F Sport Speedo Suspicions

[Andrew888]

Using my Sat nav on my phone I've noticed that my F Sport is 'off' by 4mph lower than actual speed. I used Waze, Google maps, another phone and even a Racelogic VBox and the speed is definately not right.. Anybody else noticed this on their speedo (digital ones not analogue)?

 

Very strange indeed.

[wharfhouse]

I thought that all speedos by law have to over read by a few percent so that when you are at the posted speed limit on the speedo you are actually doing a few mph less - so commonly at 70mph on the speedo you would be doing around 66mph - your scenario seems to be the wrong way around - the speedo reading less than the true speed?

[Guest]

Yes they over read by quite a bit to allow for tyres etc. It is illegal for a speedo to read slower than you're actually going.

So 10 percent means your 10k service is being done every 9k - and why you're allowed a margin over that on the warranty I suppose.

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[rayaans]

1 hour ago, S88HON said:

Using my Sat nav on my phone I've noticed that my F Sport is 'off' by 4mph lower than actual speed. I used Waze, Google maps, another phone and even a Racelogic VBox and the speed is definately not right.. Anybody else noticed this on their speedo (digital ones not analogue)?

 

Very strange indeed.

As mentioned. All speedos will be out by 8-10% above the real speed.

[Guest]

He says his car is reading lower than actual speed though. That's a problem. Correct tyre sizes is an obvious check.

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[Andrew888]

First time I've ever come across this, maybe its a Lexus rule lol. However I've always used analogue from all my cars going to Nurburgring. Spa and never has speedo out issues..

 

Such as life..

 

Cheers

 

[Andrew888]

Just now, Comedian said:

He says his car is reading lower than actual speed though. That's a problem. Correct tyre sizes is an obvious check.

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Soz mate

 

Should have clarified.. GPS actual for example 46mph - Lexus speedo 50mph.

so the car is reading higher than actual by 4mph or so..

 

Tyres are stock with stock wheels (18's)

 

 

[Guest]

That's normal.

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[Linas.P]

1 hour ago, S88HON said:

First time I've ever come across this, maybe its a Lexus rule lol.

all car by law have their speedos dialed a bit-up, because it is legal to show more, but illegal to show less. This was discussed in detail in GS forum where we looked at the law and technically they can overstate your speed up-to 30% and still be legal. In my personal experience speedometers always overstates speed by 5-15%. My IS shows 30 at 27MPH so basically ~10% as so most of other Lexuses.

[Ben1001]

Mine is 5mph OVER at  50mph (real speed 45mph).

[rayaans]

Ours is 10% up to an extent. At 70mph GPS it's showing about 74mph. 

[Bluesman]

My LS400 shows the Sat Nav doing 70mph with the speedo showing 65mph.

 

[NemesisUK]

1 minute ago, Bluesman said:

My LS400 shows the Sat Nav doing 70mph with the speedo showing 65mph.

 

What Sat Nav is that?

I'd be concerned if that difference is genuine, are the wheels/tyres to Lexus spec?

[scudney]

sat nav speed and  car speedo speed are usually 4 to 5 mph apart irregardless of make of car

[sorcerer]

3 hours ago, Bluesman said:

My LS400 shows the Sat Nav doing 70mph with the speedo showing 65mph.

 

Now, that really is illegal. As has already been mentioned, a car speedometer will always show you going faster than what you actually are. A satnav is a very accurate device, a lot more accurate than the car speedo, so I'm surprised that you've never triggered any speedcams. You need to get that sorted as soon as you can.

[Bluesman]

1 hour ago, sorcerer said:

Now, that really is illegal. As has already been mentioned, a car speedometer will always show you going faster than what you actually are. A satnav is a very accurate device, a lot more accurate than the car speedo, so I'm surprised that you've never triggered any speedcams. You need to get that sorted as soon as you can.

I do apologise, the ol grey matter gone a bit wonky. Sat Nav shows 70moh speedo is showing 76mph.

[Guest]

Every member of the forum can post, but they will all say roughly the same thing. If you can be bothered you can probably find the regulation that governs it on the EU website. Every country will have a similar but slightly reworded version. Manufacturers will have helped with it to aid construction simplification across the territories.

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[Linas.P]

14 hours ago, sorcerer said:

Now, that really is illegal. As has already been mentioned, a car speedometer will always show you going faster than what you actually are. A satnav is a very accurate device, a lot more accurate than the car speedo, so I'm surprised that you've never triggered any speedcams. You need to get that sorted as soon as you can.

It is not illegal to drive such car, what is illegal is for manufacturer to design and sell such car. The speedometer can show less speed due to many reason (mostly because of use of larger diameter wheels, different gearbox or differential ratios)... Technically you car would still be not road worthy due to "design and use", but not because of speedometer, but instead because of other modifications which made it show incorrect (less) speed.

[DanD]

This article, while not strictly related to speedo calibration, may be of interest...

http://www.telegraph.co.uk/cars/advice/the-truth-about-speeding-fines/