Originally Posted by carpediemracing

Not just in a sprint - I usually do this when I'm sitting in. In a sprint I use what I need to use.

A trick I use is to look at the rider's cogs in front of me and where the rider's chain sits. If the rider is in the 2nd or 3rd smallest cog, and I kind of know who the rider is, I know that they're in a 12-13 or 13-14, and I know that they're running a 50 or 51 or 52 or 53 or 55 (depending on who it is).

Having been obsessed with gearing all my life, I know what gear they're in, approximately. I then can adjust based on the rider's strengths/weaknesses (compared to me), my goal (jump past, sit on, etc). I decide what to sacrifice too (lower gears - increased HR but can go immediately; higher gears - recover but can't respond to quick moves).

It's not something I think about for a while - it takes maybe half a second, maybe less. It's virtually instinctive. I mainly focus on what rings they use, then use a gear up, down, or equal to what they're using.

I can also adjust (and/or deduce chainring size) if my cadence is off from theirs.

So, for example, if I'm on Kevin's wheel, I know he runs a 55 (as do a few other people). Therefore if he's in a 12 and I want to sit in, I can run comfortably in the 53x11 (similar gear). If I want to jump around him I'll sit in the 13 or something. Etc.