I would never buy part worn, my reasons are when I bought my Nissan skyline gtr in 2006 it had good quality bridgestone tyres all round loads of tread, but handled like it was on ice into round abouts and corners, would lose grip and control at quite low speeds, when I took them to be replaced the tyre fitter had a hell of a job taking them off the rim, he explained they had probably been on the car for years and the compound had gone and hard, put new tyres on and the car was transformed, if you do intend buying some be sure you know how old they are and how long the have been in storage