Re: Tire size/Speedometer accuracy
If you really care, you could raise the whole car (jackstands or lift please) and with key on spin one wheel at a time and see if anything registers on the speedo. Then start engine & let rears turn at idle in third. That would be a good set of indicators.
Might set a code also so be ready to clear.
ps "lost 350 rpm at 80" - maybe the tires grew... Nah going from 26 to 28" diameter only drops 200 rpm (2800 to 2600 in 6th). More likely the programming has a fudge factor and the speedo is non linear. Again, need to compare to GPS.
Last edited by Padgett; Dec 28, 2013 at 10:01 AM.