Tyre Load and Speed Indexes
Tyre Load Index
Some tyre sizes have an index with XL appended, which donates Extra Load capacity for SUV and like type of vehicles. PLEASE SCROLL DOWN for a comprehensive explanation of SIDEWALL TYRE NUMBERS & MARKINGS.
The load index symbol, which is found on the side-wall of each tyre, is relevant to the carrying capacity of each tyre on the vehicle, and is measured at correct cold pressure or inflation.
The European Tyre and Rim Technical Organisation Standard.
|LOAD INDEX||KG PER TYRE||LOAD INDEX||KG PER TYRE||LOAD INDEX||KG PER TYRE||LOAD INDEX||KG PER TYRE|
Tyre Speed Index
The KM/H is measured at sustained maximum speed.
|SPEED SYMBOL||SPEED (KM/H)|
|Z & ZR||240+|
How to read sidewall tyre numbers and markings.
The sidewall of your tyres is filled with important information that tells you everything you need to know about your tyre. The numbers can be a bit overwhelming to the untrained eye, so the best way to understand tire markings is to take an example and break it down, bit by bit. Below are tips and information to help you learn how to read tyre size and other tyre markings commonly seen worldwide including South Africa.
A tyre size is 185/60 R14. The 185 represents its section width. The number "60" indicates the tyre’s aspect ratio. The last number, "14" indicates wheel diameter.
Tyre Section Width
The tyre numbers in the above example tell us that the tyre is 185 millimeters wide. The first number in this series refers to the tyre's section width, or distance from sidewall edge to sidewall edge (in millimeters) when measured up and over the tyre's tread. Generally speaking, the larger this number is, the wider the tyre will be.
Aspect Ratio is the ratio of the sidewall height to the section width. The sidewall height of the example tyre above is 60% of its section width.This number can be very indicative of a tyre's purpose. Lower numbers, like 55 or less, mean a short sidewall for improved steering response and better overall handling.
(R) Internal Construction
The "R" refers to radial construction, which has been the industry standard in passenger-car tyres for more than 20 years. Prior to radial tyres, most cars came with bias-ply tyres or X-ply tyres, which had a crude construction that made for poor handling. Bias-ply tyres (which use a "B" for their description) are still used for certain truck applications.
Rim or Wheel Diameter
Wheel Diameter specifies the size, in inches, of the wheel that a tyre fits. The example tyre will only fit a 14-inch wheel
Pay particular attention to this number if you plan on upgrading your wheel size. If your wheel diameter changes, you'll have to purchase a new set of tyres that matches this new diameter.
Other Tyre Markings
(82) Load Index
A tyre's load index is a measurement of how much weight each tyre is designed to support. The larger the number, the higher the load capacity. This is one of the most important numbers on your tyre. To find out what "82" means, it must be looked up on a Load-Carrying Capacity Per Tire chart above. Remember that this is per tyre, which means you have to multiply by four to get the total capacity for a complete set of tyres. If the vehicle has its original tyres, you can just refer to the doorjamb, which lists the maximum cargo capacity with passengers.
Some vehicles are equipped with "XL" tyres. No, it doesn't mean that they're extra large, but it does mean that they are extra-load tyres. The load index on these tyres is much higher than a standard-load tyre — which is why it is important to replace an XL tyre with another XL tyre.
Remember "P-metric" and "Euro-metric sizing"? Their difference in load rating can lead to confusion and potential trouble. For a given size, P-metric tyres will have a load index that is one or two points lower than corresponding Euro-metric tyres. So if your car came with Euro-metric tyres, don't replace them with P-metric tyres. You can, however, replace P-metric tyres with equivalent-size Euro-metric ones because you gain load capacity that way.
Why is this important? Generally speaking, you don't want your replacement tyres to have a lower load index number than the originals (as indicated by the driver's doorjamb or the owner's manual), particularly with high-capacity vehicles that ride on smallish tyres, such as minivans.
Also, and contrary to popular perception, optional large-diameter wheels with lower-profile tyres tend to have less load-carrying capacity because they contain less air. And it is the volume of air inside the tyre, not the rubber itself or the wheel material that carries the load.
The load index is especially important when shopping for a tyre online, since many retailers do not specify whether a tyre is P-metric or not.
(H) Speed Rating
The speed rating is a measurement of the speed at which the tyre is designed to run for extended periods. An "H" speed rating signifies that this tyre can be run safely at speeds of up to 210 kph for extended periods. Will it explode if it goes to 220? No, not immediately. But it might if it is run at that speed for an extended time.
