quick question, do you have plastic spacers on your rims? I had 18's on my last car, which had plastic spacers on the hub so that they fit. I had my tyres fitted at Bridgestone and one of the spacers got stuck on the rim, instead of being stuck on the hub like they normally are. They rotated my rims, which caused my front rim to have 2 spacers on them, and as they are plastic, when tightening they used their torque gun, but plastic flexes. So while i was drivin home down the M2, i felt something was majorly wrong. When i stopped, my whole left rim fell off the car, with the nuts falling straight into the gutter on delhi rd. Thank *** they didnt fall off doin 100km/h on the M2. Anyways, they paid for my towing and all repairs to the car & rims. If you have spacers on your rims, maybe point this out as it may be the cause. Goodluck, hopefully it will work out for u.