Bike Chainsets: Crankset Buying Guide

The chainset lies at the very heart of your bike’s drivetrain. Made up of crank arm, chainrings; the crankset needs to be strong, light and durable. The compatibility and importance of the bike's chain in relation to the crankset cannot be overstated, as it plays a crucial role in driving the bike forward.

In our bike chainset buying guide, we’ll show you exactly what you need to know from what a crankset or chainset is, what’s included in a chainset, chainrings sizes, crank arm length and how to remove a crankset, plus a few recommendations for which chainsets offer the best solution depending on where you ride. We will be looking at road and gravel chainsets as well as MTB cranksets.

Chainsets and Cranksets Explained:

The crankset, more commonly known as a chainset here in the UK, consists of crank arms and chainrings.

Chainsets come in three main formats, single, double, and triple chainset. A double chainset enhances bike performance with its two chainrings; the larger chainring provides higher speeds, while the smaller one facilitates easier pedalling at lower speeds, which is particularly beneficial for uphill rides.

Touring or gravel bikes benefit from triple chainsets because they need smaller gears when climbing with a heavy load. However, the introduction of wide-range cassettes in recent years has improved the viability of the single chainring chainset, which still provides very low gears for touring/gravel bike-packing bikes and mountain bikes.

What is a Chainset?

A chainset is the component of the bike that you pedal to make the bike go forward. The smaller chainring offers easier-to-turn gears suitable for lower speeds and climbing. Your chainset consists of several different parts – cranks and chainrings.

The chainset is one of those bike parts that appears straightforward but conceals its complexity in the plethora of variations, standards, and compatibility issues.

Crank Arms

Two crank arms are mounted on either side of the bike at 180 degrees to each other, connected by an  axle. Most modern crank designs have the axle built into the crank arms, and then this axle is passed through the bottom bracket which is threaded or pressed into the frame’s bottom bracket shell.

What are cranks made from?

Cranks can be made from a range of materials:

• Steel - Often found on older bikes and BMXs.
• Carbon Fibre - Often found on high-end road, gravel and MTBs.
• Aluminium - Often found on low to mid-range Road, Gravel and MTB.

How do I know what chainset I need?

A key consideration when upgrading or replacing crank arms or cranksets is crank length. Most cranks for road, gravel and MTB use are supplied in lengths from 170-175mm long, but riders with legs shorter or longer than the average may feel more comfortable on cranks that better match their measurements.

Options from 160mm to 180mm cover different limb lengths – it could be worth your while to research what crank length is recommended for your inside leg measurement or speak to our expert team online or at our Oakham or Hampton Wick stores.

Chainrings

Chainrings enable the chain to drive the cassette on the rear wheel, and are the cogs with which the chain links engage., Each ring will have a specific number of teeth, determining the gearing. Chainring sizes vary. Smaller chainrings are offered in modern groupsets designed for casual riders, differentiating them from traditional options with larger chainring sizes aimed at serious racers.

They are generally made from lightweight aluminium alloy or, as is often the case with small and middle rings on mid-range cranksets, less expensive steel. 

Chainset Size:

Your choice of chainset will depend on the variety of gears you require. Triple chainsets are particularly advantageous for backpacking or touring bikes, where low gearing is essential for climbing with heavy loads. There are mostly three kinds.

Single Chainset –

There is only one chainring in a single-ring crankset. The loss of the smaller, inner ring is made up for by the single chainring’s usage of a broader-range rear cassette. This reduces the number of moving parts, and for off-road riding decreases the likelihood of the chain coming off and fewer places for mud to gather, which is ideal for gravel bikes and mountain bikes.

Double Chainset –

The most commonly seen set-up on a road bike. The double chainring crankset gives a wider range of gears with small steps between them, enabling riders to maintain a consistent cadence (pedalling speed). These chainsets come in a range of sizes depending on the type of road riding, and rider fitness.

Triple Chainset -

An earlier style of chainset, triple chainsets are frequently found on touring, vintage, or more affordable bikes. Due to the third chainring, it provides a very wide range of gears but has the downside of adding some weight. Beginners will benefit from the additional support from the easy-to-spin “granny ring” (the smallest ring) on challenging climbs.

