Leinster

long question short, can you swap rear wheels out without adjusting the rear derailleur indexing at all?


I use a spare rear wheel for my trainer wheel, with a 10 speed cassette. CAAD-10 with a 105 group, 12-27 shimano cassette on the Fulcrum 7 road wheel, 12-26 on the (stock Diamond Back) trainer wheel, so not a big difference in sprocket size. The 12-26 cassette is newer by a few years and a few thousand miles, but no significant visible wear on the 27 cassette. The chain has been replaced a couple times in the life of the bike, not sure how recently.

But the gears are out of alignment when I put the trainer wheel on, so I usually need to twiddle with the barrel adjuster on the RD to get going, or put up with some crunchy gears during a trainer sesh. Is this normal? Is the lateral position of the cassette supposed to be consistent across all wheel brands, or do you get some variation between some?

Things to consider; 10-speed cassettes are EXPENSIVE right now, so I’m not in the mood to buy new hardware for both wheels at the moment.

SoSmellyAir

Unfortunately these slight variations exist between not only different brands, but also across different models of the same brand; I had to re-index the rear derailleur when upgrading from Mavic Aksium to Mavic Ksyrium Elite, and again from going from an 11-32 cassette to a 12-25 cassette (both 11 speeds).

Here's a Shimano Ultegra CS-6700 (11-28) for $60. I don't know if that is expensive or not but it is definitely less than either of my 11 speed Ultegra cassettes, which I got on sale.

Shimano Ultegra CS-6700 Cassette | Competitive Cyclist

Other options here for $11 more if you don't want 11-28.

Shimano Ultegra CS-67000SP Cassette | Jenson USA

Leinster

Thanks! You answered my main question about the spacing, so I guess I’ll just factor in some adjustment time for future trainer sessions.

I do consider $60 a lot for a 10s cassette. Iirc, I got my 11 speed Miche Primato for about that much. I definitely don’t want to spend that for a cassette with a cog I’ll never use (the 11), and without one that I do want (who doesn’t love a 16? Bike component manufacturers, that’s who).

woodcraft

To have the two wheels index the same, the cassettes have to be the same distance from the RD.

In practice, that means that the small cog should overhang the end of the freehub by the same slight amount on both wheels.

This can be adjusted by putting shim(s) behind one of the cassettes. Thin shims can be found to buy with difficulty, or easily cut with scissors from an aluminum can.

A new cassette might improve the situation, but I wouldn't count on it.

WhyFi

Yup. Try shimming.

Leinster

cheers!

beer can shims it will be.

Leinster

Update;
I found a couple of spacers in the parts drawer.
I pulled the cassette off the DB/Trainer wheel to add a spacer, but found that the cassette on that wheel was on the outside limit; any further out and the 12t would just spin.
But I checked the Fulcrum/road wheel and it DID have a spacer. A thick one, too.
So I replaced the Fulcrum spacer with a thinner spacer. Now, based on a few work-stand cycles through the gears, the indexing works fine on both wheels with no adjustment between.

November Dave

We started having these made by customer request. More expensive than DIY, but neater, more consistent, and less hassle.

Freehub body shims.

woodcraft

A BF victory!

woodcraft

Leinster

great product! If I hadn’t self-resolved my issue, I’d be beating a path to your door.