Originally Posted by
macbride
I have a Shimano Ultegra SG-X 50F Crankset with a 10 speed cassette.
When I upshift using the front derailleur it seem to be the same as upshifting two clicks with the rear derailleur.
Is there a way to calculate the ratio of how effort changes with the two types of shifting?
Is it about 2 to 1?
Thanks!
It's simple ratios and depends on specifics.
I run tight cassettes like 13-14-15-16-17-18-19-21-23-26 10 cogs, 13-23 9, 13-21 8.
Riding 50-39, shifting from the 39 to 50 while in the 19 cog is like going to the 15 cog 4 away
39/50 * 19 = 14.82 rounding to 15 4 cogs away -
39/53 * 19 = 13.98 rounding to 14 5 cogs away
34/50 * 19 = 12.92 rounding to 13 6 cogs away
OTOH, running 11-12-13-14-16-18-20-22-25-28-32 11 cogs
39/50 * 20 = 15.6 rounding to 16 2 cogs away
39/53 * 20 = 14.7 rounding to 14 3 cogs away
34/50 * 20 = 13.6 rounding to 14 3 cogs away
Mike Sherman's gear calculator offers a nice graphical representation which can show equivalents, where you'll shift, and where you'll notice gaps based on your preferred cadence range.
With
50-34 x 13-23 I was in good shape on spacing, but was making 5-cog double shifts from 34x14 to 50x19 speeding up past 18 MPH and 50x21 to 34x15 below 16. I switched to 50-39.