If you haven’t a clue how many gears your bike has, how many you actually need or even how to use them properly, don’t worry — you’re not alone. We demystify derailleurs and sprockets and explain why in cycling STIs are a good thing to have

We’ve all heard it; most of us have probably said it, or at least thought it — why on earth does a bicycle need 33 gears? “It’s ridiculous” we hear you say — “You couldn’t possibly need that many. When I started cycling we only had three…”

So what’s the deal? Why have component manufacturers gone to such lengths to bring us technology allowing a bicycle to have up to 33 gears? Understanding the fundamentals of how gears work, and what effect varying the size of the front chainrings and rear cassette sprockets will have on your pedalling will help you choose the most suitable gearing.

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We’ve spelt it all out in the following article, so you’ll be much more the wiser, and a more efficient cyclists as a result — we promise.

The basics

What determines the number of gears on a bicycle?

It’s a simple multiplication of the number of sprockets at the rear with the number of chainrings at the front. A triple chainring set-up with a 10-speed rear cassette is therefore a 30-speed bicycle — in other words, it’s possible to use all of the 10 sprockets in combination with each of the three chainrings. Likewise a double chainring paired with an 11-speed cassette is a 22-speed set-up, and so on.

Aiming high or low?

Why have gears at all? Well, in a nutshell, gears are there to enable us to maintain a comfortable pedalling speed (or cadence) regardless of the gradient or terrain — something that no one single gear is capable of.

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A high gear, sometimes referred to by cyclists as a ‘big gear’, is optimal when descending or riding at high speeds. The highest, or biggest gear on a bicycle is achieved by combining the largest front chainring size with the smallest rear cog or sprocket — expressed as ‘53×11’, for example.

Vice versa, combining the smallest front chainring size with the largest rear sprocket size results in the lowest available gear, which will help you keep the pedals spinning when the road points steeply up.

Let’s be clear about one thing — having lots of gears is not about making the bike faster. A bike with 30 or more gears is not an indication of a machine designed to break the land speed record any more than a bike with only a single gear, assuming similar ratios.

Gear-article-main-pic-3Lots of gears: do you need them all? The short answer is ‘yes’

It’s about efficiency and having a much broader range, or choice, of gears for a given situation. Just like a car, bicycles benefit from a low gear to accelerate from a standstill, or to climb a steep hill, and at the other end of the scale a high gear helps you to achieve high speeds without over-revving.

Continuing with the car example, using too low a gear at high speed would result in high fuel consumption. The same is true of your body pedalling a bike. So, quite simply, more gears means more scope to find your preferred pedalling speed.

To put this into perspective, in the days of five or six-speed cassettes, a range of 12-25 teeth could only be achieved by having sizeable gaps between sprocket sizes. Modern 10 or even 11 speed cassettes with the same spread, 12-25, would have only single tooth increments for the majority of the shifting.

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The result is smoother, more precise shifting, as the mechanical difficulties the chain has to overcome to climb onto the bigger sprocket or drop down onto a smaller one are much reduced with smaller increments, but most importantly, the possibility is there to greatly improve pedalling efficiency. Cyclists are much more able to fine-tune their pedalling speed to suit the gradient or terrain, often resulting in a lower energy cost.

>>> How to adjust your bike’s gears

Win some, lose some

The reality, on a multi-geared set-up, particularly when there are as many as 33 on offer, is that ‘overlapping’ gears are unavoidable. In other words, some gear combinations will result in the same ratio as others using a different sprocket and chainring. For example, 53×19 is the same gear as 39×14.

Also, certain ‘crossover’ gears, at the extremes of the range, may not be recommended for use, due to the additional strain that is placed upon the chain. Old-fashioned advice, which is still relevant, is to avoid ‘crossing the chain’. See the diagram on p90 for an illustration of this.

So you’re not always getting 33 gears at your disposal, but it’s not some kind of marketing trick by manufacturers, to slyly cheat you out of gears, it’s simply the nature of the beast.

As we’ve already said, the total number is not the selling point, instead it’s the ability to have such a continual progression of closely spaced gears.

There’s no need to struggle these days because there are heaps of gearing options available so riders of all abilities can get the most from their pedalling. The trick is to know what’s what, so you’ll be able to decide what will best suit your riding. Here’s the lowdown to put you on the right track.


Guide to different types of gears

Standard double

Two chainrings at the front paired with up to 11 sprockets at the rear. Common gear ratios are 39t or 42t for the inner ring and 52t or 53t for the outer. A standard double set-up is usually the preferred choice for racing, offering the largest chainring sizes for the biggest gears possible to keep you pedalling smoothly when speeds are high.

Some reduction of the lower gearing is possible, but only as low as a 38t inner chainring, so if it’s low gears you’re after, a standard double is not the best way to go.


