Cranks & Cranksets

Compatibility depends on several factors including your bottom bracket standard, the number of speeds in your drivetrain, and your bike's frame specifications. Before purchasing, check what bottom bracket shell your frame uses, as different cranksets are designed for specific standards such as threaded, press-fit, or other formats. It is also important to match the chainring configuration to your existing drivetrain, including the number of chainrings and the bolt circle diameter. If you are unsure, bring your bike into a 99 Bikes store and a mechanic can help confirm the right fit.

Each discipline places different demands on a crankset, so they are designed with those specific requirements in mind. Road cranksets tend to prioritise stiffness and low weight to maximise power transfer on smooth surfaces, while MTB cranksets are built to handle rougher terrain, wider gear ranges, and greater impact forces. BMX cranks are typically shorter and built for durability and strength under repeated stress from tricks and jumps. eBike cranksets are engineered to work with motor systems and handle the higher torque loads that come with pedal-assist riding.

Crank arm length affects your pedalling mechanics and overall comfort on the bike, and the right choice depends on your leg length, riding style, and discipline. Longer cranks can provide more leverage but may cause issues with ground clearance or hip mobility, while shorter cranks suit riders with shorter legs or those who prefer a higher cadence. Road and MTB riders often have different preferences, and eBike riders may find that shorter cranks work better with motor-assisted pedalling. If you are unsure, a bike fit or advice from a 99 Bikes team member can help you find the right length.

If your crank arms are still in good condition and compatible with a replacement chainring, swapping just the chainring can be a cost-effective option. However, if the crank arms are worn, damaged, or you are changing your drivetrain setup significantly, replacing the full crankset is often the better choice. Upgrading the full crankset also makes sense if you are moving to a different chainring standard or spider pattern that is incompatible with your existing arms. Many modern cranksets use direct-mount chainring systems that limit interchangeability, so it is worth confirming compatibility before purchasing a replacement ring alone. If the cost difference between a new chainring and a full crankset is modest, and the crank arms have significant mileage on them, replacing the entire unit at once can save labour time and provide peace of mind across all components.