Speedometer reads fast

[Kiwi Greg]

I agree, but im pretty sure with one of the options I mentioned in coding with bimmercode it can be coded to the show the actual speed you are going not the fast one it shows. Just not sure which one exactly is it, guess I'll have to experiment.

That would be great to know & code for sure,

My 05 GTO is bang on with indicated speed, go figure

Sponsored

 

[Count Mackula]

I was about to post a thread about this till I found this. I had the same exact problem.

I was driving back home from Vegas and my buddy was following me in my Audi S5. We were doing 80 MPH in both cars he had waze on.

I couldn’t figure out why he kept pulling so much further than me at the same speed. So I called him and my Audi was doing 80 and so was his waze.
I turned mine and my speed was 78 on waze.
He then send me a picture of the Audi and his waze app displaying 80 MPH.

Every time I check the app, I’m consistently 1 or 2 MPH slower in waze

 

[Count Mackula]

Well... I should’ve read the whole thread before posting. Lol.
My fault.

 

[nibble]

AFAIK, every car from factory will read "incorrect" Speed compare to GPS. there are couple of reasons but mainly, speedo is calibrated to how much wheel is turning. Also, defacto value of how much car is used is determined by Odometer which in turn, calculated by speed you are traveling.

in short, if you have larger OD (overall diameter) wheel/tire set up, speedo will read lesser speed hence, Odometer will accumulate less. If you have smaller OD, effect reverses. faster speed, higher odo.

for example, OEM tire, 275 35 R19 which has OD of 26.58" (675.1mm) vs 295 30 R19 that has OD of 25.97" (659.6mm). 295 setup will read faster speed as well as higher OD at the end of the day. the OD of the tire also can be contributed by tire pressure. higher pressure will yield slightly larger OD than lower pressure. Further more, since pressure is also sensitive to temperature, you might see higher speed in colder weather as well.
Using GPS as Speedometer also has challenges. For one, say a car is traveling point A to B which is 60 miles. If a car arrived at B in 60 minutes, that is 60 mph probably on GPS. however, for an argument sake, let's say the car was zigzagging and added 5 miles more but arrived in 60 minutes. that should've been 65 mph. GPS based, would probably record 60 mph overall. even though it actually was 65 miles. further more, if there's lost in GPS signal, it would have hard time calculating. that can be contributed by event such as driving in tunnel, under ground, or satellite shot down, & ETC.

 

[Kiwi Greg]

Over here all new cars are a consistent 5-8 kph under the indicated speed right off the show room floor

 

[ArthurWick]

If you want exact speed shown, just use bimmercode

https://www.supramkv.com/threads/bimmercode-user-guide.6429/#post-97417

 

[TX2.0]

If you want exact speed shown, just use bimmercode

https://www.supramkv.com/threads/bimmercode-user-guide.6429/#post-97417

Today my 2.0 went through eight highway speed checks on I-10.
My speedometer read 75 through all eight.
The speed check for each was 67mph.

 

[XtremeMaC]

With Waze, even at 163mph per tacho, Waze only showed 2-3mph difference.
I've also checked at 80-120. around 80 it was 0-1mph, 120 1-2mph...
Should have used a more robust tool but wasn't really prepared.

It was ~46F out tires warmer. Don't recall the tire pressures...

 

[diablo2112]

With Waze, even at 163mph per tacho

I thought the Supra had a 155mph speed limiter?

 

[XtremeMaC]

I've removed it with BM3.
Fyi, car was pretty stable and felt it can easily do more, which we know it can.

 

[Irulea2]

It does read 2mph faster however you can correct that with Bimmercode. I never bothered because it doesn't hurt to read a couple faster when already speeding. May bake a difference when speeding 21mph over speed limit vs 19mph over.

 

[Benjilis]

I honestly don't own a single vehicle where the speedo doesn't read a bit faster than I'm actually traveling; it's generally 2-3mph over at highway speeds

what other vehicles have you owned where this is not the case?



EDIT: I just asked a few people around me and all said this is completely normal behavior (which has always been my impression).

My old VW CC would read that I’m going 5mph over what I actually was on the highway. I found this out because my radar detector would show me the speed I was going when hit with a radar.
It’s a safety feature I believe. Just ignore it and go the speed you want and get a radar detector.

Sponsored