"Check the markings on the R Nine T.... "
The tyres fitted to my R Nine T Racer are the original BMW fitted tyres and have the marking as shown in picture . Quote from the Metzeler web page :
"Metzeler-tubeless-tyres may be fitted to tube-type rims, if the following restrictions are kept: Use only Metzeler-tubes. Tubeless tyres fitted with a tube have a max. permitted speed of 230 km/h "
Without wanting to get up anyones nose I do think a lot of information ( not only about tyres ) is either urban legend or very old advice . Even manufacturers advice can be out of date . Avon still says this about fitting rear tyre to the front and vice versa :
Avon would not normally recommend this fitment. If you do this however, due to the way tyres are manufactured, you should reverse the tyre’s direction of rotation if you fit a front tyre on the rear or a rear tyre on the front of your bike.
This is an MOT failure ( copied from .Gov web site ) ;
Examples of an unsuitable tyre are:
a tyre specifically designed for front wheel use fitted to the rear wheel
If a tyre has only one direction arrow it must be fitted that way . Some tyres have no arrows or arrows in both directions showing universal fitment .
As I have said I have never specifically purchased a tube type tyre to fit on a tubed rim and i have never had a problem - apart from nails screws etc