I’m getting fed up with braze-ons with their misalignment, and their inability to accomodate unusual chainring configurations (eg 46/34).
anyone know of bike brands with decent tri geometry that allow me to use a band on (i.e clamp-on) FD?
oh and price can’t be too exorbitant. i prefer cheap materials like aluminium. Something like Yaqui is outside my budget unfortunately.
you’d be making a mistake. the chain will rub on the bottom of the derailleur cage over most of the cogset while on the small chainring.
You are a very wise man, Dan. Very wise.
Specialized Transitions use band on FD’s
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“You are a very wise man, Dan. Very wise.”
more importantly, am a very old man, very old (in bike years). since i’ve made almost every mistake, i can anticipate the mistakes others will make.
what we did (which would grant the OP what he’s looking for) is machine our own clamps onto which braze-on style FDs would bolt. just like the shimano and campy clamps. except our clamps set the derailleur back 5 degrees and at the appropriate angle, in other words, they “turned the clock back” 5 degrees for the FD. we designed and made this clamp just after we purchased merlin, because there was no good way to place a braze-on onto a round titanium seat tube (we designed, and merlin made, a tri bike called the aerial – this clamp was for that bike).
trek called us about a year later, and asked to buy that clamp from us. this is because they did not anticipate the problem i described in my previous post. they wanted this clamp not for any tri bike, but for their WSD bikes, some of which were built at 76 degrees. even bikes that are only made in this shallow angle can suffer from the chain dragging problem.
were there any of these clamps around i’d suggest to the OP this solution to the problem but, alas, i don’t know where you’d find one. trek did not buy these from us, because we were charging too much. so they took your basic shimano clamp and just put it through a secondary machining operation, canting or angling the surface that butted up to the derailleur. the idea was simply to drop the back of the FD – the trailing edge – a bit. it worked okay for them, at 76 degrees. i don’t know how well it would work at a steeper angle, that would probably be a non starter.
wow i never thought of that issue. thanks for the heads up.
actually my issue is more to do with the fact that most braze-ons i’ve come across tend to allow up to a min of a 50T big ring (because that’s the 130BCD limit) and totally ignore the compact cranks market.
there was a post i saw recently in another forum where the bike manufacturer supplied 2 different brazes with each bike, standard and compact. This was to be implemented for their 2008 bike range, but i can’t seem to find that thread now. I think it was Giant, because they use a braze that is screwed on by allen key screws rather than being welded on like most other manufacturers. At the time i thought that was a damned great idea and would around the inability to lower the FD enough to accomodate slow big rings. if only more bike companies would adopt this.
“actually my issue is more to do with the fact that most braze-ons i’ve come across tend to allow up to a min of a 50T big ring (because that’s the 130BCD limit) and totally ignore the compact cranks market.”
i don’t think they’re ignoring this market. most compacts are going to have 50x36 or 50x34. almost no compacts are going to spec less than 50, because at some point you’re going to run out of big gear. a 53x39 has a 14t spread, and a 50x36 has this same spread. but you put the 34 on if you really need some low end.
the alternative to a 50x34/36 is to go back to 130mm bolt pattern, or to stay at 110mm but put larger chainrings on the bike, not smaller rings. that’s what’s typical. very few people spec less than 50t for their big ring.
there is one way to get past this problem, and that’s just to redesign the darned braze-ons. instead of fighting over where to put these braze-ons, and which part of the market you’ll disenfranchise, all you have to do is make them longer, so that you can spec anything from 46t to 55t. what’s the big problem with this?
Do you think the OP would have any luck trying to adapt a bottom pull MTB derailleur? First workaround I thought of. Although I haven’t any experience with them, it also looks like FSA and Campy are spec’ing compart specific derailleurs as well.
Okay, this gets to a problem I’m having on the old Javelin X-frame that I’m in the process of building up. Aside from needing to figure out the derailleur cable stops on the boom tube, the FD placement is giving me worms (braze-on mount). Even with a 55/44 combo, the FD has a HUGE gap to the 55, and the chain drags when on the 44. I had to put an older Ultegra on there because the other FDs I had would interfere with the huge “seat tube” (the mechanism would bottom out on the frame and wouldn’t allow the cage to move). Any ideas? Would a compact-type FD help?
there is one way to get past this problem, and that’s just to redesign the darned braze-ons. instead of fighting over where to put these braze-ons, and which part of the market you’ll disenfranchise, all you have to do is make them longer, so that you can spec anything from 46t to 55t. what’s the big problem with this?
Does such a thing exist? I for one would **love **to see a dérailleur tab that could accommodate anything from 46-60t in the big ring, angled such that it would shift properly when installed on a steep (78+ degrees) tri bike.
I found an old Shimano 600 clamp-on dérailleur in my parts bin that has a really nice long cage - but I don’t know if the offset is sufficient so as to allow for proper shifting. As you’re well aware, this is a subject of great interest to me. 
i don’t know of anyone making such a tab.
Damn. That would rock. I wonder how difficult that would be for a builder to fashion?..