Table of Content:
Overview:
Drivetrain ratios have changed a lot in recent years. There’s lots of brands and options now that offer a large range without going to a 3x front chainring. How to pick the right drivetrain for your bike can be tricky with so many options. I'll go over some decisions a rider should consider before deciding on a drivetrain, then based of those decisions, select an appropriate drivetrain.
Manufacturers:
The two main component manufacturers, Shimano and SRAM, have a lot of options one can choose from; however, other options exist as well such as Sensah and Campagnolo. There are other manufacturers out there like Rotor and Ltwoo; however, it’s somewhat unclear what Rotor plans to do with their drivetrain, and Ltwoo is a Chinese government backed company, so may come with restrictions in some parts of the world.
The drivetrains I’ll be looking at are all 11 speed or greater. I don't have all possible drivetrains listed, but listed some drivetrains with high versatility.
Parameters to consider:
There’s a few things to consider when selecting a drivetrain.
How fast do you want to go?
How steep of a hill you want to climb
How much gear you plan to carry on your adventure
How variable is your terrain?
Simplicity
Bumpy terrain?
Once you have an idea of these parameters, you can then map that out to drivetrain specs.
Going thru each of the selection criteria:
Max Speed:
The faster you want to go, the higher a max gear ratio you want. That is the ratio between (big) chainring and smallest sprocket. The higher this ratio will means you can maintain your cadence at higher speeds. If you don't plan on pedalling down hills at 70kph, you likely don't need this to be that large. a ratio of 4.6 is probably sufficient for most people who push less than 300 watts.
Steepness of climbs:
If the hills are steep, you’ll want a low min gear ratio. (Small) chainring and largest sprocket. The lower this ratio means you can maintain your cadence as the hills get steeper. Modern science has shown that if you can keep your legs spinning at an optimal cadence, you can get up hills faster than if you were to grind your way up the hill.
Bikepacking and carrying gear:
Same as 2. The more gear you carry means it gets harder to go uphill. Force of gravity slowing you down is proportional to rider mass.
Terrain variability:
If your terrain is going to vary a lot, meaning there’s lots of ups and downs and really steep, then you want to have a large range. The range is the ratio between max gear ratio and min gear ratio. The larger the range means you’ll be able to find your right cadence across a variety of terrain. Downside with large range is the teeth difference between cogs increases, which impacts ability to find the right cadence at specific gradients. To get around this, you can opt for more gears on the cassette.
Simplicity:
Simpler means less maintenance, easier maintenance. If you plan on going on long trips to the middle of nowhere, simplicity also means less chance for parts to break down. One good example of simplicity is opting for 1x drivetrains.
Bumpy terrain:
If the terrain is bumpy, then you want to have a clutch or adjustable derailleur cage tension.
Comparison of Drivetrains:
Drivetrains cost a lot of money so selecting the right one is a big deal. Upgrading in the future if you don’t select the right one at the beginning can be costly.
The graph below compares some drivetrain ranges, max ratios, and min ratios.
The point of this graph is to allow one to determine what parameters they want to priorities then select the appropriate spec to optimize. Not all the drivetrains have a clutch rear derailleur, only those designed for gravel tend to have that. Columns denoted with a * do not have a clutch.
Price:
A lot of these drivetrains are over $1000 if you buy the groupset. Some go into the $2000 range. And some even higher. There’s no point in putting prices up at the moment as bike parts are seeing a ~10% YOY price increase these days. The cheapest one out of all these options is Sensah though. Coming in at ~$400 for a complete groupset. If price is a concern, then check out the review of the Sensah groupset here:
Summary:
Figuring out what and where you want to ride can play a big role in deciding on the drivetrain you want for your bike. I would say that the drivetrain components will make more of a difference to your riding experience than the frame so if you’re buying a complete bike from a bike shop, I’d optimize the drivetrain you want first before deciding on the frame.
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