MTB Cranks

Q: How is an MTB crank constructed?

Crank Arms The levers to which the pedals are attached. Usually made of forged aluminum (7050/7075) or 4130 CrMo steel. Spindle (Axle) Connects the two arms through the bottom bracket. Common standards are 24mm, 30mm, or SRAM DUB (28.99mm). Interface The point where the chainring sits. Either via "Direct Mount" directly on the axle/arm or via a "Spider" (usually 4-bolt).

Q: What types are there?

2-Piece Aluminum Cranks: The standard for modern MTBs. One arm is permanently connected to the axle. They are very stiff and light. 3-Piece CrMo Cranks: Originally from BMX. Consist of two arms and a separate axle. They are slightly heavier but extremely robust and almost indestructible – ideal for street and hard park riding.

MTB Cranks FAQ

What is an MTB crank and what is its main purpose?

The crank is the engine of your bike. It connects you to the drivetrain via the pedals. In Dirt Jump and Slopestyle, it must be extremely stiff so that no energy is lost when accelerating, and strong enough not to bend if you land flat from a great height.

How is an MTB crank constructed?

Crank Arms: The levers to which the pedals are attached. Usually made of forged aluminum (7050/7075) or 4130 CrMo steel.
Spindle (Axle): Connects the two arms through the bottom bracket. Common standards are 24mm, 30mm, or SRAM DUB (28.99mm).
Interface: The point where the chainring sits. Either via "Direct Mount" directly on the axle/arm or via a "Spider" (usually 4-bolt).

What types are there?

2-Piece Aluminum Cranks: The standard for modern MTBs. One arm is permanently connected to the axle. They are very stiff and light.
3-Piece CrMo Cranks: Originally from BMX. Consist of two arms and a separate axle. They are slightly heavier but extremely robust and almost indestructible – ideal for street and hard park riding.

Which crank is right for my needs?

The length of the crank arms plays a crucial role in how the bike feels:

Crank Length	Discipline	Advantage
165mm	Street, Park, shorter riders	More foot clearance for tricks (barspins), less pedal strikes.
170mm	Dirt Jump, Allround	The standard. Good balance of leverage and clearance.
175mm	Race, Enduro	Maximum leverage for power transfer, rare in DJ.

How do I install an MTB crank?

Grease the bottom bracket spindle and bearing surfaces well.
Slide the axle (usually from the drive side) through the bottom bracket.
Place the second crank arm onto the splines (ensure 180-degree offset!).
Tighten the preload bolt hand-tight to eliminate play.
Tighten the main fixing bolt to the specified torque (often approx. 50 Nm!). Use a torque wrench.

What do the specifications mean?

Specification	Explanation	Examples/Available
Axle Diameter	Must match the bottom bracket.	24mm, 30mm, DUB
Arm Length	Length from center of axle to center of pedal eye.	165mm, 170mm
Chainring Mount	How the sprocket is attached.	Direct Mount (SRAM 3-Bolt), 104 BCD (4-Bolt)