SECTIONS IN THIS GUIDE

Standard vs. triple vs. compact:

Cranks typically come stock with standard 53\39 chainrings—the same that pros push without a problem in most race situations. However, mortals do not have the horsepower to spin gears that high, so manufacturers offer triple cranksets to give average riders a wide range of gear ratios; they are very popular with the touring crowd for this reason. But, just like the standard 53\39, triples can also be excessive for recreational riders, lugging around extra gears that they never need …

Then along came the compact crankset. Putting performance back into recreational riding, compact cranksets—lighter because of less material—offer a lower final gear ratio like triples do. However, there has to be some compromise on the high end; a compact crankset’s final high ratio is lower than a standard.

Compacts allow you to run a tighter cassette. For example, instead of a 53-39 and 12-27 combo, they can use a 50-34 and 11-23. The 11-23 has a much tighter gear range that allows for fast shifts—the chain does not have to jump as much. Think of a close-ratio gearbox in sports cars. Also, consider the lighter weight of a compact crankset as compared to a standard. They spin up faster thanks to less rotational weight, like lightweight flywheels on the aforementioned sports car. Close ratios, quick shifts, and a fast spin—sounds like you can’t lose right? Well nothing comes without a cost. Expect cassettes, chains, and chainrings to wear out faster.

The three types of road cranks:

Triple: Great for recreational cyclists, touring, mountainous terrain

Pros:

• Lowest gearing for really hard pitches
• Widest range of gears for the right cadence at any speed

Cons:

• Weight
• Complexity
• Slow shifts
  

Standard: Great for stronger riders/racers, time trials, flatlands

Cons:

• High gear ratios
• If you want lower gears, you have to use a cassette with a wide gear range; as a result it shifts slower, and it’s harder to find the ideal cadence
  

Pros:

• Light weight
• Faster shifts than a triple
• Higher speeds

Compact: Great for recreational cyclists, mountainous terrain

Pros:

• Lighter weight due to fewer materials
• You can run a tighter cassette—fast shifts, cadence stays dialed
  

Cons:

• Wears out faster
• Can run out gears due to the lower final ratio

Compact FAQ’s:
Can I just change the chainrings from my standard crankset to compact?

• Yes and no. This depends on the Bolt Circle Diameter. Most standard cranks have a 130mm BCD. This diameter is typical too large for compact chainrings. Compact cranks have a 110mm BCD—smaller diameter for the smaller chainrings. So, unless your BCD is already 110mm, you do have to change the crank arms to go compact.
  

Do I have to change the front derailleur?

• In most cases no. The original FD will have to be re-adjusted to work properly. FSA does offer a compact-specific FD that follows the curve of a compact chainring’s smaller diameter. If you find your original FD is not mating up well with a compact crank, then consider the FSA compact FD.

The bottom Line:
Consider a compact if you’re not using the higher end of your standard crankset or live in the mountains. The performance gains from a lighter drivetrain will be rewarding. Don’t consider a compact if you are strong and use the high end of your standard crankset, or if you reside in the flatlands. Consider a triple if you want the lowest possible gear ratios yet still want a high end.

Crank arm length:

Take the number of years you’ve been riding and divide that by the length of your top tube in centimeters. Multiply that number by 486. Well, actually, we just pulled that equation out of our asses. Bike-fitting opinions are abundant, as are the many disciplines of cycling, and humans are not all proportionate; so there is no easy (or complex) formula to give you your ideal crank arm length. But with some deductive reasoning, you can determine if a longer or shorter crank arm would suit you the best. Here’s a breakdown:

Shorter cranks: Good for crits, cyclists with short legs

Pros:

• Faster spin/higher cadence
• Less stress on joints
• More clearance for cornering
• Lighter than longer cranks
  

Cons:

• Less leverage/torque for climbing
  

Longer cranks: Good for time trials, climbing, and cyclists with long legs

Pros:

• More leverage for turning higher gears
  

Cons:

• More stress on joints
• Heavier than shorter cranks
• Less clearance when cornering

Bottom line:
If you like to spin with hummingbird-vigor, you’ll like a slightly shorter crank arm. If you like to turn big gears with a diesel’s RMPs—then round up a bit. Just remember nothing is set in stone.

