Scot

First one my BMW said 167mph = 159.9 that GPS shows...

The Dodge on the 3rd one down was at the rev limiter in 4th gear at an indicted 167mph = 162.2

The other two I didn't get a chance to look at the speedo... once you hit 5th gear it barely accelerates...


***disclaimer*** - all of this was done on a closed course by a professional.

cdelena

My S2000 is 3% off (fast) with my summer tires but dead on with the winter tires (I trust the GPS reading). I assume it is variances in tire diameter.

budgy

Imagine on winter tires or all seasons with deep tread the difference between brand new and worn out tires, not to mention that the sizing may not be perfect to begin with. Most car speedos are a little optimistic.

Marioshi

Fairly typical. Also, tires deflect at high speed which may have an effect on your speedometer readout. Better to read high than low, save you from getting some tickets, keep the mileage down.

mosesbotbol

So the new Rolls that uses GPS and maps to shift gears must be dead on!

ZDan

There are regulations in EU countries that require the speedo to not read lower than actual speed even with oversized tires. For this reason most speedos read high by design.

Btw, life begins at 180

JonBoy

My Z4M is off by approximately 5% at 75 mph.

rob-2

But look, you have 4 bars at that speed

freq

You should be able to code that BMW to read true speed.

Scot