You could have an 11 speed cassette modified to fit your freehub body.

Tell me more.

Thx.

Remove 1.8mm from the inside of the large cog.

Does anyone sell one of these?

Any machine shop can do it.

I've converted several zipp 182 to 11 speed.

Option 1: Buy a zipp 182 Campagnolo freehub. and an extra 0.25mm Change the freehub according to zipp website instructions. Use a campagnolo 11 speed cassette with shimano gears. May need some re-dishing of wheel and cable adjustment.
Pros: campag cassettes are widely available. no machining or special bits required.
Cons: potentially most expensive solution (Freehub+cassette). zipp 182 campag freehubs are rare as hen's teeth.

Option 2: Buy a Wheels manufacturing 10-11 accelerator cassette or an Edco cassette with a 10-11 lockring.
Pros: Plug and Play solution.
Con: cassettes are expensive. also companies providing the cassettes are small, so future support are limited. if the companies decide not to continue production of these niche products then you have no solution. heavy investment needed in these niche products if you want a range of gear ratios.

Option 3: Machine the back of the cassette as mentioned earlier.
Pros: Cheap, uses existing cassettes
Cons: need to find a machine shop to do this. makes cassettes incompatible with other wheels.

Option4: Machine the lips of the shimano freehub down by 1.65mm
Pros:Plug and play solution.
Cons: zipp 182 shimano freehub has ~3mm of allowance. machining down 1.65mm leaves it very thin and has the potential to fail. would recommend only as a backup solution.

you can still use them on other wheels, using spacers

There are actually a few very effective options for your set up. Some options are free, some are inexpensive, some, not so much.

Fyi, machining the zipp freehub is not a good idea, they have often failed after this mod. And edco cassettes are expensive and many riders (but not all) seem to report that they don't shift well, but YMMV.

But a decent rundown of the options of how to make this work for you is here:
http://darkspeedworks.com/blog-11speed.htm

Hope that helps,
Greg @ dsw

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Thanks everyone!!