i have a 54 plated zafira 2.0 dti energy. its a great car but the steering troubles me recently. frankly its a fight to keep it in a straight line, one minute it fancys pulling to the right then left. when braking this can be quite savage. tyre pressures are correct and are perrelli p6000 205 55. are these a good tyre? what are recommended tyres for this model? i got bearly 18,000 out of the last set of these and im not a fast or agressive driver. any thoughts?