It has been argued that the grip of winter tyres on ice and snow deteriorates with age to such an extent that winter tyres above a certain age e. g. 10 years should be forbidden to use. Little research data do however exist. This investigation has been carried out by VTI in order to get a better background for legal decisions. The results would also be of use for ordinary consumers as a guidance. This investigation that was carried out on wet smooth ice is the third of three part studies. The first was on smooth ice at -3°C and the second on rough ice at -3°C. They have been reported in VTI meddelande 923 and VTI notat 34-2003. The aim of the investigation is to investigate the correlation between ice grip of winter tyres and their age, tread depth and tread rubber hardness and for studded tyres also stud protrusion and stud force. The investigation comprises 23 studded and 42 non studded winter tyres and four summer tyres mainly of the in Sweden popular brands Gislaved, Michelin and Good Year, primarily of size 195/65R15. Most of the tyres had been driven in ordinary traffic and were manufactured from 1981 to 2003. A small number of new winter tyres were also tested. As reference some new summer tyres were tested as well. The steering and braking performance of the tyres has been measured in a special climate controlled indoor high speed flat bed test facility developed by the VTI. Very good correlation has earlier been found between results from the facility and lap time results from ice track circuit tests with cars as well as pure braking and cornering tests with cars on ice tracks. No age related deterioration of the ice grip was found for the fully studded winter tyres with stud protrusion 1 mm and higher. The ice grip deteriorated with increasing age for non studded winter tyres and studded tyres with stud protrusion less than 0,9 mm. The results also show that on wet smooth ice studded tyres with stud protrusion 1 mm and higher are much superior to non studded tyres including the specialised studless winter tyres often called "friction tyres". The differences in friction within the groups are however quite large.