Tire Dimensions




What is the exact circumference of my tire?

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

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

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

Inch ETRTO Approx. Tire Circumference
16" 50-305 1265 mm
  35-349 1325 mm
  37-349 1330 mm
18" 40-355 1380 mm
  50-355 1440 mm
20" 35-406 1510 mm
  40-406 1540 mm
  47-406 1580 mm
  50-406 1600 mm
  54-406 1620 mm
  60-406 1650 mm
24" 47-507 1900 mm
  50-507 1910 mm
  54-507 1930 mm
  57-507 1955 mm
  60-507 1980 mm
  62-507 1995 mm
26" 25-559 1950 mm
  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
28" 20-622 2100 mm
  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
  47-622 2250 mm
  50-622 2280 mm
  54-622 2295 mm
  60-622 2330 mm
  32-630 2220 mm
  40-635 2250 mm





Why is it that tires are often actually narrower than the ETRTO tire section width?

Standard tire widths are calculated using fairly wide, standard rims. Yet in practice, narrower rims are used more often, which in turn leads to tires becoming slightly narrower as well.

In order to ensure that tires 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 tire widening after the fitting. In order to correct this tire widening, over the past few years slightly wider carcasses have been used, so that the actual widths are now much closer to the standard widths.




Will the tire fit my frame?

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

It is easy to appreciate that with the large number of different bicycle models it is impossible to check the compatibility of all framesand tires.

The following list shows the exact diameters and widths of our ultrawide tires. This should allow you to identify if there is sufficient frame clearance for the selected tire.

Image
A = max. width
B = max. diameter
C = diameter at max. width

Inch Tire
Maximum width
Maximum diameter
Diameter at maximum width
20"
Big Apple
60-406
60 mm
529 mm
469 mm
26"
Al Mighty
60-559
60 mm
684 mm
670 mm
 
Al Mighty
60-559
65 mm
693 mm
673 mm
 
Big Apple
60-559
60 mm
683 mm
616 mm
 
Big Betty
62-559
61 mm
690 mm
668 mm
 
Crazy Bob
60-559
61 mm
681 mm
625 mm
 
Fat Albert
60-559
59 mm
688 mm
664 mm
 
Fat Frank
60-559
60 mm
690 mm
664 mm
 

Racing Ralph
62-559

59 mm
687 mm
660 mm
 
Space
60-559
59 mm
682 mm
677 mm
29"
Big Apple
50-622
49 mm
727 mm
676 mm
 
Big Apple
60-622
60 mm
745 mm
678 mm
 
Little Albert
54-622
56 mm
741 mm
735 mm
 
Marathon Supreme
50-622
49 mm
725 mm
676 mm
 
Marathon XR
50-622
49 mm
725 mm
701 mm






Which tire fits which rim?

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

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

Since 2006, the combination of extra wide tires and narrow 17C and 19C rims is officially approved by ETRTO. This just caught up with reality, because this combination has already been an every day occurance in MTBs and Balloonbikes for many years and has not caused any problems.

Often the use of a wider rim is useful because it brings additional stability to the tire. The tire pressure can be reduced slightly before the stability becomes “spongy”.


European Tire and Rim Technical Organization Standards Manual - 2007

Tire section width
Rim width
(mm)
18
20
23
25
28
32
35
37
40
44
47
50
54
57
60
62
13c
x
x
x
x
15c
x
x
x
x
17c
x
x
x
x
x
x
x
x
x
19c
x
x
x
x
x
x
x
x
x
x
x
x
21c
x
x
x
x
x
x
x
x
x
x
23c
x
x
x
x
x
x
x
x
x
25c
x
x
x
x
x
x
x
27c
x
x
x
x
x
x
29c
x
x
x
x






Can I use a narrower rim?

Wide tires are often fitted on narrower rims, as with Mountain Bikes, and also our BIG-APPLE tire. This saves weight, but it is also because very few wide rims are actually available in the market.

The rim manufacturer should be consulted before such fitment and only if they judge it safe. In order to prevent excessive stress on the rim, we advise not to inflate the tire to maximum pressure.

As a general guide, MTB tires of say 54 mm width fitted on standard 17C and 19C rims should not be inflated to more than 55 psi. Very wide tires of ca. 60mm fitted on narrow rims should not be inflated to more than 45 psi. Under no circumstances should rims of less than 17 mm be used.

Tire width
Rim according to ETRTO
Recommended max. pressure with narrow rims (17C/19C)
54 mm
21C
55 psi
57 mm
21C
50 psi
60 mm
21C
45 psi