If any of you can, I suggest you try this. Sorry if it is a tad long.

Lastnight I was driving from Edm to Cgy (Alberta) About a 270km drive. My friend was also driving in his 00 Grand Prix GTP. We had FRS radios to communicate and so I asked him what he had cruise set at, and he said 125km/h, the thing is, mine was set a hair below 130 (it was on the 130 line tho) and neither were gaining... After a bit he set his at 128ish, and i had to set mine at 133.

I thought his car was off for being a 2000 model. However, he also has a sony GPS unit. To test it, he drove 125, and the gps also read he was going 124-125. I was doing 130 in my GTS.

Have any of you noticed this? Maybe the speedo is only off in mine by 5km/h.

 

(conversions aside) when cruising at 62mph, I'm actually going 60. Yeah they read a little faster than true, but no speedometer is guaranteed accurate.

 

i am sure yours is bang on, in terms of statisical odds, I would say his has a higher chance of being off since his car is 2000.

Best thing to do is to take the GPS for yourself and take it for a spin. yo uwill know right away if its off, if it is, record it on camera , document, how many clicks you got and drop your car off dude.

if thats off then who knows what else could be under the hood or your ECU

 

The VSS system in that GTP is pretty top notch. Not saying its perfect, but unless he has hub problems its probably spot-on (it's the same exact system used in Impala police cruisers so it has to be gov't tested and certified). I don't have enough information to make a claim like that on our speedos.

I do know this though. My speedo consistently reads between 2 and 3 mph higher than my actual speed. Correlating this, it matches what GeeTeeEss is seeing.

 

You mean HUD? I agree with his car, and since GPS is tracked by what 12 satellites?

Tomorrow we will take the gps in my car and see if the readings are different.

 

Still have the factory 18"s?

 

my car's spedo reads higher than my clarion GPS unit reads.

If I set my cruise at 110/115 I am doing around 100/105 between here and kelowna

 

Yes still factory rims.

Didn't get a chance to take the gps out today, maybe tomorrow.

 

As said, nothing is perfect. They only have to be somewhat accurate.

 

If you're asking about the VSS system I was talking about, no. VSS - Vehicle Speed Sensor. There's one in each front hub of those cars, and they have to be gov't certified cause they're the same parts used in police and government vehicles. I know the GM W-Bodies like the back of my hand, hell I've even got an M90 out of the same car (99 GTP) in my bedroom. The HUD (Heads Up Display) is just a readout of the same things that come through on his gauge cluster.

Looking forward to seeing your results when you take the GPS with you!

 

I gotta say, I actually noticed this the other day, but didn't think much of it.

On our highways, we have automated radar, which has a little display screen to tell you your speed. I was going about 105 KM/h according to the speedometer, but the radar screen was reading 95-97..

I also have an 84 Regal, and I'd figure that car's speedometer would be more likely to be off, but it's only off by about 3 KM/h according to that same radar.. So that kinda makes the Lancer look a little bad all things considered...

 

yea i do believe the speedometer is off...i would be driving on base..n ft. bliss military base speeds are no more than 35..so i would set the cruise at exactly 35mph..n one day they had the automated radar on n it said my speed was 32mph..i also didnt really think much of it.....atleast keeps me safe from gettin speeding tickets on base ^_^

 

thought about getting afermarket wheels/tires a bit bigger than stock size? that will solve the GTS' problem.

 

Does this just affect the speedo or the odometer aswell?

 

Odometer as well, I think.