Incorrect Speedometer - Golf mkVII?

[Guest001]

Yep its pretty common for new or vaguely new cars to be under in their speedo. My Mk6 golf is under by 8kph (110kph is really 102kph). Was the same for my 2006 Hyundi Getz out by 5kph. Look at it as a safety feature. I suspect it's deliberately done by the manufactures now because we are to stupid to follow the road rules.

Just know your difference then you can adjust your cruise control to match. Set yours to say 115kph and you'll still be under the speed limit but closer.

If you read through the thread you will see that it has nothing to do with manufacturers. It is an Australian Design Rule (ADR)
The rule basically reads that the speedo cannot read LESS than actual speed and can read over by up to 10%<>4.
Manufacturers have absolutely no say. They must comply with the Rule.
It is to allow for variations in tread wear and wheel sizes etc.

[NCGR1]

Dutch77: yes, that's true. But in the 21st century, I would have thought that we could rely on better metrics in our cars.....

Not sure what the century we are in has to do with it. There are numerous items, all with tolerances, that add up to determine the indicated speed in the cluster. How would you approach it but assure no vehicle sold to a customer indicated low? Calibrating each and every vehicle at the completion of build would certainly not be practical.

[DV52]

Not sure what the century we are in has to do with it. There are numerous items, all with tolerances, that add up to determine the indicated speed in the cluster. How would you approach it but assure no vehicle sold to a customer indicated low? Calibrating each and every vehicle at the completion of build would certainly not be practical.

NCGR1: Thanks for your thought provoking question, which I would like to answer by asking a few questions of my own (please don't read anything nefarious into my questions - they are simply intended to underscore my position).

What is the sole purpose of a speedo? Yes, it's a pretty fundamental question, but I believe that it's an important question in this issue. I hope that you will agree that the answer is to measure the car's speed!

What's the sole purpose of the road sign that has a number in a red circle (with a slash)? Again, very basic question but the answer is clearly to indicate the speed restriction - no doubt about this I hope!

IMO, when travelling on a freeway where the road sign says 110 Kms/hr- if it is better for the speed limit to be 95 kms/hr (i.e. 10% + 4 kms/hr slower), then this is what the road sign should say - and the speedo should accurately reflect the car's true speed.

I believe that when it comes to safety issues, mixing-up the two purposes above is wrong and just plain dangerous. Or, said differently, I believe that the "nanny" philosophy that compels car manufacturers to deliberately alter the speedo's reading is neither warranted, nor does it achieve a safer outcome.

You only have to look at what's happening on today's roads to find evidence regarding how under-reading speedos are affecting road safety, The inherent inaccuracy in the car's speedo is now well understood in the driving community. Commercial companies where business outcomes are link to time-on-the-road know that car speedos under read. Plus there is a good understanding of this practice amongst the wider community.

There are today readily available (and relatively cheap) ways of getting speedos with far greater accuracy (most of these are GPS based)

So, what we are increasingly seeing on our freeways is a two-speed driving phenomenon; those drivers that rely on their car's (under reading) speedos and those drivers that have chosen to use more accurate speedos. My view is that this is neither safer, nor it is a better outcome!

And it's not as if more accurate reading speedos are harder to get in 21st century cars. With the advent of OBD standards, most modern cars already record this data. For instance, the odometer on most cars in the 21st century already read to an accuracy of around 1%-2% (notwithstanding the ADR's 4% standard) -this level of accuracy probably results from litigation risk on warranty claims.

Distance travelled is of course a fundamental input to the measurement of speed and the car's speed as measured by the CAN bus is far more accurate than the speedo reading. So, in the 21st century, the car already measures speed far more accurately- it just doesn't display this speed on the speedo!

So, as a synopsis of my position, I think that it's far better, and it's proper to give the driver the very best available information for making decisions because ultimately there can be only one person responsible for the car's actions!

I'll get off my soap-box now and thanks again for your question.

[Guest001]

NCGR1: Thanks for your thought provoking question, which I would like to answer by asking a few questions of my own (please don't read anything nefarious into my questions - they are simply intended to underscore my position).

