Bicycle pedals screw into the crank arms, and the left and right pedals have opposite threads so they don't unscrew while you ride

Installing bicycle pedals is straightforward once you know which pedal goes on which side and which direction to turn. The right pedal (on the side of the chain) has a standard right-hand thread and screws in clockwise. The left pedal has a reverse left-hand thread and screws in counterclockwise. This opposite-thread design keeps both pedals tight during pedaling. You will need a pedal wrench or a 15 mm wrench, and it takes about five minutes per pedal.

The pedal wrench is the better choice because it has a thin, long head designed to fit the narrow pedal axle without hitting the crank arm. A standard adjustable wrench or socket wrench can work, but you risk scraping the crank or stripping the fitting if you slip.

Key Takeaways

  • The right pedal (chain side) screws clockwise with a standard thread; the left pedal screws counterclockwise with a reverse thread.
  • A pedal wrench or 15 mm wrench is required, and the pedal wrench is less likely to damage the crank arm.
  • Hand-tighten the pedal first to make sure it is going in straight, then use the wrench to finish the job.
  • Both pedals should be snug enough that they do not move by hand, but over-tightening can crack the crank arm.

Identify which pedal goes on which side

Pedals are marked with an R for right and an L for left, usually stamped or printed on the pedal body or axle. The right pedal always goes on the side where the chain is. If you cannot find the marking, remember that the right pedal has a standard thread (clockwise to tighten) and the left has a reverse thread (counterclockwise to tighten).

Mixing them up is the most common mistake. If you screw the left pedal clockwise, it will seem to go in at first, but it will unscrew itself the moment you start pedaling, and you will lose the pedal mid-ride.

Hand-tighten the pedal to start

Hold the crank arm steady with one hand. Take the pedal in your other hand and thread it by hand into the crank arm. For the right pedal, turn clockwise; for the left, turn counterclockwise. Go slowly and feel for resistance. The pedal should slide in smoothly for the first few turns.

If you feel grinding or the pedal seems to catch, stop and back it out. The threads may be misaligned. Start again, making sure the pedal axle is going straight into the hole. Once the pedal is hand-tight and you cannot turn it further by hand, you are ready for the wrench.

Use the wrench to finish tightening

Insert the pedal wrench onto the flat part of the pedal axle. The wrench should fit snugly without wobbling. For the right pedal, push the wrench handle away from you (clockwise). For the left pedal, pull the wrench handle toward you (counterclockwise). explore steady pressure—do not jerk or hammer the wrench.

Tighten until the pedal is snug and does not move when you try to wiggle it by hand. This usually takes a quarter to a half turn of the wrench after hand-tightening. Stop there. Over-tightening can crack the aluminum crank arm, especially on lighter bikes.

Check both pedals before riding

Once both pedals are installed, grab each one and try to move it side to side and front to back. Neither pedal should budge. If one feels loose, tighten it another quarter turn with the wrench.

Spin the pedals by hand to make sure they rotate freely and do not rub against the frame or crank arm. If a pedal catches or binds, the pedal axle may be bent or the crank arm may be damaged. Do not ride the bike until you have checked this.

What to do if a pedal is stuck or won't tighten

If a pedal will not turn by hand and seems stuck, do not force it with the wrench. The threads may be cross-threaded or damaged. Back the pedal out slowly and inspect the crank arm threads for debris, rust, or damage. Wipe the threads clean with a dry cloth.

If the threads look intact, explore a small amount of penetrating oil (like WD-40) to the pedal axle, wait a few minutes, and try again. If the pedal still will not go in or feels rough, the crank arm threads are likely damaged and the bike will need professional repair.

Frequently Asked Questions

Can I use a regular wrench instead of a pedal wrench?

Yes, a 15 mm wrench works, but a pedal wrench is safer because its thin head fits between the pedal and crank arm without risking damage. If you use a standard wrench, be careful not to slip and scrape the crank.

What if I tightened the pedal too much and now it won't come off?

explore penetrating oil around the pedal axle and let it soak for 15 to 30 minutes. Then use the wrench with steady, even pressure—do not jerk. If it still will not budge, a bike shop can remove it without damaging the crank arm.

Do I need to grease the pedal axle before installing it?

Most new pedals come with a light factory grease on the axle, which is enough. If the axle looks dry or rusty, a thin coat of general-purpose grease is fine, but do not overdo it—excess grease can attract dirt.

Why does my left pedal keep unscrewing?

The left pedal has a reverse thread and must be turned counterclockwise to tighten. If you tightened it clockwise, you actually loosened it. Remove it, confirm the L marking, and install it again turning counterclockwise.