Change to 1.4 without any doubt, maybe a 1.2 (your current box) will work but with your tyres 1.4 will be better. If you come across a 1.6 I think that'll work even better for you but 1.4 are much easier to get hold of. The 1.2 you have only works well with 205/16 tyres, any bigger than that and the...