Hi

I have a 2008 X5 with the standard 18" wheels and Michelin tires. I am planning to upgrade to the BMW Double Spoke 239 21" wheels with the Dunlop tires. I have two questions around this:

1. I am getting a good deal on the tires and the tire shop told me that I would need to replace the pressure sensors if I mount new tires. Is that correct? If I do need to, then is it better to get BMW sensors or any after market sensors? Will the after market sensors function properly with iDrive's TPMS?

2. These are the BMW Double Spoke 239 21" wheels that I am looking to buy. Does anyone know of any good deals in US, for these wheels?