TREADWEAR RATING
It has become a common belief that a tyre’s tread wear rating is a measure of dry grip. So a TREADWEAR of 120 is better than a TREADWEAR of 180. There are many dangers in assuming this.
The tread wear numbers printed on the side of a tyre form part of the US Uniform Tyre Quality Grading system (UTQG) If a tyre is to be sold in US markets it must have this rating (There is no requirement outside of US markets). There are several requirements of this grading system of which tread wear is only one. The test is conducted over a distance of more than 7,000 miles on a set road route following normal road rules and wear rates are compared to a control tyre. The purpose of this test is to give US customers the ability to buy longer life tyres. Higher numbers are better for the consumer.It is quite acceptable for a manufacture to claim a lower number, but not a higher number.
Track based tyres, even UHP tyres are unlikely to reach operating temperatures in road driving. Tyre “A” has always been a TREADWEAR 180 but the revised tyre is now TREADWEAR 240 so must be worse? Or it could be that the compound has been revised to allow higher track temperatures and so it remains harder on the road? The same applies for Race compounds, which will never achieve operating temperature at road speeds. They stay hard which can result in higher numbers than they would expect. Equally they could experience “cold shaving” where the rubber is ground and shaved away without ever becoming pliant, meaning they get lower numbers.
Another factor can be tread pattern (next). There is only a tenuous link between tread wear rating and circuit grip.
It has become a common belief that a tyre’s tread wear rating is a measure of dry grip. So a TREADWEAR of 120 is better than a TREADWEAR of 180. There are many dangers in assuming this.
The tread wear numbers printed on the side of a tyre form part of the US Uniform Tyre Quality Grading system (UTQG) If a tyre is to be sold in US markets it must have this rating (There is no requirement outside of US markets). There are several requirements of this grading system of which tread wear is only one. The test is conducted over a distance of more than 7,000 miles on a set road route following normal road rules and wear rates are compared to a control tyre. The purpose of this test is to give US customers the ability to buy longer life tyres. Higher numbers are better for the consumer.It is quite acceptable for a manufacture to claim a lower number, but not a higher number.
Track based tyres, even UHP tyres are unlikely to reach operating temperatures in road driving. Tyre “A” has always been a TREADWEAR 180 but the revised tyre is now TREADWEAR 240 so must be worse? Or it could be that the compound has been revised to allow higher track temperatures and so it remains harder on the road? The same applies for Race compounds, which will never achieve operating temperature at road speeds. They stay hard which can result in higher numbers than they would expect. Equally they could experience “cold shaving” where the rubber is ground and shaved away without ever becoming pliant, meaning they get lower numbers.
Another factor can be tread pattern (next). There is only a tenuous link between tread wear rating and circuit grip.
