On 5/20/2019 5:12 PM, wrote:


Also should have stated that with Campagnolo, the left/front Ergo shifter does not care about double or triple chainrings. So its easy to just put on a triple crank if you need low gears.

That reminded me of a friend's recent problem. She rides a classic Trek
touring bike from the mid 1980s, a really lovely machine.
http://www.vintage-trek.com/images/trek/84Trek_23.jpg
And in recent years especially, she gets a lot of use out of her triple
"granny" sprocket.

A few years ago her front derailleur wouldn't shift. The return spring
had broken. She took it to her usual bike shop. They didn't have a front
derailleur designed to fit her (old standard) 1 1/8" seat tube, so they
installed one intended for a 1 1/4" seat tube, and used shims to adapt it.

Trouble was, the shim held the derailleur far enough to the right that
it wouldn't shift to her granny. When she brought it to me, I saw it was
already at the limit of its leftward adjustment, so I grabbed an old
SunTour front derailleur and installed it.

I think that SunTour was intended for a half step plus granny setup.
Remember those? (And she once had that, but now has something like
50-42-28.) The inner (left) half of the cage was only as tall as the
outside (right) half, maybe 1/2" to 5/8" tall. Most triple derailleurs
have a much taller or deeper inner half of the cage. But I think those
might not work well with a half step setup, since the bottom of the left
half of the cage can run up against the middle chainring.

Anyway, she went away happy and rode with no trouble for maybe five
years, till a few weeks ago. She said she recently had to really coax it
onto the large sprocket, and now could no longer make that shift at all.
The cranks would jam. I was amazed to see the outer (right) half of the
derailleur cage was broken in two, along a horizontal line.

She does not ride with the cage scraping, and there was no real wear on
the inside of the cage. I think that the action of shifting from the 42
to the big ring with the half step derailleur was causing the chain to
partially jam, and the repeated jamming eventually fractured the cage.
And the cage is not aluminum; it's either chromed steel or polished
stainless steel.

In any case, I had no other candidate derailleurs to give her. The bike
shop owner eventually dug deeper into old stock and sold her a Dura Ace
front derailleur that she says works fine. I'll be interested in
inspecting it, and seeing how long it lasts.

I there's a moral, I think it's that some derailleurs are good for half
step with those close ratio shifts, and some are good for wider range
shifts.

Oh, and the other moral is, bike parts can go bad after just 35 years or so.

--
- Frank Krygowski