Anyone notice that their speedometer isn't too accurate?

[StangAddict]

I noticed on my GPS a few days ago that I was going a couple of MPH slower than the speedometer read. I've been paying attention now when I drive past the speed displays on the roadside and sure enough I'm a good 2 MPH low: car says 40, sign says 38 etc.

No mods yet. I've got 3.73s from the factory, stock wheels/tires.

Anyone else notice this?

 

[slvr08gt]

yep. i notice it too. the higher you go the more its off. especially on the autobahn at 160.

-nick

 

[techcargt]

Same thing here , mine is off about 2-3 mph depending on my speed.

 

[skwerl]

By law they are not allowed to read low. There are penalties for doing so. Therefore the auto manufacturers err on the side of caution and set them just slightly high. If you were to step up 1-2 tire sizes then it would still be pretty accurate. They have been doing it like that for 50 years or more.

 

[StangAddict]

By law they are not allowed to read low. There are penalties for doing so. Therefore the auto manufacturers err on the side of caution and set them just slightly high. If you were to step up 1-2 tire sizes then it would still be pretty accurate. They have been doing it like that for 50 years or more.

Interesting. My other cars are pretty much dead on even at high speeds. I've got three mustangs and a Jeep Grand Cherokee. The 2012 is the only one where any sort of difference is noticeable.

 

[302]

Mine is spot on. I have 3:31 gears. That might have something to do with it.

 

[JeremyH]

So your saying the roadside radars and your gps are dead accurate so the speedo must be off?

 

[StangAddict]

Mine is spot on. I have 3:31 gears. That might have something to do with it.

If Ford isn't using different speedo gears for their differential gear offerings, then there's something really wrong. lol

 

[stkjock]

If Ford isn't using different speedo gears for their differential gear offerings, then there's something really wrong. lol

The speedo's have no gears in them for adjustment to rear gear offerings...

 

[white05gt]

I had a Lincoln Ls that was off almost 10mph at 70.

 

[StangAddict]

So your saying the roadside radars and your gps are dead accurate so the speedo must be off?

Did you read the thread?

I have 4 cars, 2 GPS units and a roadside radar is permanently mounted outside of my neighborhood. The only car that's off is my 2012 mustang.

So, the answer to your question is: yes, that's what I'm saying.

The speedo's have no gears in them for adjustment to rear gear offerings...

lol what? My '92 has a gear attached at the transmission to adjust for the 3.73s in it. Where are you getting your info from? Ford being that lazy/stupid is hard to believe.

 

[fdjizm]

There is no physical speedo gear to change in the newer cars.
Your 2012 is not your 92', we can change that parameter in a tuner now.

 

[JeremyH]

Did you read the thread?

I have 4 cars, 2 GPS units and a roadside radar is permanently mounted outside of my neighborhood. The only car that's off is my 2012 mustang.

So, the answer to your question is: yes, that's what I'm saying.

Yes I read it and you did not say any of this in your orignal post guy....

I noticed on my GPS a few days ago that I was going a couple of MPH slower than the speedometer read. I've been paying attention now when I drive past the speed displays on the roadside and sure enough I'm a good 2 MPH low: car says 40, sign says 38 etc.

Roadside radars that are there to "remind" you to slow down are almost always off and usual read higher as they should otherwise they are pretty pointless. They are also often damaged, out of cal units that are donated.
There is one by the gate by the base I work at and it was last calibrated in 05.


Commercial gps units are also have data inaccuracies built into them on purpose vice military units. Also gps untis display velocity so this is speed and direction/vector, so if the ground isnt perfectly level they can be off as well proportionaly.

Speedo's aren't designed to be perfectly accurate for that matter either.

The best way is to speed match other vehicles at different speeds and verify different speedos to each other. Your going to want to do it at 40, 60 and 80 mph to get it best matched for the speeds you usually will be traveling.

lol what? My '92 has a gear attached at the transmission to adjust for the 3.73s in it. Where are you getting your info from? Ford being that lazy/stupid is hard to believe.

That was in 92, welcome to 2011 we havent had mechanical gears like that for awhile, its all pcm controlled and can be adjusted by tire height/ revolutions per mile.

 

[stkjock]

lol what? My '92 has a gear attached at the transmission to adjust for the 3.73s in it. Where are you getting your info from? Ford being that lazy/stupid is hard to believe.

You're 92 also had a push rod motor, nothing changes in 20 years of technology advancements....

There is no physical speedo gear to change in the newer cars.
Your 2012 is not your 92', we can change that parameter in a tuner now.

/\ this

That was in 92, welcome to 2011 we havent had mechanical gears like that for awhile, its all pcm controlled and can be adjusted by tire height/ revolutions per mile.

/\ and that........

 

[StangAddict]

You're 92 also had a push rod motor, nothing changes in 20 years of technology advancements....



/\ this



/\ and that........

You could have skipped all the sarcasm and just said what this guy said below. Dunce? Get over yourself.

There is no physical speedo gear to change in the newer cars.
Your 2012 is not your 92', we can change that parameter in a tuner now.

So since my 2012 came with 3.73s from the factory, shouldn't it already be in the tune?

 

[fdjizm]

Yes it should and being 2mph off is not a huge defect.
Mine is 1mph lower than my GPS and I really don't care it's not a cause for alarm.
then again who is to say GPS is the last word on accuracy?

 

[302]

ib4pink

 

[BAKnBLK2010]

You could have skipped all the sarcasm and just said what this guy said below. Dunce? Get over yourself.

So since my 2012 came with 3.73s from the factory, shouldn't it already be in the tune?

Being 1 or 2 mph off isn't unheard of and yes your car was properly calibrated from the factory. You are headed down the wrong road spouting off to Stkjock.

 

[StangAddict]

Yes it should and being 2mph off is not a huge defect.

Thanks. I'll have to mention it the next time I'm there whining about my transmission. lol If it's off at 40, makes me wonder what it's like at 70+.

ib4pink

Who's pink?

Being 1 or 2 mph off isn't unheard of and yes your car was properly calibrated from the factory. You are headed down the wrong road spouting off to Stkjock.

Is this one of those boards where you have to let mods belittle you and not stand up for yourself or risk a ban? If so, sorry Stkjock. You're right, I'm dumb. Please accept my apology.

 

[302]

Who's pink?

LOL, you'll see.