Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Bikes: Some silver ones, a black one, a red one, an orange one and a couple of titanium ones
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Originally Posted by HiYoSilver
Thanks but just to double check. My question is not with shifting but with cadence. Specificially on shifts on cassette
from 13t to 11t [ring 1 to ring 2]
from 20t to 17t [ring 5 to ring 4]
from 30t to 26t [ring 7 to ring 6]
These are 18.2%, 17.6%, and 15.4% changes in gearing. So my question is under load, can you change gears without losing much cadence, i.e. change under 10 revolutions.
I don't measure cadence but some things to think about
The jump from 13 to 11 is usually made at high speed anyway so you'll probably not notice it too much. If you use Sheldon's calculator and calculate the speed at 90 rpm, the change is from 29 to 34 mph. But when I'm doing that shift, I'm probably increasing my cadence anyway to pick up speed on a downhill and I don't notice it.
For your gearing, I'd make the shift from large ring to middle on the crank before I'd do the 20 to 17 anyway. The change is about the same going from 53/17 to 42/17 as going from 53/17 to 53/20. This is a lot closer than any of the other combinations and makes a good place to switch front rings. However even in the 53 chainring, the difference in speed is is from 19mph to 22mph. I'm not sure you'd notice that much difference. Going down in gear would probably be much more noticeable than going up.
On the 26 to 30 jump, you should be in the middle ring anyway and you'll be going from 10 to 11 mph. Hardly noticeable at all and, usually, you're climbing something and needing to drop to that gear just to keep going up the road. By this time I've usually forgotten about cadence and am more worried about where the top of the damned mountain is anyway