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

[statman]

plese let me know how you get on i am looking to change mine too
regards

gary

[motordavid]

By my handy dandy tire size calculator, it shows that your potential
replacement front tires will roll ~ 6.6% less than your stock,
eg ~695 revs per mile vs. ~740 revs.

The rears, in the size listed, will roll ~3.8% less than stock:
~719 stock vs. ~693 for replacement 19" size.

Site is:
http://www.powerdog.com/tiresize.cgi

And, all data is a ballpark, as we say here in the Colonies...

With that data, which looks semi-severe, but in reality is not, imo,
all I can say is that many of us run the staggered style 132 19" oem
wheel with those proposed tire sizes. Is my speedo off? Maybe, but i
t was "off"/optomistic to begin with. Is my odo off? Don't know, don't
think so, & I don't care really...

I have replacement oem style 19" 132s with that tire size and love them.
The rear tires/tyres do wear unevenly, on the inside due to camber.
Ride is plush, handling is same by my seat of the pants, etc.
GL,mD