Info needed on cantilevers for 26 inch to 650b conversion

2,240 views
Skip to first unread message

wood chuck

unread,
Nov 22, 2015, 12:23:17 AM11/22/15
to 650b
I know this has been done before, but what cantilevers have people had success with? Anybody tried the Shimano CX-70? Paul Motos are nice but too $$$ for me. I have a Soma Groove w/ a Kona Project Two fork. Any help is much appreciated.

mikel...@juno.com

unread,
Nov 22, 2015, 7:37:21 AM11/22/15
to dirtba...@gmail.com, 65...@googlegroups.com
i read where Tektro 720 cantis worked for a 559 to 584 conversion
____________________________________________________________
A Balance Transfer Card With An Outrageously Long Intro ...
http://thirdpartyoffers.juno.com/TGL3131/5651b6be593a336be79b7st04duc

Dave Johnston

unread,
Nov 22, 2015, 9:18:33 AM11/22/15
to 650b
I think the real question is "WHY?". Because you want to put smaller tires and raise the bottom bracket? If you have room you might want to keep it 26" and put Rat Trap pass tires on.

-Dave

franklyn

unread,
Nov 22, 2015, 9:30:14 AM11/22/15
to 650b
I found this web page on Tektro's website very helpful. It lists all the tektro's non-disc brakes. when you click into each brake product, the page lists the "dimension", which I think is the "brake reach". For example, the CR720 has a brake reach of 21-35mm. When you convert from 26" to 650b, the change in the radius of the rim is (584mm-559mm)/2 = 12.5mm. It means that the brakes need to be able to reach 12.5mm higher on 650b rims than on 26" rims. 

The 14mm (35mm-21mm) range that the CR720 has seems to be OK to cover the 12.5mm raise. However, depending on the placement of the cantilever brake posts, if the "brake reach" of a fork is higher than 22.5mm when using 26" wheels, then CR720 won't work with 650b wheels. Often, the "brake reach" of the front and rear are also different. For example, I converted a Specialized Rock Combo from 26" to 650b. The rear brake posts allow me to use CR-720, but the front brake posts were placed too high for the CR-720 to work. I ended up switching to V-brakes. Many V-brakes designed for BMX bikes have a very wide range of adjustability. For example, this Promax brake has 35mm of adjustability in terms of reach (2.5 times that of the CR720)! If you want to keep your short-pull brake levers, you can use the mini-V version of the Promax brakes. But there are several BMX V- and mini V-brakes that have this feature, which is convenient for wheel conversions. 

The beautiful way is to use Paul Monolite, but as you can see from the price, it's 5 times more expensive than the Promax. One of the pictures in my Rock Combo album has a close-up of the Promax, and it has really decent finish and it works very well--easy to install and adjust, no squeaking noise right off the bat, and has great stopping power. 

So way to know for sure is to buy the brakes you want and try it on for size. short of that, you can put a 650b wheel in the drop-out and measure the distance between the middle of the ring to the middle of the brake-post, then consult the Tektro page to see which brakes has the reach range to work.

hope this is helpful,
Franklyn

wood chuck

unread,
Nov 22, 2015, 4:43:32 PM11/22/15
to 650b
Maybe I should have been clearer on my plans: To build up a rough road bike with as many parts as I already have. And seeing as  I already have 650B wheels and tires the only thing stopping me (so to speak) is some affordable and compatible brakes.  Building or buying some 26 inch wheels and new tires really isn't in the budget just now. If Christmas wasn't coming I'd just buy a Grand Randonneur frame and go from there. So many projects, so little money.

Nick Favicchio

unread,
Nov 22, 2015, 8:01:44 PM11/22/15
to 650b
For your same reason, already having 650b wheels on hand, I converted my MB-1. However, the Tektro 720s didn't quite have the reach.

The Promax P-1 v brakes work great! The stock pads grab like the dickens but leave a lot of crud on the rims. Doesn't bother me but thought I'd mention.

If you want a used Soma GR with slightly crimped seat stays so as to fit 2" tires, let me know :).


https://motorbacon.wordpress.com/2015/11/11/soma-grand-randonneur/

Philip Kim

unread,
Nov 23, 2015, 8:38:44 AM11/23/15
to 650b
I've seen CX-70 work well. Tektro CR720s also have enough pad height adjustment. I've done this before on these brakes.


On Sunday, November 22, 2015 at 12:23:17 AM UTC-5, wood chuck wrote:

mitch....@gmail.com

unread,
Nov 23, 2015, 1:11:54 PM11/23/15
to 650b
CR720 provided easy conversion for my MB-1. The CR 720 allow 13mm pad rise is enough to convert 559 to 584, 12.5mm radius difference. Changes your mechanical advantage though--your cantis will feel less strong with the same lever/rim/pad.

--Mitch

franklyn

unread,
Nov 23, 2015, 2:36:41 PM11/23/15
to 650b
As I wrote in my earlier reply, the 13mm (or 14mm, according to Tektro's website) of CR720 only works if the canti-post is placed at the location such that you can move the brake pads up enough to reach 650b rim. If when you have 26" wheels on the bike, the brake pads sit in the middle of the slot already, then it only has 7mm of space to move up, and won't be able to reach a 650b rim on the same frame/fork.

Franklyn

cmontgo...@gmail.com

unread,
Nov 29, 2015, 3:19:46 PM11/29/15
to 650b
To throw another ingredient into the soup I converted my All Rounder to 650B using the Tektro Oryx's. 

Craig in Tucson

Tai C

unread,
Dec 14, 2017, 5:52:33 PM12/14/17
to 650b
First, I realize this is an old thread, but there aren't too many discussions on this topic, so I thought I'd add to this. I converted a 26" Gary Fisher Hookooekoo mountain bike to 650b randocross using TRP Revox brakes. The Revox's work perfectly but admittedly the brakes pads are almost at the upper limit of adjustability. The advantage of the Revox over the Tektro 720s is that, in addition to about 15mm of vertical movement of the brake pads, you can also adjust the angle of the brake pads in the Revox, which gives you a few additional mm of adjustability. For those who are wondering why one would want to convert 26 to 650b, I think it makes sense if one is converting a mountain bike for mixed terrain use, including gravel and cyclocross, as mountain bike frames tend to be stronger. Just as a side note, on my 650b Hookooekoo, I'm running 41mm width Surly Knards, and there's plenty of room for fenders.
Reply all
Reply to author
Forward
0 new messages