Compact Cranks and Cassette Range Limits?
 

I have a new Gunnar Sport frameset (road frameset) built up nicely with a full 2007 Centaur Compact group. My gearing is 34-50 and 11-25. Whenever I'm on the 34/11 the chain rubs the 50 ring. What on Earth could be causing this? Crooked frameset? Is 11 too small for a compact? It's the new Ultra-Torque BB and crankset, so installation couldn't possibly be simpler - and the arms seem to measure the same distance away from the chainstays on each side, so it doesn't seem likely.

Everything is brand-spanking-new. Any help would be much appreciated. I already took it to one shop here in NYC and the guy suggested I only ride the big ring. Wow, what expert advice!

The solution I would use is to NOT use the 34/11 combo, that's cross chaining in the worst possible way.

is it not supposed to work? if not i am 100% fine not using it. this is my first road bike so i really have no idea what the parameters are.

Cross chaining with a 50/34 crankset will almost always result in a little bit of chain rub. Simply avoid using the 34-11 combo.

Ok, great. Thanks, folks. I just assumed I'd had it adjusted improperly. Is the same true for 50-25? Meaning, should I make sure it doesn't rub the FD for that gearing? Coming from a SS/FG background, the whole concept of multiple gearing is a bit new. I appreciate the help.

In general, avoid the two cogs of each extreme. For example, avoid the 34/11, 34/12, 50/25, and maybe the 50/23.

Why they ever called 10 speeds 10 speeds is beyond me.

From my understanding (I've just recently returned to cycling, almost up to 1500 miles since I started riding in March of this year), the most efficient gears are going to be when you keep the chain nice and straight (small front chainring on big rear cogs, middle chainring (if equipped) on middle cogs, large chainring on small cogs).

If you stretch the chain diagonally (small front chainring to small rear cog, large front chainring to large cog) things become less efficient, and at the extremes the chain will rub against things making the drivetrain noisy and inefficient, and possibly damaging components.

I have a triple up front (28/38/48 which I'll call 1/2/3) and an 8 gear rear which I'll call 1-8 (1 being the largest cog, 8 being the smallest). I almost always cruise at 2/5 or 2/6. Starting from traffic lights or stop signs I'll be down in 2/2 or 2/3 and shift with just the rear to get up to cruising gear. One time riding into a 40mph headwind, when I was still in pretty bad shape, I was down in the 1/2 1/3 range. There aren't many steep hills where I ride, so I don't use the 28 very often. If I get a nice tailwind and feel like going fast I'll click up from 2/5 or 2/6 to 3/5 or 3/6, then start going to 3/7 or even 3/8.

Also, since you're new to the whole riding with gears thing, I'll also mention I've heard it's a good idea to lighten up on the pedaling while you're shifting. It's supposed to increase the life of your chain and gears, just like being smooth with a manual transmission in a car helps prolong the life of parts that are subject to getting worn out.

Thanks for the advice. One hard adjustment for me thus far has been to coast. I'm so used to riding fixed (7-8 years in NYC, DC, SF) that I still have to remind myself to coast. I'll work on the smarter shifting. Mostly, I've been playing around, shifting like crazy to see how things feel... Likely not great for my bike, but neither is riding in NYC. :)

Coasting is for wussy. Don't worry if you're always pedalling. I only coast when I'm either lazy or going around a sharp corner.