New tests prove that ESP and ABS systems are ineffective when combined with worn shock absorbers

The advance of modern safety systems, such as ESP (Electronic Stability Control), is an important step towards improved road safety as increasing numbers of car manufacturers adopt this new technology; and, while the growing sophistication of car safety systems should be applauded, new independent research shows that even vehicles with ESP and ABS (Anti-Lock Braking System) will seriously compromise road safety if they have worn shock absorbers.

New comparative tests carried out by the German Vehicle Inspection Agency, (TÜV), provide conclusive evidence that a new VW Beetle fitted with 50% worn shocks can have a braking distance up to 6 metres longer than the same vehicle fitted with 100% efficient 'new technology' shocks, such as the new Monroe Sensa-Trac shock absorber with Safe-Tech system, despite its ESP and ABS systems.

The independent research also demonstrated that the same VW Beetle with worn shocks is more difficult to control in a collision avoidance manoeuvre, thereby extending the risk to car occupants and other road users.

In light of these latest findings, Tenneco Automotive, producer of Monroe shock absorbers, the world's leading brand, is urging all drivers including those with ESP and/or ABS systems to get their shocks checked before the worst of the winter weather sets in.

Warns Jean Francois Floor, ride control group product manager of Tenneco Automotive: "It appears that when drivers check their cars, most people examine the obvious things Ð anti-freeze, tyre pressure, oil, radiator and washer fluid levels Ð but overlook what they can't see, including shock absorbers.

"Being 'out of sight and out of mind', motorists simply don't think about their shock absorbers Ð particularly if they drive newish cars Ð unless drawn to their attention during an MOT test, or when examining a used car as a potential purchase.

"Just like tyres and brakes, shock absorbers wear out gradually and imperceptibly, becoming increasingly dangerous mile by mile without the driver noticing. A regular shock absorber check can be a life-saver and these new tests show that even drivers of cars fitted with the latest technology need to be aware of the dangers that worn shocks represent, particularly if they cover a lot of miles."

The TÜV tests

The scientific tests used a 2.0 litre VW Beetle equipped with the latest ESP and ABS systems. This was firstly fitted with shock absorbers with 50% wear. The same tests were then repeated on the same vehicle but this time using new Monroe Sensa-Trac shock absorbers with the Safe-Tech system. These new Sensa-Trac shock absorbers have a continuously variable groove design, providing gradual damping to ensure firm tyre grip, whatever the road conditions. The same vehicle was used for each test to rule out variations between different vehicles.

In both instances, the vehicle was fitted with sophisticated measurement equipment to ensure precise and accurate recordings. The new VW Beetle was selected as the test vehicle as it is a trendsetter in the field of automotive design and development, and accordingly comes equipped with the latest ESP and ABS systems.

Two key tests were conducted:

• Emergency braking test at 80km/h (50mph) on a straight road where the right hand lane is then blocked to simulate an obstacle; the vehicle with worn shock absorbers showed an increase in braking distance of 6 metres - a 20.1% increase - compared with the car with new Monroe shocks. In addition, when the car was fitted with worn shock absorbers the vehicle was more difficult to control, causing wheel bounce and skidding. This is because when the ESP system tries to stabilise the vehicle, its braking distance increases, destroying the benefits of the ESP system.
• A VDA test measures the performance of the vehicle by the highest entrance speed which can be maintained without hitting the cones. In this test, the driver had to manoeuvre the car around traffic cones to simulate two consecutive lane changes; this was conducted on an uneven road surface, and had to be completed without braking. These tests found that a maximum speed of 62km/h (38.6mph) could be achieved by the vehicle fitted with worn shock absorbers before losing control and hitting the cones. When the test was repeated with new shock absorbers, the Beetle achieved an improvement in driving speed of 3.3% or 64km/h (39.9mph).

In addition, it was found that worn shocks severely affect the efficiency of both the vehicle's ESP and ABS braking systems. The tests showed that during evasive manoeuvres or emergency braking, the wheels lost contact with the road Ð dramatically reducing braking efficiency and driver control. Naturally, the higher the speed, the greater the risk when driving with worn shock absorbers.

Concludes Jean Francois Floor: "These tests are conclusive proof that no matter how sophisticated the safety systems are on your car, fully efficient shock absorbers are essential for road safety. I strongly advise drivers to get their shocks checked professionally."

Notes to editors

Monroe's 'ten dangers' of worn shock absorbers

• reduced braking efficiency results in longer braking distances
• increased risk of skidding in the wet
• aquaplaning occurs at lower speeds
• reduced efficiency of ABS braking system and ESP stability control system
• less control when cornering or caught in a cross wind
• increased wear of tyres and other suspension components
• uneven/oscillating headlight level causing dazzle to on-coming drivers
• increased driver tiredness and reduced rate of response
• increased passenger discomfort
• increased risk of 'snaking' when towing a caravan or trailer

Tenneco Automotive
The Monroe brand is owned by Tenneco Automotive, the world's largest producer of shock absorbers and supplier of components to car manufacturers such as Audi, Ford, Nissan, Toyota, Volkswagen and Volvo.

Tenneco Automotive, with 24,000 employees worldwide has a turnover of US $3.2 billion, and operates 81 facilities in Europe, North America, Australia and the Asia-Pacific region.

VW Beetle - TÜV/Monroe - test results