Someone typed this into a search engine and ended up clicking on one of my posts:
“21 sp. bike vs. 27 sp. bike, which is faster?”
At first I thought, “Seriously?!” I had a change of heart once I got my ego out of the way and thought about the question as if I were a noob asking it.
Understanding bicycle gears can be a daunting task for someone brand new to cycling. After all, they put all of those gears on there for a reason, right? But why?!
The truth is, a 14 speed race bike is just as fast as a 30 speed transmission on the same bike frame, kind of. The difference between the two is that the 30 speed will have more options after one shifts out of the highest gear. In other words, if both bikes have a high gear of 11 teeth and a big chain ring with 52 teeth, both bikes will have identical top-end speeds.
Top end speed isn’t near the end of the story. I happen to be in the speedy class of cyclists and I rarely use the high gear. While I’m speedy for an old fart, I’m not a pro. The rest of the gears on the cassette are vastly more important than the little one. On my good bike I have two chain rings up front (52 & 36 and 10 cogs in the back (11-28) – all gears, chain rings up front and cogs in the back, are identified by the number of teeth they have). I can climb anything up to a 25% grade with that setup – so, 20 gears:
Then there’s my Trek 5200 T. The “T” stands for Triple. It’s got three chain rings on the front and nine cogs in the back… 27 gears:
Now, what will be faster?
The 20 speed bike is… See, there tends a lot of overlap in the gears on a bike with three chain rings – different gear selections giving one the same basic results when pedaling at a consistent cadence. For this, we can use my gearing for an illustration. First the 27 speed triple:
Take, for instance the combination 52 (front chain ring)/15 (back cassette) and then look at 42/12… Two different gears, almost the exact same speed at a cadence of 90 rpm.
Now let’s look at the gearing for a pro compact double:
Definitely some overlap, but not as much as the triple and what overlap there is spreads over two chain rings instead of three….
The real reason gearing is important and that there are so many, is that picking the proper gear for your comfortable cadence and the existing conditions is what cycling is all about – especially when you’re cycling in a group.
My three favorite gears at home are 52/17, 52/16 and 52/15. When I’m riding with my friends, these are the three gears I spend the most time in. Those three gears match my comfortable pace on flat ground, with a cadence of 90 rpm.
However if you look at the 27 speed triple, you’ll notice a much larger hole in the three gears starting at 21.5 mph in the big ring (52 t). This is because the triple had a nine speed cassette, so the most efficient use of gears requires jumping increments of 2 teeth per cog to get all of the gears on the cassette. In other words, at my comfortable speed, I have fewer gears to choose from – and that makes riding a little more difficult when trying to maintain a consistent speed whilst riding with my friends.
Now, I do spend a lot more time in the middle 42 tooth chain ring when I ride the Trek, because as you’ll note looking at the chart above, the 42/15, 42/14 and 42/12 fit my riding preferences a little better.
Gears, cadence and riding with a group and the difference between riding a bike and cycling
This post is designed to get one to look at gearing with a finer understanding than most bike riders will have and help you avoid what bike riders do: Stick it in a gear and mash it for whatever you run into – only when the pitch heads up does the frantic downshifting start.
That is most definitely a good way to get dropped on a regular basis when you’re in a group. They put all of those gears on a bike so you can use them, so don’t be afraid to.
I pick the easiest gear I can comfortably pedal to keep up with the people I’m riding with. Pedaling an easier gear, with more revolutions (within reason), means I can accelerate quicker and I won’t fatigue my legs trying to horse the pedals around on a bigger gear.
I love the way the concept of cycling was first explained to me:
It’s like lifting weights. How many curls can you do with a 40 pound weight? Five? Ten?
Now, how many curls can you do with a five pound weight? You can go all day.
Cycling efficiently is based on the same principle.
Being a runner previously, I had a tendency to mash the pedals (as many runners do). I taught myself to spin my legs a lot faster because I was told cycling would be easier if I could learn to enjoy the faster cadence. Those who let me in on the secret were right.
I took a full winter on the trainer and developed myself into a spinner from a masher. Mashing hard gears makes one work twice as hard as a spinner to hold a good line in a group. Accelerating to match a surge is so much easier as a spinner, it’s tough to not describe it using over-the-top language. The trick is that this reality has it’s limits, and that’s where a balance must be struck.
When we “put the hammer down”, if we’re in an easier gear we’re pedaling a little faster. We’re only able to pedal so much faster before we have to upshift to a harder gear. On the other hand, if we’re already pedaling in a gear that’s too hard, if the group surges a little bit, not only is it hard to make up the gap, it takes more energy to do it and that can be a problem over the course of a long ride.
Without getting too involved and long on this post, and taking this too much further, bikes don’t have all of those gears for nothing. It’s not some conspiracy to make old bikes obsolete (for the most part, there is some of that going on), it’s not to keep you buying new bikes, and it’s not some ego-driven “I gotta have the most gears!” thing…. Having all of those gears on the fast race bikes allows riders a wider range to match their cadence to the speed they’re riding.
Finally, one last little tidbit: If you notice, as the gears get bigger on the back, the smallest four or five gears get bigger at a slower rate than the last four, five or six bigger gears. This is done on purpose. The smaller the gear on the back, the harder it is to pedal. The smaller gears or “cogs” get bigger one tooth at a time (see the nine and ten speed charts above), then they start jumping two teeth and finish with three teeth increments. When riding with the faster groups, we get into those smaller gears rather frequently. It’s not rare for us to be cruising down the road at 28+ mph (52/13 gear). When you get to the smaller gears, it’s better for “feel” to jump only one tooth at a time, as it relates to cadence because jumping two teeth would be too much of a change. Notice the speed differences between the gears, again using the charts above… The difference between 52/17 and 52/19 is 1.8 mph at 90 rpm. The difference between 52/16 and 52/15 is 1.5 mph at 90 rpm. A two-teeth jump compared to a one-tooth, and they’re only separated by three-tenths of a mile an hour.
So that gets down into the real nitty-gritty about why they offer so many gears on a bike. They’re there to match a decent cadence to any terrain. Someone who may not ride as fast may only use a few of gears, but I can assure you I use all of mine, especially on the 20 speed Venge. While I could live with fewer gears… I’d rather not.