A
Argyll Bob
Guest
I am in the process of trying to change from 53 x 39 to 48 x 34 in order to get a gearing range more
compatible with my ability and expected terrain. I found a Ritchey 110 bcd crankset which allows me
to use the smaller inner ring, so that is not a problem. It's now on the bike, and the gear ranges
for both rings are where I want them. While I could get most of the same gears with 53 x 39, I had
some high gears I couldn't use and would have to use some very large cogs to get the low gearing I
want with a 39. Here's the problem - My bike is a 1997 Softride Powerwing - a beam bike with the
tall (tapering from about 3" to 2") aluminum chainstays rather than the normal small round ones.
1. Moving the derailleur down the braze-on tab enough to get the proper distance between the cage
and chainring causes the rear of the cage to hit the chainstay.
2. The cage on a standard road derailleur doesn't curve enough to match the smaller 48t ring. It
seems that my ideal solution might be a braze-on (has to be a braze-on as this bike has no
seat tube), MTB (would have a cage curvature close to what I need, and maybe enough metal that
I could make small changes with a grinder), with a shorter than normal cage. I haven't seen
anything like this, so I'm assuming that I will have to start with an existing derailleur and
make modifications. As far as cage length is concerned, it looks like I will need to cut
enough off the bottom of an existing derailleur cage to clear the chainstay, then make some
type of cross brace to regain the stiffness. For the curvature question, I see two
possibilities: Either start with a derailleur that has enough metal in the side plates so I
can grind the outer plate to match the ring shape, or tilt the derailleur back on the mounting
tab to get the tail of the cage closer to the ring. The second option would require reshaping
the mounting ear and/or shimming above the mounting bolt - not sure if that approach would be
strong or rigid enough. So i'm looking for suggestions from the experts - what derailleur
should I start with, and how do I make it work?
Thanks, Bob Leckron Indianapolis
compatible with my ability and expected terrain. I found a Ritchey 110 bcd crankset which allows me
to use the smaller inner ring, so that is not a problem. It's now on the bike, and the gear ranges
for both rings are where I want them. While I could get most of the same gears with 53 x 39, I had
some high gears I couldn't use and would have to use some very large cogs to get the low gearing I
want with a 39. Here's the problem - My bike is a 1997 Softride Powerwing - a beam bike with the
tall (tapering from about 3" to 2") aluminum chainstays rather than the normal small round ones.
1. Moving the derailleur down the braze-on tab enough to get the proper distance between the cage
and chainring causes the rear of the cage to hit the chainstay.
2. The cage on a standard road derailleur doesn't curve enough to match the smaller 48t ring. It
seems that my ideal solution might be a braze-on (has to be a braze-on as this bike has no
seat tube), MTB (would have a cage curvature close to what I need, and maybe enough metal that
I could make small changes with a grinder), with a shorter than normal cage. I haven't seen
anything like this, so I'm assuming that I will have to start with an existing derailleur and
make modifications. As far as cage length is concerned, it looks like I will need to cut
enough off the bottom of an existing derailleur cage to clear the chainstay, then make some
type of cross brace to regain the stiffness. For the curvature question, I see two
possibilities: Either start with a derailleur that has enough metal in the side plates so I
can grind the outer plate to match the ring shape, or tilt the derailleur back on the mounting
tab to get the tail of the cage closer to the ring. The second option would require reshaping
the mounting ear and/or shimming above the mounting bolt - not sure if that approach would be
strong or rigid enough. So i'm looking for suggestions from the experts - what derailleur
should I start with, and how do I make it work?
Thanks, Bob Leckron Indianapolis