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How do you calibrate a turbo trainer?

Updated 2026-10-23 · Setting up and getting started

Short answer

Warm up for at least ten minutes, then run the spindown or calibration from your training app or the trainer's own app: it asks you to pedal up to a speed and then stop, and measures how long the flywheel takes to slow. Do it from warm, not cold, or your numbers will be wrong all session.

What calibration is doing

Many trainers work out your power indirectly, from how much resistance they are applying and how fast things are spinning. To do that they need to know how much friction is in the system when you are not pedalling at all.

A wheel-on trainer works out your power from how fast the roller is turning. A soft tyre spreads the contact, flexes, heats and slips, so some of your effort never reaches the roller and the number comes out low. This is the opposite of road advice, where a little give is a good thing.

A spindown measures exactly that: you bring the flywheel up to a set speed, stop pedalling, and the trainer times how long it takes to coast down. A longer coast means less friction. It then uses that to interpret your power correctly.

The amount of friction changes as things warm up, and for wheel-on trainers it changes with tyre pressure and roller tension too. That is why it needs doing periodically rather than once.

Do it warm, and always warm

This is the part people get wrong and it matters more than anything else on this page.

A cold trainer has more friction than a warm one. Calibrate cold and the trainer records that high-friction state as normal; ten minutes later everything has warmed up and loosened, and the numbers it reports will be wrong for the rest of the session.

Ride easily for at least ten minutes first, then calibrate, then start the session properly. If you are testing or doing anything where the numbers matter, treat this as part of the warm-up rather than an optional extra.

How to do it

Warm up for ten minutes or more at easy effort.
Open the calibration or spindown in your training app, or the trainer manufacturer's own app.
Follow the prompt: usually pedal up to a given speed, then stop pedalling completely and let it coast.
Do not pedal, touch the brakes or move about while it measures.
It will confirm when it is done, often with a number. Note whether that number is wildly different from last time.

Some trainers calibrate themselves automatically and need none of this. Check your manual rather than assuming either way.

How often, and when it matters most

Before any test or benchmark session. Always.
After moving the trainer, or after changing tyre pressure or roller tension on a wheel-on.
Every few weeks for ordinary training, or whenever the numbers feel wrong.
If your power suddenly looks much better or worse than usual with no explanation, calibrate before concluding anything about your fitness.

If your calibration result changes dramatically from session to session, something mechanical is usually moving: tension, pressure, or the bike not being clamped consistently.

Common questions

Does every trainer need calibrating?

No. Some measure directly and some calibrate themselves automatically. Check the manual; if there is no spindown in the app, it probably does not need one.

How long should I warm up before calibrating?

Ten minutes of easy pedalling is a reasonable minimum. Longer does no harm.

Will calibrating change my FTP?

It can change the numbers your trainer reports, which in turn affects a test. That is exactly why you calibrate before testing rather than after.

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