I have used a portable gps in a number of cars which shows driving speed. Every car has matched the speed the gps shows except mine. The speedo is 2 mph over the actual speed. Can this be fixed?

 

are you running stock tires for your make/model/year?

if so, a +2 mph difference, dont know if Porsche would fix that to be honest

had a BMW 540 speedo that was off by 8 mph due to up sizing of rims.

 

Tire size may be the culprit.. if the height is lower it shows more MPH..

Mike

 

2 mph?

Is it enought to even worry about?

 

Mine does the same thing but I think it is more liek 3-4 mph for my car. I'm not that worried about that unless it was like 10 mph

 

Hmmm. I don't know. An $81,000 car. It'd be nice if it were accurate.

I am running stock turbo look 18" rims and spec tires.

 

+- 2mph i consider pretty accurate myself..

 

Absolutely right. It is pretty accurate.

 

 

mines 4mph off...i can see it see it aeveryday because my escort 9500 shows the speed on it lol

 

last 2 p-cars i had were 3 mph over --

 

Get it recalibrated at an Indy shop if you want it 100% accurate.

 

I don't think there is a car in the world with a 100% accurate speedo.

 

I've got this problem too, my 2002 996tt's speedo is 3 mph too fast. It has stock wheels right now, but I'm going to put on the 1'' larger 997tt wheels soon and am waiting to see how the new wheels affect this (although I'm keeping ride height within 3/12 of an inch, so probably wont' affect).

If it was too slow, that'd be fine, but I'm annoyed its too fast because its putting 6% (at 50mph average) more miles on the car than I"m actually driving. It does seem like everyone who's noticed this problem is it being too fast, maybe Porsche is trying to make us think we are going faster than we are.

 

"Officer, my speedometer must be way off. It shows around 25 mph less than what you clocked me at - damn German electronics!"