Thanks for the replies. The tread on the rest of the front tyres is fine..about 4mm. I too had a chat with a tyre fitter & without saying what my problem was concerning my Yokohama's, he said that they, (Yokohama's) have a softer compound on the outer edge & therefore wear quite quickly! Yokohama UK have offered to inspect the tyres, when I replace them....we will see then if there is a problem with the tyre construction. On the subject of tracking, my local Toyota dealer said they tested the tracking at the recent service & found no problem. I certainly haven't driven over any kerbs since I bought the car 'new' just under a year ago, so I didn't expect the tracking to be out. My tyres on my previous car (Corolla) by the way, were Dunlops & as I stated earlier gave me 24,154 trouble free miles on the front pair!