Rubber Side Down | How To Select Gearing

There’s a mind-blowing array of gearing options available today. Heck, the number of cogs on a cassette are increasing faster than the number of blades on a razor. It seems like every week there is another cog in the mix—along with six varieties of each cassette. Sometimes it can be a little overwhelming. I have plenty of friends (okay, actually just two), and while they can turn the pedals with a vengeance, once talk turns to ‘gear ratios’ and ‘wide-range cassettes’ they’re about as lost as a penguin in the Sahara.

Now, I’m going to go out on a limb here, but I’m probably pretty safe in saying that these friends of mine aren’t alone in their lack of understanding, so without further ado, let’s take a second to break it all down.

Shop Talk

We’ll make sure everyone is on the same page before I start throwing terms around.

Cog – A toothed gear that is part of a chain drive.
Chainring – A front cog, specifically, the type that attaches to the crank via a spider.
Spider – A spider is a multi-armed fixture found on the driveside of the crankset and provides the interface between the driveside crank arm and one or more chainrings.
Crank Arm– The arm that connects the pedal to the spindle.
Spindle – Both crank arms attach to a spindle, which rotates within the bottom bracket.
Bottom Bracket – The bearing assembly housed in the frame’s bottom bracket shell. These bearings allow the crank to spin freely when the spindle is passed through either end and fixed in place between the crank arms.
Cassette – A cluster of cogs and spacers designed for use on a rear wheel with a freehub.
Gear Ratio – The front chainring tooth count divided by the rear cog tooth count for a particular combination.
Double – A crankset with two chainrings.
Triple – A crankset with three chainrings.
Standard – Referring to the ‘standard’ crankset configuration, a standard utilizes a 53-tooth large chainring and a 39-tooth small chainring.
Compact – Referring to the crank assembly, compacts usually come with a 50-tooth large chainring and a 34-tooth small chainring .
Mid-Compact – Referring to the crank assembly, mid-compacts usually come with a 52-tooth large chainring and a 36-tooth small chainring.

Cranksets

Most cranksets these days are doubles. In some instances road bikes will have triples, but triples are becoming less popular due to a wider range of gearing available in the rear, accomplishing the same ratios. For instance, with an Ultegra 52/39/30 triple paired with an 11-28 cassette the easiest climbing gear ratio can be accomplished with the new 11-speed Ultegra with a double 52/36 and a 11-32 cassette. See the table below for a full comparison of ratios between the two groups.

Ultegra Gearing

The two setups end up having the same top and bottom-end ratios

For the longest time, road bikes came with standard 53/39 cranksets. Then came the introduction of the compact 50/34-tooth combination. The compact can be a popular option for those living in hilly areas, needing the larger gearing for climbing and those less concerned about downhill speed. The mid-compact 52/36 has also emerged as a nice compromise between the standard and the compact. Each of these is designed for different riding styles and will behave differently depending on the cassette it is paired with.

Cassettes

Cassettes come in many varieties. Depending on your setup, there could be a varying number of gears. Most likely you have a 9, 10 or 11-speed cassette. On most, the smallest gear is an 11 or 12-tooth. In the last few years, the larger gears have been increasing in size to facilitate easier climbing. New derailleurs, like the Shimano Ultegra 6800 GS, have longer cage lengths to help the chain move up to these much larger gears. This is something to keep in mind if you want to swap your cassette. Make sure that your derailleur can accommodate the larger gearing. The differences between the Shimano 105 short and long cage derailleurs can be seen below.

Cage Differences

Short and Medium Cage Length Options

The short cage Shimano derailleurs can handle up to a 28-tooth gear on the cassette. If you want to use anything larger, use the medium cage length model instead. The SS (short cage) and GS (medium cage) options for the Shimano Ultegra 6800 Rear Derailleur are available as an option during checkout. If you have a SRAM component group and wish to use a cassette larger than 28 teeth, the WiFLi option on their derailleur groups will be necessary.

There are various reasons for changing gear ratios. One of the most common reasons could be too low of a top end ratio. If you find yourself spinning too quickly in the high gear, you might need a change. When I talk about spinning, I’m referring to the number of revolutions per minute of the crank arms, independent of the speed of the bike. A generally suggested cadence for riding on flat terrain is 90 rpm, although it can vary. If your cadence is too high, you most likely have a compact 50/34 and would maybe like to consider a 52/36 or even a 53/39. The opposite problem would be if you find yourself spinning too slowly when climbing. In this situation, you might consider changing to a cassette with a larger top-end gear.

When considering these cassette options, it’s also important to distinguish between tight and wide-ratio. A tight ratio cassette will have smaller incremental changes. For instance, the new 11-speed Ultegra cassette gearing steps in 1-tooth increments (11-12-13-14) on the low end, and then has wider ratio gearing at the top end (22-25-28-32). This is good to be aware of when selecting a cassette because larger jumps in gearing will have a more significant effect on cadence. New 11-speed systems can afford to have tighter ratios than older cassettes with less gears.

If you think you need to make some changes in gearing to improve your riding experience, figure out what you currently have, and what you would like to improve on. For easier spinning on hilly terrain, a cassette swap is a straightforward and easy way to improve your riding experience. It’s an easy change for the mechanics at your local shop, or it’s done easily enough at home as well. But, be aware that you may need to adjust chain length.

Rubber Side Down is a weekly column dedicated to the fledgling cyclist in all of us. Art’s Cyclery Web Content Editor, Brett Murphy is not a professional cyclist, and doesn’t try to masquerade as one either, but he does love to ride bikes. Whether you are clipping in for the first time or counting down the days until your first race, read on, learn from his mistakes, and keep the rubber side down.

2015-12-16T17:07:39-08:00