Gravel Bike Gearing
Gravel riding is challenging enough. Stop over-analyzing your gearing.
This gearing stuff is where we see a whole bunch of analysis paralysis. The simple truth is this: You don’t need a gear as high as a typical road bike has... and it would be nice to have a low gear around a 1:1 ratio for those climbs when you’re completely blown up. Easy.
Now let’s drop some numbers for you. As a starting point, think about a typical road bike with typical road gearing -- 53-39t chainrings and a 12-28t cassette.
With 700x25 tires, that bike will roll at 31.31 mph at a 90 rpm cadence in high gear. In low gear and with a 70 rpm cadence, you’ll be going 7.66 mph. Those are pretty good numbers for riding smooth pavement on skinny tires, but we just don’t need the high gear to be that high for riding mixed terrain and that low gear would be nice to see a bit lower for the long, steep climbs on loose surfaces.
The typical fix has been to switch to a compact crankset with a 50t large ring and a 34t small -- then pair that with a mountainbikeish cassette, like an 11-34t, to get a broad gear range. 34x34 yields a nice, low gear for the climbs, but 50x11 is still a waste of gearing. It’s actually a bigger gear than 53x12 -- and even more biggerer when you account for larger diameter 700x40 tires. So you change that 50t out for a 44 or a 46, but then the large and small chainrings are so close in size that you end up with a load of overlapping gear options. See how stupid this whole exercise is getting?
What if you could get the same number of useable gears with a single chainring and a wide-range cassette? Well, you can.
Check out the chart below. On the left is that ridiculous gear range with 50-34/11-34. We mortals can’t sustain 33+mph at 90 rpm long enough for that gear to be useful. Ever. Seriously. Truth is, when most of us get to a stretch of descent where you could spin out over 27 mph, we’d rather take the opportunity to coast and recover a little.
Listed to the right of that 50-34t compact example are alternating 1X options, paired with a 10-42, an 11-36, or an 11-32 cassette. The tightest 11-32 gear ranges are ideal for cyclocross racing setups (40x11-32 is the stock 1X arrangement on a Specialized Crux), but it works really well for our local, relatively flat-to-rolling mixed terrain rides. A 10-42 cassette (stock 1X gearing on a Specialized Diverge is 40x10-42) gives a monster gear range, nearly matching the full breadth of a two chainring setup, giving you a gear for just about any road you’re ever likely to come across -- paved or otherwise. The 11-36 option falls in between, giving you a slightly wider gear selection than the 11-34t, while keeping steps between gears tighter than the 10-42t.
And all that is without even mentioning that going 1X entirely eliminates one chainring, a derailleur, and a shifter from your bike. That’s weight saved. That’s fewer moving parts to go out of adjustment. The whole idea is just a win-win-win. Sup?