Our experts on: Uniform Tyre Quality Ratings

June 10, 2008 at 10:42 am Leave a comment

Apart from tyre size branding, many Australian drivers may have noticed other markings on the sidewalls of their tyres with ratings for treadwear, traction and temperature. These Uniform Tyre Quality Grading System (UTQG) ratings are based on rather outdated U.S. legislation which requires all passenger tyres sold in the U.S. to have them.

However such ratings are not a legislative requirement anywhere in Australia. In fact, Australian legislators have shied away from its’ introduction since the information contained in the tyre size provides tyre buyers with more useful information on a tyre’s performance.

I will explain why the UTQG ratings are not so useful.

There are three tyre parameters rated under the UTQG.

  • Treadwear ( tread wear compared to a standard tyre, expressed as a percentage. e.g. 200% wears half as fast, so tread wear is twice as good)
  • Traction, (AA, A, B or C with AA best)
  • Temperature ( A,B,C, with A being best)

All these comparisons are made against a “standard tyre” – now an obsolete design and construction dating back to the period when the law was introduced. All the modern steel belted radials “rate the socks off” this standard tyre.

It is a classic case of technology overtaking legislation but adding to the cost.

The evaluation for treadwear is done on a 640 km road course for a total of 11520 km, – one of the most boring road test drives ever. Every effort is made to keep the testing conditions as standardised as possible.

However, with this type of testing there are variables which may not be taken into account. Such as a heavily siped pattern (many knife slots in the tread design, often only half pattern depth), which will wear faster at first than later, but may give good braking. Also lug design off road patterns may develop unusual wear patterns early in the tread life which even out as the tyre wears down (or not). As these are being compared to a highway rib design on a highway – the comparison may not be valid.

Similarly traction ratings to the standard are made on a highway tyre surface. Off-road tyres generally have a rounder tread profile to reduce the rubber volume in the shoulder/buttress area which helps it run cooler, but promotes faster wear in the centre of the tread design.

Off-road tyres also have a lower pattern to void ratio- the pattern grooves are wider than for a highway design, so initially they too may wear faster than later on in their tread life.

Temperature ratings grade a tyres’ ability to dissipate heat when tested under controlled conditions on a specified indoor laboratory test wheel. However, as speed rating is a much more specific way of expressing a tyres’ ability dissipate heat – size branding will give provide more information than the UTQG rating.

Finally, a word of warning. The Australian Design Rules placard on the vehicle stipulates the minimum speed and load rating of the tyres fitted to the vehicle, both when new, and through State legislation, for the replacement tyres. Lurking always in the background as the enforcer is your insurance assessor. Fitting the wrong tyres may void your insurance cover!

Entry filed under: Choosing the Right Tyre, Tyre Sizing. Tags: , , , .

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