Having three chainrings brings the possibility of adding a much smaller gear option. The third chainring is usually 30t or smaller, which when paired with a large ratio rear cassette, can provide an extremely low gear for use on steep climbs. A triple is the preferred choice for riders looking for a ‘bail-out’ option, often those regularly riding in very hilly regions.

It’s also beneficial for laden touring when baggage makes the battle against gravity even tougher.


A compact is essentially a double set-up, only smaller. Both chainrings are reduced in size, usually 34t or 36t inner, paired with a 48t or 50t outer, reducing the gear ratio across the range. It’s currently a highly popular choice as the reduction in gearing at the lower end is enough for most to tackle even Alpine climbs, yet there is not a huge reduction of the top gear, still allowing fast descending.


Apex was the first of a new wave of ‘super-compact’ gearing. SRAM has based Apex gearing around a compact double chainset, but utilises a specially designed rear derailleur and large ratio cassette of up to 11-36t to significantly reduce the gearing.

This not only offers an extra low bottom gear, lower even than a triple, but also provides an equivalent or larger top gear than a triple too. In this way, the Apex set-up aims to practically negate the need for a triple — a broader range of gears, that’s lighter and better looking.

Hub gears

This type of robust, low-maintenance planetary gear system, housed in a fat rear hub, is still going strong. The popular Rohloff hub has 14 gears, while four, seven, eight, nine and 12-speed options are available from the likes of SRAM, Shimano and Sturmey-Archer.

The choice of individual gears may be less than using a derailleur system, but it’s still possible to personalise ratios by playing around with chainring and rear sprocket sizes. Hub gears are generally tough and require very little maintenance so they’re great for everyday commuter bikes, especially as most allow you to change gear without pedalling too — handy at traffic lights. Their weight is their Achilles heel, counting against them in hillier terrain and on longer rides.


PMP 33t chainring

As a simple fix to reduce a compact gear ratio a tad further. PMP’s 33t ring simply replaces the standard issue 34t, and Bob’s your uncle… the bottom gear just got lower.

Cassette ratios

What does 11-23 or 12-25 refer to? The first number is the smallest sprocket size, often 11t or 12t and the second number is the largest sprocket size, commonly anything from 21t to 28t and sometimes larger.

Gear shifting techniques

With some modern designs, it’s not always immediately obvious where the shift levers are. If you’re in any doubt, a local bike shop will run through this with you, but here’s the basics for the majority of what’s on the market. Regardless of brand, right-hand levers control the rear derailleur, and left hand levers the front.


The language of gearing

Chainring: toothed ring at the front end of the drivetrain, attached to the crank.

Cassette: cluster of sprockets at the rear of the drivetrain, containing up to 11 gears, of various sizes.

Block: another term for the group of rear sprockets, but really refers to the older, screw-on freewheel.

Derailleurs: front and rear derailleurs do all the hard work of moving the chain from one sprocket (or chainring) to the next.

Sprocket: refers to an individual gear within the cassette/block.

Ratio: describes the relationship between sprockets and chainrings, for example ‘53×12’, or the sprockets on a cassette (11-25).

t: short for teeth — to describe how many a given sprocket has — for example ‘23t’.

Gear-article-main-pic-2Know your Ergo levers from your STIs

Drivetrain: term grouping together all the moving parts that connect the crank to the rear wheel and hence drive a bicycle along — namely the chain, the cassette and the chainrings.

Cadence: pedalling speed, measured from how many revolutions the crank makes per minute — expressed in RPM.

STI lever: abbreviation of ‘Shimano Total Integration’ — a term for Shimano’s design combining brake and shift levers for road bikes, but often (mis)used generically to refer to the shift/brake levers regardless of brand.

Ergo lever: Campagnolo’s name for its version of integrated gear shift and brake levers (ie Campagnolo’s STI).

DoubleTap lever: SRAM’s slice of the pie, in terms of shifter technology — uses the same lever for upshifts and downshifts.

  • Hugh Strickland

    So, if your cycling is all about seeing how fast you can go stop reading this comment now. I use a 46/36 double paired with a 13/25 cassette. Very nice. protects the knees and gives lots of options. This is a ten cog cassette. Why did I do this? I notice that my cassettes were worn between those numbers and I did not use 11 or 12 or 27 or higher. this increased the number of cogs I would actually use. I ride about 15,000 miles a year and enjoy the ride very much.

