You can get 10mm & 15mm hubcentrics from Project Kics. I was quoted £100 per spacer for them though
I can imagine you can get the spacers but wouldn't the thread on the hubs push through past the spacer and hit the wheel. Meaning you can't get the wheel onto the spacer correctly?!? Easy to picture but hard to type
I know some wheels have holes in on the rear but not sure if all do.
I'm really struggling to understand this. I can't really see why you should need to fit longer bolts, if anything I'd have thought shorter bolts, , surely 10mm or 15mm hubcentric spacers would come with nuts that would fit flush to the spacers anyway? The wheel itself is bolted to the nuts on the spacers, if the back of the wheel doesn't have the holes for the nuts to fit in then it doesn't really matter what size the spacers are. In this case you'd have to fit another standard spacer on top of the hubcentric one, as I did with my wheels which don't have the holes on the back of the wheels.
Pete
The spacer below is bolt on (Hubcentric) so uses the hub studs to secure the spacer then has its own built in studs to secure the wheel. If this design spacer was infact 10mm thick instead of 20mm then the hub bolts would protrude too far out and obstruct the wheel from securing on the spacer.
This 10mm spacer uses the existing studs from the hub (in this case i believe longer studs have been added)