I'm approaching the 19-inch-question from the other direction. Iris, my lady, rides a Suzuki GN 400 since 1981 (from new). During the years we have aquired more than one more of these ...
Iris got a 1972 Triumph Bonneville, too. In the early 90's. It became obviously that the term 'basket-case' wasn't really describing it's state. We're still hunting for parts for it ...
Some weeks ago I planned a dual-sport-ride with a friend of our's with my Suzuki DR 750 Big. Because of a crankcase-bearing-failure of my Big, the whole affair didn't take place. But that's another story ...
While preparing for the ride (getting me an off-road-helmet with goggles, boots, trousers, shirt and armour) Iris dropped the note 'I'd like to join you on this ride ...' Something I never would have expected.
I ride one of these many GN 400 in our barn, too. Equipped with a broader and flatter super-bike-bar and a pair of old BMW-GS-footrests. I've always been thinking about converting it to a 17-inch rear-wheel to get me a proper, grippy rear-tire. Now I'm thinking about changing it's front-wheel to 19 inch to be able to get some mild off-road-rubber (Heidenau Scout) on the bike and thus transform it into a scrambler. Just to give Iris a chance to join us on dry days for some green-laning. Because I know, that she won't ride a bike that doesn't enable her to get at least one foot firmly to the ground. The GN does! And with a 90/90-19 up front and a 120 or 130/80-17 on the rear (3.60-18 and 4.60-16 original) the bike won't rise too much!
So I'm very interested in this discussion, especially concerning a front-rim that fits the original GN-hub (been thinking about the Freewind-rim myself). On the rear, the rim of a drum-braked Big will do - even with the Bigs original spokes as it seems! And, what's been new to me, that a wider off-road-tire up front would provide more grip on the road?
Kind regards, Bambi
'Find me kindness, find me beauty, find me truth ...'
(Dreamtheater, Learning to live)