Originally Posted by Drew Eckhardt

Much, much, much, much more with the compact. More than 10X more often since every transition from dead flat to a false flat up-hill and back again meant a front shift from 50x21 to 34x15 as speed dropped below 17 MPH and back again from 34x14 to 50x19 once it went back above 19 MPH.



I dropped the compact in one of my spare parts boxes and regret waiting as long as I did.

While you can get the same range and spacing with a compact crank that you used to get with fewer cogs on a triple that doesn't tell the whole story (I'd been riding 50-40-30 x 13-14-15-16-17-18-19-21 and migrated to 50-34x13-14-15-16-17-18-19-21-23 after wearing out parts because the range and spacing were the same and 2 rings must be better than 3).

When you run the numbers taking into account that a given rear cog acts like one 2 bigger with a 34 ring instead of a 39 and that the middle ring is centered on the rear cluster which provides an acceptable chainline for the smallest and largest cogs you notice that you can put out 90% more power on flat ground before you need to shift to the big ring.

My blanked advice would be that if you're not strong enough to spin a 39x21, 23, or 26 (depending on whether you prefer an 11, 12, or 13 starting cog and assuming only 10 cogs in back - you can add a gear with 11) up the vast majority of climbs in your area and still manage the rest stick with a triple and consider a smaller granny ring. You'll get less front shifting and tighter spacing in back.