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View Full Version : Who has an accurate speedo?



Joele
03-01-2008, 08:45 AM
I checked my speedo at two different speedo checks on the hume hmy last week, and both times to register at 100kph I had to travel at 106kph on the Civic speedo..

I am in a 2007 Vti but with the Vti-L wheels.. I am curious is this normal and can they actually adjust it (i.e. is it worth bringing up at the next service)?

aaronng
03-01-2008, 08:46 AM
It's normal. Happens to almost all cars except the really expensive ones with precise speedometers.

m0nty ITR
03-01-2008, 08:49 AM
Manufacturers build these tolerances into their speedos. Whether it be to allow for fatigue or so people cannot blame the car for speeding fines.

Volkswagen have a 6% - tolerance which appears to be about the same as your Honda.

markCivicVti
03-01-2008, 08:57 AM
Yeppers. Both my cars are around the same... 106km on speedo = 100kms on gps. Ones a Honda (w00t) and the other a ford.

Kiz_EG6
03-01-2008, 08:58 AM
Get a GPS with speed reading, these are very accurate, so long as you hold a speed for a length of time, say freeway driving.

Joele
03-01-2008, 08:59 AM
mm that sucks, the advantage of the digital speedo was easy to see and spot on reading, so thats out the window :-/ Well I guess I just have to calculate 6% on the speed limit.. no point doing 94kmh on the freeway.. LOL

Would also throw out the distance travelled? so when my car says 100,000km it is actually 94,000km???

m0nty ITR
03-01-2008, 09:11 AM
mm that sucks, the advantage of the digital speedo was easy to see and spot on reading, so thats out the window :-/ Well I guess I just have to calculate 6% on the speed limit.. no point doing 94kmh on the freeway.. LOL

Would also throw out the distance travelled? so when my car says 100,000km it is actually 94,000km???

No. Odometers run off a different system.

Joele
03-01-2008, 09:13 AM
No. Odometers run off a different system.

ahh cool, well thats something at least..

Kiz_EG6
03-01-2008, 09:15 AM
No. Odometers run off a different system.

YEAH, BUT WHO SAYS THEY GOT THAT RIGHT IF THEY CAN'T GET THE SPEEDO RIGHT, I THINK HE HAS A POINT, WHO HAS EVER TESTED THEIR ODOMETER?!?

aaronng
03-01-2008, 09:16 AM
I have tested my odometer/tripmeter using the signs on the freeway, and I can tell you that Joele's concern is REAL. :)

m0nty ITR
03-01-2008, 09:16 AM
There would be massive implications for manufacturers if odometer readings were incorrect. Any person that has ever signed a disposal form could file class action against them. Not to mention incorrect car values thanks to odometer errors. That's one thing that manufacturers need to be spot on.

m0nty ITR
03-01-2008, 09:17 AM
I have tested my odometer/tripmeter using the signs on the freeway, and I can tell you that Joele's concern is REAL. :)

I wouldn't trust those either. They're fitted by public servants after all.

Kiz_EG6
03-01-2008, 09:20 AM
There would be massive implications for manufacturers if odometer readings were incorrect. Any person that has ever signed a disposal form could file class action against them. Not to mention incorrect car values thanks to odometer errors. That's one thing that manufacturers need to be spot on.

...same as if all the speedos are out you mean, i think it would be safer to have an odo out by 10% than a speedo!!

As i said, find me the company that indeopendantly tests these for 10 000 odd k's on every new car to ensure 100% accuracy.

Oh and i am sure that if you change your tyre size or drive on worn tyres too long this will throw it out too!!
It would only take 1 cm less circumfetrence on a tyre to throw it out by a substantial amount over time!

one4spl
03-01-2008, 09:25 AM
The odometer and speedometer work on the same signal.

"Back in the day" you would change the gear on the speedo sender until the Odometer was accurate, and then have the speedo calibrated.

These days the speed is recorded by the computer from the ABS sensors, and sent to the speedo as data. The CPU in the cluster then it displays it by driving the needle with a stepper-motor.

Due to this fact the accuracy, or more the lack of accuracy, in your modern speedo is designed in its software and is therefore very hard to do anything about. This shits me, personally.

