How accurate are they? I drove my buddy's car and hit an indicated 202mph and am wondering if it was really 202mph. He has 19" wheels and its an EVO Stage 4GT. I thought it would go faster than that but it would just hold 202 and not climb any higher than that.

 

sorry but my experience is that Porsche analog and digital speedometers are totally nonlinear and grossly inaccurate at high speed. One may easily calculate real speed to a few% using:
rpm/gear x tire='/minute..
GPS works very well. My Garmin GP3+ have been beat against a calibrated timing system and both units are right on.
Hope that helps.

cheers

R

P.S.

What was the rpm @ max speed?

 

I hit max speed through a big bend in the highway so I really didnt have a chance to look at my rpm but it was close to redline for sure. I know a person who hit an indicated 204mph with stock wheels on his car and with the GPS it was 200mph. I just found that out and thats not bad compared to other tachs...

 

One our car, with 19" alloys, 211mph is needed on the speedo to reach a GPS verified 200mph.... 202mph is around 189-190 in our car which is probably similar to your buddies

all the best
adam