Speedometer giving false reading

bramwell · 08-17-2007, 04:58 AM

Hi, my first posting.

I have a 2007 Prius T spirit and noticed that the speedometer was reading 5-6 MPH above the reading given by both my Sat Nav PDA and GPS speed camera detector.

My dealer has checked this with a speed gun device and has found that the speedometer is reading 10% above the actual speed. He did the same check with another Prius and found exactly the same problem.

Now I understand that most speedometers read slightly higher than actual speed to give a margin of error but 10% is way too high an error.

Not to mention the fact that when the speedo is reading 70 MPH the car is actually doing 63 MPH, it means that for every 10,000 miles driven, the mileage counter reads 1,000 miles higher than it should which will reduce the trade-in value. It also has an effect on the MPG as this relies on the speed reading to calculate its values. The sat-nav will also be effected i.e. time of arrival.

My dealer says that this problem cannot be corrected as there is no adjustment for the speedometer.

Can anyone help ?

Thanks, Paul.

PS, I saw on another thread that the steering wheel buttons should light up when the headlights are on - mine does not. Is this just a European thing ?

ken1784 · 08-17-2007, 05:17 AM

<div class='quotetop'>QUOTE(Paul B @ Aug 17 2007, 05:58 PM) [snapback]497691[/snapback]</div>

Quote:

Can anyone help ?
[/b]

The speedometer dispaly is intentionally biased to meet "UN-ECE Regulation No. 39".
http://www.unece.org/trans/main/wp29...egs/39rv1e.pdf

Ken@Japan

AussieOwner · 08-17-2007, 06:46 AM

<div class='quotetop'>QUOTE(ken1784 @ Aug 17 2007, 07:17 PM) [snapback]497693[/snapback]</div>

Quote:

The speedometer dispaly is intentionally biased to meet "UN-ECE Regulation No. 39".
http://www.unece.org/trans/main/wp29...egs/39rv1e.pdf

Ken@Japan
[/b]

Wow! Thanks for the info, Ken. Just goes to show that we not only get stuffed around by our various governments and their departments, even the UN gets in to make life difficult.

gazz · 08-17-2007, 06:56 AM

<div class='quotetop'>QUOTE(Paul B @ Aug 17 2007, 03:58 AM) [snapback]497691[/snapback]</div>

Quote:

Hi, my first posting.

I have a 2007 Prius T spirit and noticed that the speedometer was reading 5-6 MPH above the reading given by both my Sat Nav PDA and GPS speed camera detector.

My dealer has checked this with a speed gun device and has found that the speedometer is reading 10% above the actual speed. He did the same check with another Prius and found exactly the same problem.

Now I understand that most speedometers read slightly higher than actual speed to give a margin of error but 10% is way too high an error.

Not to mention the fact that when the speedo is reading 70 MPH the car is actually doing 63 MPH, it means that for every 10,000 miles driven, the mileage counter reads 1,000 miles higher than it should which will reduce the trade-in value. It also has an effect on the MPG as this relies on the speed reading to calculate its values. The sat-nav will also be effected i.e. time of arrival.

My dealer says that this problem cannot be corrected as there is no adjustment for the speedometer.

Can anyone help ?

Thanks, Paul.

PS, I saw on another thread that the steering wheel buttons should light up when the headlights are on - mine does not. Is this just a European thing ?
[/b]

Hi Paul,

Mine also reads about 10% fast, In the UK this is normal its just having the digital speedo you see it more and also with sat-navs you see the real speed. You just have to note that a number of important speeds on the prius have to be converted to UK speed. The ICE starts at 44mph not 41mph as will be stated by none UK owners.

As regards to the mileometer I would assume that is correct and does not have the 10% error.

Gary

Tom_06 · 08-17-2007, 07:02 AM

<div class='quotetop'>QUOTE(AussieOwner @ Aug 17 2007, 06:46 AM) [snapback]497703[/snapback]</div>

Quote:

Wow! Thanks for the info, Ken. Just goes to show that we not only get stuffed around by our various governments and their departments, even the UN gets in to make life difficult.
[/b]

You could put new tires on with a different Revs/Mile. For the USA, the standard tire is supposed to be 855 RPM, at least when new. As the tire wears, RPM goes up and apparent speed & mileage increases.

You want the speedometer and odometer to be lower, so get a tire size that is 8 to 10% larger. Look up the specs on whatever tires you have now at either the manufacturer's web site or a place like tirerack.com.

- Tom

gazz · 08-17-2007, 07:26 AM

<div class='quotetop'>QUOTE(Tom_06 @ Aug 17 2007, 06:02 AM) [snapback]497708[/snapback]</div>

Quote:

You could put new tires on with a different Revs/Mile. For the USA, the standard tire is supposed to be 855 RPM, at least when new. As the tire wears, RPM goes up and apparent speed & mileage increases.

- Tom
[/b]

In the UK only the speedo will read fast by design for "saftey" and so there is no doubt that you are exceeding the speed limit. The miles traveled are accurate. The speed is shown different on the Scangauge but the miles traveled are the same.

skandale · 08-17-2007, 07:29 AM

As some have already posted, cars are required to show the speed with a margin of error. If you had for instance a ScanGaugeII, you would see that the car deep down within knows the true speed (or at least very close to it).

