One-Two-Three. There are different numbers for different uses. Mountain bikes typically have three and road bikes usually have only two. These past few years there has been a trend in mountain bikes to have less chainrings. Mountain bikes and mountain bike groupsets now come with two chainrings or just one. For road bikes, the triple (three chainrings) is available but rather rare. Also, single chainring options are offered by SRAM. This first appeared in their Force CX1 groupset (mainly geared toward cyclocross/CX riders). Now, they have the Force 1, Rival 1 and Apex 1 groupsets.
A Double Crankset - 2 Chainrings.
A Triple Crankset - 3 Chainrings.
How many chainrings do you need? In a sense, it all depends on your intended use. More chainrings provide you a wider range. If you live in a flat area or intend only to use your bike for city commutes, then one chainring is enough. You don't expect a long steep climb in the city. Areas with more varied terrain (flats, climbs, descents, etc.) may need two or three chainrings. Having more will provide you the options you need for different situations.
Why two, not three? Why three, not two? Choosing between double and triple chainrings requires self-evaluation and assessing your confidence. Is the range provided by two chainrings enough? Or, do you need three to pull you out of tough situations? We can look at a spectrum to better understand. The examples given are for road bikes.
Standard. The "Standard" crankset refers to the racing crankset. It has 53 teeth on the big ring and 39 teeth on the small ring. There are other possible combinations too like 52/39, 52/38, 54/42, 55/44 and even 58/44. It helps riders go fast on the flats and descents, but may pose a challenge for climbing. The "large" small ring would be too difficult to pedal comfortably for climbs - long, steep or both. These are typically used by strong riders.
A "Super-sized" Standard - 55 teeth on the big ring and 44 teeth on the small ring.
Compact and Mid-compact. The "Compact" crankset has 50 teeth on the big ring and 34 teeth on the small ring. The "Mid-compact" crankset has a ratio of 52/36 and its name refers to it being the midpoint between the Compact and Standard sizes. These combinations provide easier, more adequate gears for climbing. The Mid-compact gives a little more resistance compared to the Compact and this is more manageable for people who have difficulty spinning the small 34 teeth ring. However, there may be a challenge for the flats and descents against the "Standard" crankset. This is the size recommended for beginners and is the size of choice for those who are challenged in the climbing department.
A Compact - 50 teeth on the big ring and 34 teeth on the small ring.
A Mid-compact - 52 teeth on the big ring and 36 teeth on the small ring.
Triple. The "Triple" offers the largest range of all. Its big ring can be as large as 53 teeth (the same as a "Standard" big ring) and its small ring is 30 teeth (even smaller than a "Compact" small ring. In newer triple cranksets, the big ring is only 50 teeth, the same size a "Compact" big ring. The mid ring (middle ring) is usually 39 teeth or sometimes 42 teeth. Common Triple combinations are 53/39/30, 50/39/30 and 52/42/30 teeth. In short, a Triple is a "Standard" crankset with a 30 teeth back up chainring. For road bikes, Triples are not as common (or even known) now as Compact chainrings took their niche in the market.
A Triple - 50 teeth on the big ring, 39 teeth on the middle ring and 30 teeth on the small ring.
The More, The Better? Is a Triple better than a Double? It is true that more chainrings increase the possible range for gearing. On the other hand, more chainrings also have more redundant gearing combinations or gear ratio (the size of the chainring divided by the size of sprocket). The gear ratios of the big ring (big ring divided by the different sprockets) have some overlap with the gear ratios of the middle ring. In addition, the gear ratios of the middle ring have some overlap with the gear ratios of the small ring. With a Double, there are less overlaps (less redundancy) and this means that the drivetrain is more efficient. However, there might be losses at the two extremes (combinations with the heaviest and easiest gear ratios). With this efficiency, there is the added benefits of (1) simplicity, (2) having less weight and (3) being easier to maintain and service. For road bikes, a triple crankset and its related components (especially the shifters and the front derailleur) are difficult to find. On a side note, SRAM takes this a step further with their single chainring groupsets. These groupsets are the most efficient since there is no overlap of gear ratios.
We now conclude our topic on chainrings. We hope you got a better idea on what size of chainrings to use for your bike. Standard cranksets are good for flats and descents, but they may pose a challenge for climbing. Compact and Mid-compact cranksets are suitable for beginners or those who want easier gears climbing. If you need easier climbing gear or more diverse gearing, then you can look for available Triple cranksets online and even abroad. Some built bikes available locally come with Triple gearing. If range is not really a problem, then one could (or should) aim for having a more efficient drivetrain. If you're really confident, why not try a single chainring setup?
Remember: Biking is riding your bike. If you're not riding, you're not biking. Set up your bike with what works for you and what makes your rides great, fun and fulfilling.
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Very enlightening thank you.
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