Motorcycle Tire Sizing and Designations

- Chief

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EXAMPLE 1:

In the above graphic tire size is 120/70 zr 17.

Section Width = tire width in millimeters - 120 mm.

Aspect Ratio - This indicates the ratio between the tire's width and height. In this case, the height of the tire is 70% of its width or 84mm.

Rim Diameter - in this case 17 inches.

Speed Rating - in this case the speed rating is Z which is equal to a speed rating of over 149mph.

Construction - R = Radial

EXAMPLE 2:

130/90-16 67H

130 = width in mm.

90 = aspect ratio of 90% of width = 117mm

16 = Rim size of 16 inches

67 = Load rating (A numerical code which corresponds to the total load carrying capacity at the speed indicated by the speed symbol)
H = Speed rating (see chart)

EXAMPLE 3:

MT90-16B

M = Motorcycle

T = Tire Width Code

90 = Aspect Ratio

16 = Rim Size

B = Load Range

 

 

SIZE CONVERSION:

FRONT TIRES			REAR TIRES
METRIC	ALPHA	INCH	METRIC	ALPHA	INCH
80/90	MH90	2.50/2.75	110/90	MN90	3.75/4.25
90/90	MJ90	2.75/3.00	120/80	MP85	4.50/4.75
100/90	MM90	3.25/3.50	120/90	MP85	4.50/4.75
110/90	MM90	3.75/4.00	130/80	----	5.00/5.10
120/80	-------	4.25/4.50	130/90	MT90	5.00/5.10
120/90	MR90	4.25/4.50	140/80	-----	5.50/6.00
130/90	MT90	5.00/5.10	140/90	MU90	5.50/6.00
			150/80	MV85	6.00/6.25
			150/90	MV85	6.00/6.25
SPEED
RATING		MPH		KM/H
Q		99		160
S		112		180
T		116		190
U		124		200
H		130		210
V		149		240
W		168		270
Y		186		300
Z		Over 149 mph		Over 240 km/h

 

LOAD AND PRESSURE

Load index may be expressed either as a numerical code or a letter code. Most of the time manufacturers will provide the max load information on the sidewall so there's no confusion.

In this instance the maximum load is 520 lbs. This is the weight the tire is capable of handling when it is properly inflated.

 

PRESSURE:

The maximum tire pressure is indicated. But you should only fill a tire to the MOTORCYCLE manufacturer's recommended level. Overfilling can lead to premature wear and poor handling. Also measure the pressure when the tire is cold. Measuring when hot will skew the numbers.

Most tire manufacturer's have websites which will provide information on the recommended pressure for each motorcycle. You can also check your owner's manual or contact a local dealer.

 

TIRE CALCULATION:

Tire Diameter =

(Section Width X Aspect Ratio X 2 / 25.4)+ Rim Diameter

Ex. 130/70 R18

130 x .7 x 2 = 182 / 25.4 = 7.165 + 18 = 25.16 inches

 

TREAD WEAR AND MFG DATE:

Tires will also have a USDOT id and will indicate the week and year of manufacture. (See above). Prior to 2000 there were only three digits with the last on being the year.

Some tires may have raised triangles, or the letters TWI, to show where the tire wear indicators are in the tread. When these marks are equal to the tread, it's time for new tires.Additionally the sidewall may also include "tubeless" or TL, "tube type" or TT, and the tire composition, materials, ply etc.

 

Tire links:

Avon
www.avontyres.com/
Bridgestone
www.bridgestone-usa.com/
Cheng Shin
chengshintires.com/index2.html
Continental 
www.conti-online.com
Dunlop 
www.dunlopmotorcycle.com/
IRC Tire 
www.ircthailand.com/products/rubber.html
Kenda
www.kendausa.com
Maxxis 
www.maxxis.com/
Metzeler
www.us.metzelermoto.com
Michelin 
motous.webmichelin.com/
Pirelli
www.us.pirellimoto.com

 

 

Pictures Courtesy of AMA.