Motorcycle Tires 101
An Essential Guide to Your Motorcycle Tires
Information is a handy thing to have, and this is particularly true when it comes to something as important to your health
as your motorcycles tires. Accordingly, tire manufacturers and the federal government have devised a system that lays out just about everything you
need to know and placed it conveniently on the tire sidewall. The problem is that much of that information is in a sort of
code that needs deciphering before the message means anything. What follows is a guide to doing just that.
It’s important to understand that while the law requires certain information, tire manufacturers have a lot of leeway in the
way that material is formatted. They’re also free to add anything they deem pertinent, or even mildly interesting, so the
amount of information and its placement can vary greatly between manufacturers or even between two similar tires from the
same maker, so don’t be surprised if your tires don’t look exactly like our examples.
Manufacturer’s Name:
This one is self-explanatory, it identifies the tire maker, and lets you know who to thank, or blame, if your tire elicits strong feelings.
Tire Type:
This identifies the particular tire within the manufacturer’s range. It may appear as a name,
for example, Cobra (Avon), Lasertec (Metzeler), or Battlax (Bridgestone),
or as an alpha numeric designation like AM26 (Avon).
If there’s enough room, some tires may include both.
Tire Construction Detail:
The construction detail section describes the internal construction of the tire. Among other things, it’ll list the type of material used to build the tire carcass, and how many plies are used.
It may not mean much to you, but it’s pornography to a tire geek!
Advanced Variable Belt Density:
Remember what I said about the manufacturers being free to add information they thought you might like? Well, this little tidbit is basically advertising.
It refers to the belt that runs throughout the circumference of the tire.
Tire Size Designation:
This one’s a biggie, kids. It tells you the size and profile of your tire, what size rim it fits, and, in most cases,
includes information on the tire’s speed rating and construction, though these will always be listed separately.
Over the years three basic systems have been used: the inch, which is the oldest, and formerly the most popular;
the alpha-numeric, which was a little confusing and never very popular; and the current favorite and all-time most popular, the metric.
While both inch and alpha-numeric systems are still in limited use, primarily among vintage bike enthusiasts,
we’ll pass them by in the interest of brevity and concentrate on the metric system, which has become the standard of the industry.
In our example, the size designation is 170/60ZR17. The first number represents the tire’s nominal width, which is the width of the tire from sidewall to sidewall when the tire is mounted on its rim and properly inflated, but not under load. This is called the section width. In this case it’s 170 millimeters, and no, they never actually print the “MM” on the sidewall. The second number represents the nominal height of the sidewall as measured from the tire bead, where it contacts the rim, to the point where the tread meets the ground.
This is called the aspect ratio. Where it gets tricky is that this second number, 60 in this example isn’t a dimensional measurement but a percentage of the tire’s width. In this case, 60 percent of 170 is 102, meaning we have a tire that’s 170 millimeters wide, and a side wall that is 102 millimeters high.
The Z represents the tire’s speed rating. Let me digress here and point out that unless the tire is Z-rated – meaning it’s good for sustained travel at 150 mph or more – the speed rating isn’t normally included in the size designation label. Manufacturers usually place the Z in the size description when the tire is W- (168 mph) or V- (186 mph) rated to indicate that this version of the tire is intended for high performance use and for bragging rights.
The R tells us that this is a radial tire; if it were missing we could rightly infer that the tire used bias ply construction, and in every case that would be listed somewhere on the tire as well. The 17 means this tire is designed to fit a 17-inch rim. Armed with this information and only this information, you now know enough about your tire’s construction to safely replace it, no matter the circumstances.
Load Index and Speed:
This box will contain a two-digit number followed by a single letter. The number tells you how much weight the tire can bear at its maximum inflation pressure. The letter indicates the maximum speed the tire can handle, also at its maximum pressure. The speed ratings can be a little confusing – as a rule, the higher the letter, the higher the speed, but there are exceptions. H, for example is rated at 130 mph, while an S-rated tire is only good to 112 mph. A fuller description of both load and speed ratings can found on most tire company websites or in their catalogs.
ECE Approval:
This stands for the Economic Commission of Europe and means that they’ve approved the tire.
Tubeless or Tube Type (sometimes “tube type when fitted to a spoked wheel”):
This indicates whether the tire can be used with a tube for spoke wheel applications and/or installed without one when appropriate.
Directional Arrow:
The arrow indicates which way the tire should rotate when the motorcycle is moving forward.
Manufacturing Date Code:
This is another handy piece of information. The date code is a four-digit number that tells you what week and year the tire was built. For example, 1716 means your tire was built during the 17th week of 2016.
DOT Compliance Symbol and DOT ID Number:
These indicate that the tire is both legal to sell in the US and traceable should the DOT need to recall them for any reason.
Maximum Load and Pressure:
This one seems redundant as it repeats information we already have. However, in this case, rather than use a symbol, the maximum load is spelled out in pounds. The maximum pressure setting is always cause for confusion. This number represents the maximum amount of pressure the tire can safely withstand at its maximum load. It is not the recommend tire pressure for normal use.
Most motorcycles will have their stock tire sizes, and appropriate tire pressures on a sticker appearing low on the bike’s frame or swing arm.
Pattern Code:
The manufacturer’s tread pattern code; it’s of academic interest only.
Country of Origin:
If you need to know.
Lastly, there are two indicators missing from the illustration that are sometimes present. The first is the balance mark – a dab of paint that tells the tire installer where the tire’s light spot is; the second is and the wear indicators, which are small triangles, or the letters TWI (tire wear indicator) imprinted at several points around the tire’s circumference. These show you where the tire’s wear indicators are located.
Finally: Please understand that while the foregoing provides you with a guide, and hopefully a better understanding of the type of tire your motorcycle requires, it’s by no means complete. In all cases, either the original equipment manufacturer or the tire builder’s catalog should be consulted when questions concerning tires arise.
Embed the article on your site