What is the sole purpose of a speedo? Yes, it's a pretty fundamental question, but I believe that it's an important question in this issue. I hope that you will agree that the answer is to measure the car's speed!

What's the sole purpose of the road sign that has a number in a red circle (with a slash)? Again, very basic question but the answer is clearly to indicate the speed restriction - no doubt about this I hope!

IMO, when travelling on a freeway where the road sign says 110 Kms/hr- if it is better for the speed limit to be 95 kms/hr (i.e. 10% + 4 kms/hr slower), then this is what the road sign should say - and the speedo should accurately reflect the car's true speed.

I believe that when it comes to safety issues, mixing-up the two purposes above is wrong and just plain dangerous. Or, said differently, I believe that the "nanny" philosophy that compels car manufacturers to deliberately alter the speedo's reading is neither warranted, nor does it achieve a safer outcome.

You only have to look at what's happening on today's roads to find evidence regarding how under-reading speedos are affecting road safety, The inherent inaccuracy in the car's speedo is now well understood in the driving community. Commercial companies where business outcomes are link to time-on-the-road know that car speedos under read. Plus there is a good understanding of this practice amongst the wider community.

There are today readily available (and relatively cheap) ways of getting speedos with far greater accuracy (most of these are GPS based)

So, what we are increasingly seeing on our freeways is a two-speed driving phenomenon; those drivers that rely on their car's (under reading) speedos and those drivers that have chosen to use more accurate speedos. My view is that this is neither safer, nor it is a better outcome!

And it's not as if more accurate reading speedos are harder to get in 21st century cars. With the advent of OBD standards, most modern cars already record this data. For instance, the odometer on most cars in the 21st century already read to an accuracy of around 1%-2% (notwithstanding the ADR's 4% standard) -this level of accuracy probably results from litigation risk on warranty claims.

Distance travelled is of course a fundamental input to the measurement of speed and the car's speed as measured by the CAN bus is far more accurate than the speedo reading. So, in the 21st century, the car already measures speed far more accurately- it just doesn't display this speed on the speedo!

So, as a synopsis of my position, I think that it's far better, and it's proper to give the driver the very best available information for making decisions because ultimately there can be only one person responsible for the car's actions!

I'll get off my soap-box now and thanks again for your question.

Your argument falls down at the first hurdle because not all cars have canbus.

[brad]

I do wonder if the bigger issue isn't so much our (crap) speedos or our crap laws that say our speed limit is a limit & you'll be punished if you exceed it.

eg: In Australia on a 2 lane motorway you'll often get Joe Blow in his Jetta driving along at the front of the queue in the RH lane. Beside him is a truck which is speed limited to 100. Joe Blow thinks the truck is being naughty because Joe's speedo says 110kph when in fact Joe is only doing 101kph. Joe is a law abiding citizen and wants to retain his right to travel at the speed limit and overtake so Joe just sits there with a 1kph variation between him & the truck beside him while the traffic banks up behind him & Joe gets angrier & angrier because those folks who have a speedo that is only reading 4kph under (the minimum allowable variation under the ADR) are getting more and more frustrated.

Of course, in Europe, the UK & the USA (I've driven in all three and seen how people drive) they don't seem to be as hung up about speed limits & Joe Bloe would give the throttle a squirt & move over. People overseas don't seem to take as much offence at being told to get out of the way.

BTW: I still claim the odometer is wrong too (about 3%-5%), therefore many people are getting their 15k service done at about 14250-14500km. It's not much but over 10 years....

[DV52]

Your argument falls down at the first hurdle because not all cars have canbus.

Hillbilly: hi again and thanks for your response. Yep, you have identified the pivotal basis for my argument. That's exactly why the ADR's "nanny" rules prevail. It's all because not every car on the road has a CAN bus! Man-we have got to give credit to those far sighted legislators- if only they could turn their superior intellect to solving world poverty (only kidding)!

