Hi all. I have a '59, R-69, and prev. had Dunlops, 110/90 on the front and 120/90 on the rear. Actually those were on the bike when I bought it and were near new, so "waste not, want not", I left them on. The bike cornered like it was on rails. I could not upset the cornering line if I tried. Also, very steady on the straight, even loaded for camping. Only problem was getting the rear wheel off for any type of service. I usually ended up removing the diff. to remove the wheel, even after letting the air out.
Anyway, when it came time for new tires, a respected expert suggested the handling would be "quicker" with 100/90 on the front and 110/90 on the rear[and suggested Michelins]. I really don't notice it turning in "quicker", but I do notice what I feel is some level of instability on the straights. Not quite a wobble, but maybe a twitcheness[is that even a word?] I've ck'ed steering brngs, the front swing arm adj, as well as the rear swing arm. Also ck'ed the wheel brngs and all seem ok. I know the R69 orig had 3.50x18 on front and rear. If I went to a 110/90 on the front [to match the rear] would it "slow the steering up" ? thanks, rj