SingeDebile

I would have said the same if he was still using the original tire size for the bike... but the fact that he is both switching to much smaller tires and switching to a smaller wheel size... but as is mentioned above who knows maybe the the OP will prefer it

..the geometry of the derailleur can affect the shifting significantly, an example would be how you cant use the 9sp sram stuff even with friction shifting (far from working with indexed) https://www.rivbike.com/products/show...ube-kit/17-101

Zaphod Beeblebrox 

yeah I honestly didn't consider 9 or 10sp mostly because the OP mentioned moving to 7 speed. But yeah that link goes to show ya that no matter what I'd think (or know) will work there's always gonna be at least one exception.

I haven't tried it, and I don't think I'd beleive it until I saw it myself but I would be honestly shocked to learn that you *can't* use a 9 or 10 speed rear cassette with friction shifting given a RD with enough travel. I can understand how the narrower spacing would make it more difficult (possibly even very difficult) to pull off accurate shifts but my brain doesn't allow me to picture it simply not working at all.

honestly, even the case that Rivendell mentions in that link

My feeble mind cannot process how thats possible. You let out all the cable and the shifter goes to its limit. You take up all the cable and the shifter goes to its other limit. Everything in between is a matter of where you stop the lever. I'm not saying they're making it up....just saying I simply can't fathom it.

cuda2k

Doh, just thought of something. 27 -> 700c = 4mm difference in rim radius. What ever brakes you go with will not only need to reach where the 27" wheels are now, but that 4mm length on top of that. A lot of canti-levers may not have that much adjustment, and will likely lose some of it's power being that much closer to the pivot point.

mazdaspeed

The current cantilever brakes will not reach, I know that much. I have tested long reach callipers and those do reach, although a mm or two may need to be shaved off of the bottom of the front brake arms as to not interfere with the cantilever bosses.

RobbieTunes

Keeps him alert.

SingeDebile

By changing the place where the pivots on the two parallel plates of the derailleur pivot you can affect how far it moves, in a way that is not necessarily a direct 1:1 relationship (for example your research determines that its more important to have accurate shifting on the smaller cogs you make the derailleur move further there, with the ratcheting mechanism to match it, also the physical distance between the cogs may be different as well) When you have a 9 or 10 speed drivetrain these differences can add up in a bad way.

though in practice these differences are not always that big or can be adjusted for like this article on getting 9speed ergo's to work with a shimano drivetrain https://www.hubbubcustom.com/articles_ergopower.html

illwafer

my opinion:
i think you should try a different set of cantis that will adjust for 700c. some are better than others.

these cheapo shimanos have always worked well for me:


it won't work as well as having the bosses moved, but it will probably work well enough.

mazdaspeed

It's too late, the brakes were purchased before making this thread

USAZorro

Nah. It's not too late until you hack the canti mounting posts off.

illwafer

save those brakes for the next time you get a 27" bike w/o cantis.

mazdaspeed

You guys aren't gonna convince me to keep the cantilevers, sorry... lol That said I won't cut the bosses off. Furthermore, I've decided not to keep the original parts I'm not using since I might as well sell them to people that will appreciate them more than I, and recoup some of the expenses from the current build (wait till you guys see it when it's done )

mazdaspeed

The more I think about it the more tempting the tektro cantilevers are. ASSUMING the braking power will be as good as dual pivots, AND they can reach the 700c wheels. Thoughts?