Speedo question

[Boardmember]

I’ve suspected but now have “proof.”

 

My speedometer registers ~1.5 mph faster than I’m traveling.  (It vacillates between 1 & 2, so I say 1.5).  Verified a couple ways.  Stock size tires.  Just rolled 9000 miles this morning.

 

Can the dealer recalibrate to make it accurate?

My MPG readout in the DIC is equivalently optimistic, I hand calculate every fill up.   Related, no doubt.  How about my ODO?   Is it reading slow?

[ChristopherDB]

Most speedometers exaggerate the actual speed, this is normal. Dealer will tell you it's within spec.

[m3n00b]

Totally normal. My other cars do this too.

Sent from my SM-G965U using Tapatalk

[Boardmember]

That’s reassuring.  Sort of.   2.8% variance at 70mph?   

 

How owl does that factor into my optimistic MPG reading?   Does my odometer show 2.8% more mileage than I actually travel?

[qwank]

you say stock size tires, does that mean stock wheels and tires that came on the truck or aftermarket wheels and tires stock size? 

[Boardmember]

The GMC snowflakes.  

[Ravenkeeper]

Your MPG has nothing to do with your MPH.  Your fuel economy is a rough ballpark number anyways, so is your calculations, will vary by gas station and how you fill it up. 

 

If you know where there is a stationary radar, or several of them, set your cruise for that speed limit and see what it/they say(s).  There are several around Edwards AFB, the trailers are calibrated, the one on the posts aren't, I think, or at least have never seen the ones on the posts removed for calibration.   Also, make sure that your tires are serviced to spec.  I've noticed that if I have them at 32PSI, speedometer is off slightly, usually .5MPH in my favor.  Around 37PSI, speedometer and radar seem to match, on the money.

 

The radars on the posts, some of them will blink when you're speeding, other/most of them will blink no matter what speed you're doing.

 

[Boardmember]

Interesting on the psi having that sort of an impact.  

 

While were discussing, the psi readings on the DIC Give only a general indication too.   I try to run 36psi cold.

[Ravenkeeper]

14 hours ago, Boardmember said:

Interesting on the psi having that sort of an impact.  

 

While were discussing, the psi readings on the DIC Give only a general indication too.   I try to run 36psi cold.

Agreed, I trust the PSI on the DIC more than the PSI on the pump at the gas stations.  BUT, I do check them with a pressure reading stick. 

[Boardmember]

I have two digital gauges from Sears.   My family just smiles and nods knowingly at each other...