******UPDATE to Post on 8-28-2012: Using 36psi for front and 40psi for rear tire. Loving the handling.
These pressures are much higher than BMW OEM reconmended, but then again these tires are much different than tires were 30 years ago.
******Original Post:
Following the recommendations of http://www.kleineboxer.de I mounted Bridgestone's BT45 on my 1983 R65.
For sportive solo riding the following sizes are a must:
Front: BT45 90/90-18
Rear: BT45 110/90 -18
According to kleineboxer.de, the BT45 has become the standard tire in Germany for the R65 , few continue using Metzeler.
I agree with my fellow German's: The narrow BT45s turn the R65 into a confidence inspiring hoot in the twisties. I also find the BT45 fairly compliant on grooved roads.
They are also said to be very good in rain due to dual compound. I personally don't push corners hard on wet roads, especially not on oil-polluted wet roads in the US.
Straight traction is definitely good on wet roads.
As for lifetime: Some have managed to kill this tire within 3000miles, using a R65! That's fine with me.
I don't ride the R65 extensively. And once a tire is 3 years old, I needs to be changed IMO.
BTW: I run these tires with tubes on the snowflake wheels.
kleineboxer.de is a dedicated and rather active site for R45 and R65.
Helmut