Don't you just love the way Triumph seemed to mix and match parts for their bikes in the late 60s. I've slowly been dismantling the T90 I bought recently and as we all know, there's a mixture of thread forms used on the various studs, bots and screws. What I wasn't expecting (although I suppose I should have been) was the different wheel bearings they used. The QD rear wheel hub has a pair of 'Imperial' size bearings... 3/4" I.D x 1.7/8" O.D. x 9/16" wide. The front wheel hub has metric bearings 20mm I.D. x 47mm O.D. x 14mm wide. Why was that, do you suppose? The imperial bearings for the rear wheel are about 4 times the price of the ones for the front.