The cranks have a huge impact on efficiency and control of your bike ride. Your performance and riding comfort can be affected to the great extent by the type and size of the crank that you use on your BMX bike.
There are many factors that contribute to the efficacy of crank, mainly its performance depends on the arm length, weight, material used, joint type etc.
Among the options available in the market there are one, two or three piece crank sets with either splined or bolted joints. Not every crank is suitable for your style of riding.
It is necessary to take all that in to account while buying a crank set for your BMX. Here in this comprehensive guide to buying BMX cranks, we have provided all the information you need to have for making the right choice.
BMX Crank Buyer’s Guide
For a basic bike, the crank is a part of the chainset. The BMX bike cranks are generally sold separately considering how the BMX riders are more particular about their bike cranks than other riders.
Here in in this buyer’s guide, we have explained the points to be considered while buying crank for your BMX bike.
Mainly the BMX bike cranks are available in three types, 2, 2.5 and 3 piece cranks. Some basic bikes or kids’ bikes come with a single piece crank but these are weaker in construction and cannot be installed on all bikes.
The three-piece crankset has two separate crank arms and a spindle. These arms are attached to the spindle through the splined interface while assembling.
In the 2 piece crank, one of the arms is welded to the spindle, only the other arm is needed to be attached while assembling on the bike. The 2.5 piece crank is similar to 2 piece crank but instead of welding, the pre-fitted arm connected using removable joint with the spindle.
The weight of the BMX crank depends mostly on the material used. The cranksets are made up of steel, Cr Mo, aluminium alloy, titanium and carbon fibre.
The carbon fibre cranks are lightest in weight, the whole set weighs around 1 pound. The regular steel cranks are the heaviest with weight more than 2 pounds.
Bottom Bracket Size
The crank set spindle passes through the bottom bracket and the bracket set is fixed in your bike frame, thus you need to consider the bottom bracket size of your BMX bike while selecting the crankset.
Most of the BMX bikes have 19, 22 or 24mm mid-bottom brackets. The size describes the internal diameter of the bottom bracket bearings through which the spindle of the crank is going to pass.
If you are buying the crank and the bottom bracket set, you need to buy the matching sizes. If you are buying only the crank then you should check the bottom bracket bearing size to buy the crank with matching spindle size.
There are 19, 22 and 24mm spindle diameter BMX cranks available in the market. The spindles with larger diameter have more hollow volume than the ones with a smaller diameter. That makes them stiffer and lighter.
You need to consider the fact that a larger diameter of the spindle means the bearings to be used must be comparatively smaller.
Crank Arm Length
The crank arm length is axis to axis distance between crank spindle and pedal axel. This size can be anything, but the available and practical crank arm length for BMX bike is 160 to 180mm.
The short crank arm would be advantageous for those who perform spin tricks. Whereas the longer arm provides you with extra leverage and thus can generate higher torque. You can choose the arm length depending on how you want to ride your BMX.
Tubular / Square-shaped Crank Arms
The crank arms are basically tubes in different shapes. The shape of that tube doesn’t have any functional effect. These are just about the aesthetics.
The BMX cranks are available in simple round or elliptical shaped tubes and also available in square or more complex shapes.
Bolt-Drive or Bossless
Depending on how the sprocket fits on your crank they are called bolt-drive or bossless cranks. On the bolt drive cranks, the sprocket is connected with the crank with sprocket bolt. These cranks have a boss on the back to encase threads for the bolt.
The bossless cranks come with mostly 48 spline spindles, on which you can insert a spline drive sprocket. These weigh lighter as compared to bolt-drive cranks.
The BMX cranks can be broadly classified into three categories based on spindle interface, namely splined, splineless and socket interface. The splineless spindle interface is accompanied with split crank arm and makes an unreliable joint.
The splined spindles range from 6 splines to 48 splines. A crank spindle with a higher number of splines is of better quality and durability. Thus, most of the good quality cranks come with 48 spline spindles. But with 48 splines it might get tricky aligning the crank arms.
The socket interface having six wedges and lock bolt to secure the crank arm is another type of spindle interface. This is easy to install and align, has little or no chance of slipping and also has less chance of wearing lose.
Most of the good quality metal BMX cranks are heat treated. In the manufacturing process, the components go through many processes like forging, welding, cutting, machining and grinding. These processes alter the properties of the material. To compensate this, and uniformize the properties of the whole crank set, it needs to go through heat treatment.
Heat treatment also strengthens the material and hence improves the durability of the crank. Look out if it is heat-treated before deciding to buy.
The BMX bike cranks have to sustain too much abuse compared to any other type of crank or any other component in the BMX bike itself. Thus, it needs to be strong enough to sustain the abuse and to last long.
The heat-treated chromoly material cranks with socket interface has proven to be the most durable among others. But practically, the durability also depends on the manufacturing quality of the particular brand.
Let this article serve you as a buyer’s guide. With all the information provided in this guide to buying BMX cranks, you are now equipped with everything that you need to know for making the right choice of the BMX bike crank.
When you consider a BMX bike crank to buy, test it on all the parameters listed above. If it stands good against all these then only you should go ahead and place the order.