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Cycling and Gears – Everything the Noob Needs to Know about Road and Mountain Bike Gearing


April 2015

The inspiration for this post was a mountain bike ride that I took on Wednesday.  A little more than 17 miles on Wednesday, on dirt roads.  I have a nice mountain bike but it’s not like my road bike.  It’s a heavy, hulk of a thing and it’s an 8 speed drivetrain rather than the 10 speed on my road bike.  Shifting, of course, is just as easy on either bike.  For the road bike, a flick of the wrist against the brake lever (or middle a finger for a harder gear) and I’m in a new gear.  A flick of my thumb on the mountain bike (I have the under/under shifters rather than the older over/under shifters).


The 20 speed Double Road Bike or the 24 speed Triple Mountain bike?

Where this gets interesting is the 8 and 10 speed drivetrain and how the number of gears help (or hurt) speed.  For we older folk, who grew up with ten speeds, where the total number of gears were ten, or maybe fifteen if you had a triple crank up front, you might think the 24 gears of an 8 speed triple on the mountain bike would trump the 20 of the 10 speed double on the road bike, for building and maintaining speed – and you would be wrong.  Never mind the differences between the two bikes that make the road bike vastly faster anyway.  Even if we were to take into account that the mountain bike is 5 mph slower, on average, there is a huge problem built into the 8 speed transmission of the mountain bike that makes maintaining speed miserable and that makes those 10 and now 11 speed cassettes awesome.

My Rockhopper has an 11 tooth to 34 tooth 8 speed cassette (the size of the gear is measured in the number of teeth)  That means you’ve got 8 gears to span a difference of 23 teeth.  On my Venge I’ve got an 11t to 27t (it came with a 28 originally)…  So I’ve got ten gears to span a difference of just 16 teeth…  Do the math, and the average jump from gear to gear on the mountain bike is just shy of 3 teeth.  On the road bike it’s only 1.6

Here’s the gears on the 8 sp.:  11,13,15,18,21,24,28,34
And on the 10 sp.:  11,12,13,15,17,19,21,23,25,27

Down at the small end of the cassette, there is a difference of two teeth for the first three gears on the 8 speed, while the first three gears on the 10 speed road cassette only go up by one…  After that, there’s a difference of three teeth for the next three, four on the fourth and six on the fifth to get you to 34.  On the road cassette, it’s a jump of two all the way till the largest cog.  11 speed cassettes are even better, giving the cyclist an extra gear at the hard end with a difference of only one tooth.  Why is this important?  First, the gears are closer the smaller they get because the smaller cogs are harder to pedal.  As you get easier, the jump gets bigger, especially on the mountain bikes.  Got that?

Okay.  Maintaining speed on the road (dirt or paved) is all about maintaining a cadence.  With a jump of three teeth or more into a harder gear (smaller), there’s a huge leap in the power required to maintain speed.  This doesn’t matter so much on a slower single-track, where there are often intense changes in elevation so you rarely have long stretches where you’re pounding down the trail, trying to pick the perfect gear.  You’re often up and back down the cassette in the space of a few hundred yards.  Conversely, on the road, hills are usually less sharp and the bikes are much lighter so you don’t need quite the range on the cassette and with the extra two gears and only a two teeth jump, it’s a lot easier to pick a gear to match a desired speed and cadence.  In short, the closer you can get the gears (especially as they get smaller on the cassette), the easier it is to find a desirable gear to match your cadence and the amount of force you can put on the pedals.

Now, with that out of the way, I wanted to get into a little bit about how to use the gears.  We have 20 to 33 gears on a bike for a reason – to use them.  They’re not there to look cool (in fact, some would argue that having more than 22 is useless my Trek is a triple and I do love it down south in the mountains).  Most people, if you really pay attention, don’t shift near enough.  I use every gear on my 10 speed cassette (except the 27 tooth cog to prevent cross-chaining) and it has been successfully argued that we don’t even have hills on that 3o mile route.  We do, of course.  They’re just not all that big.  In any event, it’s a rare day that I’ll ever use the baby chain ring, but I do use all of the gears on the cassette, multiple times.  I shift constantly as the elevation changes…  As soon as my cadence starts to slow or when it gets harder to maintain, I shift.  There are times when it makes sense to try to muscle through a gear (if my breathing is too fast or heart rate is too high, for example or if the top of the hill is within a few dozen meters) but they are few and far between.  It’s almost always better to shift and maintain a high cadence while maintaining the speed to keep up.

