Let’s get a little technical
On our gravel tour a couple of weeks ago, half of the bikes were 2x and the other half 1x, which pretty much says it all for the cycling industry right now. Not surprisingly, the 2x bikes were over 5 years old and the 1x bikes were less than 3.
We had lots of chatter about gearing and drivetrains and why one does something better and questions about gear ratios.
What became fairly clear was there wasn’t a lot of clarity about it either so I thought I would spend some time talking about gears and drivetrains, while trying really hard not to bore you with history or bike geek level detail — we’ll see how successful I was (or wasn't). Buckle up and let me know if you want more of this kind of thing in the coming months. Okay, ready; let’s do this.
The very first bikes didn’t have gears. You ran them just like striders, or directly pedaled the wheels with the crank attached to the center of the hub, until the late 1800’s when chains arrived and away we went with all that’s possible to power a bicycle.
What started with two gears (one on each side of the rear hub so you had to remove the rear wheel and flip it around to use either your climbing gear or your speed gear) developed into 5 gears on the back, with two gears on the front to give us our 10 speeds of the 1940’s-70’s and then began expanding from 1-2-3 on the front and 5-6-7-8-9-10-11-12-13 today. Ask anyone who ever used a 3x9 drivetrain why they gave up cycling and this was likely it- the finicky nature of having three gears up front that needed to mesh properly with 9 gears on the back was akin to doing calculus while drunk and being chased by a bear.
This very brief overview of history could be expanded upon for hours, losing ourselves completely and end up nowhere but going round in circles (wait, that sounds exactly like every bike ride!), so what I’d like to focus on for the rest of our time here is three concepts which are what we have as today’s options- number of gears on the front, number of gears on the back, and the ratio of those gears.
Go into any bike shop and you will find bikes that have either 1 or 2 chainrings — that’s what the gears on the front of the bike are called, attached to the cranks (which the pedals are connected to). Every mountain bike that is worth its name has one gear/chainring, hereby called a 1x (one by) from now on. Shimano and SRAM only make 1x mtb drivetrains and you will see their parts on 99.99% of all mtb’s over $2000. Gravel bikes often have 1x drivetrains as well, but not always. Shimano likes to have 2 chainrings on their gravel bike setups, hereby called a 2x (two by), but not always. Very rarely will you find a SRAM gravel bike with a 2x as they are early converts to the 1x world for their gravel bikes. Campagnolo only makes 1x gravel drivetrains and do not make any mtb parts but have by far the widest array of options for their road bike setups. Road bikes always have two chainrings, except SRAM is starting to change the game again as we will see below.
The only way to alter a 1x chainring is to change the size of the gear, defined by the number of teeth, which affects how easy or hard it is to pedal. If you have a 2x, you can create two different pedaling gears, one for going up the hill the other for coming down. For going up a hill, you want a small gear in front, the smaller the easier. Today, you almost never see anything smaller than a 28t (28 tooth) chainring because of how many gears and how wide the range is on the back. A standard mtb chainring is usually 30-34t depending on how steep the country is you live in. A 1x gravel setup will have a 40-44t chainring.
2x systems are different because now you are looking to cover as much range as possible depending upon your specific variables- the conditions within which you live, who you have to try to keep up with plus anything else you’d like to accomplish. A front derailleur can only accommodate a 16t change so your 2x has to be less than 16t different from large to small. If you want an easy uphill gear, you can have a 28 but you can have no more than a 44 as your big gear. If you want to have a really fast flatland gear, you can have 60 but that means your smallest gear can only be a 44.
Making sense? Keep this in mind as we now look at the rest of the story on the back end.
It’s still possible to find a 10 speed cassette on a new bike today, but we don’t ride those. The technology on the new bikes we ride today are either 12 or 13 gears on the back (note that there are also varying degrees of quality and costs of parts from each company which we are not going to cover here, nor are we going to touch on electronic vs non).
