Tires

Tires (tyres as British like to write it. Arabic: كاوتش العجل) are one of the most important part of your 4x4's suspension. Tires could make soft ride in hard terrain, can enhance cornering and general handling of the car, can enable dunes driving (with low inflation) or handle rocky puncturing desert marble (high inflation), etc. A broken tire during driving on high speed could be dangerous if you're buying the wrong ones. For this and more, you have to make wise choices of tires everytime you select new ones for your 4x4.

Most of the specification of any tires are written on the side by standard symbols. We have here two main types of tires described.

Reasons to change your tires

  • unfit for new use of the car: started serious offroading that requires different quality of tires, etc.
  • need to change the size (usually a requirement for dunes offroading)
  • expiry date is past
  • cuts and puncturing are becoming too often exposing the rider to risks during off- and on-roading
  • <add more from local experience please>

When tires are changed with different size tires

You may like to use this website to calculate differences in size and how they impact the 'height' of the car and change in readings of the speedometer:
 
For example, if you changed your Cherokee XJ's tires from stock size 225/75R15 to 235/75R15, then you can watch for those changes:
  • Sidewall Height: this has been increased by 0.3 inches (0.76 cm) which contributes to height of car by the same
  • Speedometer (Arabic: عداد السرعة) readings: when it reads 100, you're actually going on 102kph

Tips for wise choice of new tires

  1. additionally protected sidewalls are important for offroaders. A/T has those automatically and LT as well. P class has to be explicitly specified by manufacturer and most likely not supported by inside belts like LT. A/T has a mixture of both.
  2. size is not much larger than stock wheel size unless you know what you're doing; lifting the car by tire sizes may slow the car acceleration and be too heavy for the steering while not gaining enough ground clearance and breaks the defenders if special lifters applied to vehicle body
  3. tread pattern (Arabic: النقشة) is important: the bigger the gaps, the more it can deal with sand and not mud. this causes much noise on road though.
  4. buy recently produced tires (some are about to expire). Check the dates using the codes explained below.
  5. <add more from local experience please>

Tips on good maintenance of tires

You shouldl always check your 4x4 Owners Manual for such guidelines. Here are some of the most common for almost all types of cars. 

Tires rotation

Rotation reduces the wearing on one side more than the other which allows longer life of all tires. Depending on the Owners Manual and/or tire manufacturer, the rotation is recommended to change every 10,000km. 

 

Tire balancing (Arabic: ترصيص)

This should be done by a specialised technician (ِمكنة الترصيص عند معظم بتوع الكاوتش) if driver notices a slight or medium vibration of the car. The balancing is usually to compensate for rims' imbalances but it better be done after placing the tire on the wheel.

Important Note: when the vibration is not attached to a certain speed, comes suddenly and violently, then this is may be the "stabilizer shocks" has gone bad.

Special Tires

Different terrains and loading for the vehicle requires different types of tires. Some of the most interesting for our 4x4ing activities is sand driving. Two types of tires stands out for that; Low-pressure, and Sand-tires.

Low-pressure tires

The following truck shows tires that are designed to be on low-pressure, and therefore they come with some additional precautions not found on normal tires. 

Anybody can deflate their tires to enhance their traction with the sandy surface they're driving on. Now all tires edges (with steel threads called 'beads') are held tightly locked to the rim by air pressure, so when deflation happens, the risk of the tire coming out of the rim increases specially when the driver is turning and something like this affects the tire:

 

Wheels Rims with Bedlocks

It's obvious that the usual rims won't hold the tires in place, so a rim with 'beadlocks' was designed with bolts and nuts around the edge of the rim to keep the tires in place as in this photo:

To get a better understanding of how those rims hold their tires, here's a cross-section in one of them:

Note how the beads to the outer side of the wheel are held locked in place by many nuts and bolts.

Notes on Beadlock Rims

  • beadlocked rims could use any tires and not only low-pressure tires (tires that are 'designed' to be used at very low-pressure)
  • low-pressure tires are famous for snow, but maybe used (if can handle desert heat) with sand dunes as well
  • in spite of the tough looks and interesting function of beadlocks, using inner-tubes for such tires maybe are necessary since one tire side is locked and not the other, so you may lose all air from the other side.

Egyptian Suppliers for Beadlocked Rims

  1. <please add here> 

Sand-tires

They're sometimes called in Egypt 'baloon' tires and other than their breadth which helps them 'float' over soft sand, they have 'paddles' (Arabic: حراشيف) on them which help gaining traction. The v-shaped paddles works best when the vehicle is turning. This extreme design is no-good for the asphalt and the tire would be damaged.

Tire Specifications

There are several ways to mark tires to show their specifications. We'll focus here on what's more relevant to 4x4s (sedan is simple part here).

Tire markings

Passenger (P) markings

 

 

 

Light Truck (LT) markings

Generally they're described here but are slightly different in the way markings are explained. 

 

 

Size markings

Now let's start by the explaining each of those codes marked on the tire for the Passenger tires:

Vehicle Rating ("P" or "LT")

 

This is the letter "P" in P205/65R16 or "LT" in LT205/65R16. If the tire size appears without a letter as 205/65R16 it's understood that it means "P" and nothing else. 

