There have been several threads regarding the purpose of the coloured rings on tyres. It seems that some new tyres have them, while others do not. I was not able to find any official word from the tyre manufacturers - they seem not to be saying anything about this. This is what I did find: 1. Most of the information I found on the Internet was written by tyre experts, who all agree that this is some sort of 'bar-coding' system that the tyre manufactures use, mainly as part of the manufacturing process. 2. Some also say that only tyres made as OEM for car manufacturers have coloured rings - so in essence any tyre with colour rings sold at a tyre shop is surplus as it was originally made to be supplied to a car factory to be fitted on a new car, rather than being sold as retail. According to this, retail tyres do not have such coloured rings. 3. However, two experts, and one of them is someone I personally hold in very high regard - Tony Bones from Wheels in Motion - say that while most rings are indeed just an internal bar-code and as such have no importance to the customer, one ring is of great importance, read here: http://www.mbclub.co.uk/forums/wheels-tyres/99918-new-tyres-their-radial-markings.html 4. Someone on this forum also suggested that MO tyres differ from non-MO tyres in that all MO tyres have the same radial marking, i.e. the deviation is always the same (see Tony's post above). My experience? I bought 4 new Michelins at Costco recently (not for the Merc), three had coloured rings, all different, and one had no rings at all. I then Bought 4 Conti MOs a couple of months ago, all four had identical coloured rings at the same location. One of the new Contis had a puncture and needed replacing, and lo and behold the new Conti Mo I bought today had the exact same colour marking as the four purchased two months ago - in spite of the fact that its manufacturing date was different so it would have come from a different batch to the original four Conti MOs. I wonder what are other members experienced?