  • Jake Siney


  • MadBob

    Yes, but there is a strong reason for that, all the speed signs on the roads in the UK are in MPH not in KPH, and all distance signs in Miles not Kilometres, so nobody of any age talks about KPH, although most ages are capable of working in either metric or imperial measurements; both fractional and decimal. We’re just multi talented I guess! (it makes up for our formidable lack of skill in languages) 😉

  • COL S. Trautman

    First of all, all pros are on 11-28 with a lot of them choosing a compact, I guess you haven’t seen many cyclists and the sort of set up they use OR you live somewhere with no hills and the bikes tend to have that sort of gearing. All bikes come with a 28 or higher these days and and with 95 percent of them having compacts, or triples with a few racing or aero bikes having 52/38.
    So, like it or not, 39/23 isn’t a practical ratio for hills except if the roads where you live never get steeper than 3 or 4 percent and aren’t longer than a couple or hundred meters. 39/23 is a joke.

  • Roger

    The “hubris” that made him one of the best cyclists ever? Sounds good to me!

    There was a fantastic

  • Roger

    I would consider standard to be 11-23. Anything lower than 39×23 would be of use only to cyclists riding extremely step and/or long hills and/or riding a heavily laden touring bike.

  • COL S. Trautman

    Actually the standard cassette of today is an 11-28, with pros using even 32s sometimes, and why is an 11 top a no no?

  • Dave2020

    Hi there. Glad you like it.

    Maintenance is just clean and re-lube. A ‘standard’ width chain in better alignment runs smoother and lasts much longer and the indexing is absolutely reliable, as it’s in the hub, not in the lever. A 40mm chain-line would allow clearance on a very fat tyre.

    A universal standard race cluster would be 12-25t. The four biggest sprockets can be 21, 25, 30, 36, if you wish. I don’t want 2-tooth jumps on any cogs smaller than the 19t and an 11t top is a no-no. So, even on a wide ratio block, most gear changes are the smallest increments possible. Likewise, I’d use a close ratio triple for racing; 39-46-53 or 39-47-55. Yes, there are many duplicated ratios, but the way I see it – you’ll never drop the chain (on the cobbles), if you’re using the middle ring. For mountains/touring 30-39-50 is fine.

    I recently fitted an expensive new triple chainset on my old race bike. The non-adjustable chain-line is 6mm too far out and the total Q factor, including badly designed pedals/shoes/cleats has increased by 2cm! Shimano think this is forty years of progress? I don’t think so.

    I’m not sure I can find the enthusiasm to make a prototype sample, because I’d prefer to invest the time refining a 21st. century design, with no chain and a direct-drive stepless transmission.

  • COL S. Trautman

    Perfect chain line and no dish in the back sound like a dream! I often fantasize about this on a quality steel frame and 28 mm tyres with really wide rims (to maximize the potential of wider tires). What about bottom gears though, can you have quality internal rear hub that could match a 34/32 combo? and what about increments? maintenance? thanks, I really love this.

  • Kent

    I was surprised that you UK’ers still use the Imperial measurements so casually in everyday life! Though it’s the same here in Canada, it’s officially metric but everyone born before 2000 talks in imperial…aside from speed though. No one has a clue what 60MPH is.

    nice video, I still really want that cervelo though haha

  • Dave2020

    “Lots of gears: do you need them all? The short answer is yes”.

    Maybe so, but not the way that derailleurs have developed over the past 25 years.

    (Please) Take (away!) the industry standard double chainset with a 14t jump x 11 speed cassette. In practice that’s 16 ratios, due to duplication. At a time when 8-speed was the maximum, because of chain width, I offered Campagnolo a rear hub design, at the Milan show, where 11 sprockets were displaced axially relative to a tensioning cage with a fixed chain-line. That’s a perfect engineering solution, giving you a full complement of sequential close ratios and no dished spokes.

    So, there was never any need for a narrow chain and the only lateral displacement was the shift across the double or triple chainset; i.e. no cross-chaining. The only reason for not adopting the better design was that it was a departure from the industry standard rear dropout. In other words, there was NO good reason – to develop the conventional derailleur to its present state of barely competent function, short working life and numerous incompatible specs.

    In the confused mind of the ‘strong’ rider, a stigma has become attached to the triple and, in their foolishness, they take pride in being able to climb in the big ring (e.g. Hinault). This hubris tempts them into giving the short answer of “No”!

  • Tony Cooper

    No there not…people these days are being sold the useless so called compact! that nearly replicates every gear within a couple of inches or so…Sold regularly to the masses that just go onto to the 34…to make life easy. 36-50 is better with a larger big sprocket..27-28, similar gearing, wider spread. and not having to change onto the big ring so often, when cruising and knowing a slope is comming. Having grown up with mashing a 42-52 around with a 23 on the back and hostelling with that. Yes compacts and smaller gears are good as we age. But the compact isn`t the way.

  • Edward Hutton

    48 times 27 divided by 18 fixed wheel a cracker

  • Rupert Rivett

    Just using a 72 inch gear at the moment 🙂