how can i prove my speedometer is not off?

[AzItaliaSS]

Let me check and I will post

[AzItaliaSS]

just type in "speedometer" in android market and there are several to pick from

[AzItaliaSS]

it would be best to get the app, drive the care and lock in cruise at 20,30,40,50 mph to get accurate reading how much it is off by, should give you a good average

[justin2fast4u]

i tested it and mine is fine, its hers that is off, how much would tire size change the speed? because she may have a big problem, im guessing hers could be 7-10mph off...when we were both doing 60 she left me, like was 6 or 7 car lengths ahead in a matter of seconds

[evilbeef54]

Going up a tire size could easily throw it off by 10%

[Coyotekiller]

Tell her to take her car to a garage and get it fixed. Any mechanic should be able to fix it. I've donethis several times when changing tire sizes

[Steve Dallas]

Really? REALLY???? No one posts the most obvious and easist way to do this?

GPS? That has a little built in inaccuracy for civilians. I've seen mine vary by 2-4mph when I'm on cruise control. The altitude is off by quite a bit as well.

Either no one remembers the old-school way of doing this...or are just lazy these days. You know that most highways have mile markers. If you set your cruise control at 60 (hopefully level road, though not absolutely necessary), and start your stopwatch as you pass the mile marker. When you pass the next one, you stop it. If you did one mile in one minute, then you are doing 60mph. Simple. Accurate.

[14pilot]

Explain to me why you have to prove anything to her in the first place ?

FWIW, proving something to a woman = proving that one is an ass....

[The Stig]

maybe I'm the only one who thought of this, but who's to say she isn't just screwing with you?

[1BADLS3]

Originally Posted by Steve Dallas

Really? REALLY???? No one posts the most obvious and easist way to do this?

GPS? That has a little built in inaccuracy for civilians. I've seen mine vary by 2-4mph when I'm on cruise control. The altitude is off by quite a bit as well.

Either no one remembers the old-school way of doing this...or are just lazy these days. You know that most highways have mile markers. If you set your cruise control at 60 (hopefully level road, though not absolutely necessary), and start your stopwatch as you pass the mile marker. When you pass the next one, you stop it. If you did one mile in one minute, then you are doing 60mph. Simple. Accurate.

I came in here to post exactly this. Must be a Northwest/pioneer thing. We don't need no stinkin' GPS!!!!

If you pass a mile before 60 seconds is up at 60mph, your speedo is reading too fast. If you haven't reached a mile at the end of 60 seconds, your speedo is probably reading slow.

FWIW, visually, most speedometers read about 2mph high, and it's considered standard variance and is also added protection when you get busted. 2mph could mean the difference between a ticket for reckless or not.

[Hellfighter]

slab on some 24's on that "ho, and you be riding fast".... lol not

[1BADLS3]

Oh, and the other thing-- bigger wheels/tires will make the odometer read slower than you're actually going.

I figured this out when I bought my Jeep. My partner had driven our other car to the dealership, and I called him on the way home because I couldn't understand why he was going 5 under in a 60 zone. He never drives that slow. Turns out the computer was never corrected, so we fixed that with a tune and update for the new tire size.

[5cents]

With newer cars, with on-board computers, it's just a matter of reprograming the computer if you change tire sizes. For older cars, there's a little gear where the speedo-cable screws into the transmission that can be changed to compensate for tire sizes.

[doubletap407]

GPS!