Quoted message said:I've been riding with the Ultegra 10 speed drivetrain for about a year
and haven't been able to dial things so that I can shift to the
smallest rear cogs while in the smaller front ring. I can usually spin
freely in the 15 without scraping the outside edge of the front
derailleur, but not below. I'm not so concerned with running the 53
tooth ring across to the larger rear cogs.
Is this normal for Shimano 10 speed setups? Should I not expect to be
able to use every possible gear combination without scraping?
It's not practical to have a 10-speed (or even most 8 or 9-speed and many
7-speed and so on) drivetrain that allows use of all possible combination of
front & rear cogs without issue. It's not even physics, it's geometry. If
you move the crankset out far enough that your chain clears the larger
chainring (when you're in the smaller one) and you're in the smallest rear
cog, you'll find it very noisy and difficult to shift into any of the larger
rear cogs (when in a larger chainring) because the chain will be trying to
peel itself off the teeth. There are all manner of trade-offs that involve
durability of cogs & chain, ease of shifting, noise...
Having said all that, bikes will sometimes have a bottom bracket that's out
of plane (not perpendicular to the drivetrain). That can make matters much
worse than they need to be. If you've got a long straightedge, place it
across a chainwheel (or between them) and make sure that, as it heads
towards the back of the bike, it stays parallel to the frame.
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
