Di2 cassette shifting issue on trainer

[bikehaus]

When in the large chainring, and trying to shift down (moving the chain towards the left) to the third and second largest cogs, the chain skips and doesn't catch/engage to the new cog.

This only appears to occur on the trainer. I tried two different cassettes (same range) thinking one could be worn, but the issue occurs on both. This could still obsscure the real issue, but it's at least something to try and isolate the issue.

The chain does move to the largest cog (32t)

I can get the chain to shift on these cogs if I click the shift button twice. Any thoughts?

[ultimobici]

Is the distance between the frame and smallest sprocket the same as with your regular wheels?

[bmrk]

The cassete offset differs between the trainer and wheel freehub. You can adjust the derailleur indexing when changing between them or use a 0.5mm spacer behind the cassete on the trainer (guessing given the problem description).

[ms6073]

Would be nice if Di2 offered the ability to save derailleur offsets as profiles such that you could switch back and forth between road wheels and direct drive trainers. While it is supposed to be standardized, the spacing of freehubs can differ between manufacturers and when I faced this issue with our Tacx Neos and I initially just made adjustments to the rear derailleur via Di2, but this gets tedious so I opted to shim the cassettes on the trainers using a combination of shims in .1 mm, .2mm, and .3mm widths sourced in the US from McMaster Carr.

[ultimobici]

Would be nice if Di2 offered the ability to save derailleur offsets as profiles such that you could switch back and forth between road wheels and direct drive trainers. While it is supposed to be standardized, the spacing of freehubs can differ between manufacturers and when I faced this issue with our Tacx Neos and I initially just made adjustments to the rear derailleur via Di2, but this gets tedious so I opted to shim the cassettes on the trainers using a combination of shims in .1 mm, .2mm, and .3mm widths sourced in the US from McMaster Carr.

With the app it is possible, in a way. Once the gears are set on the bike you can note the offsets front & rear. Then on the trainer you can reset the gears to match the trainer. It is a bit of a faff but you just have to change to the pattern for each. However, the best solution is to move the cassettes to match up.

[kofsw4]

Would be nice if Di2 offered the ability to save derailleur offsets as profiles such that you could switch back and forth between road wheels and direct drive trainers. While it is supposed to be standardized, the spacing of freehubs can differ between manufacturers and when I faced this issue with our Tacx Neos and I initially just made adjustments to the rear derailleur via Di2, but this gets tedious so I opted to shim the cassettes on the trainers using a combination of shims in .1 mm, .2mm, and .3mm widths sourced in the US from McMaster Carr.

Anybody have a source for these kinds of shims in UK? I also have a difference in cassette position between my wheel and trainer. Was a bit annoying when on 11 speed but I lived with the noisy drivetrain but it's much worse now I'm on 12 speed.

Difference in indexing is about 7-8 clicks outwards when i put the bike on the trainer, if anybody knows what this might equate to in terms of shim width? I tried a 1.85mm 10/9/8 speed spacer but that's far too much, can't even get the cassette lockring on.

[kode54]

Check your B screw. That could limit the jump to the larger cogs.