I noticed 8mm sag on the RR suspension of my Z4mr, sprigs look ok. I have a 12 month warranty so I took it to the dealer who after charging £80 told me it was within their tolerance range and if I wanted they could look at it more in dept (at a price). The service guy also told me that this is normal due to driver weight and fuel tank but never had this problem with my previous Z. Any ideas?