A letter(s) indicating the intended use or vehicle class for the tire. It's ALWAYS placed before the numbers in the tire's size as shown below: 

  • P: Passenger Car. Softer tires allowing low-inflation that allows softer rides, but has less reliability in rough off-road terrain
  • LT: Light Truck. Harder built tires with additionally thick side-walls that can resist side-walls puncturing better but has to be inflated on high PSI (eg, 40) to disallow fatigue of belts.
  • ST: Special Trailer; tire size designed only for boat, or car trailers. They should never be used on cars or trucks
  • T: Temporary tire or spare wheels that shouldn't be used except as such.

Width of tire ("205")

This is the number 205 in P205/65R16. 

The first number in this group indicates the width of the tire approximately at its widest, measured from sidewall to sidewall, in millimeters.

Aspect Ratio ("65")

This is the number 65 in P205/65R16 and it inidcates a ration in %.

The sidewall height as a percentage of the width. 65% for P205 means that the sidewall is 133mm high.

Construction Type ("R")

This is the "R" in P205/65R16.

  • B:Bias belt (where the sidewalls are the same material as the tread, leading to a rigid ride). Bias-ply is also called cross-ply. Almost doesn't exist anymore.
  • D: Diagonal. Almost doesn't exist anymore.
  • R: Radial. This design achieves the best economy of fuel, and flatness on ground when deflated which is useful in desert driving. The industry standard.

Rim Diameter ("16")

This is the number "16" in P205/65R16

Of the rim (Arabic: جنط) that the tire is designed to fit, in inches. For stock 4x4s, it's usually 15, 16, and 17 inches (432mm). For low-profile tires, it could reach 19 or more.

Quite rarely, the diameters is expressed in millimeters such as in P205/65R430. Also, another very rare size is in inches but with halves, such as R16.5 or R17.5. 

Load Index ("105")

It is a code number that describes how much weight the tire can carry at maximum inflation pressure. See Tables below for codes of load index and their loads. When choosing a new tire, make sure you read the Owners Manual for recommendations.

Speed Rating ("S")

It is a letter code, from A to Z, which indicates the maximum speed capabilities of the tire.

Usually the Load Index and Speed Rating are written together like 105S indicating a load up to 925 Kgs (at each tire with overall vehicle curb weight of about 3.6 tons) with max safe speed of 180 kph.

See Tables below for codes and their relevant loads and speeds.

Special Size Format 

In some special cases with specially large tires, size is expressed as in 37X12.5R17LT:

  • 37: measure in inches (=940 mm, almost 1 meter!) in the full diameter of the tire from end to end
  • 12.5: measured in inches (=320 mm) to indicate the width of the tire at the widest point
  • R: Radial (like mentioned before)
  • 17: measured in inches for rim's diameter (like other measurement)
  • LT: light truck (like mentioned before)

 

Plies ("E")

The last letter in a standard tire size indicates the number of layers used in the construction of the tire. The higher the number of plies in a tire, the stronger the tire is and the more air pressure the tire can safely hold. Higher ply tires require more air pressure to maintain proper wear and avoid quick fatigue by the metallic belt.

  • "No letter" the tire has the standard 4 plies.
  • "C" indicates 6 plies.
  • "D" indicates 8 plies.
  • "E" indicates 10 plies.
The number of plies indicates the number of layers of rubber-coated fabric in the tire. In general, the greater the number of plies, the more weight a tire can support. Tire manufacturers also must indicate the materials in the tire, which include steel, nylon, polyester, and others.
 

Conditions

  • ATR (A/T): All Terrain Radial tire 
  • M+S or M&S: Mud and Snow. For snow, tires have metal spikes (only for ice/snow-covered roads, not allowed to tread on asphalt road) and the code becomes M+SE.
  • M&S + snow flake shape: Dedicated Winter Mud and Snow 
  • OTR: The Off The Road tire classification includes tires for construction vehicles such as wheel loaders, Graders.
  • RF: Run flat Several innovative designs have been introduced that permit tires to run safely with no air for a limited range at a limited speed.

Maximum Tire Pressure

This number gives the maximum cold pressure required to carry the maximum load for which the tire is rated. The maximum pressure number is not the same as the recommended tire pressure for your vehicle.

Cold pressure could be measured 3 hours after the last stop of the car. 

Maximum Load

This is different from recommended load or Load Index. Do not exceed this load or you may cause injuries.

Quality Rating

This includes 3 tested measurements made relative to a standard tire in labs. It comprises traction, treadwear, and temperature grades.

Traction

Represents the tire's ability to stop on wet pavement as measured under controlled conditions on asphalt and concrete test surfaces. The traction grades are:

  • AA: best traction
  • A: good traction
  • B: not so good traction
  • C: bad traction

A tire graded "AA" may have relatively better traction performance than a tire graded lower, based on straight-ahead braking tests. The grades do not take into consideration the cornering or turning performance of a tire.

