![\"8415_shimano_105_5700_chainset_silver\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/8415_shimano_105_5700_chainset_silver-768x576.jpg\")
<\/p>\nWhat makes a good chainset? Which chainsets aren’t suitable for you and your riding? What options are worth considering? All these cranky questions are answered in this guide.<\/p>\n
Chainsets, or cranksets, are the front section of the drivetrain and although they all look similar and perform the same function, they can be bewilderingly different on closer inspection. Crank length, number of rings, number of teeth, bottom bracket system and manufacturer compatibility and so on.<\/p>\n
Let\u2019s start by breaking down the chainset into its constituent parts.<\/p>\n
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Most road bikes have two chainrings at the front, known as a ‘double’. Touring bikes or bikes built for long days out in big mountains sometimes have three chainrings up front, known as a ‘triple’. Track and single speed bikes have just one chainring, you\u2019ve already guessed it, known as a single ring.<\/p>\n
![\"17079_shimano_ultegra_fc_6800_chainrings_34t_39t\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/17079_shimano_ultegra_fc_6800_chainrings_34t_39t-e1431525488723-768x532.jpg\")
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Chainsets are designed as single, double or triple ring and you can\u2019t simply add another ring to make things easier or harder as the fittings are specific to\u00a0each of the three types.<\/p>\n
You will also hear the term ‘compact’. Compact chainset is a double ring chainset with fewer chainring teeth on both rings compared to a ‘standard’ chainset. Fewer teeth = lower gearing = easier to climb.<\/p>\n
Most compact systems have a smaller bolt pattern which means you can only use certain size rings but some new types – such as Shimano Ultegra 6800 – use rings which are compatible with both compact and standard sizes (in 6800 range).<\/p>\n
Cranks are also available in 4 and 5 arm versions so if replacing rings ensure you have the correct bolt pattern on your rings to match the cranks. The technical name for bolt pattern is BCD (bolt circle diameter).<\/p>\n
![\"Bicycle-BCD\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/Bicycle-BCD.jpg\")
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The lower the number of teeth on a chainring the easier it is to pedal. Most standard double chainsets are 39 x 53 (39 teeth on the smaller ring, 53 teeth on the larger ring). The increasingly popular\u00a0compact versions have 34 x 50 rings.<\/p>\n
As well compact chainsets making climbing easier, you can also run a low ratio cassette on the rear, with an 11 tooth smallest sprocket, so as to get the same large gear rations as you’d have with a standard. Win-win really.<\/p>\n
![\"11466_shimano_ultegra_6800_chainset\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/11466_shimano_ultegra_6800_chainset-e1431525927239-768x585.jpg\")
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To muddle things a bit(!) Shimano\u2019s 11 speed 105 and Ultegra groupsets now have 36 x 52 chainset option. This does seem the perfect middle ground and is also becoming increasingly popular.<\/p>\n
Triple road chainsets usually have a 30 x 40 x 50 ratio. Triples are often used mostly on bikes where carrying loads is common and so a very lower gear is needed.<\/p>\n
The two crank arms are right and left specific. The right crank arm holds\u00a0the chainrings and the left just has a pedal on the end of it. They are connected to each other via the bottom bracket system.<\/p>\n
The length of the arm can have a significant\u00a0effect on performance and comfort. Crank arm lengths range from 165mm to 180 mm. Although it doesn\u2019t sound much, a few mm\u2019s difference can really be noticed when you’re pedalling.<\/p>\n
![\"19384_hope_single_spider_crankset\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/19384_hope_single_spider_crankset-e1431526036218-768x200.jpg\")
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The options are 165, 170, 172.5, 175 and 180 (although 180 is very rare and usually only used by tall professionals in time trials where they need extra leverage for extra power).<\/p>\n
Crank length depends on leg length. Those with very short legs would be better off using 165mm cranks. 170mm is pretty standard on bikes up to medium then 172.5 and 175 on large frames.<\/p>\n
![\"5639_shimano_105_5700_bottom_bracket\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/5639_shimano_105_5700_bottom_bracket-e1431527182689.jpg\")
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With bottom bracket (BB) systems it has become rather technical\u00a0of late! But it is necessary to know the difference. Hey, if you are still reading this so far – well done!<\/p>\n
The most important aspect here is the size of the bottom bracket shell on the frame. This will determine BB\/crank compatibility.<\/p>\n
![\"5923_campagnolo_centaur_carbon_power_torque_chainset_black\"](\"https:\/\/www.merlincycles.com\/blog\/wp-content\/uploads\/2015\/05\/5923_campagnolo_centaur_carbon_power_torque_chainset_black-e1431525949199.jpg\")
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The most prevalent these days being ‘outboard’ or ‘external’ bearing type on ‘standard’ sized bottom bracket shells. Modern chainsets have the bottom bracket axle attached to the cranks\u00a0and the bearings sit outside of the frame.<\/p>\n
There are also several older types such as square taper, ISIS and Octalink which all need a corresponding (and separate to crank arms) BB.<\/p>\n
Oversize BB systems such as BB30 and BB386 all have an oversize axle attached to the crank, with compatible press fit bearings sitting in the similarly oversized BB shell of the frame.\u00a0Oversize BBs only work in oversize BB shell-ed frames.<\/p>\n
If you have a frame with an oversize BB but you wish to use a ‘normal’ chainset then there are solutions available. There are a few companies making ‘reducers’ or ‘converters’ for non-oversize chainsets in oversize BB frames.<\/p>\n
The best way to start your search is find out what you have at the moment and why you need to change it. Count the number of teeth on each chainring, it\u2019s marked on them, and also the length of the crank arms. Current groupset manufacturer is the starting point ie Shimano, Campagnolo or SRAM, although you may wish to research what other brands are compatible with that system<\/p>\n
If you just want a straight replacement that\u2019s no problem, just copy what is on your bike, ie manufacturer, groupset, number of teeth and crank length.<\/p>\n
If you have a standard chainset and want lower gearing then get a compact.<\/p>\n
For more leverage get longer crank arms, usually a benefit for time trials or other similar solo events against the clock.<\/p>\n