Road Bike Crankset: Explained

Road bike chainsets are typically double chainring setups, and usually come in one of three chairing size combinations – 53/39, 52/36 and 50/34. The former is geared towards advanced riders and the racing end of the spectrum, and the latter offers ‘easier’ gearing options for entry-level cyclists and for those living in hillier environments.

The 52/36 (semi-compact) is the happy medium many riders prefer. In addition to these three combinations, there has been a development in sub-compact ring sizes. This has been brought about by the boom in gravel cycling, where riders prefer and benefit from easier gears for off-road riding and bikepacking.

Traditional (standard) chainsets: 

Road bikes will feature a double chainring setup with 39- and 53-tooth chainrings as a common standard. These combined with 10-, 11-, or 12-speed cassettes offer a wide choice of gears for climbing. The big outer chainring ensures the traditional setup is more suited to hard-riding cyclists who can sustain a high pace – such as in a race or fast training situation, or where the terrain predominantly consists of flat, smooth surfaces.

Compact chainset: 

A compact chainset spans the midpoint between the speed of the traditional larger chainrings and the climbing power of the lower gears of the smallest ring on a triple chainset. This means the small ring can be disposed of, saving a great deal of weight. They typically feature a double chainring setup with 34- and 50-tooth chainrings and have become incredibly popular for their combination of power and climbing credentials.

Semi-Compact chainsets: 

The semi-compact, sometimes called the mid-compact, has slightly reduced gearing over the standard crankset. It has a 52-tooth big chain ring and a 36-tooth small ring. It bridges the gap between easier compact gears and the faster standard gears. This is a hugely popular choice among modern cyclists, providing the full gamut of speed while making the climbs a little more manageable. 

Sub-compact: 

The sub-compact chainset drops the gear spread to 46/30, perfect for big climbs or more leisurely cycling. However, where they’ve really come into their own is on the gravel bike, facilitating the transition from fire road to trunk road, and mountain climb to trail where differing surfaces require a wider range of pedalling cadence. 

Single chainsets: 

Uses the same wide cassette technology as single-ring mountain bike chainsets. Not often seen on road bikes, their popularity is growing and they are used by an increasing number of professional race teams to varying levels of success. It is commonly used on Cyclocross and Gravel bikes.

Triple chainsets:

A further option, but generally only seen used by entry-level cyclists, is the triple chainset  with rings of 30-42-53 teeth. This provides the ultra-low ‘granny gear’ option for ‘sit and spin’ type hill climbing but adds extra weight.

Road Bike Crank length:

Most road cranks are supplied in lengths from 170 to 175mm, but riders with legs shorter or longer than the average may feel more comfortable on cranks that better match their measurements. Options from 160mm to 180mm cover different limb lengths – it could be worth your while to research what crank length is recommended for your inside leg measurement.

Most road cranksets use aluminium cranks, but top-end models can often use carbon fibre for ultimate weight saving.

Chainrings:  As above, road chainsets usually use two rings with the  traditional  39-53 setup geared towards race riders and the 34-50  compact  chainset favoured by climbers and leisure cyclists. Alternatively, you can opt for a  triple ring for the maximum range of gears.

Staff Picks - Best Premium Road Bike Chainset:  

SRAM Red eTap AXS DUB E1 Chainset

Staff Picks - Best Value Road Bike Chainset

Shimano Claris FC-R2000 50/34T Compact Chainset

MTB Chainsets: Explained

For years, MTB cranksets have transformed from the standard 3x chainset to the standard 1x today. With the majority of bikes now coming with a 1x (single chainring) chainset – only some entry-level bikes will come with a 2x (two chainrings) or 3x (3 chainrings) chainset.

Chainrings: MTB chainsets will use one, two or three rings, depending on the intended use.