Temperature grades

Represents a tire's resistance to heat and its ability to dissipate heat when tested under controlled laboratory test conditions. The grades are:

  • A: best  resistance to heat
  • B: good resistance to heat
  • C: bad resistance to heat

The grade "C" corresponds to the minimum performance required by federal safety standard. Therefore, the "A" tire is the coolest running, and even though the "C" tire runs hotter it does not mean it is unsafe. The temperature grade is established for a tire that is properly inflated and not overloaded. 

Tread wear

The tread wear grade describes how long the tire manufacturer expects the tire to last. A Course Monitoring Tire (the standard tire that a test tire will be compared to) has a rating of "100". If a manufacturer assigns a tread wear rating of 200 to a new tire, they are indicating that they expect the new tire to have a useful lifespan that is 200% of the life of a Course Monitoring Tire.

U.S. DOT & Safety Standard Markings

 

DOT

The "DOT" marking indicates that the tire meets or exceeds the U.S. Department of Transportation's safety standard for tires, and that the following characters and numbers are codes to indicate manufacturer, tire part numbers and date of manufacturing of this tire as described below.

Manufacturer ("CC")

The first two letters following the DOT marking are codes to identify the manufacturer of the tire and the manufacturing plant. You can find all codes at this link: http://www.harriger.com/tires.htm 

Plant Code ("9L")

The third and fourth characters following the DOT marking are codes representing the Plant Code of this manufacturer.

Brand Characteristics ("YYY")

These codes are record for the manufacture that may be printed or not. If so, they are follow no industry standards and could be neglected by our inspection. In specific cases they act like part-numbers and are used by manufacturers to notify owners that a specific codes maybe recalled and replaced.

Manufacture Week ("11")

The first pair of digits identifies the week the tire was manufactured. In this case, the tire was manufactured in the 11th week. The number 01 would indicate the first week of January, whereas the number 52 would indicate the last week of December. Week 11 of the year would be around third week of March.

Manufacture Year ("05")

As per the standards AFTER year 2000, the last pair of digits identifies the year. In our example "05" means 2005. In the example at the picture below, DOT U2LL LMLR5107 indicates Year 2007 and Week 51 which is approx third week of December.

For tires manufactured BEFORE year 2000, it was thought that a tire will expire within 10 years so one number for the decade was used as year 1998 represented as "8" in the tire shown below along with week 40 which approx end of October.

If the numbers hows partially without year such as "DOT EJ8J" then flip it to other sidewall and you'll find the complete code including week and year numbers.

 

 

 

Important Tables

Speed Rating Codes 

Code kph Code kph
A1 120 
A2 10  130 
A3 15  140 
A4 20  150 
A5 25  160 
A6 30  170 
A7 35  180 
A8 40  190 
B 50  200 
C 60  210 
D 65  240 
E 70  over 240 
F 80  270 
G 90  (W)  over 270 
J 100  300 
K 110  (Y)  over 300 

 

Load Index Codes 

 

Code Kilograms (per tire)
60 250 
61 257 
62 265
63  272
 64  280
 65  290
 66  300
 67  307
 68  315
 69  325
 70  335
 71  345
 72  355
 73  365
 74  375
 75  387
 76  400
 77  412
 78  425
 79  437
 80  450
 81  462
 82  475
 83  487
 84  500
 85  515
 86  530
 87  545
 88  560
 89  580
 90  600
 91  615
 92  630
 93  650
 94  570
 95  590
 96  710
 97  730
 98  750
 99  775
 100  800
 101  825
 102  850
 103  875
 104  900
 105  925
 106  950
 107  975
 108  1000
 109  1030
 110  1060
 111  1090
 112  1120
 113  1150
 114  1180
 115  1215
 116  1250
 117  1285
 118  1320
 119  1360
 120  1400
 121  1450
 122  1500
 123  1550
 124  1600
 125  1650

 

Other Abbreviations

  • BSW: Black Sidewall, WSW: White Sidewall, OWL: Outline White Lettering, ORWL: Outlined raised white lettering, RWL: Raised white lettering, 
  • VSB: Vertical serrated (Arabic: مشرشر) band, BSL: Black serrated letters
  • E4: Tire approved according ECE-regulations, the number indicating the country of approval.
  • TL: Tubeless
  • TT: Tube-type, tire must be used with an inner-tube (Arabic: alfv(
  • Made in ...: Country of production
  • C: Commercial; tires for trucks or vans (example: 195/70R15C) but it's just a redundant code since these higher loads are reflected in the codes of load ranges, etc.
  • SFI, or Inner: Side Facing Inwards; inside of asymmetric tires
  • SFO, or Outer: Side Facing Outwards; outside of asymmetric tires
  • SL: Standard Load; tire for normal usage and loads
  • XL: extra Load; tire for vehicles of heavier standard weightsو RF: Reinforced tires (similar to extra load)
  • ←, → (arrows): some tires are directionally designed and must be used as the arrows point
  • MO, MOE, N-x, (Star), RSC (in a circle), TPC, AMx, etc.: are signs of tires designed specifically for certain brands such as Mercedes Benz (MO and MOE) and AMx (Aston Martin).