bead-seat-diameter.jpg

Which tyre fits safely on which rim?
[all dimensions in millimetres]
Tyre width
Rim width
(interior)
18 20 23 25 28 32 35 37 40 44 47 50 54 57
13 X X X X                    
15     X X X X                
17       X X X X X            
19         X X X X X X        
21             X X X X X X    
23                 X X X X    
25                   X X X X X

Note: This chart may err a bit on the side of caution. Many cyclists exceed the recommended widths with no problem

Schwalbe have a more detailed chart here.