The test procedure of AutoSock
The purpose of testing AutoSock was to investigate the safety and service characteristics of an innovative system which considerably improves driving performance on winter roads in comparison with summer tyres. The objective of testing and inspection was to review whether both a general type approval by the German Federal Agency for Motor Vehicles (KBA) and the TÜV mark or GS mark for the final product could be obtained.
Road tests
The first test series were conducted with 2 passenger cars, one with front- and one with rear-wheel drive. The AutoSock was compared with summer tyres and winter tyres. Due to the findings obtained and the experience gathered during the tests, the product was also compared with a reference snow chain in the tests conducted on a snow covered test course. The same driving maneuvers were conducted with all combinations. A uniform tyre size was used on both test vehicles.
Award of a quality mark
Various quality marks can be acquired from TÜV Süddeutschland Group. Their main differences lie in the defined test criteria and scope of testing and inspection necessary for their award. It is in the customer's interest to acquire a top-quality mark (TÜV Mark and GS mark), this mark being based on a precisely defined, sophisticated test program.
1. Tests on ice
The tests were conducted on an ice stadium in September 2000. The following criteria were investigated:
· Acceleration (traction)
· Braking distance
· Lateral guidance properties
All tests included comparison with high-quality winter and summer tires.
1.1 Acceleration (traction) on ice
The test vehicles were accelerated at full throttle in second gear against the engine's drag torque from 5 km/h to 15 km/h; ESP was deactivated. The distance covered until the vehicle reached a speed of 15km/h was measured. Similarly, the speed and acceleration curves were determined from the records.
1.2 Braking on ice
The surface on which the brake test was conducted consisted of ice. The test vehicles were decelerated from a speed of more than 20 km/h down to standstill by full-brake application and activated anti-lock braking system [ABS]. Speed and braking distance were measured by means of a Doppler radar sensor. Braking distance and speed were recorded and mean deceleration was calculated.
1.3 Assessment of lateral guidance properties on ice
A circular track with a diameter of 16 meters was covered at maximum possible speed.
Out of ten circles driven, the five best times were selected and a mean value was calculated.
2. Tests on snow
In order to ensure constant test conditions for the measurements throughout the entire test series, some of these tests were conducted at night. The following criteria were investigated:
· Acceleration (traction)
· Braking distance
· Lateral guidance properties
In these tests, the AutoSocks were also compared with a reference snow chain to gain some experience with a view to a possible future test and better assess the product's prospects of success. The surface on which brake and acceleration tests were conducted was prepared regularly to ensure constant snow quality.
2.1 Acceleration (traction) on snow
On a gentle slope, the test vehicles were accelerated at full throttle in second gear from
20km/h to 35 km/h against the engine's drag torque; ESP or traction control were deactivated. The distance covered until the vehicle reached the required speed was measured.
2.2 Braking on a snow-covered surface
The brake tests were conducted on an area with packed snow. The test vehicles were decelerated from more than 40 km/h to standstill by full-brake application; ABS was activated. The braking distance needed to decelerate the vehicle from 40km/h to 5km/h was measured. Speed and braking distance were measured by means of a Doppler radar sensor. The braking distance and speed were recorded and mean deceleration was calculated.
3. Handling on snow (mountain course)
Handling was assessed by two different drivers on two different courses each.
One course was a level, set handling course, the other a winding, snow-covered mountain passes. Assessment on the mountain pass was divided into two parts. The first consisted of subjective handling assessment. For this purpose, the road had to be driven at a suitable speed with as little slip as possible. For the second part, the vehicle was driven at maximum possible speed.
The tyres were evaluated in line with the following criteria:
· General traction performance
· Traction performance on the mountain pass
· Tracking uphill
· Tracking downhill
· General cornering performance
· Hill start
· Starting on a level road
· Brake performance
4. Summary of the results obtained on a dry and wet road surface
Attention should be drawn to the fact that the AutoSock should only be used on snow-covered or ice-covered roads and that their use on dry and wet road surfaces can only be approved in exceptional cases (multiple transitions from dry/wet and snow-covered/ice-covered road surfaces).
5. Testing as anti-skid device conducted by TÜV Product Service
As the results obtained over the course of the test series were mostly very positive, the decision was taken to have the AutoSock tested as snow-chain by TÜV Product Service. In all tests, the AutoSock were compared with the so-called reference snow chain.
The TUV graph below compares the handling of a car using AutoSock, snow chains and normal winter tyres on snow.
The results show that:
1. AutoSock has easily got the best general traction, uphill and downhill course holding and brake behavior.
2. AutoSock is only slightly behind snow chains when it comes to hill start traction and ground level starts.
3. AutoSock is a great improvement over winter tyres in every area, except hill starts where it is a match.
The mounting of the AutoSocks does not require much effort. They are easy to handle, even when the wheels are already stuck. After mounting has been completed, the AutoSocks align themselves automatically.
6. Result
After extensive consultation with TÜV Product Service GmbH, the TÜV Mark for "winter traction aid" was awarded on July 20, 2001. To safeguard the interests of AutoSock, a highly sophisticated test program was devised. With the development of this test mark, we succeeded in obtaining a quality label which, owing to its stringent requirements, satisfies both the requirements of end users, i.e. a high utility value and the requirements of AutoSock. So far, no other winter traction aids made of fabrics have been approved by TÜV.