s and such, and he used his oxy-acetylene rig with a low temp spreader. brushed on flux, got stuff hot, flowed in brazing wire just like soldering. en route to his place to do this job, I'd picked up a can of rattle-can red paint to cover the damage, fully planning on eventually repainting the whole bike, and holy crap, the rattle can red /exactly/ matched the red powder coat I'd had this bike painted a few years earlier.





that bike happens to be an old cruiser converted to a 7-speed, which now stops like its got an anchor out.

Mr. Fly

I agree that the 650B size serves a gap between 26" and 700c wheels, in terms of optimizing frame geometry. Perhaps like you, if I want to run a semi-wide tire (30mm) with fenders and do not want to compromise frame geometry, I'll have to accept a bit of TCO with 700C. 650B will eliminate that TCO for me.

Nevertheless, 650B isn't magical and there is no reason why it should magically make you climb faster, all things being equal. But of course, not all things are equal because 650B is still fairly boutique and most available 650B tires are fairly high-end. Ergo, you can't compare a run-of-the-mill 650B tire to a similarly run-of-the-mill 26" tire because most 26" tires suck. I know this because I have a Surly LHT and Atlantis 2 that run 26" tires, and it had been a real adventure to find 26" tires that don't feel like rocks or roll like molasses. You can find 20,000-mile or puncture-proof 26" tires (or both!) but good riding 26" tires are rare as hens' teeth. The only two acceptable 26" tires I found are Schwalbe's 26" Kojaks, and Compass Bicycles' 26" tires. The latter, especially, roll really well and I can attest that they are in the same general ballpark of excellence as the Grand Bois Cypres. They are pricey though, but excellence seldom comes cheap.

So, an alternate solution that you can consider trying (in lieu of trying to jerry rig 650B wheels on a 26" frameset) is to invest in a pair of nice-riding 26" tires. The experiment shouldn't be too expensive even if it fails for you since you can always sell the slightly used tires for most of their purchase price.

Mr. Fly

There are adjustable leverage brake levers. The Avid Speed Dial and some Shimano levers have this functionality where one can vary the leverage. Unfortunately, that's only if the OP wants to use 22.2mm MTN bars and not 23.4mm road drop bars.

Six jours

Do you have personal experience with them? The pictures seem to show a thick, heavy tread and I have discounted them because of it.

renyay

I've tried the Soma New Xpress 26" tires. They were expensive (for me) and about as far as I care to go in that experiment. I know what I want, and I'm just looking for advice about brakes.

renyay

I find it kind of hard to believe, that everyone else finds it so hard to believe, that I'm doing such a conversion. Similar conversions have been done many times, and again, I'm not asking for opinions on what I'm doing, just advice on brakes.
Re-brazing the bosses is an option. So is using long reach caliper brakes. I'd like to try brakes like the old Onzas or Avid Tri-Aligin's before doing that. My original question was if anyone experience with those, or brakes like them.
Thanks.

renyay

I'm not interested in climbing faster. But I will climb more easily on a 650b vs a 700c. And again, not interested in using 26". This post wasn't intended to be a debate about tire sizes, and I'm really not interested in everyone's judgment of my project or ideas. I should have just asked a one sentence question and avoided explaining my reasons for inquiry.

pierce

I got the brake bosses I put on my cruiser here,
https://www.cycle-frames.com/bicycle-...-BRAKE-BOSSES/

I remember some more now, I didn't hand file them to fit after all (that was my original plan). my friend made his jig with the 'official' center-to-center distance of 75mm adjusted upwards to about 80mm because my cruiser had rather wide old school rims. and then we measured the tube radius on both the forks and stays, and measured center to center on the stays and forks, and setup his milliing machine to cut that out of the base of the bosses while they were bolted to the aluminum bar jig.

when we brazed them, we secured the frame (or forks) so the bosses were pointing straight up, so they were held in place by gravity, before brazing them on.

I would only think of doing this if your frame and forks are steel, and not real thin wall. if the frame is thin wall steel, have a bicycle frame builder do it, as a backyard welder/brazer will likely get things too hot. if the frame is alloy, they need to be mig welded I think, thats way beyond me.

pierce

btw, re: climbing difference, its really just that the wheel sizes effect your gear-inches. smaller wheels act like a lower gear ratio. you can do much the same with cassette and/or crank changes. Look at the gearing on a small wheel recumbent.

krome

Actually, with the Paul moto bmx, the amount of cable pull can be influenced by the position of the pads on the arms. For this, the pads will be further away from the pivot than usual, so the amount of cable pull required should be less, therefore it might work fine with short pull levers.

pierce

standard cantilevers are already short pull. moving the pads farther from the pivots mean they become even shorter pull, needing even stronger cables that move less distance.... or you need cantis with longer levers, which AFAIK, aren't typically available. unless maybe you use v-brakes which are nominally long pull, but by moving the pads up 0.5" you've effectively reduced their pull length.

xenologer

cr720's have wide and low set arms, probably not too great with the taller rims.
consider a medium or low profile brake with arms that angle upwards.
how about an old shimano nonthreaded canti brake ? those have tons of adjustment, might even have the brake post angle upwards as needed (more than normal ) then file the pads to be square with the rims

pierce

if you end up having to do that (angle and file the pads) you'll probably find you'll need to replace the pads more often or the angled pad body will bottom out on the rim. and you may have to keep up with trimming any 'flanges' that develop on the pads.

on a caliber application where we put a 700c wheel on a 27" bike, I had to use a little rattail file to extend the brake pad mounting slot a millimeter or so lower so the pads would hit square on the center of the rims. in this specific case, there was plenty of material to the brake arms.

the only cantilevers I have a clear mental picture in my head of are the VERY early Shimano Deore ones on my 1st generation stumpjumper, these used the 'post' style pads, which went through an adjustment bolt that was on a spherical washer... I don't remember ANY adjustment for how high the pads hit the rims other than the angle and extension. but I guess the later cantis are different.



my 1st gen stumpie was so early it had mafacs on it, which I promptly swapped for a set like these, they had the same geometry.


hmmm, these new-for-2012 Shimano CX50 cyclocross cantis have quite a range of vertical adjustment