Just seen this http://www.rocknrollbikes.com/trials/brakes/brake-parts/onza-disc-brake-converter.html

But not sure how it fits between the frame and hub?

Obviously I’d need a new hub etc. but how do you allow room for it?

I’ve seen a Hope version in pictures but never for sale/ in the flesh.

That looks like it’s different to the Hope version in that the Onza one fits on the outside of the dropout, hence the need for the longer skewer. That has the significant advantage that you can use a normal hub whereas the Hope method requires a shorter axled one.

I have a Hope one FWIW, the Onza version looks better IMO though I guess there could be more issue with flexing and also it won’t work with frames that don’t have flat dropouts (on the outside face).

take a look at a2z.
I’ve got one that just clamps around the drop out, no need for the bar to the canti brake mount.
Used if for several years with no problem.
Only thing is that I need to remove the skewer completely to remove the rear wheel.

I have an A2Z too 🙂

It works well but needs flat dropouts (again) and a seatstay that’s up to the job of being pushed against (instead of the bar to the canti boss).

I used a hope one on my old FS before having a mount welded on and I have the hope one somewhere in my spares box. They were a good solution for older frames and the only problem was it took a little longer to change a flat but you kind of got used to it. The hope one didnt need flat dropouts from memory, they certainly werent flat on the bike it was fitted to. I was keeping it to fit to another bike but SS’ed it instead and left the Vee’s on.

Does the a2z one clamp on the outside of the frame?

It clamps on both sides of the dropout

This is how it looks off the bike

The silver plate clamps on the outside of the rear dropout, the black part on the inner side.

The QR goes through the smaller hole.