Why are tyres often narrower than the stated tyre size?

In order to ensure that tyres have sufficient frame clearance, tire manufacturers generally prefer to keep production closer to the lower end of the permitted tolerance (+/- 3 mm).

Carcass casing materials have become more and more sophisticated over time. That reduces the tyre widening after the fitting.

Furthermore, inflation pressure also plays a major role. With maximum inflation pressure the tire becomes wider than with low pressure. And a recently fitted tire still widens over time. This can make a difference of 1 to 2 mm.

The tyre width is measured at the widest point, i.e. outside the lug.

Will the tyre fit into my frame?

The question whether tyres will fit into a particular frame is often asked in relation to our ultra-wide tyres.

Please bear in mind that with the large number of different bicycle models it is impossible to check the compatibility of all frames and tyres.

The following list shows the exact diameters and widths of our ultra wide tyres. This should allow you to identify if there is sufficient frame clearance for the selected tyre.

 

 

 

 

 

Inches Size Tyre Maximum
width



(A)
Maximum
diameter



(B)
Bead seat
diameter with
maximum width
(C)

24"

60-507 Crazy Bob 61 631 570

26"

60-559 Big Apple 58 683 625
    Big Ben 60 689 628
    Crazy Bob 64 685 629
    Dirty Dan 65 694 623
    Fat Frank 61 687 630
    Hans Dampf 60 684 621
    Ice Spiker/Ice Spiker Pro 60 686 615
    Magic Mary 60 687 621
    Nobby Nic 60 686 624
    Rock Razor 60 683 620
    Rocket Ron 60 687 628
    Space 63 693 621
    Super Moto 58 684 624
  65-559 Magic Mary 67 701 636

27,5"

60-584 Dirty Dan 66 714 649
    Hans Dampf 63 710 645
    Magic Mary 62 713 641
    Nobby Nic 62 712 648
    Rock Razor 61 708 637
  65-584 Magic Mary 67 720 695
    Nobby Nic 68 719 691
    Rock Razor 67 713 690
    Ice Spiker Pro 69 724 697
  70-584 Magic Mary 72 727 697
    Nobby Nic 72 723 692
  75-584 Nobby Nic 77 732 694

28"

50-622 Big Apple 48 722 670
    Big Apple Plus 51 729 677
  55-622 Big Apple 55 741 688
    Big Ben 57 744 688
    Marathon Almotion 55 744 687
  60-622 Big Apple 59 750 691

29"

  Hans Dampf 62 749 684
    Magic Mary 61 751 678
    Nobby Nic 59 751 687
    Racing Ralph 59 747 686
    Super Moto 59 750 691
  65-622 Nobby Nic 64 754 726
Which tyre fits which rim?

The inner diameter of the tyre must match the rim bead seat diameter. For instance, a tyre size 37-622 fits on a 622 x 19C rim.

Furthermore, the tyre width must match the rim width. The following table shows possible combinations of tyre widths and rim widths according to ETRTO.

There are many additional combinations which are not listed in this table, but nevertheless, work out in practice very well. It goes without saying that you ride with these combinations at your own risk. Unfortunately, the ETRTO standard in reality often lags behind. For example, very wide rims become more and more popular these days. The usage of wider rims also makes sense, because they support the tyre’s stability. You can reduce the inflation pressure, before the riding behavior becomes spongy.

 

Possible combinations of tyre width and rim width (crotchet type rim) according to the ETRTO

 

Tyre width in mm Tyre width in mm Rim width in mm (crotchet type rim)
13C 15C 17C 19C 21C 23C 25C 27C 29C 30C 35C 40C 45C 50C 65C 70C 75C 80C 85C 90C 100C
18 X                                        
20 X                                        
23 X X                                      
25 X X X                                    
28   X X X                                  
32   X X X                                  
35     X X X                                
37     X X X X                              
40     X X X X                              
42     X X X X X                            
44     X X X X X                            
47     X X X X X X                          
50     X X X X X X                          
52     X X X X X X X                        
54       X X X X X X                        
57       X X X X X X                        
60       X X X X X X X X                    
62       X X X X X X X X                    
65                   X X X                  
70                   X X X X X              
75                   X X X X X              
100                             X X X X      
110                                 X X X X  
120                                   X X X X

Blue marked combinations are recommended by SCHWALBE.

What is the exact circumference of my tyre?

In order to accurately program a bicycle computer, it is generally necessary to enter the exact tyre circumference.

The tyre circumference varies depending on the rim, the inflation pressure and the load on the tyre. For these reasons, it is not possible to list an exact tyre circumference. In order to accurately program a bicycle computer, we recommend a simple rolling test with the rider on the bicycle.

 

 

 

 

 

 

 

 

 

 

Inch ETRTO Approximate Tyre
circumference

16"

50-305 1265 mm
  35-349 1315 mm
  37-349 1330 mm

18"

40-355 1380 mm
  50-355 1440 mm

20"

23-406 1420 mm
  28-406 1450 mm
  35-406 1510 mm
  40-406 1540 mm
  47-406 1580 mm
  50-406 1600 mm
  54-406 1620 mm

24"

47-507 1900 mm
  50-507 1910 mm
  54-507 1930 mm

24"

57-507 1955 mm
  60-507 1980 mm

26"

35-559 1990 mm
  40-559 2030 mm
  47-559 2050 mm
  50-559 2075 mm
  54-559 2100 mm
  57-559 2120 mm
  60-559 2160 mm
  37-590 2100 mm
Inch ETRTO Approximate Tyre
circumference

27"

32-630 2200 mm

27,5"

54-584 2195 mm
  57-584 2215 mm
  60-584 2240 mm

28"

20-622 2100 mm

28"

23-622 2125 mm
  25-622 2135 mm
  28-622 2150 mm
  30-622 2160 mm
  32-622 2170 mm
  35-622 2185 mm
  37-622 2200 mm
  40-622 2220 mm
  42-622 2230 mm
  47-622 2250 mm
  50-622 2280 mm
  40-635 2250 mm

29"

54-622 2310 mm
  57-622 2330 mm
  60-622 2340 mm

The approximate tyre circumferences for the most common sizes are listed in the table below.