How much front der. rub is "normal?"

JH said:

As other posters have noted about their bikes, I get a small amount of
front derailleur rub when I stand/pedal hard, and the chain is on the
big ring. I can trim the front derailleur to eliminate the problem.
But is it really a problem? Does it indicate too much BB flex? Or is
a small amount of front derailleur rub in certain circumstances
considered normal?

I notice rub when pedaling hard, but my BB is worn and allows some play
to the cranks, I know I have to change it.
I guess you already checked that, but who knows...

It could be your frameset, i get lots of rub when i jump on the pedals
on my ALAN small-tubed aluminum bike. In damon rinard's frame
deflection tests there was a substantial amount of variance in bottom
bracket deflection in different models of bike.

- Don Gillies
San Diego, CA

It could be your frameset, i get lots of rub when i jump on the pedals
on my ALAN small-tubed aluminum bike. The same drivetrain with the
same adjustment does not produce chain rub on a (larger) schwinn
paramount. In damon rinard's frame deflection tests there was a
substantial amount of variance in bottom bracket deflection in
different framesets.

- Don Gillies
San Diego, CA

JH said:

As other posters have noted about their bikes, I get a small amount of
front derailleur rub when I stand/pedal hard, and the chain is on the
big ring. I can trim the front derailleur to eliminate the problem.
But is it really a problem? Does it indicate too much BB flex? Or is
a small amount of front derailleur rub in certain circumstances
considered normal?

With a traditional steel frame (Columbus SLX, Reynolds 531)- it was
quite common. Just read a review of my Fuso Lux from '87 where they
noted that the chain rubbed when climbing (this was a $1200 frame even
then) but it was normal.

For more modern steel frames, I don't know if they licked that problem.

Aluminum frames- not common at all except for whippy smaller tube frames.

This is one reason why I like having an Al frame for loaded touring.

Rob