Honda CB360T - what is a good modern rear tire replacement?
A good replacement for the original 3.50-18 rear tire on your Honda CB360T would be a 100/90 or a 110/90-18. You may also see it written as 100/90R18 or MU90-18. Each tire manufacturer has their own, slightly different, way of writing a tire size.
For more detailed information about what may be printed on the sidewall of a tire and what it means, check out Tire Conversion Chart.