I have noticed since I bought my 04 STI last Oct. that the speedometer is a little off. When I pass those stupid things the police put up that tell you how fast you are going they always say I am doing nearly 4mph slower than I really am. I thought it may have been just that one, but I passed several in a different town and they showed the same thing. Not really a lot I guess only being like 4 mph but I'd like the instruments in my $30K car to be correct or at least within +/- 1mph. Anyone else have this problem or know how to correct it? BTW. My car is stock.

How fast are you going when you pass them? The STi speedo is known to be off by about the amount you are describing, but it really only gets that bad at higher speeds. I know you said the car is stock... That includes stock wheels and tires?

The limit is 35 where the local one is placed. I have even sped up to see if the reading would get worse but I don't do much more than 50-60 and I still see the same result. It bugs me everyday b/c I pass it on the way home from work and it makes my radar detector go off. Yes, the wheels and tires are stock. Even on my old Integra I had 18" wheels and 35 series tires and the speedo didnt change at all. I guess it's b/c it was mostly plus sizing.

The stock size for the STi in Japan is 235/45/17, if the speedo is calibrated for JDM sized tires, ours will always be off. Why piss and moan about being slower than you think? Less speeding tickets that way. Use it to your advantage, set your cruise control to 10 over and you'll always be less than 10 over.

With a quick and dirty calculation, the speedo is only 1.4% fast. The good news is for ~$700 you can fix your problem.

That's cool. Thanks for the help. I did a search before I started this thread and didn't come up with anything really. I just wanted to be sure that this crap is normal. It will probably be wayyyy off when I get different wheels anyway huh?