Power match: using your power meter with a smart trainer

If you own both a smart trainer and a separate power meter, you have probably noticed they do not always agree. Your power meter might read 10 watts higher than your trainer, or 15 watts lower. This inconsistency creates a problem: which number do you trust? More importantly, which number should control your workout intensity?

Power Match solves this by using your power meter as the source of truth while still letting your smart trainer control resistance. When enabled, Ride Cave continuously adjusts the trainer's target power to compensate for the difference between the two devices. The result is that your power meter shows the workout's intended targets, not whatever your trainer happens to report.

Beta status and supported devices

Power Match is currently in beta. The feature uses the standard Bluetooth Cycling Power Service (UUID 0x1818) and should work with any spec-compliant power meter. The following devices have been tested or are expected to work based on their Bluetooth implementation:

Pedal-based: Favero Assioma (DUO and UNO), Garmin Vector and Rally series. Crank-based: 4iiii Precision, Stages power meters, Quarq, Power2Max, SRM. Hub-based power meters following the Cycling Power Service standard should also work.

Note that Web Bluetooth is only supported in Chrome and Edge browsers. Safari and Firefox do not support Web Bluetooth. If you encounter issues connecting your power meter, please report them to us with your device model so we can investigate. See our troubleshooting guide for common solutions.

Why power meters and trainers disagree

Power meters and smart trainers measure power at different points in the drivetrain. A crank-based power meter measures the force you apply at the pedals. A trainer measures resistance at the rear wheel or internally in the resistance unit. Energy is lost through the chain, cassette, and any flex in the frame between these measurement points.

Even when both devices are perfectly calibrated, they will typically differ by 2 to 5 percent. Individual units also have their own calibration offsets. A trainer that reads 5 watts low combined with a power meter that reads 5 watts high creates a 10 watt gap at threshold power.

This matters because many riders use the same power meter indoors and outdoors. If your trainer reads low, you might train at higher actual power than intended, leading to excessive fatigue. If it reads high, you might not push hard enough to get the training stimulus you need. Consistency between indoor and outdoor power readings makes training zones meaningful.

How Power Match works

Power Match uses a feedback loop. When a workout interval calls for 200 watts, Ride Cave checks what your power meter actually reads. If it shows 210 watts while targeting 200, the system knows the trainer is set too high. It reduces the trainer's target power to compensate, continuing until your power meter reads the intended 200 watts.

The adjustment happens continuously throughout your workout. As intervals change or your power drifts, Power Match keeps tweaking the trainer target to maintain accuracy. You see the original workout targets on screen while the trainer receives adjusted commands behind the scenes.

Several safeguards prevent the system from overreacting. An 8 watt deadband ignores small differences, since minor fluctuations are normal and correcting them would cause unnecessary resistance changes. Rate limiting caps adjustments at 10 watts per second, preventing jarring shifts when power readings change suddenly. The system also applies smoothing to power meter readings, using an exponential moving average to filter out noise.

Setting up Power Match

To use Power Match, connect both your smart trainer and a Bluetooth power meter in the Ride Cave settings. The power meter connection is found in the Power Meter section, separate from your trainer. Once connected, Power Match activates automatically during ERG mode workouts.

A sensitivity slider lets you tune how aggressively the system responds. Lower sensitivity values create smoother, more gradual corrections. Higher values respond faster to changes but may feel less stable. The default of 0.5 works well for most setups. If you notice the resistance hunting or oscillating, try reducing sensitivity.

Power Match only operates in ERG mode, where the trainer actively controls resistance to hit power targets. In simulation or freeride mode, you control intensity through gearing and cadence, so there is no target for Power Match to adjust.

What you will see during a workout

When Power Match is active, you will see your original workout targets displayed normally. If the system is making significant adjustments, a purple indicator shows the adjusted trainer target. For example, if your workout calls for 200 watts but your power meter reads high, you might see the target as 200W with a PM indicator showing the trainer is actually set to 192W.

Your ride recording uses power meter data when available, giving you consistent power numbers whether you ride indoors or outdoors with the same meter. This makes comparing efforts more meaningful and keeps your training stress calculations accurate.

When to use Power Match

Power Match is most valuable when you use the same power meter for outdoor rides. The whole point is consistency: hit your zones using the same power numbers you see on the road. If you only train indoors and always use trainer power, there is less benefit since your zones are already calibrated to that device.

Dual-sided power meters work particularly well since they capture your complete power output. Single-sided meters that double one leg can introduce their own variations, but Power Match still helps maintain consistency with your outdoor data.

Some riders prefer trainer power because it reacts faster to cadence changes. Power meters measure at lower frequency and the smoothing in Power Match adds slight latency. For steady-state intervals this is not noticeable, but during short sprint efforts you might feel a small delay in resistance changes.

Technical details

For those interested in the implementation: Power Match uses a proportional controller with several stabilization mechanisms. The deadband prevents corrections when error is below 8 watts. When error exceeds the deadband, the effective error is reduced by the deadband amount before applying the sensitivity multiplier. This prevents step changes at the deadband boundary.

Rate limiting prevents the adjusted target from changing by more than 10 watts per second. This smooths the response during rapid power changes and prevents oscillation. The exponential moving average on power meter readings uses an alpha of 0.2, providing roughly 3 to 5 seconds of settling time.

Adjusted targets are clamped to reasonable bounds: minimum 50 watts and maximum of the target plus 100 watts. If your power meter disconnects during a workout, Power Match automatically deactivates and the trainer returns to using unadjusted targets.

Power Match has been designed to feel natural. The goal is not just accuracy but a smooth riding experience where the technology stays out of the way and lets you focus on your training.