[DV52]

I do wonder if the bigger issue isn't so much our (crap) speedos or our crap laws that say our speed limit is a limit & you'll be punished if you exceed it.

eg: In Australia on a 2 lane motorway you'll often get Joe Blow in his Jetta driving along at the front of the queue in the RH lane. Beside him is a truck which is speed limited to 100. Joe Blow thinks the truck is being naughty because Joe's speedo says 110kph when in fact Joe is only doing 101kph. Joe is a law abiding citizen and wants to retain his right to travel at the speed limit and overtake so Joe just sits there with a 1kph variation between him & the truck beside him while the traffic banks up behind him & Joe gets angrier & angrier because those folks who have a speedo that is only reading 4kph under (the minimum allowable variation under the ADR) are getting more and more frustrated.

Of course, in Europe, the UK & the USA (I've driven in all three and seen how people drive) they don't seem to be as hung up about speed limits & Joe Bloe would give the throttle a squirt & move over. People overseas don't seem to take as much offence at being told to get out of the way.

BTW: I still claim the odometer is wrong too (about 3%-5%), therefore many people are getting their 15k service done at about 14250-14500km. It's not much but over 10 years....

brad:I agree. Your example (much more eloquently put than my explanation) is what I meant by the "two speed phenomenon" that is becoming more prevalent on our roads!

[Guest001]

I do wonder if the bigger issue isn't so much our (crap) speedos or our crap laws that say our speed limit is a limit & you'll be punished if you exceed it.

eg: In Australia on a 2 lane motorway you'll often get Joe Blow in his Jetta driving along at the front of the queue in the RH lane. Beside him is a truck which is speed limited to 100. Joe Blow thinks the truck is being naughty because Joe's speedo says 110kph when in fact Joe is only doing 101kph. Joe is a law abiding citizen and wants to retain his right to travel at the speed limit and overtake so Joe just sits there with a 1kph variation between him & the truck beside him while the traffic banks up behind him & Joe gets angrier & angrier because those folks who have a speedo that is only reading 4kph under (the minimum allowable variation under the ADR) are getting more and more frustrated.

Of course, in Europe, the UK & the USA (I've driven in all three and seen how people drive) they don't seem to be as hung up about speed limits & Joe Bloe would give the throttle a squirt & move over. People overseas don't seem to take as much offence at being told to get out of the way.

BTW: I still claim the odometer is wrong too (about 3%-5%), therefore many people are getting their 15k service done at about 14250-14500km. It's not much but over 10 years....

For a change we agree LOL .

Have just done 13,000k in Canada and USA and if we werent travelling about 8 MPH OVER the limit you got blown into the weeds.
Passed lots of Highway Patrol cars who didnt move for that speed but dont try more than 12 over or they would have you.

None of this every K over rubbish. They had heaps of signs about seatbelts though.
Much more realistic speed limits as well. Up to 85mph in lots of places and the roads werent as good as the Gold Coast highway either.
Thank god as we were doing 500m some days

Incidentally my Landcruiser reads Dead on at 100kph on standard tyres and has from new so must comply with ADR rules

[i286]

I do wonder if the bigger issue isn't so much our (crap) speedos or our crap laws that say our speed limit is a limit & you'll be punished if you exceed it.

eg: In Australia on a 2 lane motorway you'll often get Joe Blow in his Jetta driving along at the front of the queue in the RH lane. Beside him is a truck which is speed limited to 100. Joe Blow thinks the truck is being naughty because Joe's speedo says 110kph when in fact Joe is only doing 101kph. Joe is a law abiding citizen and wants to retain his right to travel at the speed limit and overtake so Joe just sits there with a 1kph variation between him & the truck beside him while the traffic banks up behind him & Joe gets angrier & angrier because those folks who have a speedo that is only reading 4kph under (the minimum allowable variation under the ADR) are getting more and more frustrated.

Of course, in Europe, the UK & the USA (I've driven in all three and seen how people drive) they don't seem to be as hung up about speed limits & Joe Bloe would give the throttle a squirt & move over. People overseas don't seem to take as much offence at being told to get out of the way.

BTW: I still claim the odometer is wrong too (about 3%-5%), therefore many people are getting their 15k service done at about 14250-14500km. It's not much but over 10 years....

brad, completely agree with you. We are on the same page here. Pity there isn't more people out there who actually understand the facts you wrote about and correct their habits, we would have safer roads and much more enjoyable drive.
So called "do gooders" are causing even more delays and frustration which in extreme cases end up as a road rage, which is not only ugly but dangerous and completely unnecessary and avoidable.

There is a handbook called Driving in Victoria: Rules and responsibilities , on the page 64 it is about overtaking on a two way road. I will quote part of it
" When safe, accelerate and overtake the vehicle, then indicate left when safe to return to your lane. You must not exceed the speed limit at any time. ".

Well, this is plain wrong, it is dangerous and unfortunately unsafe. To overtake safely on a two way road you actually need to exceed the speed limit for a short time. I am talking about 15-20 kmh over the limit for a few seconds. It is necessary to spend least amount of time on the "wrong" side of the road.

Folks, do not get me wrong on this. I do not promote, encourage or call for road users to ignore or break the road rules and to create their own rules. Not at all. At the end of the day we all want to get where we are going unscratched and safe.

I challenge the Government, Police, VicRoads, Road trauma experts and all other people involved in creating of this particular rule to undertake simple demonstration of the same and to see if they like it.
I am more than happy to volunteer myself, my car, my time and fuel cost to prove my point.

Hillbilly, thanks for sharing your overseas experience. It is really necessary to have first hand experience of driving in other developed countries around the globe to see how some of the rules we have could be altered and result in increased safety.

[brad]

Another small observation but in Europe a lot of the trucks are speed limited to 80 or 90 kph (I have no idea if this is country specific or done by a random number generator). Because the trucks are going so much slower, overtaking is pretty easy even if you're in a 1.6L Opel Zafira with 4 up.

[AALocksmiths]

I don't know if the MK7 cluster is the same setup as the MK4 but on the 4 you can remove the needles and push them back on in any position, so you would be able to move the needle to read accurately instead of playing around with the electronics. This way would be a bit more fiddly as you would have to move the needle, put the cluster back together then go for a drive, then repeat until it is correct

[pologti18t]

The ADR has been harmonised with the EU. So blame those bunch of nanny-meisters.

[Eaglehawk]

To overtake safely on a two way road you actually need to exceed the speed limit for a short time. I am talking about 15-20 kmh over the limit for a few seconds. It is necessary to spend least amount of time on the "wrong" side of the road.

I've done this very manoeuvre in front of an unmarked cop car. It was a single lane each way, 80 km/h. I was behind a semi trailer doing 60km/h. I waited for the broken lines, and started the overtake. Another car appeared, so I completed the overtake by hitting at least 110.

The cop didn't catch up until at least 5km further down. He thought my overtake was "bordering on unsafe", but let me off with a warning because he saw I didn't continue to exceed the speed limit during the rest of the 5km. (Obviously, THEY had to exceed the speed limit to catch up with me, I found that mildly ironic...)

I totally agree with you. The rule is stupid, and not a safe "law". I don't want to be stuck unseen behind a slow large vehicle, nor would I put my family at risk doing <20km/h faster "overtake".

[Mountainman]

BTW: I still claim the odometer is wrong too (about 3%-5%), therefore many people are getting their 15k service done at about 14250-14500km. It's not much but over 10 years....

My Mk7 Golf has an odo that is nowhere as inaccurate as the speedo which reads 105 at a true 100. When the odo has indicated 100km the Garmin sat nav says 99.1km. So I guess I'm only getting my services done about 140km to early.

My Forester is even more inaccurate - speedo 100 = 93 and odo 100km = 98.7km.

Typically most people seem to cruise on an indicated 110 in 100 zones but I notice they nearly all seem to slow up to an indicated 100 or less when going through the fixed speed cameras.

[frogg]

Just did an interesting test.... Recently got a ODB2 bluetooth device. When comparing the EHS and GPS speeds on my phone, they are roughly within 0.5 km/H of eachother, however both the digital speed and needle display about 4-5 km/H above these.....

So I guess it is hard to tell whether the odo is over reading by much.... There will Def be more discrepancy as the tyres wear, but the EHS speed will also be out of this is the case?

Unless they can do some trickery that works out what the rolling Diameter of the tyre should be based on the ABS sensors and performs some autocorrection of the value to the ECU?

I Could just be full of s#!t though....