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Tires 101: An Introduction: Difference between revisions

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====Metric sizing====
====Metric sizing====


This is the most common designation for tires. This is the one that reads "120/80V-16". It breaks down as follows:  
This is currently the most common designation for tires. It breaks down as follows:  


120/80V-16:  
120/80V-16:  


*The "120" is the nominal width of the tire, in millimeters.  
*"120" is the nominal width of the tire, in millimeters.  
*The "80" is the aspect ratio, expressed as a percentage of the width.  
*"80" is the aspect ratio, expressed as a percentage of the width.  
*The "V" is the speed rating for the tire.  
*"V" is the speed rating for the tire.  
*The "16" is the diameter of the wheel that the tire is constructed for.  
*"16" is the diameter of the wheel that the tire is constructed for.  


So, we can look at a tire and read a little bit of the code. But how do the numbers interrelate? Here's the scoop:
So, we can look at a tire and read a little bit of the code. But how do the numbers interrelate?


The nominal width is approximately how wide the tire is at the widest part of the tread. In this case, the width is about 120 mm. There is some variance from tire maker to tire maker, and from brand to brand, so one tire may be 124 mm wide, while another may be 118 mm.  
*The nominal width is approximately how wide the tire is at the widest part of the tread. In this case, the width is about 120 mm. There is some variance from tire maker to tire maker, and from brand to brand, so one tire may be 124 mm wide while another is 118 mm.  


The aspect ratio is approximately how tall the tire is in relationship to its width. Thus, a 120/80 tire is about 95 mm tall, from the bead to the tread surface.  
The aspect ratio is approximately how tall the tire is in relationship to its width. Thus, a 120/80 tire is about 96 mm tall, from the bead to the tread surface (120 x 0.8 = 96). [[Ride height and different tire sizes|See here]] for more information on tire height.


The speed rating indicates at what maximum speed the tire is considered safe for continuous use. In this instance, the V stands for speeds up to 149 mph. A table of speed ratings is listed below.  
The speed rating indicates at what maximum speed the tire is considered safe for continuous use. In this instance, the V stands for speeds up to 149 mph. A table of speed ratings is listed below.  
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====American sizing====
====American sizing====


The second example above reads "4.50H-16". This is the so called American system, and reads as follows:  
The second example above reads "4.50H-16". This is the so-called American system and reads as follows:  


4.50H-16:  
4.50H-16:  


*4.50 is the nominal width of the tire in inches. In this case, about 4.5 inches, or about 120 mm.  
*"4.50" is the nominal width of the tire in inches. So, about 4.5 inches, or 120 mm.  
*H -- The speed rating, in this case indicating a tire safe up to 130 mph.  
*"H" is the speed rating, in this case indicating a tire safe up to 130 mph.  
*16 -- This tire is intended for a 16 inch rim.  
*"16" says that this tire is intended for a 16 inch rim.  


The American system is a little quirky when it comes to aspect ratio. Generally, a tire is a high profile tire, with about a 90% aspect ratio, unless the width is indicated with a ".10" or ".60" designation. This indicates a lower profile tire, on the order of 75-85 percent. Thus, a 4.5 inch tire with an 85 percent aspect ration would be shown as a 4.60. A 4.0 inch low profile tire would be a 4.10.  
The American system is a little quirky when it comes to aspect ratio. Generally, the tire is a high profile tire, with about a 90% aspect ratio, unless the width is indicated with a ".10" or ".60" designation. This indicates a lower profile tire, on the order of 75-85 percent. Thus, a 4.5 inch tire with an 85 percent aspect ratio would be shown as a 4.60. A 4.0 inch low profile tire would be a 4.10.  


====British sizing====
====British sizing====


The last method of tire designation is the British system, which we showed above as "MR80S-16". This breaks down like so:  
The last method of tire designation is the British system, which we showed above as "MR80H-16". This breaks down like so:  


MR80S-16:  
MR80H-16:  


*MR is a letter code indicating the width of the tire. In this instance, MR indicates a 120mm tire.  
*"MR" is a letter code indicating the width of the tire. In this instance, MR indicates a 120mm tire.  
*80 is the aspect ratio, expressed as a percentage of the width.  
*"80" is the aspect ratio, expressed as a percentage of the width.  
*H is the speed rating, once again for 130mph sustained running.  
*"H" is the speed rating, once again for 130mph sustained running.  
*16 is the diameter of the wheel that this tire is intended for.  
*"16" is the diameter of the wheel that this tire is intended for.  


Since the British system uses an alpha code for the tire width, a table is included below to indicate what metric and American widths are included. The table also includes the recommended rim widths for those tire widths.
Since the British system uses an alpha code for the tire width, a table is included below to indicate what metric and American widths are included. The table also includes the recommended rim widths for those tire widths.
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