My 08 Mazda 6 2.5 sport developed the same off centre steering wheel problem which seemed to happen overnight. I took it to a national tyre chain to check the tracking. They told me that speed humps and pot holes could cause the problem. They made adjustments and told me that everything was now spot on and to come back in a fortnight for re-checking. Despite this the problem remained. I told them that I had recently had two new tyres put on the front and asked if this could cause the problem. The mechanic (a term I use with reservation) told me that there was absolutely no possibility of a connection between the too. It was now becomming a problem that was difficult to live with. I was desparate to get to the bottom of it, as i was concerned that there maybe a more serious issue. I decided to try another garage to get the car checked out, they suggested that laser and digital steering geometry setup was the answer to my problems. I handed over my 25 quid and hey presto... the problem was still there, if anything a tad worse. In desparation I asked them to swap my new tyres to the rear. Would you Adam and Eve it, the steering wheel was now dead centre once more. So before spending any money try swapping the tyres round first, it may just work for you too.