A pedal that wobbles, clicks or keeps backing out is more than an annoyance. A loose pedal can damage the crank threads, and if it comes off while you are riding it can cause a fall. The cause is usually simple, though. This guide helps you work out what is loose and how to fix it.
First: is it the pedal or the crank arm?
Many riders blame the pedal when the crank arm is actually the problem. Check each separately.
- Pedal loose: grab the pedal body and try to move it up and down and side to side. If the movement comes from where the pedal screws into the crank arm, the pedal is loose or the threads are worn.
- Crank arm loose: grab the crank arm itself and try to push and pull it sideways, toward and away from the frame. Movement or a knock at the center of the bike points to a loose crank bolt or a worn crank interface, not the pedal.
- Pedal bearings: if the pedal spins roughly, grinds or has play along its axle, its own bearings may be worn.
Common causes of loose pedals
- Wrong thread direction or cross-threading: the two pedals use opposite threads (explained below). Forcing a pedal onto the wrong side can damage threads and lead to loosening.
- Not tightened enough: pedals are often installed only hand-tight.
- Dry or dirty threads: without a thin layer of grease a pedal may not seat properly, and it can loosen or seize over time.
- Worn or damaged threads: riding on a slightly loose pedal can chew up the threads in the crank arm, after which the pedal cannot hold.
- Worn pedal bearings: damaged bearings can cause wobble that feels like a loose pedal.
- A loose crank arm: here the whole crank moves, not just the pedal.
Which way do the pedal threads go?
Pedals are designed to tighten as you pedal. To do that, the two sides use different threads:
- Right pedal (drive side, where the chain is): normal right-hand thread. Turn clockwise to tighten and counterclockwise to loosen.
- Left pedal (non-drive side): reverse, left-hand thread. Turn counterclockwise to tighten and clockwise to loosen.
A simple way to remember it: when tightening, you turn the wrench so the pedal axle moves toward the front of the bike on top of the turn. Many pedals are also stamped “L” and “R” on the axle end.
How to tighten a loose pedal
- Identify the side using the L and R markings, or by noting that the drive side is where the chain is.
- Use the right tool. Most pedals take a 15 mm pedal wrench. Some take an 8 mm Allen key from the back of the crank arm. Check yours.
- Back the pedal out and look at the threads on the pedal and in the crank. They should be clean and undamaged.
- Clean and lightly grease the threads with bike grease or the compound the pedal maker recommends.
- Thread the pedal in by hand for several turns to ensure it goes in straight. If it resists early, stop. Forcing it is how cross-threading happens.
- Tighten firmly with the wrench. Use the torque value from the pedal manufacturer if you have it, since values differ between pedals.
- Test: wiggle the pedal, ride briefly, then recheck after your first ride.
Why do my pedals keep coming loose?
If a pedal tightens fine but loosens again, consider these possibilities:
- It may be on the wrong side, or the threads may be damaged.
- The threads in the crank arm may be stripped. Many crank arms are aluminum, which is softer than a steel pedal axle.
- The pedal may not have been fully seated before final tightening.
- The pedal bearings may be failing.
- It may actually be the crank arm that is loosening. If you are asking why a crank keeps loosening, the crank has its own fixing that needs correct installation and tightening, which varies by crank type, so check the manufacturer’s instructions.
Stripped threads and worn bearings
If a pedal will not hold, or you see shiny, torn or flattened threads, stop riding it. A mechanic may suggest a thread repair insert, a replacement crank arm, or a new pedal. Some pedals can have their bearings serviced, but on inexpensive pedals replacement is often more practical.
When to go to a shop, and what it costs
Take the bike in if the pedal will not tighten, the crank arm moves, the threads look damaged, or you are not comfortable working on cranks. Costs vary by region and shop, and depend on whether you need a simple tightening, a thread repair or new parts, so ask for a quote first.
Pedals slipping versus pedals loose
If your foot slips off the pedal as you ride, the pedal may be fine. Possible causes include worn pins or smooth platform surfaces, shoes with slick soles, or clipless cleats that are worn or poorly set up. Replace worn pins, check cleats and try shoes with a firmer sole.
How to prevent loose pedals
- Grease the threads when installing.
- Tighten fully, to the manufacturer’s specification if available.
- Check pedals and cranks as part of your regular routine; see the bike maintenance schedule.
- Do not keep riding on a pedal that wobbles.
FAQ
How do I tighten a pedal? Use a pedal wrench or Allen key, turn the right pedal clockwise and the left pedal counterclockwise, after cleaning and greasing the threads.
Can I fix a pedal with damaged threads by tightening it more? Not reliably. If the threads are stripped, more force will not help and a repair or replacement is needed.