Thank you all for your replies, I think I have it narrowed my search down to three tires and would like to get your impressions of my choices and the sizes I have picked out. I am looking at the Michelin Pilot Activ (Front 100/90 - 19, Rear 4.00 - 18), Dunlop K70 (Front 3.50 - 19, Rear 4.00 - 18), and the Shimko 712 (front 100/90 - 19, Rear 110/90 - 18). Are the metric sizes correct for my bike? It originally came with 3.50 -19 front, 400 -18 rear. Since I am the original owner of this bike, by riding style has tamed down over the years.
Thanks again for your help.
Hi bubba,
you bike left the factory with "inch" sized tires. Front; 3-1/2"-19 & rear 4"-18. These tires were "square" that is, the tire section's width = it's height.
Modern tires have Metric section measurements and ain't "square"
For instance the 100/90-19 tire specified for an XS650 front wheel has a width of 100mm and a height that's 90% of it's width
Similarly the 110/90-18 tire specified for an XS650 rear wheel has a width of 110mm and again, a height that's 90% of it's width.
So no the tire sizes ain't quite the same but yes, they are correct.
And as an added bonus, modern rubber grips the road a lot better than the original rubber did.