What do you mean smaller? you can always hire a custom machine shop to make things one off.
the 6 bolt pattern is used on most disc hubs.. Shimano's CenterLock spline a recent exception..

threaded hubs with the thread on the left side are a common thing in older tandems.
its RH BSC thread like a freewheel, but because its on the left and the force applied is tightening due to braking.

there are threaded to 6 bolt adapters for tandems rear hubs, as a result.




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