I would be grateful for advice on tyre configuration.Having just purchased a 2005 2.0d X3 Sport the rear tyres need attention .The fronts are KUMHO 235 50 18 & the rear has one Kumho 235 50 18 with little tread & one (new) Autogrip 235 50 18 .Can I replace the Kumho with another Autogrip,or should they be Kumho's all round? Looking forward to your advice. Paul