Speedometer not accurate?

[bar10dah]

Ah, okay. I misunderstood. I thought you were saying your speedo reads 110% of actual and +4 of actual at the same time throughout the entire range. I was tired last night when I read that...

Those are pretty big margins that the cops will let you get by with. Here, it's really up to the cop's disgression. He can write you a ticket for doing 1 MPH over. Or, he can let you go by at more than 20 MPH over. Just depends on who the cop is and what his mood is at that moment.

And, you're the first Boxster owner that I've read that has a speedo that's linear. All others report the same ~3-4 MPH higher reading throughout the entire speedo range. I wonder why yours is different? Stock wheel sizes?

[SoK]

Going 73 as read from the digital readout in the dash, i'm going 69 - 70 by radar.

[Bob O]

Based on the readings from my GPS, mine always varies by 5% at all speeds. At an indicated 80 the GPS reads 76, and at an indicated 50 the GPS reads 47-48, etc, etc. I've tracked this over many trips and it never changes. I just live with it. As was posted above, it's apparently a law in Europe and the fines for having the speedo read slow are, from what was discussed in a previous thread, pretty substantial. It's not that big a deal to me. If you can figure out what the factor is to correct for the error (assuming it stays constant, which it does on mine) it becomes pretty automatic when on the road.

[Bruce Wayne]

And, you're the first Boxster owner that I've read that has a speedo that's linear. All others report the same ~3-4 MPH higher reading throughout the entire speedo range. I wonder why yours is different? Stock wheel sizes?

yep 18" as per the pics.. though i was tired when i wrote that too.