1x mountain bikes are 1x 12 gears on the back, whether they are from SRAM or Shimano. Those 12 gears can vary but are almost always 10-51 or 10-52, meaning that the smallest gear in the cassette has 10t while the largest has 51 or 52t. What is most important here is that the range, or teeth, is as large as possible, which for both companies is about the same and is 510-520%. Typical for these cassettes is that there are 2t jumps between gears at the small end, 3t jumps in the middle and 6t jumps as the gears get more teeth with a final 8t jump as it goes to the “granny” gear.
A 1x gravel cassette is offered in 12 speeds from Shimano and 13 speeds from SRAM and Campagnolo. It gets significantly more complicated from here so let’s try to break it down by company.
Campagnolo offers the widest range of options of cassettes for gravel bikes because they are the awesomest- 9-36, 9-42 and 10-44. Keep in mind that details count so by keeping the range as small as possible, the jumps between each gear change are kept as small and subtle as possible. Conversely, the larger the range the bigger the jumps between gear changes so the cadence changes are larger. To dial in your desired course or home territory, select the best cassette option to match with the correct front chainring size. For our RFV backyard, I run a 40t front chainring with a 10-44 cassette on my gravel bike. Campagnolo offers 36-44t front chainring options so I can adjust my range accordingly and perfectly. If I were to change one thing on my current gravel bike, it would be to put a 38t front chainring on because there are a couple of hills I’ve ridden in the past year that are above 20% and the 40-44 ratio is not quite easy enough for those hills. But since there are only a couple of them and I’ve already figured out workarounds, I will not be buying a new chainring this year.
SRAM offers one gravel cassette- 10-46. It’s a good range and covers most everything when paired with the correct chainring.
For Shimano road and gravel bikes, 2x is the name of the game right now. To get the best setup, use their 12 gears on the rear to mesh with your desired outcome on the front. What’s the perfect road setup with them? 2x12. Shimano has a brand new 1x12 gravel drivetrain that looks just like SRAM and Campagnolo’s, except the latter have one more gear so their’s are a 1x13.
For road riding, the smallest yet most effective change in gears is ideal, be it going faster on flat terrain or up a steep hill. That means the cassette (the gears that attach to the rear wheel) has a couple of variables- either keep the gears as close as possible to each other for your 12-13 options, or spread the range as wide as possible to give the most versatility and let go of small cadence changes, or choose something in the middle that does a little bit of both. Ideal fast gear combinations involve 1t changes so that you can smoothly roll over undulations whereas massive terrain changes, like mountains, mean you spend a lot of time in your easiest couple of gears, and then come down in your hardest. If you are shifting regularly, you want to keep your cadence (the speed at which your pedals turn) roughly the same all the time so, as the terrain changes gradually, a small gear change matches and keeps your legs spinning at the same speed.
The relationship between the front chainrings and rear cassette creates your gear ratio. In general terms, the larger the number of the ratio, the faster you go. On my road bike, I have a 29-45 chainring and a 10-29 cassette. To find the ratio, you take the big chainring (45t) and divide it by thevsmallest gear on the cassette (10t). By dividing the chainring teeth by the cassette teeth, we find my ratio is 4.5. The opposite is true when going up a hill, but gets more complicated depending on whether you have a 1x or a 2x (which can help you decide the right drivetrain for you). If you have a 2x, then your small gear is usually 16 teeth smaller than your big chainring, so in this case it would be a 29t. Now, we look at the cassette and see which one you picked- I chose a tight gearing setup for my cassette, the biggest gear on my cassette is a 29, which gives me a ratio of 1.0. If I want a wider range, I could choose a 10-34 which will keep the fast gears a 4.5 but give me an easier uphill gear, .85.
Stick with me on the numbers for a moment- each ratio equates to a distance measurement once you take into account a couple more variables, tire size and crank length. Tire size is the most important thing to consider next because the bigger the tire you run, the longer it takes the wheel to rotate. Combine tire size with your ratio and you begin to understand that each time you turn your cranks, the rear wheel rotates a fixed distance, changing the gears, changes the ratio, which then changes the distance (longer or shorter). The higher your ratio, the bigger the distance but the more effort it takes to turn the cranks (thanks to a whole bunch of physics we are not going into, today). The lower your ratio, the easier it is to push the pedals but the shorter the wheel rolls.
