Fuel Economy (Rolling Resistance):

5 categories – A through E, with a rating arrow pointing to the level for the particular tire. Note the multiple colors to help distinguish the grades from each other.

The test is ISO 28580. It’s a single point lab test. It covers all three of the types of tires covered by the regulation. Here’s a link to the test method:

ISO-28580-2009.pdf (The first 8 pages!)

There is a separate procedure utilizing the SRTT (Standard Reference Test Tire) to account for differences between test locations.

Please note that other countries utilize the same rating system in their regulations, although they might use stars, leafs, or numbers instead of letters!

There are grades for 3 kinds of tires:

• C1 = Passenger Car tires
• C2 = Van tires (the European equivalent of LT tires) They sometimes refer to these as Light Duty Commercial tires.
• C3 = Truck/Bus Tires. They sometimes refer to these as Heavy Duty Commercial tires – although, some in the tire industry use the term “Medium Truck tires”. (Heavy Trucks would be those too large to be legally used on highways in the US without special permits – but not big enough to be called Mining Trucks).

The standards are to the right (below).

Please note that RRC = Rolling Resistance Coefficient = RRF (Rolling Resistance Force) _÷ (divided by) the test load.

The test yields a force value (RRF), while RRC has to be calculated. The units are Newtons/kiloNewton. The unit for force is named for Issac Newton.

Wet Grip:

5 categories – A through E, with a rating arrow pointing to the level for the particular tire. Note that the colors are all different shades of blue.

The test is ISO 23671. It’s an on-vehicle ABS braking test, testing the stopping distance from 80 kph (50 mph) to 20 kph (12 mph). The reason for 20 kph (12 kph), rather than zero is to avoid some of the weird things ABS systems do at these low speeds! The test is conducted on asphalt with specific characteristics.

Here’s a link to the test method:

ISO 23671:2021 – ISO 23671:2021 (The first 10 pages!)

Please note that there is a version of this test involving the use of a traction trailer.

Also please note that you will find some places on the internet that say the low speed is 5 kph (3 mph), but that is incorrect. The test method calls for 80 to 20 kph! (Which is why I provided a link to the test method!)

The test speeds are such that the effects of hydroplaning are small even for deep water. But the water depth = 1.5mm (0.06″, slightly less than 1/16″). In other words, wet, but well below where hydroplaning takes place!

The test utilizes the SRTT (Standard Reference Test Tire) to account for differences between test locations and test conditions (like the weather).

To the right (below) are the actual grades according to the Wet Grip Index, G.

Please note that the California Energy Commission is proposing that all Passenger Car tires sold in California have at least a G index of 1.00 – which place the worst tires in the lowest class. The effective date of their proposal is January 1, 2028. January 1, 2029.

It is unclear how these grades apply to C2 (Van tires) and C3 tires (Truck/Bus) because of reference to the 16″ SRTT. There are other SRTT’s which would be more appropriate for C2 and C3 tires.

Please note that the index is 25% less than the SRTT for passenger car (C1) tires. I suspect they did that so that the Index would always be greater than 1.00 for passenger car tires. That also means the 16″ SRTT is a Grade C!

Another way to look at the Wet Grip Grades!

Sometimes the wet grip grades are indicated by the longer stopping distances for the lower grades. I suppose this helps consumers understand, but the engineer in me doesn’t like this.

Nevertheless, here it is:

Noise:

3 categories – A through C. The actual rating is bolded (and larger) below the speaker icon. The actual value is indicated inside the speaker icon (“XY” in the diagram to the left (above). Interestingly, this is the only rating where the value is displayed.

BTW, dB is the abbreviation for decibels. It’s a logarithmic scale with a rating of 2 being 10 times as strong as a rating of 1, but the way an ear perceives this, a “2” is twice as loud as a “1”. Normal tire noise levels are around 70 dB.

Also, there are weighting systems for describing sound. “A” is weighted the way humans perceive sound – meaning humans don’t hear very high or very low frequencies. This is usually expressed as dB(A) or dBA

Decibel = one tenth of a Bel – named after Alexander Graham Bell.

The test is a vehicle (engine off) pass-by noise test conducted on asphalt at 80 kph (50 mph) for C1 and C2 tires, and 70 kph (43 mph) for C3 tires. The test surface has specifications that are too involved to describe here, but it’s a form of what we normally call asphalt.

Please note that this test doesn’t define how noisy the tire will be INSIDE the vehicle! That’s because the vehicle could have a lot of insulation.

This is a link to a test method, but this one appears to have limits, not grades! . R117rev.2E

Snow Traction:

If the tire meets the minimum snow traction level, the use of the symbol to the left (above) is permitted. I like to refer to this symbol as the Alpine symbol, but it is commonly known as the 3PMSF (3 Peak Mountain Snow Flake) symbol.

If the symbol isn’t displayed on the label, the tire likely doesn’t meet the EU criteria. Please note, the use of the symbol is voluntary, so it is possible that some tires that COULD meet the criteria might not display the symbol.

The EU version of the test is an on-vehicle braking test – 25 kph to 10 kph (15 to 6 mph). The acceptance criteria is 107% of the 16″ SRTT.

The North American version is an on-vehicle acceleration test, conducted at 8 kph (5 mph). The acceptance level in North America is 110% of the 14″ SRTT and 112% of the 16″ SRTT. This makes the North American version a bit more stringent than the EU version.

It is unclear how C2 (Van tires) and C3 tires (Truck/Bus) are evaluated due to the different SRTT’s used.

Please note that the symbol, the limits, and the test were designed to define what a “Winter” tire is, but some “All Season” tires can pass the test and are sometimes labeled as “All Weather”. Also some “All Terrain” tires also meet the limits, but have no special designation.

Ice Grip:

To the right (below) is the Ice Grip symbol. I like to call it the Nordic symbol as tires that pass this test as more suitable for Nordic countries – as opposed to those countries near the Alps (Alpine).

To qualify, the tire must get 118% of the 16″ SRTT on a smooth ice surface- indoor or outdoor. It is an on-vehicle ABS braking test. Test speed is not specified. The comparison is in deceleration rate.

It is unclear how C2 (Van tires) and C3 tires (Truck/Bus) are evaluated. Best guess is that it hasn’t been established yet (at the time of this article.)

This version of the regulation includes a QR code in the upper right hand corner of the label. That should link to a complete listing of the tire in EPREL – the EU site for all the ratings.