Adventure Tires - sizing on 1984 R100T

[goodworkmax]

I'm baffled by how difficult it has been to find reliable or consistent information on selecting updated metric tire sizing to fit my '84 R100. The bike has 20 year old Metzeler Enduro 3's on it. They're pretty tired (pun) at this point.
Would like to put a pair of Shinko 705's or TKC70's on but struggling to determine the size and fitment. Has anyone done this? Can someone please let me know what metric tires you have been able to fit onto an 81-84 R bike?

Thanks,
Max

 

[20774]

Max -

This page shows the specs for a '78-80 R100T...suggests that inch-size tires are the standard, 3.25x19 and 4.00x18:

http://www.bmbikes.co.uk/specpages/R100T.htm

For the '78-84 R100RT, it also indicates that inch-size tires are the normal:

http://www.bmbikes.co.uk/specpages/R100RT.htm

I think if you wanted to go the metric route, I'd be looking at a 90/90x19 up front and a 110/90x18 in the rear. Metric aren't necessarily the better choice but might be easier to find. There are suitable inch-size tires out there!