Quote:
Originally Posted by Boss330
I was also thinking of the factory set of wheels available. But since the law in EU allows tires to be changed as long as they are within +/-5% of standard rolling circumference, any manufacturer has to make allowances for aftermarket tires being as much as +5% over standard rolling circumference (not diameter BTW, diameter and circumference are two different things you know  ).
Every manufacturer does this and depending on the tires that are on the car, and speed range (some have a higher tolerance at higher speeds), the "error" might range from 1% to 10%.
The M5 also has winter tires that are 255/40R19. The 265/40R19 summer tires are 1,17% larger and makes a difference of 1km/h in speedo reading.
The 167-172MPH runs done by M5 owners, have in reality been 155MPH when they have verified true speed on a GPS during their runs AFAIK. I'm pretty sure you can find several posts confirming this  |
Thanks again... BTW 5% difference in diameter is equal to 5% difference in circumference and cause 5% difference in speed calculation since it's based on the circumference and number of rotations