My car has the stock tires/rims.
My speedometer is off by 2 Mph@60 (speedo reads 62Mph at a real world 60Mph.)
At 124 on the speedo I am moving at 121 on the GPS
(tested on the track of course)

Here's the twist:
When I am at speedo 22, I am moving at 20Mph on my GPS
Is this normal?
Does the 8 figure the correct speed and add two Mph?

 

Sounds pretty normal to me. Speedometer accuracy can be affected by several factors including slightly different aftermarket wheel/tire size, incorrect tire pressure, slight wheel slip and especially tire wear. Less than 1% error is not bad since a speedometer is not a precision instrument by any measure

 

our speedo's have been lawyer proofed... so the speedo display actually is the measured speed (as seen on the CAN bus) +2mph

 

It's not a fixed 2 mph. At 25 mph, mine reads high by about 2 mph. At highway speeds, it's 3 to 5 mph high. I'm still on the OE tires, and keep the pressures at the specified 32 cold.

I think that's consistent with most of the speedo error posts.

Ken

 

It's off by 4% -- the legal maximum (I believe)

4% above or 2% below -- funny how that works out isn't it.

Why? To run out the warranty faster, of course. There were lawsuits in the US about this with most major car companies last year. Don't have links handy but I'm sure you guys can find it.


/just because you're paranoid don't mean they're not after you