Listed above is a complete list of the various tyre speed ratings, and their associated letters.The "Z" rating used to be the highest rating for tyres having a maximum speed capability greater than 240 kph, but as tyre technology improved, it is was ultimately split into the "W" and "Y" rating. A "ZR" may sometimes appear in the size designation, as a sort of nod to the prior rating, but it will also be used in conjunction with a W or a Y.
The DOT code is used by the Department of Transportation (DOT) to track tyre production for recall purposes. If a tyre proves to be defective, this number helps keep track of where these tyres ended up so that buyers can be notified of the problem. At the end of the DOT code you'll find a four-digit number. This is the manufacturing date of the tyre. The first two digits stand for the week; the other two are the year. For example, if your tyre had "1610" listed, it was manufactured on the 16th week of 2010.
If you come across a three-digit number, you have a tyre that was manufactured before 2000. A DOT tyre code of "127" indicates the tire was made on the 12th week of the seventh year of the decade. But it's difficult to know whether that was 1997 or even 1987. According to official sources, some tyres produced in the 1990's may have a small triangle following the DOT number to identify the decade. But any tyre that has a three-digit code is history. Tyre experts recommend that tyres that are six or more years old be replaced, regardless of tread depth.
Sometimes the DOT number will be located on the inside of the tyre. In this case, you can either jack up the car to inspect it, or check with your local mechanic or tyre shop. You should also make a habit of checking the manufacturing date on your spare tyre as well.
Maximum Air Pressure
This number refers to the maximum amount of air you can put in a tyre before you harm it. It is not the recommended tyre pressure; that number can be found in your owner's manual and on the doorjamb. Remember that all tyre pressure readings are based on cold temperature and NOT whilst tyre is hot.
A traction rating can also be found on the sidewall of all modern tyres. It can be represented as AA, A, B or C. This is a rating of a tyre's traction when tested for straight-line braking on a wet surface. For this rating, AA signifies the best traction performance and C indicates the worst.
The temperature rating refers to the ability of the tyre to withstand heat under high speeds. The ratings, from best to worst, are: A, B and C.
Finally, you might find the word "TREADWEAR" on the sidewall followed by a number like 120 or 180. This is a rating of the tread's durability, as tested against an industry standard. The reference number is 100, so a tire with a treadwear rating of 200 has an 80 percent longer predicted tread life, while a rating of 80 means a predicted tread life only 80 percent as long as the industry standard.
In addition to all of the above, here is a comprehensive list of other markings you can find on your sidewall.
- "Star": Original tyres for BMW
- A/S: All-season tyre
- A/T: All-terrain tyre
- B: Bias construction, typically for motorcycles.
- C: Commercial / passenger car tyre
- BSW: Black SideWall
- C: Commercial; tyres for light trucks. Similar to LT (below)
- E4: Tyre approved according to ECE-regulations. See The E Mark below.
- EL: Extra Load; tyre for vehicles of heavier standard weights
- FR: Flange Rib - the area above the bead of the tyre that acts as a protection for the outer lip of your alloy wheel against light contact with kerbs etc.
- H/T: Highway/terrain tyre. For SUVs and 4x4s - less aggressive than full off road tyres - design for some use on-road
- LT: Light Truck tyres.
- M0: Original tyres for Mercedes-Benz
- M+S, or M&S: Mud and Snow - see car tyre types
- Made in ...: Country of production
- MFS: Max Flange Shield - a rubber ring around the tyre designed to help prevent damaging the wheel flange when close to a kerb
- M/T: Mud/terrain tyre. Similar to A/TN(number): Original tyres for Porsche.
- OWL: Outline White Lettering
- P: Commercial / passenger car tyre
- RB/RBL: Raised Black Lettering
- RF: Reinforced tyres
- RIB: A rubber ring around the tyre designed to help prevent damaging the wheel flange when close to a kerb. Same as MFSRW
- RWL: Raised White Lettering
- SFI, or Inner: Side Facing Inwards; inside of asymmetric tyres.
- SFO, or Outer: Side Facing Outwards; outside of asymmetric tyres.
- SL: Standard Load; tyre for normal usage and loads
- SUV: SUV / 4x4 tyre
- TL: Tubeless
- TT: Tube-type, tyre must be used with an inner-tube
- TWI: Tread Wear Indicator.
- WSW: White SideWall
- XL: Extra Load; tyre for vehicles of heavier standard weights. Same as EL
- Arrows: Denotes rotation direction for directional tread.
In addition (yes, there's more), these are what you'll find on run-flat tyres
- DSST: Dunlop Self Supporting Technology
- EMT: Goodyear Extended Mobility Tyre
- RFT: Bridgestone Run Flat Tyre
- ROF: Run On Flat
- RSC: Runflat System Component
- SSR: Continental Self Supporting Runflat
- ZP: Michelin Zero Pressure
- TPMS: Tyre Pressure Monitoring System