We can use weight lifting as the example here.  Most people, especially men though, if you put a five-pound weight in their hand, will be able to do curls all day long.  Up that to 30 pounds and you won’t be able to do as many reps.  Well, pedaling in a hard gear works on the same principle.

As President Clinton used to say:  Shift early and shift often.  Err, wait…


  1. Good post. When I was doing club rides on my 8-speed 11-32 equipped bike I found the hardest problem was maintaining the correct cadence to match the group speed. One gear was too fast an RPM but clicking to the next meant grinding it out.

    Having small jumps between cogs makes everything so much smoother. I use a 12-26 on my roadie with a 30/39/50 up front. I’d prefer a double as the 39/50 is a great shifting combo and I can’t remember the last time I used the granny ring. The new 11-speed 105 looks very slick!

    • bgddyjim says:

      What you started with, an 8-speed in a club ride, is exactly the problem with the older drivetrains. Can’t match a cadence to the tempo of the group. Fortunately, I haven’t had any problems with the 10/11 speed drivetrains. They’re close enough for government work.

      I’ve got the 52/36 Pro Compact and absolutely love it. Two extra teeth on the big dog and I’ve only wished I had a 34 one time (18% over 1.25 miles… It’s a bear of a hill).

  2. wanderwolf says:

    really interesting! I’m not a biker, but it’s cool to learn things about them since I do ride.
    Also, the last line made me lol. Thanks.

  3. bribikes says:

    I have been wondering about the reasoning behind and differences between the double and triple. Now I know, thanks 🙂

  4. Sue Slaght says:

    Fabulous example comparing reps with weights to riding in different gears. Such a great visual learning tool.

    • bgddyjim says:

      Thanks Sue. My buddy Mike and I were talking on a ride the other day about how rare it is to see someone shift well leading into a hill.

      • Sue Slaght says:

        I’m working on getting better at it. Heaven knows I need all the gears I can get. 🙂

      • bgddyjim says:

        On the lead up to a hill, make sure your cadence is right around 90… The second after you feel a little drag on the pedals going round, shift down… As soon as you feel it drag again, downshift again. You’ll be amazed at how fluid and perfect it is… You’ll fly up hills with 2/3’s the effort of most everyone else.

        I’ve gotten so good I have to soft pedal, or even coast for a few seconds… Uphill.

      • Sue Slaght says:

        It’s the same advice I got from another strong cyclist like you. When I get it just right it’s a beautiful thing. I will be remembering your words on the next hill. 🙂 Thanks!

  5. I assume that Rockhopper is a 26? New mountain bikes are 29 or 27.5, with double or single chain ring and 10-11 gear cassette. My dual suspension CAMBER is faster than some of my old road bikes!

  6. How do your knees feel after grinding out that ride on your MB? That is a decent ride on a MB.

  7. MJ Ray says:

    You’re not gonna like this…

    Maintaining speed on the road (dirt or paved) is really all about maintaining efficient power propelling the drive wheel. Sure, most people have a particular cadence where they produce peak power, but they lose efficiency by having the chain bent, by having the chain change direction more times than needed and pull taut against a spring, by having the chain dangling down to collect dirt thrown up by the front tyre and slowly grind itself into oblivion, by having the chain not properly connected to the cogs every time they shift (so extra shifting isn’t completely free).

    It depends why you ride, too. If it’s for transport, then minimising journey time also includes other factors. While someone is brushing their bike’s teeth, cleaning its chain, fiddling with indexing screws, changing clothes and unpacking a QR bag, my messenger bag lifts out of the basket or off the hook on the chainguarded hub-geared bike and I’m off doing the next thing 😉

    (Or more often around here, they don’t seem to bother cleaning and tuning the bike and it squeaks like hell as I overtake…)

    • bgddyjim says:

      I do like it! The loss, due to the incidentals that you mention, is negligible when viewed against overloading the muscles so shifting early and often still makes the most sense – when we boil it down to speed, and top speed is what I was looking at in this post. As far as others not properly maintaining their bicycle, well you can lead a horse to water but you can’t make him clean and lube his bike.

      • MJ Ray says:

        Imagine the mess spreading lube with hooves would make…

      • MJ Ray says:

        More seriously, it depends if you measure speed in miles per hour or journey per minutes.

      • bgddyjim says:

        Well, yes and no… Technically it depends on how you measure the journey as a whole. My journey starts at the start line and ends at the finish line (maintenance is just a requirement of my cycling)… If you measure the journey as from the start line to the point where the bike is cleaned and relubed, then you have a point – but you also have to take into account for the fact that a chain only needs to be relubed once every 300-400 miles. (Boeshield T-9 – gotta love it).

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