Rear wheel options

Is there a rear wheel options i.e. larger diameter, end with same diameter tire but shorter sidewall profile?

I don't know, but if you find one, LET ME KNOW!

If you do a search on posts by Miles, when he was here he was going to have a rear wheel custom made for his rstd so he could run radials on it. He sold the bike before he did it but the thread has discussion about the wheel company. I think he was going to have the stock wheel converted to a 16" or 17" rim size. 16" is the smallest rear rim size for radials. I believe he was investigating using the same size rear radial as the gold wing and having the stock RSTD rear rim modified accordingly.

If I find the thread I'll post the link.

I don't think there are any off the shelf swap options for the rear like there is for the front (i.e. Stratoliner, Roadliner wheel). In theory an FJR rear rim should bolt to the final drive, since you can swap in an FJR final drive the same as you can a Vmax drive. Assuming the FJR rim offset is the same as ours, the other Problem is the FJR weighs half of what our bikes weigh, and you probably can't get a tire in that size with the correct load rating for our bikes.