I fitted some BF Goodrich All Terrain tyres to my syncro the other day, the size was 225/75 16″ and I think they are pretty much the maximum size that will fit. It was not all plane sailing however as they were catching on the the rear wheel arches where they join the sills and the plastic rear bumper (not for long as it soon wears away). I ended up grinding off the edge and dressing back the lip on the wheel arches slightly. They were also rubbing on the front wheel arches occasionally depending on steering input etc. this was where they join the sill so I also dressed back this very slightly with a hammer.