Single ring: 

Single rings were originally used by gravity riders who spent most, if not all, of their time descending, and so didn’t need a wide gear range. However, pioneering work by SRAM to introduce 11- and 12-speed cassettes widened the gear ratios achievable with a single ring up front. The introduction of clutch derailleurs and narrow-wide chainrings improved chain retention, bringing single-ring chainsets into the domain of enduro and cross-country riders. Today they dominate the trails because of their simplicity and chain retention.

Two Chainrings: 

Some MTB riders still use double-chainring (2x) chainsets, but their gearing ranges have been equalled by the huge ratios achieved by 11- and 12-speed cassettes used with single-ring cranksets. However, some riders continue to favour their double rings despite the extra weight, and good savings can be made as quality two-ring cranks continue to be released for more budget-focused riders.

It is worth noting that not all mountain bike cranksets are built the same. The crankset you choose will depend on the type of riding you do and the type of bike you ride. Cranksets designed for pedal-heavy MTB disciplines such as cross-country (XC) racing will need to be lower in weight, while those aimed at the gravity market need to be stronger at the expense of lightweight and will use a narrower range of gears.

Direct Mount MTB Chainrings

Many ‘traditional’ chainrings are mounted via four or five bolts that secure the ring to a crank “spider” that is then attached to the crank arm. In recent years, direct-mount chainrings have become popular, installed directly onto an integrated crank, lacking the usual 4- or 5-arm spider.

A direct-mount chainring simplifies things, creating a strong and robust system that is easier to maintain and most of the time lighter as well.

Staff Picks - Best Premium MTB Chainset:

SRAM XX1 Eagle Boost 148 DUB 12 Direct Mount X-SYNC 2 Crankset

Staff Picks - Best Value MTB Chainset 

Shimano Deore FC-M6120 12-Speed Chainset

How to remove a crankset

If you want to fit a new bottom bracket or replace old chainrings, you’ll need to get your cranks off. Removing your crankset can be an easy do-it-yourself job or one you take to your local bike shop. If you are looking to do it yourself, here are a few steps to removing your crankset:

Loosen the non-drive side crank bolts: Using a 4mm Allen key, loosen the bolts holding the left-hand (non-drive) side crank off the crank spindle.

Remove the adjustment cap: Shimano cranks have a special cap that protects the spindle and bottom bracket. Using the bottom bracket tool, fit the smaller ring into the crank arm and unscrew it.

Remove the crankset: it should be simple to remove the left-hand (non-drive) crank from the spindle. After taking it out, you should be able to extract the right-hand (drive) crank (complete with the spindle connected) from the bottom bracket.

Depending on your crankset, the way you remove it may differ! If you are struggling to remove it you can speak to one of our tech experts who can help you out!

Drivetrain component brands

At Sigma Sports we stock a huge range of components from brands including SRAM, Campagnolo, Shimano and many more for use on and off the road. Beyond a new chainset, we can help you upgrade your bike's cassette, rear derailleur & mech, front mech, bottom brackets or even full groupset. Our extensive components range has replacement and upgrade parts for every budget.

Bike Chainset FAQs

Chainline – What is it and why does it matter?

Chainline refers to how straight the chain runs from the front chainring(s) to the rear sprockets. The perfect chainline is when both sprockets are in the same plane, this reduces sideward motion or stress on the chain. To determine your chainline you measure from the centerline of the frame to the centre of the chain.

You can measure the front chainline directly with a simple ruler. Simply hold the ruler against the seat tube or down tube and measure the distance from the middle of the seat tube to the middle of the chainring teeth. In the case of triple chainsets, measure to the middle chainring. In the case of doubles, measure to the halfway point between the two rings.

When should a crankset be replaced?

Often cranks shouldn’t need replacing unless they are crashed, damaged or not looked after; however to keep them in good shape, parts like chains should be replaced before they wear and cause damage.

Your chain should be replaced every 2,000 – 3,000 miles depending on your riding style. However, the best way to determine if you need a new chain is by using a chain wear indicator to measure how badly your chain has stretched.

If your crank is starting to show signs of wear – such as noise whilst riding – then you most likely need a new crankset. Using the same damaged one will not only cause accidents but lead to more damage.