Tacx Flux 2 Smart Review – Direct Drive Trainer Tested

Switching from a wheel-on trainer to a direct drive unit is one of those changes that’s immediately obvious the first time you pedal. The rear tyre comes off, the bike locks onto the trainer’s freehub, and the whole back end of the bike stops moving around. The power numbers stabilise. The noise drops. If you’ve been riding on a wheel-on trainer for a season and started to notice its limitations, the Flux 2 is a serious answer. I’ve used this with athletes who are following structured training plans and want power data they can trust, and it’s one of the more competitively priced direct drive units that doesn’t ask you to accept meaningful compromises.

Specs at a glance: Direct drive, no rear wheel required, 7.6 kg flywheel, 2000W maximum resistance, 16% incline simulation, ±2.5% power accuracy, ANT+ FE-C and Bluetooth, 64.2 x 67 x 46 cm footprint, 23.8 kg. Requires a mains power connection. Does not fold. Cassette body included, cassette sold separately — check compatibility before ordering.

Pros

• The step change from wheel-on to direct drive is immediately apparent — the bike is stable, the power numbers are clean, the noise is substantially reduced
• 7.6 kg flywheel gives a realistic sprint inertia that lighter-flywheel units can’t match
• ±2.5% power accuracy is adequate for FTP testing and all structured training work
• 16% incline simulation is convincing — steep Zwift climbs feel genuinely difficult
• 2000W resistance ceiling is beyond what any amateur will reach
• Tight integration with Garmin head units and the Garmin ecosystem if you already ride with a Garmin device
• Compatible with Zwift, TrainerRoad, Sufferfest, Rouvy and all major training platforms

Cons

• Requires a mains power cable — not practical for a garage or shed without a socket nearby
• Does not fold — the footprint is fixed at 64 x 67 cm, so storage requires dedicated space
• You need to purchase and fit a cassette separately — this is an additional cost and requires basic workshop tools
• At 23.8 kg it’s not something you move frequently
• Power accuracy of ±2.5% means occasional small discrepancies against an external power meter, though not enough to affect training decisions

What it’s actually like to use

The first session on a direct drive trainer after a wheel-on unit is a noticeable shift. On a wheel-on trainer the rear tyre presses against a roller, and however well you set the contact pressure, there’s always a degree of movement. The bike rocks slightly, especially when you get out of the saddle, and the power numbers reflect that instability — they bounce around on short efforts in a way that makes it harder to hold a precise wattage. On the Flux 2 the cassette sits directly on the trainer’s freehub and the axle locks into the trainer legs. The bike doesn’t move. Power data from 10-second efforts becomes readable. FTP tests feel more controlled because the resistance tracks more accurately to what the software is asking for.

The 7.6 kg flywheel is worth discussing because it’s one of the Flux 2’s strengths. Flywheel mass is what gives indoor training its outdoor feel — heavier wheels maintain momentum through the pedal stroke and require genuine force to accelerate out of a corner or up a short punch. At 7.6 kg the Flux 2’s flywheel is on the heavier end for this price bracket, and it shows during sprint work and fast cadence changes. The trainer doesn’t feel like a resistance machine; it feels more like riding a real bike at effort.

The 16% incline simulation is one of the steeper ceilings in the direct drive category. For most Zwift riders this is more than sufficient — the majority of climbs in Watopia and the other worlds top out below that gradient. I’ve tested this on the steeper Zwift Alpine segments and the resistance genuinely accumulates at the rate you’d expect. It’s not a simulation that makes a shallow gradient feel steep; the numbers line up with what’s on screen.

Power accuracy at ±2.5% is the honest published figure, and in my experience it’s realistic. Running the Flux 2 alongside a Quarq power meter at threshold efforts, the numbers typically sit within 1–2%. The occasional larger deviation happens at very high short-duration efforts, but for the training that matters — FTP tests, sweet spot blocks, VO2 max intervals at a specified power — the Flux 2 gives you numbers you can build a training plan around. I wouldn’t use it as a reference meter for precise sprint profiling, but for everything else it’s fine.

A note on cassette fitting

The Flux 2 ships with a cassette body (freehub) but no cassette. You’ll need to fit your own before the first ride. Most road riders running a modern 10- or 11-speed Shimano or SRAM groupset will find their existing spare cassette works fine; the freehub is compatible with 7-speed through 11-speed Shimano and SRAM. If you’re running Campagnolo or a 12-speed system, check the compatibility list before ordering.

Fitting a cassette requires a chain whip and a cassette lockring tool, both of which cost under £15 combined if you don’t have them. The process takes about five minutes and there are clear instructions available from Tacx. I mention this not to make it sound complicated — it isn’t — but because a few riders I’ve coached were surprised to find the cassette wasn’t included. Budget for it and have the tools ready before the trainer arrives.

The mains cable is the other practical factor worth thinking about in advance. The Flux 2 draws power from a mains socket and the cable is not especially long. If your training space is a garage or shed without a socket directly adjacent to the bike, you’ll need an extension lead. This is a minor logistical point but worth sorting before your first session rather than discovering it when you’re ready to ride.

Garmin ecosystem integration

Tacx was acquired by Garmin in 2019 and the integration between the Flux 2 and Garmin devices has become progressively tighter since. If you ride with a Garmin Edge head unit, the trainer connects directly without needing a phone or a separate app in the loop. Power data feeds cleanly into Garmin Connect and Training Peaks. The Tacx Training app is solid for structured sessions and interval work, though most riders I coach default to Zwift or TrainerRoad for day-to-day use. The Garmin ownership doesn’t constrain you to the Garmin ecosystem — the trainer broadcasts on ANT+ FE-C and Bluetooth simultaneously and works with any compatible platform — but if you’re already invested in Garmin hardware, the experience is particularly smooth.

Verdict

The Tacx Flux 2 is the trainer I’d recommend to any rider who is doing three or more indoor sessions per week, following a structured training plan, and ready to commit to a fixed indoor training setup. The direct drive experience is qualitatively different from wheel-on in ways that matter for serious training: the bike is stable, the power data is reliable, and the flywheel feel is convincing. The practical limitations — mains power required, no fold, cassette needed separately — are real but manageable if you plan for them. At its price point it competes well against the KICKR Core and the Saris H3; the Garmin integration is a genuine advantage if you’re in that ecosystem. For riders ready to take indoor training seriously, this is a capable and honest machine.