Tyres, rims & wheels 101

In addition to information about date of manufacture and tyre type, the markings applied to the sidewalls include size indicators: ”205/65 R 16 95 V” indicates a tyre width of 205 mm and an aspect ratio of 0.65: 1. The R stands for ”radial design”, 16 indicates the rim diameter in inches, 95 indicates the weight or load index, and V is the speed index.

Fuel efficiency

A measure of the tire’s rolling resistance, which has an impact on your vehicle’s fuel efficiency. Rated from A (highest rating) to G (lowest rating).

Wet grip

A measure of the tire’s braking ability on wet roads. Wet grip is rated from A (highest rating) to F (lowest rating).

Noise

A measure of the external noise generated by the tire, in decibels. The black sound waves indicate the noise class of the tire, from 1 (quiet) to 3 (loud).

The wheel alignment should be checked every 30.000 km and when mounting a new set of tyres.

Normally, different tyre sizes may not be installed on a single axle. The exception is in case of a puncture, when, for example, instead of another wide-base tyre, only a narrow spare tyre or spare wheel for temporary use. Observe the manufacturer's instructions!

These tyres may be used for longer distances without pressure and may be mounted on conventional rims. In any case, a functioning air pressure check system is stipulated.

1. If you get a puncture

Modern tyres are very sturdy and can cope with most things. Punctures, though, can and do still happen. A tyre specialist should check your tyre after a puncture to decide whether it can be repaired.

2. When your tyres worn down to the legal limit of wear

It’s a good idea to check your tyres regularly for tyre wear on their profile. Check for the tread wear indicators situated in each of the main grooves of the tread. These indicators are small raised areas at the bottom of the grooves of the tread pattern.

3. If your tyre shows signs of aging

Tyres have no predictable life. It does’t matter when the tyres were made. Tyres age even when not used, or if only used occasionally.  There are many factors that will affect the life of the tyre such as temperature, maintenance, conditions of storage and use, load, speed, pressure as well as driving style.

4. If your tyre is damaged

Your tyre can be seriously damaged if it impacts any solid object on the road, like a kerb, pothole, or sharp object. Any visible perforation, cut or deformation must be checked thoroughly by a tyre professional.

5. If you identify abnormal wear

Abnormal uneven tyre wear - in patches, in the centre, at the edges - may indicate a mechanical problem like improper wheel alignment, or a problem with wheel balance, suspension or transmission.  It could also be that you're driving with the wrong tyre pressure. If you notice abnormal wear, contact your tyre specialist.

Treadwear

The treadwear grade is a comparative rating based on the wear rate of the tire when tested under controlled conditions on a specified government test track. A tire graded 200 would last twice as long on the government test course under specified test conditions as one graded 100. It is an oversimplification to assume treadwear grades will be proportional directly to your actual tire mileage. The relative performance of tires depends upon the actual conditions of their use and may vary due to driving habits, service practices, differences in road characteristics and climate.

Traction

Traction grades, from highest to lowest, are AA, A, B and C. They represent the tire's ability to stop on wet pavement as measured under controlled conditions on specified government test surfaces of asphalt and concrete. The testing does not take into account cornering, hydroplaning or acceleration. The test tire is installed on an instrumented axle of a traction trailer, which is towed by a truck at 65 kilometers per hour (km/h) over wet asphalt and concrete surfaces.

Temperature

The temperature grades, from highest to lowest, are A, B and C. These represent the tire's resistance to the generation of heat.

If your tires are mounted on rims, stack them underneath a tire cover. (When stacking tires, be sure to stack no more than four tires for safety reasons.)

If you tires are not mounted on rims, store them upright and cover. Do not stack on top of each other or hang from ceiling.

If your tires have whitewall or raised white lettering, store them with the whitewall or raised white lettering facing each other. Otherwise, black rubber could stain them. (The results are not pretty.)

Store tires away from motors, generators, furnaces, sump pumps and switches because they are sources of ozone.

ENWL                                    Extra Narrow White Letters

ROBL                                     Raised Outlined Black Letters

OBL                                        Outlined Black Letters

OGL                                        Outlined Gold Letters

ORBL                                     Outlined Raised Black Letters

ORWL                                    Outlined Raised White Letters

OWL                                       Outlined White Letters

RBL                                        Raised Black Letters

RWL                                       Raised White Letters

RRBL                                     Recessed Raised Black Letters

SBL                                        Serrated Black Letters

SRBL                                      Serrated Raised Black Letters

SOWL                                     Slanted Outlined White Letters

SVSB                                      Slanted Vertical Serrated Band

VSB                                         Vertical Serrated Band

WL                                           White Letters

WS                                           White Stripe

WW                                          White Wall

Tire Class - "P"

The first character(s) in a tire size designate the tire's class. In this example, "P" indicates that the tire is a passenger car tire. An "LT" before the tire size designates a light truck tire, and no letter before the size indicates that it is a European metric tire.

Section Width - "205"

A metric tire's section width is measured in millimeters. This measurement is taken from sidewall to sidewall. In this example, the section width of the tire is 205mm.

