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Road Bikes, Cycling, Gears and Cassettes… All You Need to Know to Make Your Go-Fast Bike Go Fast

A post in which I geek out so you don’t have to….

The cassette is one of the least faffed about components on a bike but has the most profundity in relation to… Okay, not that geeky.

Here’s the deal; the humble cassette can make your bike a dream to ride, or a nightmare.  The sad thing is, most cyclists will just take what comes on the bike without giving it a second thought. Two teeth on a big chainring can mean the difference between the perfectly appointed climbing machine and always feeling like you’re in too high, or too low a gear – and it will have everything to do with the cassette.

My road bikes are the perfect examples, because I set one up to be a climber, and one to be my go-fast bike. Ironically, the go-fast bike is lightest by about three pounds but let’s not get lost in the woods.

So let’s get right into this, folks. The standard these days is the 11-28 cassette, ten or eleven speed doesn’t matter. The bigger cogs jump the same on both, the last two cogs increase in size by three teeth, then four.

I, being naive, bought two high-end 11-28 cassettes last year. One went on my go-fast bike, the other on my climber.

On the climber, the 11-28, coupled with a 50/34 compact crank, was simply fantastic. I had an extra gear on every hill I climbed last year, and I could comfortably pedal up to 40-mph before running out of gears. Each gear had its place and I used every one of them at some point. From 4-mph up an 18% hill, to well in excess of 40-mph down a few hills.

The 11-28 cassette, by contrast, sucked on the go-fast bike. My Venge, being the go-fast bike, has a 52/36 chainring combination up front. Where this gets dicey is in the bigger, easier gears on the back and the big ring up front.

  • 11/28 Tooth (11, 12, 13, 14, 15, 17, 19, 21, 24, 28)

We get into trouble with the bigger chainrings. Specifically, that jump from 21 to 24 teeth. The 21 tooth gear is good for about 21-22-mph. The 24 is good for 18-1/2. When you’re a 21 to 23-mph average rider, that hole between the 21 and 24 tooth gears is in a horrible place. The best way to describe this is that each tooth is worth 5 rpm for your cadence. When you jump 3 teeth, that’s 15 rpm.  This leads one to feel like they’re always in the wrong gear whilst riding somewhere between 19 and 20-ish-mph.

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With the Trek and its 50/34 chainrings, the 19 and 21 tooth gears are the cruising gears and the 2-tooth, 10 rpm jump is easily managed.  The 11-28 cassette is perfect on that bike.

It all boils down one’s average pace.  I wrote in the opening that I’m a 21-23-mph average cyclist.  On the weekends we’re often a little slower than that, call it 19 or 20-mph for an average.  If I was a little faster, maybe a mile or two an hour on the high side, the 21 to 24 tooth hole wouldn’t bother me as much as my normal cruising gears would be 17, 19 and 21.

There are two ways to fix the problem with the Venge.  Obviously, swapping the 52/36 chainrings out for a 50/34 combo would fix a lot – if the combo works on the Trek, it’s going to work on the Venge, too.  My buddy, Mike talked me out of that, though.  The Venge doesn’t have the same use as the Trek.  The Trek is my “take anywhere, touring bike”.  The Venge is just meant to go fast, so I opted for the simple cassette fix.  I picked up an 11-25 tooth cassette.

  • 11/25 Tooth (11, 12, 13, 14, 15, 17, 19, 21, 23, 25)

No three or four tooth jumps.  I won’t be able to climb as well, but I should be able to handle anything up to short 20%’ers.  Heck, if I lose a few pounds, I should be able to do better than that.  With the 11-25 cassette I won’t have any holes to worry about with the easier gears on the big ring.

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In the end, there are several important factors to be taken into account.  If I were riding in hilly terrain regularly, I’d probably stay with the 11/28 cassette and go with compact 50/34 chainrings for the improved climbing characteristics.  If I were a little slower, I could look into an odd gear cassette, maybe a 14-28…  That would get my gear jumps down into a two-tooth range.  If I really wanted to get crazy I could have gone with an 11-21 or 11-23 “corncob” which would mean 1 tooth cog increases but horrible climbing characteristics.  Or, if my Venge was my only bike, I could go with three cassettes; a corncob for flat cycling, an 11-25 for mixed terrain and a 14-28 for hilly days.

Oh, and if the Venge was my only bike, I’d go with a compact 50/34 crank up front.  No question about it.

The point is, if you’re experiencing holes in your gearing that often make you feel like you’re in the wrong gear, cycling isn’t supposed to be like that, and there are simple fixes to correct that – as simple as swapping out a cassette.  The operation takes a wrench, a special nut to remove the cassette, and a chain whip… and about three minutes.

Ride hard my friends.

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