How to: Cranks



Two main requirements for the cranks are definitely strength and durability. There are three basic types of cranks,1-piece, 2-piece and 3-piece with different crank arms lenght ranging from 135mm up to 190mm according to rider's inseam length (see the sizing chart below).

      Inseam length     Crank Length                   
                20"                   140mm
21" 145mm
22" 150mm
23" 155mm
24" 160mm
25" 162mm
26" 166mm
27" 171mm
28" 175mm
29" 177mm
30" 180mm
31" 182mm
32" 185mm


1-pc = designed for 1/2" pedals
2-pc = two piece cranks. Spindle is attached to one of the cranks arms
3-pc = three piece cranks. Spindle, Left crank arm, Right crank arm


See the picture above from the left: 2-pc cranks, 3-pc cranks with 19mm spindle and complete bottom bracket, 3-pc Primo cranks with 22mm spindle.



There are various types of spindles in BMX. Dividing according to the shape: 4-edged, 6-edged, 8-edged, 48-spline. Dividing according to the size: 19mm, 22mm, 24m. The spindle diameter determines the size of bottom bracket bearings. More about bottom brackets in this topic.


See the picture above from the left: 19mm 48-spline spindle, 22mm spindle for Primo cranks.

19mm spindle - For all riders up until 70Kg of weight  
22mm spindle - For all riders over 70kg


Be aware of some crank sets that are suited mainly for one riding style (flatland, dirt/park, racing). Those will be quickly destroyed if you use them otherwise. On the other hand, If you see any crank set with "suited for Street riding" in their name/description, be sure those are universal for everyone and will last for years.

In case of switching you rear hub from LHD(left hand drive) to RHD, it is important to check on your crank arms and see if there's a sprocket boss(hole for the sprocket bolt) on both of the arms (LHD/RHD compatible). It's impossible to put one of the crank arms on in the opposite direction.

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