One of the most important decisions a cyclist has to make, is what gearing setup to purchase. There are different gearing options in the front (crankset) and in the back (cassette).
In general terms, bikes are often referred to as Double or Triple setups. What this is actually referring to is the Chainring (or crank) on your bike. That's the large gear in the front attached to the pedal. A double has two chainrings and a triple has three.
Most bikes that you see will typically come with a double or triple. However there are a also a couple of other popular variations - a Compact Double and a Fixed Gear (fixie) bike.
A triple crankset is what you'll find on many hybrid bikes and on some road bikes. Hybrids use them because weight is not a factor (double cranksets weigh less) and hybrid cyclists aren't interested in performance and weight, as much as they're interested in climbing up a steep hill without working too hard. Triple cranksets have smaller gears that make hill climbing easier. If you watch someone going uphill on a hybrid, you'll see them spinning their wheels really fast (perhaps 110 rpm). That's because they're not strong enough to climb the hill in a bigger gear. So triple's are the perfect gearing for hybrids.
Triple cranksets used to be very popular on hybrid and lower-end road
bikes, however many manufacturers are converting to compact double cranks instead. Doubles now come in such a wide gear range that a triple is no longer necessary.
If you're not a particularly strong cyclist or you're carrying a lot of weight, then a triple is for you. The disadvantage of a triple is that they weigh more than a double, and shifting between each of the three (triple) chain rings can be troublesome. They just seem to have more mechanical issues, and you're more likely to have your chain "jump off" of the sprockets when shifting.
Cyclists like to call a triple crankset "granny gears", meaning that only their grandmother would use a triple. Chances are that these same cyclists have wished that they had a triple when climbing a mountain. They're just too macho to admit it.
A double crankset is what you'll find on most high-end road bikes. There's two reasons why - they're lighter and have fewer mechanical issues than triples. Light weight is important to road cyclists and dealing with shifting problems is pretty much eliminated with a double. The disadvantage of having a double, is that if you're not a strong cyclist, than you won't have a low enough gear to get up a steep hill. You need to try out a double on your regular rides to see if you're strong enough to use one.
If you're not quite strong enough for a Double, a Compact Double crankset bridges the gap between a double and triple. It's light, has few mechanical issues, and gives you lower gearing for climbing hills. However, the lowest gear isn't quite as low as a triple; so you really need to try out a compact double before deciding if it's right for you. There are newer cassettes with up to 32 teeth which make a compact double very attractive for climbing. See below for more details on gearing numbers.
A fixed gear bike is typically used for city riding, where you don't need to do a lot of shifting, and you'd prefer to eliminate all of the extra weight that gearing adds to the bike. Some strong recreational cyclists have a "fixie" bike that they'll occasionally use in place of their normal road bike, because it's great exercise. Instead of shifting to make their ride easier, a fixie makes their ride harder. Go figure.
Within each of these groups you'll find that there's various combinations of cassette (rear wheel) gearing. Some manufacturers offer 9 or 10 gears on the rear wheel, while others offer 11. You'll need to try out bikes that have various gear setups in order to determine what's right for you, and where you ride.
Understanding Gear Numbers
A chainring will be described by the "tooth count" on each ring. For example a standard double would be "39/53" and a compact double "34/50". The higher numbers (the big ring) are for going fast, and lower numbers (the small ring) are for climbing. So when you're climbing you'll want to be in the small ring which could be either a 34 or 39, depending upon which chainring you have. Since smaller numbers equate to easier climbing, the 34 gear on the 34/50 is a better choice for climbing than the 39 on the 39/53.
In the rear of the bike is the cassette, and the numbers are calculated opposite of the front chainring - larger numbers equate to better climbing. This has to do with how many times the wheel will rotate, vs. how many times you turn the crank or chainring.
Cassettes come in wide ranges of "tooth count" and recently newer cassettes with a higher tooth count have reached the market. For example, a 12/25 cassette has been a very popular choice among strong cyclists for many years. It's a good mix of gear ranges for most terrain. What's becoming more popular are 11/28 cassettes, which provide better climbing for recreational cyclists. Remember, higher numbers in the cassette equate to easier climbing. Therefore the 28 in the 11/28 is better for climbing than the 25 in the 12/25.
Putting this all together, for climbing ease you would choose the compact double with a 34 chainring and a 28 gear cassette. This combination would work for most recreational cyclists in our region.
What if you're carrying extra weight or you're just not that good at climbing hills? There is a solution for you. Cassettes now come in 30 and 32 tooth gearing. A 32 tooth cassette paired with a 34 compact double will get just about any cyclist up any hill. This configuration compares very closely to a triple chainring in low-end gear range. The downside is that you'll sacrifice some gearing combinations in the mid-range.
Thirty and 32 tooth cassettes won't fit on every bike. They require a special derailleur that can reach all 32 teeth. If your bike didn't come with this type of derailleur, you'll need to check with a bike shop to see if an upgrade is possible.
To visually understand all of this "gear talk" take a look at the interactive gear calculator below.
Visually Compare Gearing Online
There are online gear calculators which can produce big charts or spreadsheets showing every possible gear combination on a bike. These aren't really helpful to the average cyclist because they're just a bunch of numbers and don't convey climbing ability or speed.
We've come across a great "interactive visual" gear calculator online from Tableau Software which really shows you how different gearing setups compare.
Below is an example from the Tableau calculator. The upper Bike 1 setup is a standard 50/39 chainring, and 12/25 cassette. The lower Bike 2 setup is a compact double 50/34 chainring, and 11/28 cassette.
The speeds and ranges of each gear on each bike are represented in dots. Orange dots are each gear when using the small chainring and blue dots are for the big chainring.
You'll notice right away that Bike 2 with the compact double and higher rear tooth count (28 vs. 25) has orange dots that go farther to the left (circled in green). These dots represent the speed you'll be traveling in each gear when turning the crank at 90 RPM. Bike 1 can only take you down to 11 MPH and Bike 2 will go as slow as 8 MPH at 90 RPM. The net result is that the compact double is more suited for climbing.
So why would a cyclist choose the standard setup over a compact? Because if you're a really strong rider and you can power up the hills, the lower gears in a compact are useless to you. Look at the dots on Bike 1 (standard setup) you'll see that you have more gears to choose from in speeds between 14 and 32 MPH, vs. the compact. If you've ever been on a ride and you just "can't seem to find the right gear" (up is too hard and down is too easy), then you'll understand why stronger (perhaps competitive) cyclists wouldn't use a compact. They want as many gear choices as possible in the speed range they'll be riding.
Since no one gear setup is ideal for every type of riding, many cyclists have different bikes, or different gear setups for different types of rides. If you're going on Skyline drive in the Shenandoah mountains (lots of hills), use a compact setup. For regular riding "around town" use a standard gear setup. So consider having a different gear setup on your second bike. That way one can be a city bike and the other, a climbing bike.
Be sure to check out this great resource online and experiment with various gear setups. The calculator does not have an option for triple chainrings. Click here for the website.
It's relatively easy and not very expensive to change cassettes on a bike (less than $100.00) . The crankset & chainring are a different story - it's more difficult and can become very expensive. So choose your chainring carefully, because you may just keep it for the life of your bike. You can always start out with a wider range cassette, such as an 11/28 or 12/30, and then change to a 12/25 as you become a stronger rider.