With the increased popularity of 29ers, some frame designers have really struggled with being able to get chainstays short enough and yet still allowing tire clearance and preventing tire rub on either the seat tube or front derailleur. Some have gotten around this by wedging in a top swing derailleur (or even eliminating it all together and running 1x10, etc.). But it seems you still can run into problems in certain designs still having tire rub on the front der. cable.
While working on my wife's bike recently (and trying to fit a 29x2.25" tire on the rear without removing the front derailleur), I questioned why all front derailleurs are designed with the movement all taking place behind the seat post. Why can't the design be flipped and clear up all that space between the tire and the seat tube?
(see my quick illustrations below)
The first one shows the setup like most bikes are currently.
The second one shows it with the hinge part of the derailleur (in RED) in front of the seat tube (and the cable in front as well).
This might help keep some mud and gunk out of the moving parts as well!
Seems like such a simple change that there must be some reason others haven't tried it before. Thoughts? Any engineers/designers out there care to chime in?
Mtbr's 2016 Winter Biking GearReviews and Roundups
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Thread: front derailleur redesign?