How to Install Pedals on a Bike | Left and Right Threads Explained

Pedals look symmetrical, but they are anything but. The right pedal (“R”) threads clockwise on the drive side, while the left pedal (“L”) threads counterclockwise on the non-drive side. One wrong turn damages the crank arm. The fix for a clean install is simple: grease the threads, identify the correct pedal, and start every thread by hand. Tools like a 15 mm pedal wrench or a 6 mm or 8 mm hex key handle the final tightening, but each step above matters in order.

Know Which Pedal Goes on Which Side

Pedals are side-specific, and the thread direction is a hard rule. Most modern adult bikes use pedals with 9/16-inch spindle threads, but some bikes (often cheaper or older models) use other standards, so verify compatibility before you start. Most pedals are stamped with an “R” or “L” on the end of the spindle or near the wrench flats; look for it before you begin.

Here is the direction that applies on both sides:

• Right pedal (drive side): tighten clockwise, loosen counterclockwise.
• Left pedal (non-drive side): tighten counterclockwise, loosen clockwise.

The left pedal is reverse-threaded specifically to stop it from unscrewing as you ride — forward motion tightens it rather than loosening it. Forcing the wrong direction risks stripping the crank threads.

The Installation Process: Grease, Hand-Start, Tighten

Start by applying a thin coat of grease or assembly paste to both pedal threads. This prevents the pedal from seizing in the crank arm over time and makes future removal far easier. Park Tool’s repair guidance recommends this step before fitting either pedal. Skip it, and you risk a pedal that fuses to the crank, often requiring a breaker bar or a new crank arm to fix.

Hold the pedal in line with the crank arm and thread the spindle in by hand first. Hand-starting several full turns is the only reliable way to confirm the thread is seated properly before a wrench touches it. If the pedal resists, it is almost always the wrong pedal, the wrong side, or a cross-thread start — back it out and check before applying force. Once the spindle is fully hand-tightened, use the tool to finish the job to a firm snug fit, not a maximum-torque overtighten. Most pedals use 9/16-inch threads with a 15 mm wrench flat; many modern road and mountain pedals also accept a 6 mm or 8 mm hex key from the inboard end instead. Either tool works.

Use both wrench flats and the hex key depending on access: the hex key is often easier if the crank arm leaves little room for a pedal wrench to swing.

Common Installation Mistakes to Avoid

The most frequent mistakes are both predictable and avoidable:

• Cross-threading: starting the spindle with a wrench instead of your fingers forces the thread into the wrong path and damages the crank. Always hand-start first.
• Skipping the grease: dry threads seize under load and corrosion, making removal nearly impossible later. Grease or assembly paste is not optional.
• Mixing left and right pedals: fitting the left pedal on the right side (or vice versa) cross-threads immediately. Check the “L” and “R” markings before threading.

Inspect both the pedal threads and the crank threads before installing. If either side shows damage — galled threads, visible distortion, or stripped sections — replace the damaged part rather than forcing the fit. A damaged crank thread will not hold a pedal securely and can fail while riding.

If you are looking to upgrade for a long trip, our roundup of top-rated bikepacking pedals for long rides covers tested options across the key styles.

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