Crank & Pedal Basics: Threading, Torque & Spindle History

The left pedal is deliberately reverse-threaded

Every adult crank uses a 9/16-inch, 20-tpi thread for its pedals, and that thread is universal — any pedal fits any crank on that spec alone, which is why pedals carry no compatibility rule in this builder at all. But there's a real threading quirk worth knowing before you ever put a wrench to a pedal: the right pedal threads in normally (clockwise to tighten), while the left pedal is deliberately left-hand threaded — you tighten it counterclockwise, the opposite of what most people instinctively expect. This isn't an accident or a manufacturing inconsistency; a pedal's axle threads are slightly undersized relative to the crank's internal threads, and under normal pedaling load, a standard right-hand thread on the left side would gradually work itself loose through precession — the reversed thread exists specifically to make pedaling load tighten the left pedal instead of loosening it. Cross-threading a pedal by forcing it the "normal" direction on the left side is one of the most common home-mechanic pedal mistakes, and it can damage the crank's threads badly enough to need a repair. Typical pedal install torque runs around 40 Nm — snug, not gentle.

Self-extracting crank pullers hide the spline fit during install

Many modern two- and three-piece cranks use a "self-extracting" or "one-key release" design, where the puller mechanism is built into a threaded retaining ring under the crank-bolt cap. It's genuinely convenient for removal — no separate crank-puller tool needed — but it has a real downside during installation: unlike an open-spline crank, where you can visually confirm the spline is seating correctly as you press it on, a self-extracting crank's cap hides that view, so a misaligned press-on can go unnoticed and damage the crank. If a crank isn't seating the way you expect during install, the safer move is to remove the retaining cap, confirm the crank is seated correctly by hand and eye first, and only then reinstall the cap — rather than torquing through resistance and hoping it's just tight.

Chainring bolts are torqued far below the crank bolt

It's worth knowing that a chainring's own mounting bolts and the crank-arm-to-spindle bolt are torqued to very different specs — chainring bolts typically run roughly an order of magnitude lower than the crank bolt. Treating a chainring bolt like it needs "crank-bolt tight" is a good way to strip or crack it; if you don't have the specific torque figure for the bolts in hand, err toward the lighter end rather than assuming more is safer.

Why modern 1x rings don't need a chain guide

Modern single-chainring (1x) setups almost never run a separate chain-retention device, and that's not an oversight — it's a direct result of the alternating-width ("narrow-wide") tooth profile cut into modern 1x-specific chainrings. Each tooth alternates between a slightly wider and slightly narrower profile, matched to the alternating wide and narrow gaps in a chain's own links, which grips the chain tightly enough through the whole pedal stroke that a chain-drop guide became unnecessary for most riders. It's the same underlying tooth-shaping idea SRAM Transmission's T-Type chainrings extend further for their own chain design, covered in the UDH & SRAM Transmission guide.

Older spindle interfaces you might still run into

Every crank in this catalog uses one of the modern external-bottom-bracket spindle interfaces (DUB, 24mm, 30mm, or e*thirteen's p3), but older or budget bikes may still use one of three earlier, mutually incompatible three-piece crank spindle standards: plain square taper, Shimano's splined Octalink, and the industry-consortium splined ISIS Drive. None of these interchange with each other, and none interchange with today's external-BB standards — a square-taper crank can't go on a splined spindle, and Octalink and ISIS don't interchange with each other despite both being splined designs. This is background knowledge rather than something you'll run into shopping this catalog's current parts, but it's useful if you're helping diagnose an older bike.

How BuildMyMTB checks this

None of the above — pedal thread handedness, crank-puller technique, fastener torque, or historical spindle standards — is a build-compatibility check the engine runs. Pedals genuinely carry no fit rule at all (the 9/16" thread is universal), and crankset spindle interface is checked against the bottom bracket, covered in the Bottom Bracket Standards Explained guide, not against anything in this guide. Everything here is install-order and service knowledge, useful once you're actually assembling or servicing the parts rather than shopping for them.

Practical takeaways

• Remember the left pedal tightens counterclockwise — threading it the "normal" way is the single most common way to cross-thread a crank.
• If a self-extracting crank feels off during install, pull the cap and check the spline seat by hand before torquing further.
• Don't torque chainring bolts like crank bolts — they're specced far lower, and over-tightening can crack them.
• If you're working on an older bike, check which of square taper, Octalink, or ISIS Drive it actually uses before ordering a replacement crank or BB — none of the three interchange.