Swap from rear wheel to KICKR without adjustment

Has this ever happened to you? You have a KICKR, LeMond Revolution or other smart trainers with integrated cassette and every time you change your bike from trainer to wheel you need to adjust the limit screws on the rear derailleur?

You could just put a 30-year-old steel-framed bike and fit spare parts and stuff you were lucky enough to get for free and somehow got working together. But it might be easier to match the alignment of wheel and trainer.

Cassette locknut to axle locknut is the key

The rear dropout presses against an axle locknut AND Shimano 10-speed cassettes have the same spacing; MTB and road.

So the position of the cassette relative to the edge of the axle locknut must be the same on your rear wheel as on the KICKR… or close enough. That means that the cogs will be in the same position above the derailleur in each gear too.

From https://www.sheldonbrown.com/cribsheet-spacing.html

Brand and model Center-to-center
Spacing
Sprocket Thickness Spacer Thickness Total Width
Shimano
10-speed
3.95 mm 1.6 mm 2.35 mm 37.2 mm

Measuring

A vernier caliper makes this easy, but any good metal rule with fine markings will work.

IMG_3783 (2)
Vernier flush against the axle locknut, probe against the cassette locknut – 2.8mm

Measure the rear wheel and then the KICKR and calculate the difference. I used the edge of the cassette locknut, being careful to avoid the taper. You could use the flat of the smallest cog; just be consistent.

Start with the rear wheel

(The rear wheel must be true and centred on its axle.)

Adjust the derailleur for the rear wheel first. Sweet shifting on the road is the most important benchmark. Check that the cage doesn’t interfere with spokes in the lowest gear or the chain stays in the highest.

Space the KICKR’s cassette to match

Add or remove spacers from the KICKR to match the rear wheel closely. Shimano 10-speed cassette spacers are available in 1mm and 1.85mm sizes, though I’m sure I have a 0.5mm one somewhere.

Fit the KICKR and check the shifting

Shifting should be the same on road and on the KICKR. Some fine-tuning at the barrel adjuster  may be necessary

The cassettes can be different; I had a 28T-11 on my KICKR and a 32T-11 on my wheel without a problem. As long as your derailleur can take up the chain on both, it will work.

Marginal gains – little things to try

If the shifting is close but not quite the same, you should look for other differences. For example, I found two other factors on my bike that had a minor effect, including a problem where my long cage derailleur touched the KICKR case in my lowest gear.

Protruding dropout screws

The screws holding the dropout were protruding and pressing against the axle locknut on the KICKR, but not so much on the rear wheel. That millimetre or so was enough to affect the angle of the derailleur cage on the KICKR. I filed the screws down to sit flush. The other benefit is that the locknut now sits squarely against the dropout and not just on a few stress points.

IMG_3779 (2)
Tiny QR skewer nut and the very tiny dropout screws (Trek Domane)
IMG_3781 (2)
Dropout screws filed flush. Note: the axle locknut had been touching the screws

Big, old quick release skewer is more powerful?

I suspect that it takes more effort to close a lightweight QR skewer compared to a big, old QR. So it is easier to put more clamping force on the KICKR than on your rear wheel. I can’t directly measure the difference; I just noticed that the derailleur cage moved inwards more after clamping on the KICKR. A slight reduction in force made a difference without compromising the connection to the trainer.

Or use an old bike

Enough with the advice. Time to play TrainerRoad on my 30-year-old steel-framed ‘ute’ with 10-speed spare parts and free bits.

IMG_3785 (2)
Barely any space between the smallest cog and the dropout adapter!
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