Tyres, rims & wheels 101

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Sidewall information

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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.

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EU tire label

The new EU tire label provides important information about safety and environmental aspects of a tire. Similar to the energy label found on kitchen appliances, the EU tire label makes it easy to compare tires in terms of wet grip, fuel efficiency and noise. Explore the links below to find out more.

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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).


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).

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Wheel alignment

Wheel alignment, sometimes referred to as breaking, is part of standard automobile maintenance that consists of adjusting the angles of the wheels so that they are set to the car maker's specification. The purpose of these adjustments is to reduce tire wear, and to ensure that vehicle travel is straight and true (without "pulling" to one side).

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

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Tyre mixing

Anyone who combines makes, new and used, or summer and winter tyres is putting their life at risk: in extreme cases, uneven reactions of tyres result in uncontrollable handling.

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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!

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Run flat tyres

Run flat tyres, or emergency tyres, are tyres which feature a self-supporting structure. In this case, the chassis is reinforced, the carcass and the belt are modified, the sidewalls and the bead zone are more rigid.

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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.

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When to change tyres

Below, we list five major reasons when you should seriously consider changing your tyres:

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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.

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The UTQG tyre quality classification

The UTQG (Uniform Tire Quality Grading) rating is made up of three components:

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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 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.


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

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Oversized rims

Oversizing the rim and tyre has the purpose of improving one’s car performance and especially looks. It basically consists in mounting bigger rims paired with tyres that have a smaller height/width ratio. It is important to check that after these changes the overall diameter of the wheel is within +/-3% from the original diameter.

Tyre storage

Store your tires in a clean, cool and dark location away from heat or gas. Preferably under a tire cover, which you can purchase at your local tire dealer or auto parts store.

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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.

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Sidewall markings

BCS                                        Black Circumferential Serrations

BL                                           Black letters

BSL                                         Black Serrated Letters

BSB                                        Broken Serrated Band

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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

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Tyre dimensions

Let’s say we have a tyre with the following markings on the sidewall:

P205/65 R16 92H

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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.

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Rim dimensions

Let’s say we have a rim with the following symbols: 5.5 J x 14H2 ET 49


5.5       - rim width in inches

J           - the letter symbolizing the shape of the rim border

x          - one-piece rim

14        - rim diameter in inches

H2       - rim profile

ET49    - 49mm offset

Wheel balancing

Wheel balance refers to the proper distribution of weight around a revolving tire and wheel assembly.  Wheels that are not balanced can impact for the vehicle and your safety.  We recommend that you have your wheels balanced every 10-15,000km.

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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

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Treadwear indicator (TWI)

The profile base of the tread features integrated treadwear indicators, and these form narrow, continuous bars on the profile at 1.6 mm tread depth. Depending on the manufacturer, the position of these bars is at the top of the sidewall and indicated by triangles, the letter combination TWI (Treadwear indicator), or small company trademarks.

Load index

Abbreviated as "LI". The load index is part of the size description of the tyre and provides information about the load-bearing capacity. In order to determine the maximum load per tyre, the identifying number must be indexed with a table. The range for cars extend from LI 50 = 190 kg to LI 124 = 1,600 kg.

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Indice de greutate Sarcina pe anvelopa (kg.) Indice de greutate Sarcina pe anvelopa (kg.) Indice de greutate Sarcina pe anvelopa (kg.)
60 250 96 710  132  2000
61 257 97 730  133  2060
62 265 98 750  134  2120
63  272 99 775  135  2180
64 280 100 800  136 2240
65 290 101 825  137  2300
66 300 102 850  138  2360
67  307 103 875  139  2430
68 315 104 900  140  2500
69  325  105  925  141  2575 
70  335  106 950  142  2650 
71  345  107  975  143  2725 
72  355  108  1000  144  2800 
73  365  109  1030  145  2900 
74 375  110  1060  146  3000 
75  387  111  1090  147  3075 
76  400  112  1120  148  3150 
77  412  113  1150  149  3250
78 425 114 1180 150 3350
79 437 115 1215 151 3450
80 450 116 1250 152 3550
81 462 117 1285 153 3650
82 475 118 1320 154 3750
83 487 119 1360 155 3875
84 500 120 1400 156 4000
85 515 121 1450 157 4125
86 530 122 1500 158 4250
87 545 123 1550 159 4375
88 560 124 1600 160 4500
89 580 125 1650 161 4625
90 600 126 1700 162 4750
91 615 127 1750 163 4875
92 630 128 1800 164 5000
93 650 129 1850 165 5150
94 670 130 1900    
95 690 131 1950  


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Speed index

Also referred to as the speed class, this indicates the maximum speed permitted for a tyre type. The categories are as follows:

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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

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Correct air pressure

The correct air pressure is very important for the mileage and life cycle of tyres as well as for the driving safety. If tyres are underinflated, then this could cause unfavourable pressure distribution and overheating up to danger of the tyre bursting. It also increases rolling resistance, which causes increased fuel consumption. Regular inspections show that only every fourth car is being operated with sufficient air pressure.

Nitrogen-filled tyres

Nitrogen is suitable for filling tyres. The effect is that tyres normally lose pressure at a slower rate, since the diffusion speed of nitrogen is lower compared to normal air. Tyres filled with special tyre gas may also be filled up again with normal air at any time.

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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.

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Tyre tread

The tread has direct contact with the road surface and is responsible for the power transmission together with the other tyre components. It is responsible for acceleration and braking power in the direction of travel and transverse power during steering and in curves. The quality of the tread is significantly determined by the chassis (belt, carcass), bead and sidewall components, and ultimately by the design of the profile on the tread.

Tyre repair

Knowing the difference between a proper tire repair and an improper tire repair could be critical to vehicle safety. A tire industry study showed that nearly 88 percent of the tire repairs are performed improperly. An improper tire repair could pose a safety hazard to you and your family and could also affect a tire manufacturer's warranty.

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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

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Tyre rotation

The importance of tire rotation is emphasized in the Owner Manual. Generally, the rule of thumb is to rotate tires every 5,000-8,000 miles (8.000-13.000 km), or whenever uneven wear is noticed.

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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.

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Rim types

Steel rims and aluminum rims are both commonly used by car manufacturers as stock rims on vehicles. They have slightly different physical properties with their own advantages and disadvantages. Aftermarket upgrades are available for each type.

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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.


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.


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.


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.

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Noise and vibrations

Below are the most common (but not the only) causes of noise and vibration problems:

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- 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.

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Signification of DOT from the tireside



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