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.
Cranks Arms: These are the essential arms connecting 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 quite often today is 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 jumping curbs and bunny hoping up the steps, the impact on reconnecting with the pavement will exert huge forces on the pedal-crank and crank-spindle interface, so 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.”
Chainring: A fancy name for the front sprockets. Different manufacturers, just like cars, design them with various bolt patterns so it is essential to identify what specifically will work with your crankarm-spider-spindle combination and front derailleur.
Bottom Bracket Shell: This is the tube welded to the lowest point of your bicycle frame designed to accept a set of bearings and the main spindle (bottom bracket assembly). 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 tpi (teeth per inch) thus it is important to get the right match. It is not really part of the chainset, but you must know its specifications in order to replace any components.
Bottom Bracket Assembly: This bicycle part comes in numerous combinations and configurations, but essential includes the drive spindle, a set of bearings and cups that thread into the shell to hold all of these parts in place. This assembly allows the pedals to freely rotate and put power to the chain.
Spindle: The last piece of the puzzle is the drive axle. It comes in a number of different 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. The bottom bracket bearings and cups are sold separately to match spindle diameter and length.
Where buying a complete crankset becomes confusing is that these key 7 pieces (2 cranks, spider, chainrings, spindle, retaining cups and bearings) are not always sold in the same way or have one set of sizes.
It is essential to know what specifications are necessary 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.