[Conquistador]

Originally Posted by oldnick

bit baffled by this

wasn't the car originally fitted with the same size tyres at both ends ?

if so the 235/30's are fine , your speedo will under read by 2% which is just fine , presumably the sensor is off the front end , will normally over read by 5-7% oe

but why the 265's? they will be 5% out ...presuming this is 4wd I wouldn't consider this difference even if it didn't affect the balance of the car ; presuming you have the same width rims front and rear one size is liable to be outside the permitted width for the tyre anyway

with regard to pressures , get your axles weighed in your normal running condition , then contact the tyre manufacturers , give them the loads and they will quote you pressures from their ETRTO charts as a base pressure to work up from

Nick, should have mentioned it's a BMW Z4, not an A8 or S8 any more, hence why the tyres are slightly fatter at the back for the deep dish alloys.

The speedo being slightly out was my other concern but I'll address that immediately afterwards.

These are the new wheels:


These are the current wheels, with run flat tyres. Handles horribly: