Speedo Accuracy

[Scarlet Pimpernell]

I checked my speedo against what is stated on my Dell PDA Nav software...

and....

At a speedo indicated 70mph (with cruise) the PDA was showing 66mph....I would have said that the GPS was accurate with a steadily "moving target", so I reckon a 5% over reading by the Lex speedo!!!

PS - break the law at your own peril...that's my disclaimer!

[Kazi]

Sounds about right, they have to have a slight margin on the speedos.

[deejaygee]

I checked my speedo against what is stated on my Dell PDA Nav software...

and....

At a speedo indicated 70mph (with cruise) the PDA was showing 66mph....I would have said that the GPS was accurate with a steadily "moving target", so I reckon a 5% over reading by the Lex speedo!!!

PS - break the law at your own peril...that's my disclaimer!

And your point is - all manufacturers are the same!

[Scarlet Pimpernell]

The law I believe states that a speedo can over read by upto 10% and under read by no more than 1mph...using same PDA/Software these are my very recent findings:

Peugeot 407 (x3) - : bang on

Ford Focus - 6mph

Vauxhall Astra - 4mph

Citroen C4 (x5) - all bang on, but sometimes I swore the last one I had was under reading by 1mph!!

Mazda 6 - 3mph

Audi A4 - 4mph

Lexus New IS - 4mph

So it can make the difference between a speeding ticket (GATSO etc) or not...that's the point...

Beware if you drive a French car...

PS - should add that these are all recorded at 70ish and with my PDA/Dell NAv software...

[deejaygee]

So it can make the difference between a speeding ticket (GATSO etc) or not...that's the point...

I still disagree, what is the point - if you just read your speedo as being accurate like the majority of people you will never get a speeding ticket anyway..........................

[Ro1]

I have a Garmin I3. Speed is generally indicated approx 7% slower than the IS250 speedo. In theory, a 12+ channel GPS receiving a strong signal from multiple satellites should be far more accurate than the speedo.

As far as I know, the tolerance allowed by speed checks here is 5% + 1 MPH. Therefore, sticking to the GPS reading may still help you avoid getting a ticket. However, the point of driving within the speed limit isn't necessarily to avoid tickets.

[Pip]

The speedo generally shows 10% less. It so the manafacturers can cover themselves.

[rap03]

Jamboo. Can you test at a lower speed. Interested to know if it is a fixed or variable difference.

It's also interesting that the Lexus GPS doesn't show your speed like the handheld or PDA GPS systems.

[Scarlet Pimpernell]

Jamboo. Can you test at a lower speed. Interested to know if it is a fixed or variable difference.

It's also interesting that the Lexus GPS doesn't show your speed like the handheld or PDA GPS systems.

Didn't mention it above but I did check it at 40mph, where the GPS showed 38mph...

I know the idea is not to get a ticket and stick to what your speedo says, but I now have a degree of confidence in that should I see the dashed lines, hit the breaks, see the needle swing to below the allowed speed at that point, I may be able to sleep well...

Over 200,000 miles driven in the last 9 years, and no tickets or cautions yet (speeding or parking)...but now that I've said it...famous last words... :o

Especially when this is the first car that I have ever owned where it's all too easy to break the speed limit and not have a clue...

[derekyau]

N.B. I don't know about the DELL Nav software, but with my Tom Tom 3, you will notice that the updates to the speed reading are staggered - i.e. update every second or so (digital), and so if you were accelerating, or not able to hold a constant velocity, then even with 12 GPS+ signal, it wont be totally accurate.

I agree that it is common knowledge that all car manufacturers generally have a percentage margin of error on the accuracy of a cars built in speedo.

D.

[Stoffe]

Hi!

How is it working in england with speeding? I mean at what point are you loosing your license, and how much is the speeding tickets? In sweden we have a new updated law due to increasing speeding. at 6 km/h over the limit you will get a 1200 SEK ticket (that would be like £95) and at 12 Km/h over you will get the double and so on. Until 31 km/h over the limit where you loose you license. Then depending on how fast you were going or where you were speeding it's up to a jury to decide for how long you will loose it or if you will ever get it back. If you loose it for more than one year you will have to do the driving test all over from scratch, which is a pretty expensive story. Not to mention the scary part to go by underground where ever you are suppose to go ;)

I do not like this system!

[Scarlet Pimpernell]

So it can make the difference between a speeding ticket (GATSO etc) or not...that's the point...

I still disagree, what is the point - if you just read your speedo as being accurate like the majority of people you will never get a speeding ticket anyway..........................

it's an anorak thing

Take your point, but the number of times I go over the markers, look at the speedo and panic 'cos I accidentally went over the limit :o so now I know when to panic and when not to...

I suppose Lexus wouldn't want the car based system to show the MPH, 'cos we'd all complain...

Seriously though - I am a careful law abiding driver and only break the law by accident! Honest!