Author Topic: Motorcycle Tire Size Designation and Conversion, Tire Speed and Load Ratings  (Read 3221 times)

smallengineshop

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Sometimes buying tires and tubes can be confusing. The confusion arises from there being several different ways to represent tire sizes, tire load ratings and tire speed ratings. I often times use the metric tire size to replace the tires on my KLR, but than use the inch size to buy tubes for the same tire. Knowing how to convert between the two is helpful when buying tires and tubes. You can use the charts below for this, or a factor number and formula for converting between metric and inch tire widths. Here is the number and formula:

MW = Metric Width
IW = Inch Width

IW(25.4) = MW or MW/25.4 = IW

For example, the rear tire on my KLR has a metric size of 130/80-17, but tube manufacturers will often display their tube sizes using inch units. 130 in 130/80-17 is the tire width in millimeters. To convert 130 mm to inches I simply plug 130 into the formula, which gives me: 130/25.4 = 5.11, so the closest tube size of 5.10-17 is a good fitting tube for my 130/80-17 tire size. (The number 17 is the rim diameter in inches. The rim diameter is displayed in inches in both the metric and inch tire size.)

Metric Tire Designation:


Inches Tire Designation:


Alphanumeric Tire Designation:


  • Aspect ratio is a percent number, which defines the height of the tire and says the height is a percent of the tire width. For example a 130/80-17 tire size has an aspect ratio of 80. This means the height of the tire is equal to 80%(130mm tire width) = 104mm
  • Load Rating is the maximum weight a tire can carry.
  • Speed Rating is the maximum speed a tire can go carrying the maximum load.


Street Front Tire Size Conversion Chart

Metric     Alphanumeric     Inch
80/90     MH     2.50/2.75
90/90     MJ90     2.75/3.00
100/90     MM90     3.25/3.50
110/90     MN90     3.75/4.00
120/80     N/A     4.25/4.50
120/90     MR90     4.25/4.50
130/90     MT90     5.00/5.10


Street Rear Tire Size Conversion Chart

Metric     Alphanumeric     Inch
110/90     MP85     4.50/4.75
120/90     MR90     4.50/4.75
130/80     N/A     5.00/5.10
130/90     MT90     5.00/5.10
140/80     N/A     5.50/6.00
140/90     MU90     5.50/6.00
150/80     MV85     6.00/6.25
150/90     MV85     6.00/6.25


Off Road Front Tire Size Conversion Chart

Metric     Alphanumeric     Inch
60/100     90/80     2.50/2.75
70/100     90/90     2.75/3.00
80/100     100/80     3.00/3.25


Off Road Rear Tire Size Conversion Chart

Metric     Alphanumeric     Inch
80/100     80/90     2.50/3.60
90/100     110/90     3.60/4.10
100/100     120/80     4.00/4.10
110/100     130/80     4.00/4.50
120/100     140/80     5.00/5.10


Tire Speed Ratings (New Style)

Speed Rating     Maximum Speed (MPH)
J     62
K     68
L     75
M     81
P     93
Q     99
R     106
S     112
T     118
U     124
H     130
V     149
W     168
Y     186


Tire Speed Ratings (Old Style)

Speed Rating     Maximum Speed (MPH)
J     62
N     87
P     94
S     112
H     130
V     149
Z     149+

Motorcycle Tire Load Index

Load Index     Kilograms     Pounds
43     155     342
44     160     353
45     165     364
46     170     375
47     175     386
48     180     397
49     185     408
50     190     419
51     195     430
52     200     441
53     206     454
54     212     467
55     218     481
56     224     494
57     230     507
58     236     520
59     243     536
60     250     531
61     257     567
62     265     584
63     272     600
64     280     617
65     290     639
66     300     661
67     307     677
68     315     694
69     325     716
70     335     739
71     345     761
72     355     783
73     365     805
74     375     827
75     387     853
76     400     882
77     412     908
78     425     937
79     437     963
80     450     992
81     462     1019
82     475     1047
83     487     1074
84     500     1102
85     515     1135
86     530     1168
87     545     1201
88     560     1235
89     580     1279
90     600     1323
« Last Edit: July 07, 2017, 02:44:26 PM by adminjoe »
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