Power Metres
Browse used power metres for sale from riders across the UK. These measure the torque you put through the drivetrain with strain gauges and broadcast it as watts, with most units claiming accuracy of ±1% to ±2%. The category covers crank-arm, spider, pedal and hub-based designs, and suits riders training to numbers rather than to feel.
Which type of power metre should I buy?
Left-crank units such as Stages and 4iiii measure one leg and double it, which is the cheapest way in and the least forgiving of an uneven pedal stroke or an old injury. Spider-based units like Quarq and SRM read total force at the chainrings and are the quiet, accurate middle ground. Pedal-based systems such as Favero Assioma and Garmin Rally move between bikes in minutes and give a true left/right split, at the cost of exposure to pedal strikes. Hub-based units tie your numbers to one wheel and are now uncommon.
Power metre or heart rate monitor?
Power is the work you are doing at this instant; heart rate is your body's delayed response to it, drifting with heat, caffeine and how you slept. A heart rate monitor costs a fraction as much and is enough for steady endurance riding, but intervals shorter than a few minutes are only repeatable with watts. Most riders who train seriously record both in the same file.
What do I need to use one?
The metre stores nothing itself. It broadcasts over ANT+ or Bluetooth, so it needs a bike computer, a smart watch or a phone app to display and record the numbers. Dual-broadcast units pair with almost anything; older ANT+-only models will not talk to a phone without a dongle, which is worth establishing before you buy.
What should I check when buying a used power metre?
Fit comes first: crank-based units are tied to a spindle standard and chainring bolt circle, and pedal-based ones need crank arm clearance and the cleat system you already use. Then check the battery door and its O-ring, since a perished seal lets water into sealed electronics that cannot be repaired. Look over the strain-gauge pod for impact marks and chainstay rub, and on pedals, spin each axle by hand to feel for play or notchy bearings. Ask the seller to run a zero offset and tell you the figure — one that has drifted a long way from the factory value points to a strained gauge.
How much should a used power metre cost?
Left-only crank units sell for the least, and dual-sided pedals hold value best because they carry over to whatever bike you own next. Set the saving against the risk: the gauges are sealed and unserviceable, so a fault usually means the whole unit. Buying new makes sense if you intend to train to these numbers for years, mainly for a warranty on the one part nobody can fix.