Rim & Tyre replacement question

[trapdoor]

Hi all,

After some advice for those that have swapped to bigger rims/tyres...

Currently have 18" Style 143 wheels with 235/50 18's - am looking to swap to a set of 19" staggered which have the following tyres fitted

Fronts 255/50, Rear 285/45

My worry is that taking the rim size, tyre widths and profiles into account, the whole wheel/tyre diameter will be about 35mm bigger on the 19's. Will that have an effect on speedo reading (under/over, and by how much) and the Nav speed & arrival calculation.

Is there a coding issue when fitting bigger wheels?

Never changed from stock wheels before, but mine are a bit tired (pardon the pun) and have been offered a 'delivery miles' set of an X5 with RFT's which is tempting.

Thanks in advance