650b conversion of 700c canti bike

[Bernard Duhon]

 

 

Have any of you converted a700c canti bike to 650b using the canti studs?

 

Ideas?

 

Bernard

 

[iamkeith]

I have no experience or wisdom to share but, unless the brake posts were mounted unusually low and you could use the adjustability of Paul Motolites or similar, it seems the process would have to start with using a pair of these extenders in the opposite manner from which they were intended.  Cheap way to experiment.  If you scroll down on the page, there are other, similar devices:

https://www.danscomp.com/promax-brake-post-extender-black-ba21-0000pe01-bk/p1441682?gad_source=1&gclid=Cj0KCQjwkZm_BhDrARIsAAEbX1HTGdB4vVYiA7qBgEm96CxZ-5nmIYddR9yCoWdOUDklrswRu29zC1EaArRUEALw_wcB

[iamkeith]

From one of the descriptions:

MCS Brake Post Extender Description:

The MCS Brake Post Extenders is a simple way to move your brake mounts if your brake pads aren't quite lining up with your rim. You might be putting a 1-1/8" or 1-3/8" wheel on a frame intended for a 1.75" or vice versa. With these brake post extenders, you can move your brakes either 16mm forward or backward depending on your application.  

Note: You will need to swap the sides that the extenders are on to change the orientation.

[Bernard Duhon]

Thank you so much that seems to be the ticket.

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From: rbw-owne...@googlegroups.com <rbw-owne...@googlegroups.com> on behalf of iamkeith <keith...@gmail.com>
Sent: Friday, March 28, 2025 1:19 PM
To: RBW Owners Bunch <rbw-owne...@googlegroups.com>
Subject: [RBW] Re: 650b conversion of 700c canti bike

 

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[Steve]

Interesting adapter. 

Bernard, if you give them a try please post an evaluation of how they perform. I'm wondering if they might produce a judder or squeal, especially on the fork.  I have an older 700c canti touring bike that I'd love to mount 650Bs on so I can swap tires and wheels between it and my Platypus.

Steve in AVL

[Bill Lindsay]

iamkeith recommended the use of brake post extenders and included a link.

I am going to respectfully disagree.  That's not going to work, IMO.  That product is a BMX product.  BMX bikes that take V-Brakes or other post-mounted brakes almost always have brake posts that are replaceable; they thread into a welded-on piece.  To use that extender, you first remove your post, then bolt the extender on in place of your post, and then thread your post into the extra hole of the extender.  Most adult bikes do not have removable cantilever posts.  The cantilever posts are a single piece brazed on in a single location.  Unless the OP happens to have a 700c bike that by chance was built like a BMX bike, then that product won't work

Bill Lindsay

El Cerrito, CA 

[Steve]

Well then.....

Looking at the bolts that are included with the various extenders they do appear to be a much larger diameter than the bolts that the brakes themselves mount with.

[Bernard Duhon]

Thank you for that bit of wisdom

 

I have no BMX experience.

 

From: rbw-owne...@googlegroups.com <rbw-owne...@googlegroups.com> On Behalf Of Steve
Sent: Friday, March 28, 2025 3:19 PM
To: RBW Owners Bunch <rbw-owne...@googlegroups.com>
Subject: [RBW] Re: 650b conversion of 700c canti bike

 

Well then.....

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[iamkeith]

Oops sorry.  I don't have bmx experience either, and those didn't show an installation example, so I assumed they were somewhat universal.  Makes me wonder why ALL posts aren't removable.

[Josh Zielinski]

26" to 650B is relatively easily done on a canti post outfitted bike.  I recommend using Vbrakes and (BMX brand?) ProMax makes one with plenty of room for the conversion.

700C to 650B is more challenging if cantis are in place.  While desirable because the frame may accommodate bigger wheels  already (canti outfitted 700c tend to be tourers or CX bikes) the posts need to be moved by someone with frame building skills.  It's expensive but can be worth it if the frame is a good fit.  Still much more affordable than a custom bike and/or most off the shelf canti frames that will fit 650B.

I wouldn't trust any removable type canti posts that may be out there.  Too much pressure and too much to go wrong. 

Josh Z

Oregon 

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