I dont' know why but my 02 996T speedo is 3mph off. Do all of them read higher at highway speeds? FYI i'm using my GPS to compare the speeds.

 

I heard most car speedo read higher than actual speed at high speed.

 

As long as it is consistently 3 mph off, I don't see a problem

 

If someone has a GPS could theyverify if porsche purposely has done this? I don't believe tire wear can cause such a difference. This should not effect the odometer correct?

 

Yes it's done on purpose, the law requires it. Or at least over here in Europe.

With that said, Porsche speedos are widely regarded to be the most accurate in the industry.

 

with the drift box mine was off by 3-4 mph.

 

I've researched this. My first Porsche, a '96-build '97 Boxster, read consistently 10% high. This was confirmed by running past two standing radar guns. I made passes at 30, 40, 50, 60, 70, and 100 mph on the speedo and the readings were 27, 36, 45, 54, 63 and 90. Porsche never fixed it, said it was fine and even had a factory rep refute everything I showed them.

My second Boxster read 2-3 mph high.

My first Turbo read about 8% high.

My current Turbo S reads 2-3 mph high.

Funny, though, about this law, because every other German car I've owned had a very accurate speedo. Funny too that, coincidentally, Ferrari and Corvette speedos tend to run high. I come to the conclusion that optimistic speedometers are a cheap subsitute for performance or an intentional measure to keep people from killing themselves because they "think" that they're going faster than they are.

 

My car was (1) mph off at 160 mph.

digital speedo = 160 mph
AX-22 = 159 mph

as tested "in mexico"

MK

 

Mine runs high...not sure how much, but I'm getting a Pbox and will let you know.

 

My AX22 GPS shows 3mph slower than that of the OEM speedo.

 

My '96 993TT showed 4mph high at 140 (140 showed 144). This was proven to be correct with radar and with GPS. We also tested this on 2 other 993TT's with the exact same results.

At 70, all 3 cars read 2mph high.

No variance could be determined between the 3 cars tested

 

I have the same issue with my GPS... 3-4 mph discrepancy.

 

Glad to hear i'm not the only one. I really hate how it's not accurate. I would like to know how fast i'm going and make my own judgement. I realize I always want to go 3mph faster so I'm going the speed i'd want to.

 

Mine is consistently 3-4 mph high between 35 and 90.

 

Did anyone get a fix from the dealer or do all of us has to accept this?

If anyone has a GPS could you please verify the speed and let us know.

Thanks all!