The Crankset is the key bicycle part that converts human physical motion into the rotational power you need to get your bicycle moving. Your success and enjoyment will be a function of its performance. To upgrade or maintain you first need to know what goes into making a great crankset; cranks, spiders, chainring, shell, bottom bracket and spindle each have a roll to play. Here’s a bit of terminology to get you going.



The Bottom Bracket Shell:

This is the steel tube welded to the lowest point of your bike frame. It is designed to hold a set of bearings and the main axle. It is typically threaded to accept the bottom bracket assembly. English, French and Italian bikes are NOT all the same diameter or threaded with the same teeth per inch so it is critical to match your frame’s BB shell with the intended bottom bracket assembly .

Bottom Bracket Assembly:

This bike component includes a drive spindle, a set of bearings and matching cups that thread into the shell to hold all of these parts in place. This assembly allows the crank arms to freely rotate and put power to the chainrings.

Spindle:

This is the drive axle. It comes in a number of different lengths, diameters and end configurations, depending on the attachment link between crank and spindle. It may or may not come independent of the bearing assembly. In two piece cranksets is attached to the right crank arm. It is important to make sure that the bottom bracket bearings and cups match the spindle diameter and length.

Cranks Arms:

These are the arms that connect the bicycle pedals to the spindle or axle. The left hand bike crank is typically bolted to the end of the spindle. The right crank arm can be attached in a similar fashion, but in today’s chainset designs it is often permanently mounted to the drive-side spindle and spider.

Buy cheap if you are a casual road rider but if your passion in life is aggressive off road riding, consider the impact on jumping logs and the huge forces on the pedal-crank and crank-spindle connection, and invest in quality arms.

Spider:

These are the star shaped arms that radiant out from the right crank to hold the front sprockets or “chainring." Sometimes they are an independent casting and sometimes they are a one piece carbon fiber crank arm plus spider combination.

Chainring:

This is a fancy name for the front sprockets. Various manufacturers, just like in the automotive industry like to design them with various bolt patterns so it is important to identify what specifically will work with your crankarm-spider-spindle combination and front derailleur.

Buying a complete crankset becomes confusing because these 7 key pieces (retaining cups and bearings, 2 crank arms, a spider, chainrings, and axle,) are not always sold in the same configuration or have one set of sizes.

It is important to know what specifications you need to know so repairs and upgrades can add speed and reliability to your riding experience. Read further on myWheelsAndMore.com website for information and lots of pictures that will add clarity to this article. Find out what you need to know and why and how bicycle parts suppliers and manufacturers continue to tweak their crankset designs for weight, durability and speed gains.