I think 5" is too wide for the rear. With a 5" rim you must have at least 160 width tire (on my Supermono I have just that, BT090 160/60 on a 5" rim) and that will not fin in my GG swingarm. The tyre will hit the swingarm, and the chain will hit the tire.
The
OEM wheel kit has a 4.25 rear rim. Perhaps that could tell us something
OTOH,
the rim is quite affordable. If you buy this one and lace up on an original gg hub, you are done. They also have spokes. As we have discussed, the front is easier, there you could fit almost anything (within reason).
There is also an
undrilled front rim. Then, you could drill it to the gg lacing pattern. But you'd have to be sure that it is undrilled, and that you know how to drill it
