speedometer accuracy

[hapaschold]

recently in my area the police have been using the mobile radar to tell ya how fast your going signs.......

my e350 is always reading about 2 to 3 mph faster than sign flashes ( at 45mph) , but yet my navi and wife s car is matched to the mobile radar.

this gotta have a long term affect on the accumulated mileage on odometer [img]/ubbthreads/images/graemlins/shrug.gif[/img]

wonder if dealer could calibrate to a more precise match.

[stroked_van]

I think it costs about $70 to have dealer recal the speedo.

[pon]

I don't think the procedure has much lee way for fine tuning. I have a 5" lift and 295 tires. The programming is restricted to entering the ratio and tire size for the 6.0 (as I understood it) so it took some creative work on the tech's side to find a combination that was equivalent. He also ended up calling the Ford tech's. I am spot on right now though. Less than a 1/10th of a mile off in 10. I paid $40 but it took two attempts and they didn't make any money on it! I think $60-70 is the norm. I would try to find a hiway mileage milemarker check before trusting radar. Even with the other vehicle observations.
Pat

[ddog]

Try comparing with a GPS. That is probably the most accurate.This THREADwith post by Smokey appears to indicate you can change the revs per mile setting to improve the accuracy. There is another more recent thread on this that I can't seem to find.