This custom setup has extremely close gearing with your small chainrings. You'll want to shift 2 or 3 cogs to feel much of a difference. And you'll be limited to very slow speeds.
It doesn't seem useful to me at all. Shifting through the
full 7 usable gears in the 22 chainring, it will only change by about
1 mph at slow hill climbing cadences, and just
3 mph at a fast spin 100 rpm.
(11 not shown)
21-34 and 22/30/40 chainrings:
22 chainring in red, 30 in black, 40 in blue. Showing an extremely wide range of cadences from 33 to 100 rpm.
The 22 chainring spins out at a top speed of about 8 mph. The 40 chainring gets almost to 15 mph.
the calculator link
21-34 calculator.
What is this chart showing? Each gear combination is a colored row. The bar shows mph speeds from the slowest (33 rpm cadence) up to the fastest spin cadence (100 rpm.)
The
bottom red row is the 22 front / 34 rear. At 33 rpm, 1.6 mph-that's difficult to balance at such a slow speed. At 100 rpm, just 5.0 mph. (the calculator has a tab labeled "Speed" that shows mph numbers instead of a chart.)
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Compare:
A stock
12-32 cassette with the same 22/30/40 chainrings. Note the change of scale in mph on the chart.
calc link
12-32 calculator
The 22 chainring still has close shifts, but they are usefully close here.