Aspect Ratio - "65"

This number refers to the height of the sidewall. It is a percentage of the section width. In this example, 65 percent of the section width of 205mm equals 133.25.

Tire Construction - "R"

The "R" in this example indicates radial tire construction.

Wheel Diameter - "16"

This indicates the wheel diameter in inches.

Load Index - "92"

The load index indicates the maximum amount of weight a tire can safely carry. Load index ranges from 0 to 279 and corresponds with the load-carrying capacity of a tire. Passenger car tire load indices typically range from 75 to 105. It is very important to maintain the proper load index for your vehicle when replacing your tires. See our load index chart for more information.

Speed Rating - "H"

A tire receives its speed rating from the U.S. Government by meeting minimum standards for reaching and sustaining a specified speed. In general, a higher speed rating will result in better vehicle handling. See our speed rating page for more information and a list of the various speed ratings.

Proper wheel balance ensures that the spinning wheels do not have a heavy spot that can cause vibration and premature wear of tires, struts, shocks and other steering and suspension parts.  This is accomplished by placing measured lead weights on the opposite side of the 'heavy spot' (the noticeable tread wear on your unbalanced tire).  Balanced wheels help to ensure a smooth drive.

Some good signs that your wheels are unbalanced are:
- vibration and noise
- erratic wear pattern on tires
- a bouncing wheel rather then a spinning wheel while driving

Top speed for car tyres

SI                     km/h

Q                     160

R                      170

S                      180

T                      190

H                     210

V                      240

W                    270

Y                      300

ZR over           240

Top speed for C tyres (tyres for larger vehicles)

SI                     km/h

K                      110

L                      120

M                     130

N                     140

P                      150

Q                     160

R                      170

S                      180

T                      190

Other advantages:

- Nitrogen reduces the running temperature of the tyre. The moisture content of nitrogen leads to a cooler running tyre, which is advantageous when the car or bike is operating at its maximum load and speed capacity.

- Nitrogen in tyres improves the ride quality. That gas is very slightly lighter than air and thus, benefits the tires in terms of un-sprung weight.

- It is assumed that Nitrogen increases tyre life. It reduces the operating temperature during times of load and speed and thus, enhances the life of a tyre.

- It is believed that nitrogen keeps tyre pressures more constant. The gas is assumed to provide more stable pressure range in connection to the tyre temperature. However, again, the factor is applicable in times of heavy load/high-speed conditions.

- Tyres are susceptible to loss of pressure as a result of being porous in nature. Due to its chemical structure, Nitrogen leak out slowly as compared to compressed air. Therefore, it slows the rate of pressure loss.

- Oxygen reacts with the tyre and rim materials causing oxidation or the rust formation in the metal parts. Nitrogen, being an inert gas, does not react with the tyre and rim materials.

One key process in a proper tire repair is removing a tire from the wheel to inspect any damage that may occur to the inner liner of the tire.

RMA offers tire dealers and automotive repair outlets a detailed wall-chart for proper tire repairs. Among the criteria to perform a proper repair are:

- Repairs are limited to the tread area only

- Puncture injury cannot be greater than 1/4 inch (6mm) in diameter

- Repairs must be performed by removing the tire from the rim/wheel assembly to perform a complete inspection to assess all damage that may be present

- Repairs cannot overlap

- A rubber stem, or plug, must be applied to fill the puncture injury and a patch must be applied to seal the inner liner. A common repair unit is a one-piece unit with a stem and patch portion. A plug by itself is an unacceptable repair

On vehicles with a compact spare, a 4-wheel rotation scheme is required.

On front-wheel and all-wheel drive vehicles, move the front wheels straight back to the rear, and cross the rear wheels from side to side while moving them to the front.

On rear-wheel drive vehicles, move the rear wheels straight forward, and cross the front wheels from side to side while moving them to the rear.

Weight

Aluminum rims weigh less than steel rims. The decreased weight in aluminum rims provides a small boost in fuel economy. The amount of increase in fuel economy is proportional to the weight differential.

Durability

A steel rim is more durable than an aluminum rim. This is because of the extra weight in steel rims and also the way they are forged in the factory.

Construction

Steel wheels are usually stamped while aluminum wheels tend to be machined and cast. Aluminum rims tend to be more uniform than the steel ones, resulting in a more consistent fit.

Options and pricing

Aluminum rims give you more choices when it comes to styling and tend to be more expensive than steel rims. Steel rims tend to be more cost-effective for both stock and aftermarket options.

Considerations

Consider buying aluminum rims if you live in an area with mountains or heavy traffic. Some aluminum rims are designed to encourage better airflow and can reduce heat in the tire.

- Tire / wheel assembly is out of balance
- No hub centric rings on aftermarket wheels  >Buy Hub Centric Rings
- Incorrect mounting hardware for aftermarket wheels
- Tire is poorly seated on the rim
- Irregular tire wear
- Out of round rim
- Out of round tire

Do not ignore apparent impacts, pulling, or vibration. This could be an indicator of tire damage as much as mechanical problems that should be inspected by a professional. If there is a problem with your tires and the way they have been installed they will most likely begin to shake and vibrate your vehicle at between 80 and 100 km/h.