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Discussion Starter #1 (Edited)
Alright so I've come into a set of BST's that were living on an S4RS, and they're to go on my HYM1100S. I've pulled the Hyper's wheels and measured the critical points, issues are as follows...

On the fronts, the distance between the outer surfaces of the wheel bearings are 126.45mm for OEM and 120.24 for BST. I'll chock up the 0.23mm to bearing install variance and that leaves 16mm to make up. I'll whip up a couple 8mm spacers for either side and that'll be sorted easy.
The less easy bit is the brake discs. The distance between mounting surfaces is the same, thankfully, but the BST hubs have a 6x80mm bolt pattern and OEM uses 5x90. So, I need to find rotors that have a 6x80 bolt pattern and 305mm diameter with 9.75mm offset.
Does anybody know of a bike that uses such a size? If not, I'll have to make my own disc inners.

Then on the rear, the spokes are fouling against the caliper by a couple mm. I could make a spacer plate for it, a few mm shouldn't really effect much but as a rule I'd prefer not to push the wheel off center at all. Possibly a smaller rotor would work, allowing me to push the caliper further inwards towards the rotational axis and away from the sweep of the spokes. Might also be able to machine down the caliper, though I'm not sure how much meat there is to take away before I start eating into the internals.
You guys have any ideas here?
 

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You must have gotten a really good deal to be willing to do all that to make the wheels fit.
 

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Discussion Starter #3
I did get a helluva deal. Significantly less than the new cost of the front wheel for both with brand new tires.
But I'm also an aerospace machinist with experience building custom bikes... so a little screwing around to get them to fit isn't too far out of field for me.
Making spacers for the front is easy. For the rotors it seems there are a handful of options with the correct bolt pattern and offset, just need to figure out what will be the best option and see what's available on eBay... still open to donor bike suggestions. Most of the options are 320mm rotors, so I'll make spacers for the calipers and get a brake upgrade out of the deal too.
A clean solution for the rear is still eluding me. Best thought on that currently is a 1-2mm spacer under the wheel and just shave down the caliper a bit, but I need to look into it and see how much meat that caliper has to give as the contact area is right over the piston.
 

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S4RS have the new five bolt disk pattern like your Hypermotard.

The wheels must be from S4R or other pre 2006 Ducati as they have the old six bolt pattern. S4R uses spacer between the wheel and the left fork. Check the distance between the forks on your Hypermotard and then compare it with S4R distance between the forks. If the distance is the same then you most likely can use the S4R spacer.

S4R left side axle spacer: Page 80 #2 on the diagram and S4R five bolt brake disks

You can also get 320mm rotors from S4R and either make 15mm spacers or use spacers from Streetfighter S on the calipers to rise the calipers up so they will fit the 320mm disks. You may or may not need to add another 5mm to the Streetfighter S spacer which are 10mm. It may fit. If not then just add stainless washers until it fits. As for offset, only superbikes and 1200cc Streetfighter S and Diavels have 10mm offset disks. All other bikes don't use offset disks. The offset on superbikes is there to expose the disks to more airflow and improve cooling. I would double check the offset again.

Streetfighter S caliper spacers: Page 66 #32 on the diagram
 
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