To pick your perfect drivetrain, first decide where you are riding- flat, hilly or mountains. Flat terrain gearing should be designed for speed on a road bike, so bigger on the front and tighter on the rear. A 56-40 chainring combination is what my buddy John Rader uses on the front of his Texas bike which he brings up here occasionally, but Shimano also offers it in a 46-36 for those of us who live in the mountains year round. Understand the difference yet? John cares about going faster on flat ground while we care about going easier uphill- neither one is wrong unless applied in the wrong terrain. Shimano offers two cassettes so keep that in mind as we transition into ratios because the difference between an 11-30 and an 11-34 is subtle. For reference, Campagnolo offers four (10-29, 10-33, 11-32, 11-36) and SRAM offers four another way (10-28, 10-30, 10-33, 10-36).
The ratio of your gears ideally matches the terrain you are riding upon. Flat land has a 0% incline so your forward progress is determined by your muscles and wind resistance. If it is very windy and you are not very strong, you will want an easier gear to pedal then if you are lucky enough to have a strong tailwind and legs like Pogi. The ratio of gears on the front and back will give you your cadence, which most people prefer to keep between 70-90 rpm. For each turn of the pedals, the chain rotates the rear wheel a certain amount, the higher the ratio of the front gear to the rear (for John’s 2x road bike in Texas, 56-10 or 5.6), the more inches the wheel will roll, in this case 149”. John’s easiest gear on his bike is a 40-34 (1.18) which equates to 31” of wheel movement per crank revolution. Compare that to what’s available on our 1x12 mtb (32t chainring and 10-52 cassette)- 94” for the hardest gear while only 18” for that super low granny gear. Here’s where you figure this stuff out.
Hold the number concept for a little longer as we now consider our mountainous backyard- a typical paved road in our valley is not more than a 7% grade (Maroon Bells), a gravel road is usually below 12% (Watson divide) but a mtb trail can be 18-25% (about the same as a green run at Snowmass or the climb up Mushroom Rocks).
Let’s only consider pedaling up a hill for now, and I will use myself as the determiner, keeping in mind that you readers are all varieties of stronger or less than I. I have found that a one to one gear ratio is adequate for me on my road bike for going up our paved hills in this valley.
Let’s break that down- my road bike weighs about 16lbs., has 34 mm tires, the paved roads here are not that steep and I like to pedal at roughly 90rpm so the size of the front chainring is the same size as the largest cog on my cassette (my granny gear) giving me a 1-1 ratio or 1.00 which gives me a 27” gear. For my 18lb. gravel bike, I have a 40-44 (25” gear with 45mm tires) so the ratio is .91 to hopefully ride my 90 rpm over Watson Divide — but I wish it were a 38-44 (24” or .86) to go up anything steeper, a tiny but perceptible change. Riding a 25lb. mtb with 2.4” tires up Three Gulches or Glassier or Hunter Cr, I need to have a 20” gear (.68 or 34-51) to keep from hyperventilating but a 30-51 (17” or .59) is probably going on the next bike. The shorter the distance that the wheel rolls, the easier it is to pedal and vice versa.
Holy shit, that’s a lot of esoteric detail, I can’t believe you are still reading this but thanks for hanging in there!
Let’s wrap up and go for a ride.
Gearing is all about how you prioritize- if you want to keep it simple, get a 1x drivetrain for your gravel or road bike. SRAM has completely broken away from the other companies in their versatility and ease of combinations so you can now mix and match their road, gravel and mtb parts to create pretty much anything you want, as long as you don’t care about tiny, incremental gear changes. You can now put a mtb cassette on your road bike, 10-52, and combine it with just the right size front chainring, something around 42-44 should do nicely, to give you enough easy gears to go up anything and enough inches to pedal back down. If you want the most perfect arrangement on your road bike, Campagnolo 2x13 is where you should head and pair one of their 7 different chaining combinations with 4 choices of cassettes giving you an ideal range with minimal gaps between gears.
Maybe next time we can talk about something simpler, like why everyone’s cranks are getting shorter.
Hope this helps unlock your potential.
Cheers
