JimV8

I have always wondered if the speedo was reading too high and had my son drive my truck at predetermined speeds along side and found 944 reads 10 kms too high constantly and wonder if anyone else experienced this and if there is a fix.

rberry951

Mine was off about 8mph when I got it with stock tire size, was closer on when I put bigger tires on it. I've heard many of my friends say they have run with a GPS and their speedometers were all off a bit. I don't know what you can do about it other than find out the exact amount it's off at highway speed and make a mental note so you don't get a ticket.

bearone

the speedo could be off in the truck too so it's not a real good benchmark.

go by traffic around you, are you faster or slower when driving at the posted speed.

87951

JimV8

I am slower than traffic around me and often wondered why everybody was so far over the limit and why when I'm at the posted speed everybody is on my bumper. I checked out wheel and tire dia and thats ok so I guess at this point best to just make a mental note. GO FASTER.

bearone

or get a speedo calibration ck.

look on the brite side, if you go the speed limit you won't get a ticket.

87951

lleroyb

I found a close correlation between my speedometer and a GPS up to about 120 MPH. At 60 mph it was dead on for the hiway speed check. Many report the speedometers get real optimistic at higher speeds.

Lou

billthe3

According to the radar speed signs around here, my speedo is close to 4mph fast at 50. Which is almost annoying, because I don't want to get any bigger wheels/tires because the current size looks good. I haven't bothered to see what size they are though, so I don't know if they're the stock size.

inactiveuser92616

I went to a wider tire, which is acompanied by a taller sidewall for the same series. Speedo fixed.

joes

Tire rack has tire revs /mile on their tire specs. I compaired those with the factory wheel sizes and ordered tires that were the closest , it got mine very close.

Rich Sandor

Porsche speedometers have always been generally 8-12% optimistic. Wheel/Tyre size can affect the speedo reading as well.

billthe3

Yeah, I figured they were like bmw ones and set to be fast. Still annoying though - especially on my dads bmw. The limiter is set to 130 on the speedo, but because its off so much the car is probably only going closer to 120.