compact double question

[carback]

Hi,
I have a compact double on my road bike. I've noticed a bit of chain rub when I am in the big ring and the largest cog (easiest gear) at the back. The chain rub disappears when I drop it down to the 2nd largest cog.

Is it normal to have a bit of chain rub with that gear combination, or do I need a small adjustment? I'm more familiar with triple chain rings, and do know that in a triple chain ring configuration you're not supposed to use your easiest gear at the back and your largest ring at the front (or hardest gear and smallest ring), but wasn't sure if the same held true in a compact double.

thanks

[ny biker]

I don't use the big ring much on my bike due to knee issues, but I have similar experience when in the small ring and smallest cog. It's that way regardless of any adjustments that are done on my derailleurs.

So I only ride in that combination for short stretches, otherwise I shift up to the big ring.

[Chicken Little]

It's cross chaining. You might be able to adjust it away. Not a lot of play at those settings.

[zoom-zoom]

It's less of an issue with my CD than with my triple, but I still avoid big-big and little-little combos. Just a gear or two either direction is fine.

[Pedal Wench]

Cross-chaining is bad for your chain and the chain rings - it causes excessive wear, so try not to ride in those combinations. If you're halfway up a hill and it's too late to shift down, it won't destroy the chain immediately, but try to avoid either the big-big combination and the small-small combination.

[Wahine]

Agreed, it is possible with a compact double to tune it such that you don't get chain rub in that combo but it's really not good for your chain, cogs etc so it's best if you avoid it.

[Pedal Wench]

I meant to also add that in those combinations, you're putting maximum stress on your rear derailleur - it's using every link of your chain, so it has to get out of the way, or it's taking up the maximum amount of excess length in the chain, so it's very easy to damage your RD in these combinations.