Bad karma, good karma: A dumb trainer goes smart

I have literally run my turbo trainer ragged.

In the middle of the twelve-day, 282-kilometer “Heavy Metal Truants: Eighth of Spades” virtual charity ride, my Minoura LR340 turbo trainer decided to strip its own threads and give up the ghost.

The T-shaped nut above is key to the operation of many of Minoura’s turbo trainers. Photo credit: Steve Tan of the Hands On Bike blog.

With the little T-shaped nut (Minoura part “BF-11”) stripped of its threads, there is nothing left for the threaded tension knob to hold on to. Further down the line, this means there is no longer any way for the resistance roller to reliably contact Hyro’s rear tire, since the single point of failure is now gone.

I went on to complete the 282 kilometers, courtesy of a bodge, but I was doing so with very uneven resistance and rear wheel slippage. I was also making a much bigger mess of things post-workout, as more rubber particles of what was formerly my rear wheel flew off and made their way onto the floor. I was unsure before, but I now have no doubt this was from the inconsistent rear wheel contact my bodge had given me.

The challenge was over, and so was my turbo trainer – or at least, it needed repairing. After doing a bit of Internet sleuthing, I learned the BF-11 T-shaped nut is notoriously hard to find outside of Japan. Why not simply upgrade to something better?

A Wahoo KICKR direct-drive smart trainer. Photo credit:

Smart trainers have become all the rage due to the COVID19 lockdown. A lot of them are just too rich for my blood, especially the direct-drive ones where you hook the bicycle to them directly in place of the rear wheel. They’re also not a good fit for me. I cannot yet dedicate one bicycle and/or one room for training, and the faff of switching Hyro from outdoor riding to indoor training modes will probably get old pretty quickly.

A friend of mine said I may have had good karma, as I managed to land a great deal on another friend’s second-hand Wahoo KICKR SNAP as he traded up to the direct-drive route.

Despite its considerable weight, it folds up into a fairly compact package.

Much like my incapacitated LR340, the KICKR SNAP is a wheel-on turbo trainer. A threaded rod pushes a resistance unit’s roller against the rear wheel, where its attached flywheel provides the resistance. Both fold up pretty compactly for storage, too.

The similarities end there.

That is one massive flywheel. Note the two LEDs for Bluetooth and ANT+ connection.

The first and most obvious difference is the weight. This 2018-vintage, second-generation KICKR SNAP is much heavier at 17.2 kilograms – almost three times the weight of the LR340. Much of the added weight is in the substantially beefier, 4.8-kilogram flywheel – almost five times heavier than that of the Minoura. A heavier flywheel is supposed to help improve the road feel of a trainer; it can better simulate somewhat the sensation of coasting to a stop after you stop pedaling. Direct-drive trainer flywheels tend to be even heavier still.

This thing is fully assembled – no DIY bolting of the resistance unit to the frame needed. Speaking of which, the KICKR SNAP frame is a little more substantial than the LR340’s, its width no longer fitting neatly inside the yoga mat I’d been using previously. Hyro also sits a tad higher when clamped in, but the perceptible difference is negligible.

A pretty solid frame holds everything and your bike together.

The second major difference is the “smarts”. While it can be used (somewhat) in an unpowered state, its real value comes at the cost of plugging it in to a wall outlet. When energized, the KICKR SNAP can use its Bluetooth and ANT+ radios to communicate to your smartphone and sensors for cadence and heart rate. You can then control the trainer via Wahoo’s smartphone app, or via a compatible cycle computer or head unit.

Finally, the real draw of the KICKR SNAP for me is its onboard power measurement, advertised to be accurate to +/-3%. Since I started cycling in 2013, power meters have been these much-ballyhooed training tools, immune to the external influences that render heart rate monitors flawed, calculating this magical metric of power purely through pedaling torque and cadence. Over the past seven years, they’ve gotten better and cheaper, but still cost a decent paycheck or two for most people. While the KICKR SNAP’s power meter is obviously restricted to indoor training, it’s a start.

Note how the KICKR SNAP’s legs just fall outside the area of my yoga mat.

So what are the downsides to a wheel-on smart trainer? You have those inherent by design – the wear on the rear tire, as well as the risk of stripping out the threads of whatever tension mechanism holds the resistance roller against it. (The tension adjustment nut seems a lot beefier here though, being a solid section of metal rod with a threaded hole tapped through it.)

Apart from those, the main disadvantage is that the trainer needs to account for more variables: most importantly the wheel size and the tire’s air pressure. This is why the KICKR SNAP’s power meter has a slightly lower accuracy rating than its direct-drive brethren.

It’s this increased variable count that Wahoo attempts to address via a spindown test – a procedure done every now and then to ensure the trainer and its power meter are properly calibrated for the operating environment’s temperature. While many smart trainers need this done, with the wheel-on kind, it has to be done more often.

Moving from a “dumb” trainer like the LR340 to the KICKR SNAP, I feel there is a staggering amount to study and digest. I’ve only just scratched the surface of what this thing can do; consider this post an introduction. With outdoor riding still not quite a good idea in the wake of the pandemic, expect the next few posts here to explore the KICKR SNAP’s capabilities.


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