How to use an indoor cycling app without a smart trainer — a speed sensor is enough

Nearly every indoor cycling app is written as though the smart trainer is the entry ticket. Six hundred pounds of direct-drive hardware, and only then do you get to ride. It leaves out an enormous number of people: anyone with a perfectly good fluid turbo in the garage, anyone who rides rollers, anyone who simply is not ready to spend that much on something they are not yet sure they will use through the winter.

You do not need one. With a speed sensor on your back wheel — about the price of two coffees and a taxi — you can ride a real route in a 3D world, see your distance and time build, and have the session land on your calendar afterwards. We build Moveee Indoor, so this guide uses it as the worked example. It is also honest about the things a speed sensor cannot do, because plenty of guides on this subject are not.

What you actually need

That is the whole list. No dongle, no ANT+ stick, no app install, no subscription to start. If you own a bike, something to hold the back wheel, and a laptop, you are one small sensor away from riding.

Setting it up, once

Step two is the one people skip and then wonder why their speed looks silly. A wheel speed sensor counts revolutions; turning revolutions into kilometres per hour needs the circumference of your specific tyre. Moveee tells you which size it has assumed the moment you pair — "using a 700×25c tyre (2105 mm)" — so if that is not your wheel, you will know within two seconds rather than after a season of wrong numbers. We wrote a short guide to getting the tyre setting right, including how to measure it properly with a tape and a piece of chalk.

What riding is actually like

You pick a route — one of yours, or one from the library — and the world builds itself around it from real map and elevation data. You pedal; your wheel turns; the sensor reports its speed; you move up the road at that speed. The scenery, the distance, the time, the route profile: all real.

There is one difference from a smart-trainer ride that you should understand before your first session, because otherwise it will confuse you. When a hill appears, your speed does not drop. With a smart trainer, your watts go through a physics model that works out how fast those watts would carry you up that gradient, and the trainer makes it harder. With a speed sensor, there is no watts figure to run through physics — the sensor's speed is the world's speed. You climb the hill at whatever speed your legs and your gearing are producing.

That sounds like a flaw, and in a race it would be. For training it matters far less than you would expect, because the resistance you are pushing against is still real: it comes from your trainer's own resistance curve and the gear you have chosen. Ride in a harder gear and you work harder, exactly as on the road. What you lose is the automatic part, not the effort.

What gets recorded

The ride saves to your calendar like any other. You get duration, distance, average and maximum speed, the route you rode, and your heart rate if you paired a strap. If your sensor is a combined speed-and-cadence unit, your cadence is recorded too, at no extra cost.

What you do not get is power, and Moveee will not invent it. There is no watts figure, no Normalised Power, no TSS, and no FTP estimate from a speed-only ride. Some apps will show you a "virtual power" number derived from your speed and an assumed resistance curve; we do not, because that number is only as true as the assumption that your trainer is one of a handful of known models, set to a known resistance level, with a known tyre pressure, after a known warm-up. Change any one of those and the number moves without your fitness moving at all. A dash is more honest than a confident wrong number, so the power readout shows a dash.

If you want the full ledger of what is and is not there, we set it out plainly in what speed-only riding gives you and what it does not.

How to make it a real session

Without watts you need a different way to steer effort, and there is a perfectly good one that cyclists used for decades: heart rate, plus how hard it feels. Pair a chest strap — it connects over its own Bluetooth service, entirely independently of the speed sensor — and you have a number that responds to effort rather than to gearing.

The practical method is to use your gears as the resistance dial. Pick a gear that puts you at the heart rate you want, hold it for the interval, drop to something easy for the recovery, repeat. It is exactly how a turbo session worked before smart trainers existed, and it still works. We go through it properly in using your gears as the resistance dial.

Is it worth it, honestly?

If the alternative is not riding indoors at all, then obviously yes — a thirty-pound sensor that turns a dusty turbo into an hour on a real route is one of the better deals in cycling. If the alternative is buying a smart trainer next month anyway, the sensor is still worth it: it will keep working afterwards on your outdoor bike, and it lets you find out whether you actually enjoy riding indoors before spending the six hundred.

The honest limit is this: a speed-only setup is excellent for keeping the engine turning over through a bad-weather stretch, for structured-ish heart-rate work, and for company on a dark evening. It is not the tool for measuring progress precisely, because the thing you would measure progress with — power — is not there. When that starts to bother you, that is the signal to upgrade, and we have written about when the upgrade is genuinely worth it.

Until then: fit the sensor, set your tyre size, and go and ride something.