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Chainsets
 
 
 
 
The term chainset refers to the left hand crank arm, right hand crank arm (together with spider) and chain rings as a whole unit.

There are countless different types of chainsets available, and it is important to get the right one for your needs. The chainset is part of the drive train of the bike and will have a significant effect on the gearing if smaller or larger chainring sizes are selected. This can be advantageous, for example if you find that the standard gearing on a road bike is too large for the steep climbs on your local routes, then a ‘compact chainset’ will reduce the gear ratios.

Things to Consider

Number of Rings:
This can vary from a single ring, up to a triple, both for road and off road models.

Crank Arm Length:
Sized usually in 2.5mm increments. The most common sizes are 170, 172.5 and 175mm lengths. It is best to replace cranks with the same size as those fitted as standard, unless there is a specific need to shorten or lengthen.

Fitment:
The chainset attaches to the bottom bracket axle. How this is done has changed over the years. The type of bottom bracket and chainset fitting must match in order for them to fit together (see Bottom Bracket Buyers Guide for more help with this).

Older crank use a wedge-shaped pin, called a cotter pin, for attachment. Newer cranks slide onto a square taper fitting (be aware that Shimano and Campag are different tapers and are incompatible with each other), or perhaps a splined fitting, such as ISIS or Shimano’s Octalink. Other systems have been attempted such as Cannondale and FSA using BB30, which is a much larger oversized splined aluminium axle, and a hexagonal mount was designed by Tune, but these are much less common outside of specialist applications.

The most recent development is for the chainset and bottom bracket axle to integrate with each other, such that the axle is part of the chainset. In some cases the bottom bracket bearings are actually housed within the frame, but more commonly they are in external bearing cups, such as Race Face X-Type, Shiomano Hollowtech II or Campagnolo’s Ultra Torque. The benefits of this modern style of chainset is decreased weight, increased stiffness and performance and greater strength.

Many children's bikes, less-expensive bikes or some BMX bikes have one-piece crank where the two cranks and bottom bracket spindle are forged as one piece of steel.

Intended Use:
It is no good buying a cheap lightweight chainset if you intend to ride of big drops and go jumping. It will not be up to the task. As with most bike components, specific chainsets are made to fulfill different riding criteria. A super lightweight carbon cross country chainset might not last five minutes in the hands of a downhiller, just as vice versa, a toughened heavyweight chainset, would be overkill and pointless additional weight to a weekend leisure rider. Equally if you ride thousands of road miles in a year, invest in a quality product that will go the distance and not need replacing so frequently. Basically, make sure you match the product to your requirements.
 

Off road Variations:

 

Triple:
The most common form of mountain bike chainset, it offers a wide spread of gears from the three different chain ring sizes. Most commonly these are 22/32/44 teeth, but these can be changed according to personal preference.

Double and Bash:
This is a dual ring set-up, effectively the middle and inner rings, whereby the outer ring is replaced by a guard, known as a Bash Ring’ to protect the other chainrings. It is ideally suited to more aggressive riding, such as freeride or downhill, where impact to the chainset would cause damage.

Single Ring:
As it’s name suggests, just a single chainring, usually used with a device to keep the chain on, and hence popular with downhill riders. Alternatively it could be used for a hub geared set-up such as Rohloff, where all the gears are in the rear hub, so multiple rings are not necessary. More simply it could be used to make a single speed mountain bike. Often a specific chainset is not required for a single ring set-up, they are often standard triples, with the other rings removed. This set-up can also be used with a bash guard to protect the ring.
 
 
 
Standard Double:
The standard issue, two ring set-up with a combination of 42/52, or 53/39 being the most common. The large outer ring makes high speeds possible on fast descents, or time trials, whilst the inner is small enough for most to use for all round road riding.

Compact:
Also a two ring set-up but with both rings reduced in size. 50/34, or 48/36 are two possible combinations although others are available. This type of chainset is ideal for the rider who wishes to lower the gear ratios of a standard road bike without having to change other gear components.

Triple:
Road bikes can use a three ring set-up that is similar to a mountain bike, in that the inner ring provides a very low gear for steep hill climbing. This can be beneficial when riding over mountainous routes such as in Sportive events. 52/42/30 is the standard chain ring configuration. Bear in mind that a triple requires a specific shifter, front mech, rear mech and sometimes bottom bracket, so is not an easy addition to make to a standard set-up.

This Buying Guide gives our customers general advice on Chainsets. It is a guide only and we always recommend visiting one of our stores or contacting one of the experts in our sales team on +44(0)1293 574 900 if in doubt about your needs.
 
This story was last updated on 16/01/2012