Cross Gearing - How Many Combos Are Bad?

[TopTube]

I know it's a no-no to ride with the gears in opposite extremes - big front ring and biggest rear cog or small front ring and smallest rear cog. And I know those gearings would could chain rub on most bikes ...

But should I expect there to be two or three gears at each extreme where I hear rubbing? On the little front ring, the two or three smallest rear cogs have chain rub, and vice versa on the big ring.

It's a brand new SRAM Force 10sp set up. Shifting works well both up and down, so I'm not sure what to adjust. I'm hoping it's not related to frame geometry and the chain line. (Which doesn't seem all that extreme, but what do I know ...)

Thanks,

Andrew

[DaveM]

Depends what it's rubbing on. The problem with cross chaining isn't so much rubbing but that it puts excess stress on the chain and derailleurs. Going into them isn't going to brake anything, but the more time you spend there the more wear.

If the chain is rubbing on the front der, you may either need to adjust the front cable, or you may just need to learn to "trim" the front der. I'm not sure if SRAM force has a trim adjustment or not.

If the chain is rubbing on the middle chainring when it is on the small one in front, not much you can do about that.

[Dan Malloy]

I have a 2008 Trek Madone with Dura Ace (10-sprocket cassette). I recently moved to Alabama and took my bike to a local shop because the chain has been skipping teeth, so it's time to replace the chain, cassette, or both. I explained that the problem occurred most on the fourth sprocket (from the inside) and the small chainwheel. The tech asked if I ever used the fourth sprocket/large chainwheel, cautioning me that this was very bad for the chain. I hadn't heard someone say that for about 20 years. My understanding was that new technology made that a thing of the past. After all, the fourth sprocket is in the middle of the cassette. How could that be a problem?

Who's right here? Could fourth sprocket/large chainwheel be a bad combination?

[DaveM]

I'm not aware of any "new technology" that has made cross chaining any better. But hard to believe that going from big to 4th is a big no no. As you say, this is almost the center of the cassette. Sad to say, but the high end stuff like this is made for short term performance, not durability. Seems to me that riding a bike with 10sp Dura Ace is "very bad for the chain" period.

[Dan Malloy]

Yeah, that just doesn't make any sense. The tech was telling me to always use the small chainwheel except for the high gears, which I guess he means the two or three smallest sprockets. Maybe he believes that the small ring is centered to the sprocket and the big ring is offset.

Sheldon Brown has a good post on the benefits of today's bushing-less chains, mainly having to do with lube flow. The Dura Ace setup doesn't seem to wear any faster than the Ultegra on my previous bike, but it shifts much more crisply and the brakes are noticeably better.

Thanks for the feedback!