More About Range and Ratios

On a ride very recently I started yapping about the new gravel bike I built. My conversation partner asked a few questions about the frame and the drivetrain. He then said, “I’m still curious about the pros and cons of 1x and 2x drivetrains. I think you should write a full-nerd blog post on this.”

Obviously, this is not my fault.

I think we should start with the salient points of this post, which are:

1. Modern 1x drivetrains give you a LOT of range, more than older triple-chainring setups
2. These 1x drivetrains with all the range DO have bigger steps between the gears

The difference between this post and that one is that this one is going to compare a modern 11-speed road double drivetrain to a modern 11-speed 1x drivetrain, whereas the other was a bit more geared (ha!) toward someone with an old(er) drivetrain considering a 1x upgrade.

Range

It’s probably impossible to work through this stuff without applying a little bit of high-school learnin’, so let’s dive a bit deeper. The range of a cassette is [(teeth on big cog) / (teeth on small cog)]. The range of an 11-32 cassette (and this can be a 9, 10 or 11-speed cassette; the number of gears doesn’t matter in terms of overall range) is 291%.

Likewise, the range of the crank is the number of teeth on the big ring divided by the number of teeth on the small ring. The range of a compact cranks (50/34) is 147%. The range of a single-ring crank is 100%; the big ring and the small ring are the same, so the ratio is one.

This, friend, is where the rubber hits the road with respect to drivetrain range. Your drivetrain range is the product of your cassette’s range and your crank’s range. I have an 11-32 cassette with a range of 291%. If I put that cassette on my single-ring cross bike, the range of the entire drivetrain is 291% (2.91 for the cassette multiplied by 1.0 for the crank). If I put that cassette on my road bike with a standard (53/39) crank, the range of the entire drivetrain is 2.91 * 1.36 = 3.95 or 395%. Said another way, the addition of a standard crank gives me 36% more range. If I had a compact crank, the addition would yield 47% more range.

To recap: on a single-ring setup, the drivetrain range is the cassette range. On a multi-ring setup, the drivetrain range is the range of the cassette multiplied by the range of the crank. If you look through the above tables, you’ll see that you can get a 10-42 single-ring cassette with 420% range, nearly the same as a compact crank with an 11/32 cassette. Whichever way you elect to get here, 420% range is a lot.

Ratios

I’m giving serious consideration to renaming this section “Steps,” because what I’m really trying to describe here is how much you “feel” the gear change. Does that change feel about right, or does it feel maybe a little too big? I got the “Steps” name from this article which is quite a bit more exhaustive than mine. One thing to keep in mind: while the number of cogs on a cassette doesn’t matter with respect to range, the number does matter with ratios. More gears means smaller steps across the range.

Here’s a bit of data that gets right to the root of this “Step” idea. For a long time, 11-25 was the cassette on darn near every new bike. We’re seeing a lot of 11-32 on bikes these days. 10-42 is the big-range 11-speed cassette that we see this on many single-ring new bikes.

I think this sort of bears out what many of us have felt in our legs: wider range cassettes definitely have bigger steps between gears. The average step between gears on a 10-42 cassette is 50% bigger than those on a 11-25. Fifty percent is a big number. Too big? Hmmmm.

Big Finish

Let’s go back to the guy I was riding with the other day. I know what he’s doing. He’s trying to figure out how he wants to equip a bike he’s building in the back of his head. And I want to give him good advice for several reasons. I like the guy, and I thus want him to be happy. I also don’t want to get a reputation as the guy who gives people bad bike advice. Regardless, here’s a quick pro/con list on single-ring setups.

Pros:

• Lighter weight (no front derailleur, no front shifting junk)
• Simpler
• No dropped chains or crappy front shifts (= greater confidence)
• Wide range is still possible

Cons:

• Might need to swap front rings to optimize the gear range
• Bigger steps between gears are required to get the same range as a double
• Switching cost could be high (shifters, derailleurs, etc.). Is this really a con? Maybe it’s just a fact.

Speaking personally, the simplicity of a single-ring setup is great. Perhaps I’m the only person who has thoughts such as, “I need one easier gear right now, but maybe I’ll ultimately need three easier gears, so should I mess around with the front derailleur or just knock out one shift in the back?” See!? Cycling is relaxing!

Also, personally, it seems to me that tight ratios (smaller steps) matter most when you’re riding with a fast group and are not in total control of the pace. In those situations it can indeed be a bummer to find yourself alternating between spinning too fast or pushing too hard at a low cadence.

Perhaps this is a localized conundrum. I happened to speak with a guy from SRAM at Interbike last fall. I asked if maybe a clutch derailleur was coming to eTap so that it could better support a single-ring setup. I mean, why not? SRAM totally popularized 1x. His response, “Oh you Michigan guys and your single-ring setups.” So though SRAM might be fired up about 1x, maybe the thought is that every product doesn’t need to support it. For comparison, it took until about right now for Shimano to come out with a clutch road derailleur.

Lastly, I think everyone needs to put it in context of what you have and what you’re willing to endure. If a single ring just seems too strange, don’t do it. If you’ve got an open mind, give it a whirl. If your life revolves around Shimano drivetrains, you might not enjoy the pleasures of a shift on an agricultural-feeling SRAM drivetrain. Said differently, 1x vs. 2x is one of many considerations in a new bike’s drivetrain.

Was this remotely helpful, John?