Mixing cogs from diff speeds on a cassette?

[Gabe77]

I've been splicing cassettes for a while, and happily so. My do-all bike is running the HG800 11-34 spliced with the junior 14-28 Ultegra for a 14-34 range. That's been running flawlessly but I found an old unused 11-36 10 speed XT cassette. I'm tempted to replace the 27-30-34 cogs with 28-32-36 from it. In experimentation it seems to work OK although I had to play around with spacers to get the 11s to 10s spiders have the approximately right gap.

The capacity etc is all fine and I have previously run an 11s chain on a 10s system without trouble. Has anyone done this and should I foresee trouble? It seems an easy way to get back to a 12t starting cog on all those pesky 11s groupsets that insist on 11t starting sprockets.

[spoonrobot]

I've been running a similar cassette:

R7000 11-28 11s
11 12 13 14 15 17 19 21 23 25 28

Modified to 11-36
11 13 15 17 19 21 23 25 28 32 36

The 32-36 cogs are a one piece spider from Deore HG-50 10s cassette. Like you I had to use a shim (or two?) from MTBTools to get the spider-to-spider spacing right from the 23-25-28 R7000 spider to the 32-36 HG50 spider. Other than that it works fine, shifting feels normal as the shift gates seem to line up correctly.

I think the issue with mixing comes if done in the middle of the cassette where the cog and spacer spacing, as well as shift-gate alignment matters more. For adding to the beginning or end of the cassette it seems easier to align things to work flawlessly.

[Ralph]

I've done the same with Campy cassettes a couple times but it's hard to get it to shift exactly the same. Mixing a 14-23 with a 12-30 or 13-29. Example: On Campy cassettes...a 19 tooth cog that follows a 17 tooth cog is not the same cog as a 19 tooth cog following an 18 tooth cog. The 19 in a 13-26 is not the same cog as a 19 in a 13-29 as an example. This holds true for other combo's as well. But they shift good enough to set up for one hilly ride.

Imagine this is true for Shimano and Sram as well.