Use the chart below as a rough guide to make an educated choice. Data here is generalized; manufacturers’ fames sizes are not all the same, just as cyclists’ muscles, bone structure, and riding styles are not all equal. If you enter “crank arm length calculator” into any popular search engine you will receive plenty of hits to help bewilder you even more.

Cassettes:

Think of your drivetrain as the ones in big rigs with multiple gearboxes/transmissions. The crankset is your main “gearbox;” the cassette is your secondary “gearbox.” After you decide on your crankset, you then dial in your ideal gear ratios with the cassette.

Wide Gear Ratio (i.e. 11-27)

Pros:

• Lower gear for hill climbing
• Haul extra weight, touring, spare tire
  

Cons:

• Large jump in between gear ratios makes ideal cadence harder to achieve
• Slower shifts
• Heavier
  

Tight Gear Ratio (i.e. 12-21)

Pros:

• Faster shifts
• Manage cadence—close ratios
• Lighter weight
  

Cons:

• Hard low gear
• Lower life expectancy
  

Bottom line:
If you want your crankset to have a gear ratio for mountainous terrain, run the cassette with the lowest possible gear (i.e. an 11-27). If you want snappy shifts for crit racing or time trials, run a cassette with tighter gearing (i.e. an 11-21). There are many variations in between. Keep in mind cassettes are rotational weight, so you will not only benefit from dialing in the ideal gear ratio, you could also potentially drop some unneeded weight.

Other crankset options to consider:

External vs. Integrated Bottom Brackets:
Unlike external bottom brackets, which have cups that thread into the frame (more parts to deal with), integrated bottom brackets have bearing cups built into the frame. However, despite having to deal with more parts, the benefit to having external BBs is that they can be changed (depending on the manufacturer), and they fit a frame standard that has been around for many moons. Integrated BBs are manufacturers’ latest attempt, along with oversized axles and stiffer frames, to achieve ever higher levels of simplicity and efficiency.

Square-taper Bottom Brackets:

Pros:

• Large ball bearings handle high loads
• Serviceable
• Inexpensive, good for commuter bikes
  

Cons:

• Flexy axle—square tapers can break
• Crank arm-to-axle interface can come loose if improperly installed
  

Isis/Octalink:

Pros:

• Solid crank arm-to-axle interface
• Stiff Axle
  

Cons:

• Tiny bearings (tiny because of the larger axle) can wear out faster
• Doesn’t handle high loads
  

Outboard Bearing:

Pros:

• Large bearings handle high loads
• Stiff oversized axle
• Solid crank arm-to-axle interface
  

Cons:

• Bearings are not serviceable; like Octalink, they need to be replaced when worn out

Integrated Bottom Brackets:

Pros:

• Less parts
• Lighter weight
• Stiffest interface/axle
• Large bearings handle high loads
  

Cons:

• Frame could be damaged when replacing bearings—press fit
• Bearings are not serviceable

Bottom Line:
When changing cranks make sure that they are compatible with the bottom bracket you currently have. Or change the BB with the cranks. Typically, all new bikes have either outboard bearings (Truvativ GXP- or Shimano-compatible) or an oversized integrated standard—depending on manufacturer—such as BB30.

Aluminum vs. Carbon crank arms

Aluminum crank arms have been the industry standard because of their inherent stiffness; before then, we were forced to run heavy, flexible steel cranks (amazingly, some elite big-box brands still spec steel crankarms …). Now carbon has taken over as the most popular high-performance material used to produce crank arms. Of course, there are exceptions; most notable is the new Dura-Ace 7900. Manufacturers aim to balancing performance, weight, and price. Here’s the breakdown:

Aluminum

Pros:

• Stiff
• Less expensive to manufacture (Dura-Ace FC-7900 aside)
  

Cons:

• Heavier (Dura-Ace FC-7900 aside)
  

Carbon

Pros:

• Construction and weave can be tweaked for performance gainsLightweight
  

Cons:

• More flex than aluminum
• Expensive construction
  

Installation tools:

Torque wrench
BB tool
Vice Whip
BB socket