Minor correction - the first R80G/S - note the "/" came out in 81 with an 18" rear wheel which was pretty much the standard then, and in 88 BMW came out with the R100GS, which came with a 17" rear wheel.
There's no problem getting good 18" rear tires. It's the front 18" or 19" depending on what year R100 that's harder.
BUT - you could buy a gorgeous mint R80/100G/S/GS for less than the cost of the conversion.
Notes - the old one is lighter and simpler, but the forks aren't good, have been known to break, but the rest is mostly bulletproof. The later ones have good forks, but the driveshaft is a "standard replacement part." i.e. every 50,000 miles.
There's lots of discussion on both, good and bad, and there's the story on my own G/S under our trip pages.
Buy an R100GS and be happy!
------------------
Grant Johnson
Share the Dream!
at:
www.HorizonsUnlimited.com