The importance of having tyres with the right load rating
The load rating of a tyre is something not often thought of by people purchasing tyres yet it is one of the most important aspects to consider especially if you are travelling off-road and/or towing a large trailer or caravan to ensure you are travelling both safely and legally.
Since 1973 Australian Design Rules (ADRs) have required cars to be fitted with a tyre placard which specifies the wheel and tyre combinations recommended by the vehicle manufacturer. This tyre placard also specifies recommended air pressure, load capacity and speed rating of tyres.
*ADR’s now state minimum Speed Ratings:-’ Passenger Vehicles’ ‘S’=180kph:: 4WD vehicles:- ‘N’=140kph*
Tyre placards are generally found in 3 places on a vehicle. 1. Glovebox lid, 2. On the 'B' pillar (drivers or passenger side) near the door striker plate, 3. On the inside of the fuel flap.
Replacement tyres fitted to a vehicle must be of a load rating equal to or exceeding that specified on the placard for that tyre or exceeding the maximum listed rating for any other tyre. Drivers should be aware that these ratings exist to protect the public from the possible outcome of overloading a tyre. Overloading a tyre by carrying more weight than it is designed to carry, or running lower than specified pressure can cause heat build up and destroy the tyre. (Tip:- Always inflate your tyres back to highway pressures before you hit the bitumen after any four wheel drive excursion where lowing of tyre pressures was necessary).
The above tyre placard relates to a Toyota Prado 4wd with two sizes and the relevant load rating for each tyre. In the case of the popular 265/65R17 tyre the load rating of 112 equates to 1120 kg per tyre. This is the minimum load rating for any tyre in this size (or larger) 'Must' have but if you are frequently loading up the vehicle (internal loading and/or towing) or off-roading using lower tyre pressures it is advisable to fit a light truck rated tyre with a higher load rating ie Mickey Thompson STZ in the size 265/65R17 is light truck rated with a load rating of 120 (1400 kg per tyre) or go up a size to 265/70R17 (26mm taller) with a load rating of of 121 =1450kg per tyre).
'The load rating on a tyre can be found on the sidewall near the bead of the tyre.'
In this case the Mickey Thompson MTZ P3 in the size 265/70R17 has a load rating of 121 for normal use or 118 if used in a dual wheel capacity. The Load Rating chart below relates the Tyre Load Index to the corresponding load in kilograms.
Important Note:- The Load Index rating represents the load-carrying capacity of tyres inflated to maximum psi: This means the load-carrying capacity reduces as tyre pressures are reduced.
Remember:- A higher load rating equals a stronger tyre so it will run cooler under load with the added benefit of a stronger tyre being more puncture resistant and will achieve higher mileage under normal operating situations.
The next time you are looking for new tyres please take the time to consider:-
- Your vehicle’s minimum tyre load rating requirements
- The type of driving you are intending on doing especially any long distance travels.
- Whether you will be carrying and or towing any heavy loads.
If you have any queries on the choice of Mickey Thompson tyres for your vehicle and or tyre pressures to be adopted under varying driving conditions for your vehicle visit the Mickey Thompson Tyres website or call 1300 MICKEY (1300 642 539) during business hours.
The choice of a correct load rated tyre for your individual vehicle and driving requirements will ensure that you get the maximum performance from your tyres and importantly, that you arrive at your destinations –‘Safely’!