159 Speedo accuracy
I have a 159 1.9jts and recently changed the wheels to 18" with 235/45/18 tyres. I'm a little confused by Alfa because this wheel and tyre combination gives a rolling diameter 4.04% bigger than the standard 16" wheels with 215/55/16 tyres the car was built with.
This means that the speedo with one of these wheel/tyre combinations is inaccurate. Legally the speedo can be up to 10% fast but not slow (at an accurate 60mph reading between 60 and 66mph.
So what do I need to do? Can the speedo be recalibrated through the ECU by a dealer? Is my speedo now slow and inaccurate? Should I care? Any ideas??
Also, while I'm in an inquisitive mode, other than the stroke of the crankshaft, what are the differences between the 1.9 and 2.2 jts engines?
Big questions for a Sunday evening!!