Comparative test of the effect on wet ice friction of adding a special aggregate in the tread rubber of a retreaded M+S tyre type

• Main Author: Nordström, Olle
• Format: Report
• Language: English
• Published: Statens väg- och transportforskningsinstitut 2001
• Subjects: English; Sweden; Retread tyre; Additive; Aggregate; Test; Test rig; Friction; Braking; Steering; Iceland
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:vti:diva-1294

The investigation carried out on commission by New Industries, Iceland, comprised comparative tests with a total of 10 new retreaded passenger car tyres classified M+S with the same tread pattern with and without special aggregates mixed into the tread rubber compound. The tests were carried out in the VTI tyre testing facility on smooth and roughened water covered ice at a speed of 30 km/h. Water covered ice can be regarded as one of the most dangerous road conditions. Both braking tests and steering tests were performed. The braking tests measured maximum braking friction corresponding to ideal ABS braking performance and friction with a locked wheel. The steering tests measured maximum lateral friction and friction at a 20-degree side slip angle (skid angle). The latter value represents conditions in skidding of the whole vehicle or excessive steering angle when entering a curve. The results on water covered smooth ice show that a new non studded winter tyre can get about 30% improved braking friction and about 40% improved steering friction by means of mixing the special aggregate composition into the tread rubber compound. Testing this improved tyre on water covered stud roughened ice showed that the friction for normal driving is practically the same as on smooth ice. If the vehicle gets in a 20 degree broadslide, rough ice gave up to 40 per cent improvement compared to smooth ice. Repeated tests however quickly reduced this improvement to 10 per cent. The values obtained on smooth flooded ice with the best tyre aggregate tread compound allows cautious driving while the reference tyre friction is insufficient for keeping a vehicle on the road even for a skilled driver under these very severe conditions.