But I'm surprised to hear of 10% off. My current car (a 2005 Peugeot 1007) is about 4-5% off, which I thought was the norm. Since 10% off is the limit for the UN regulations (in Norway at least, a new car is illegal to sell if it's speedometer is more than 10% optimistic), Toyota seems to have gone very close to the limit.

I remember reading a tread here or on PriusOnline where a Swede had checked his speedometer from 0 to 170kph, finding that the speedometer seemed to have 3 steps of "error". The faster you drive, the bigger difference between displayed speed and true speed. Sadly, I cannot find that posting tight now, but I'll try to find it.

EDIT: Here is the thread. Post #26 has the results from the Swedish jury: http://priuschat.com/index.php?showtopic=30709&st=0

Stein

patsparks · 08-17-2007, 07:57 AM

My motorbike has a 11% error in the speed reading but less than 1% error in the odometer.
I haven't noticed this with my Prius, will check it against my GPS.

bramwell · 08-17-2007, 10:50 AM

Hi,

Thanks for the responses - especially the PDF Ken.

I would agree with Stein that 10% should be deemed too high and reading other threads, some owners have said that their speedometers are exactly correct or pretty close.

It's a shame that there is not an adjustment that can be made by the dealer.

I'll just have to keep my maths up to date and subtract 10% all the time.

By the way, my Peugeot Estate is 2 mph above the speedometer reading which I would consider acceptable - you would think that a digital speedo would be at least as accurate as an analogue one.

Paul.

ken1784 · 08-17-2007, 12:05 PM

<div class='quotetop'>QUOTE(Paul B @ Aug 17 2007, 11:50 PM) [snapback]497802[/snapback]</div>

Quote:

It's a shame that there is not an adjustment that can be made by the dealer.
[/b]

Hi Paul,

Please be aware that a dealer or any car manufacturers can't adjust it unless the speedometer reading is out of range from the regulation.

Ken@Japan

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08-17-2007, 04:58 AM	#1
bramwell Join Date: Aug 2007 Posts: 3 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Hi, my first posting. I have a 2007 Prius T spirit and noticed that the speedometer was reading 5-6 MPH above the reading given by both my Sat Nav PDA and GPS speed camera detector. My dealer has checked this with a speed gun device and has found that the speedometer is reading 10% above the actual speed. He did the same check with another Prius and found exactly the same problem. Now I understand that most speedometers read slightly higher than actual speed to give a margin of error but 10% is way too high an error. Not to mention the fact that when the speedo is reading 70 MPH the car is actually doing 63 MPH, it means that for every 10,000 miles driven, the mileage counter reads 1,000 miles higher than it should which will reduce the trade-in value. It also has an effect on the MPG as this relies on the speed reading to calculate its values. The sat-nav will also be effected i.e. time of arrival. My dealer says that this problem cannot be corrected as there is no adjustment for the speedometer. Can anyone help ? Thanks, Paul. PS, I saw on another thread that the steering wheel buttons should light up when the headlights are on - mine does not. Is this just a European thing ?

08-17-2007, 07:29 AM	#7
skandale Join Date: Jun 2007 Posts: 101 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	As some have already posted, cars are required to show the speed with a margin of error. If you had for instance a ScanGaugeII, you would see that the car deep down within knows the true speed (or at least very close to it). But I'm surprised to hear of 10% off. My current car (a 2005 Peugeot 1007) is about 4-5% off, which I thought was the norm. Since 10% off is the limit for the UN regulations (in Norway at least, a new car is illegal to sell if it's speedometer is more than 10% optimistic), Toyota seems to have gone very close to the limit. I remember reading a tread here or on PriusOnline where a Swede had checked his speedometer from 0 to 170kph, finding that the speedometer seemed to have 3 steps of "error". The faster you drive, the bigger difference between displayed speed and true speed. Sadly, I cannot find that posting tight now, but I'll try to find it. EDIT: Here is the thread. Post #26 has the results from the Swedish jury: http://priuschat.com/index.php?showtopic=30709&st=0 Stein

08-17-2007, 07:57 AM	#8
patsparks Uneducated bird-brain Aussie Join Date: Jul 2007 Location: Adelaide South Australia Posts: 4,438 My Car: 2004 Prius Package: Base Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 12	My motorbike has a 11% error in the speed reading but less than 1% error in the odometer. I haven't noticed this with my Prius, will check it against my GPS.

08-17-2007, 10:50 AM	#9
bramwell Join Date: Aug 2007 Posts: 3 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Hi, Thanks for the responses - especially the PDF Ken. I would agree with Stein that 10% should be deemed too high and reading other threads, some owners have said that their speedometers are exactly correct or pretty close. It's a shame that there is not an adjustment that can be made by the dealer. I'll just have to keep my maths up to date and subtract 10% all the time. By the way, my Peugeot Estate is 2 mph above the speedometer reading which I would consider acceptable - you would think that a digital speedo would be at least as accurate as an analogue one. Paul.