Not sure if others have noticed, but my 2008 Clubman (non-S) with the 17" wheel package (205/45R17 run-flats) has a bit of an optimistic speedo.

When I'm cruising at 100kph, my GPS has me at about 93.

Anyone else have this discrepancy? I'm a good 7% off.

 

It's been noted in several other threads. Most people find that it's 3-5mph off when comparing a GPS speed and the indicated speed.

 

BMW specs allow for a 10% + 2.4 mph error in this displayed speed. This is actually intentional; if you plug a ScanGauge in, it will show you the true speed.

 

My '08 with 16" wheels is only 2 mph off, which is much better than my 07 MCS with 17" wheels. It was a full 4 mph off. You learn to adjust.

 

not just several but close to fifty different threads here.

Actually it is plus 10% +2.4KPH and minus 0% and this is because many of the European nations have this as their Federal Standard.

And believe it or not (and i have tested it) that from a brand new set of 17" tires to a fully used set (down to the wear bars) there will be a 1.2 MPH difference in your speedometer. 16" are about 1.35 MPH and 18" are about 1.07 MPH