goldbcfc said:
its really not hard just put your widths/offsets in and then compare new info. It tells u how much they will stick out or fall short inside hub.
http://www.1010tires.com/Tools/Wheel-Offset-Calculator
I seen those quantum44 on a grey Z4 coupe at bmw show santapod last month was one of the best Z4 id seen they suit really well. There all different width though some are 9J rear some are 10J and some are 10.5J.
this is a better in depth guide to use and allows you to play with tyre sizes to match the ratio to your old fitment but if your struggling just use the first link above
http://www.wheel-size.com/calc/?wheel1=235-40-19X8.5ET50&wheel2=265-35-19X10ET38&fcl=50mm&wcl=30mm&scl=50mm
Thanks for them links, has helped a lot. Will be having a big think this weekend. Really liking these http://www.bmautosport.co.uk/showroom/product_info.php/new-cades-apollo-alloys-hyper-silver-with-deep-concave-wider-rears-p-117