I've found tires not that hard to find,they are old VW beetle sizes I think I got the front here http://www.selecttire.com/Nankang-CX...dials-C56.aspx
175/65/15 I a 185 would go in there also.
Coker tire has a bunch 135 or 145
Even Walmart has a 165/80/15 Cheap !
Tire Rack has 3 different 145/65/15 2 winters and a Conti summer tire.
We're always going to have diameter issues (as if any BMW speedo was even close) so I guess one gets as close as one can and soldiers on.
hopscotching who laced up your wheels ?
I just reattached my chair to the bike, I have a reasonably flat garage,I laid a level on the chair frame it was slightly nose high unloaded,putting the small auto wheel lowered it a bit, Drone my current axle height is 11 1/2 so your figures are pretty close.I put my bike back to as close to the way I got it before putting on the front wheel bike very close to straight up unloaded, loaded it has slight lean out and less than 1" of toe in. In case no ones figured it out sidecar alignment is all subjective and probably not many are identical.
A sidecar installer who will remain unnamed at this point fixed my first rigs original owner up with gl1100/ural with 20" of wheel lead, I only asked the seller had the chair been professionally installed he said yes of course, I didn't know enough at that point, Claude and Brock of Side effects educated me and my welding buddy and I chopped her up and started over, so much pain so little time.It was from your neighborhood Drone but I'm not holding that against you.
On the other hand I have a spare tire mount I will carry a bmw wheel with something mounted on it.DB
165/80/15 Nankang vs 175/65/15 Continental WInterContact