The factory *can* make a perfect speedo, and indeed you will find that cars these days are consistently inaccurate, so they aren’t protecting themselves from manufacturing inconsistencies. They are just protecting you from yourself, and I don’t appreciate that. I want my speedo to be accurate, I want to chose my speed and choose my consequences (*waves to QT*).

As stated above, you can use a GPS and get a very accurate reading from it by which to make yourself aware of how inaccurate your car’s speedo is.

aaronng
03-01-2008, 09:53 AM
There would be massive implications for manufacturers if odometer readings were incorrect. Any person that has ever signed a disposal form could file class action against them. Not to mention incorrect car values thanks to odometer errors. That's one thing that manufacturers need to be spot on.

Oh, lookie here: http://hondaodometerclassaction.com/

Class actions against odometer readings are not uncommon. :)
The only reason why they can get away with higher odometer readings than normal is because the speedo tolerance in the ADR allows for it. Also, having a different tyre rolling diameter affects it. So when you compare a Civic VTI to a 2007 Civic Sport with its different rim and tyre size combo, you get different speedo readings.

denot
03-01-2008, 11:23 AM
is this why we are allowed to drive 10% more of the max speed on any road (e.g. on our car it will say 66 but on Police camera it says 60)

Kiz_EG6
03-01-2008, 11:26 AM
is this why we are allowed to drive 10% more of the max speed on any road (e.g. on our car it will say 66 but on Police camera it says 60)

They only give 2k's grace in Vic regardless of the speed and that's only coz their speed detection equiptment is not 100%, that 10% thing is an old wive's tale at best, maybe in the 1970's!!

one4spl
03-01-2008, 11:29 AM
Well actually they give you margin on top of the margin your speedo gives you. Not that they discuss it publicly but in QLD the margin is 10km/h.

So, you could be doing an indicated 118 or so before you will be fined in a 100km/h zone in many cars.

PS. I am not a lawyer, and am just summising based on my experience fixing speedos and driving on queensland roads.

aaronng
03-01-2008, 11:33 AM
In VIC, you get done for 3km/h above your ACTUAL speed. So having the speedo read 6% lower is good.

In NSW, I'm not sure what the tolerance is, but doing 86km/h in an 80km/h zone past a camera doesn't make it flash, so the tolerance is larger than in VIC.

Kiz_EG6
03-01-2008, 11:43 AM
Who is with me that this information should:
A: Be the same across the country
B: Be made readily available for everyone, so that it out rules the heresay.
C: All rigts, resposibiltities etc of the driver be made clear, as this all seems to be a grey area.
D: Rights and responsibilities in an accident, eg what information you need to give/receive, who is at fault in what situation, eg someone backing out of their driveway (very grey)

I am saying that the AUSTRALIAN government should make available ONE book, containing all laws about speeding, drink driving, modifying, hooning, etc.
I cannot get a straight answer on the "hoon" laws here, it seems that if i accidentally squeek my wheels at the lights (even for 1 sec) they can potentially impound my car, given a grumpy enough cop!!

It is way too grey and i believe that information about this could make the roads far safer than they are now.

How many times have you guys been beeped or roadraged for not indicating in a zip merge, because some old man does not have any idea about the proper laws!!

Sorry, maybe should have been a new rant thread!!

Joele
03-01-2008, 11:58 AM
Who is with me that this information should:
A: Be the same across the country


Tell me about it its a joke...

- In NSW you get P at 17 in VIC it is 18..
- In NSW all L and first year P are limited to 80kmh in VIC they are NOT.
- In VIC you can get booked 3kmh over the limit, in NSW you have 10%

And thats just what I know from the very little I have visted NSW. Its a pain in the butt driving from one state to the other with all these different rules.. :thumbdwn: And P plate drivers drive into NSW and have to follow NSW rules, yet 17yo NSW P plate drivers are allowed to drive in Victoria?

Joele
03-01-2008, 12:01 PM
How many times have you guys been beeped or roadraged for not indicating in a zip merge, because some old man does not have any idea about the proper laws!!


Actually funniest I have seen is a driver from NSW doing a hook turn in victoria, they did go to the left lane to turn right, but they turned straight accross the traffic (not waiting for the lights to change... Only really funny as there was no accident... :zip:

denot
03-01-2008, 12:12 PM
Actually funniest I have seen is a driver from NSW doing a hook turn in victoria, they did go to the left lane to turn right, but they turned straight accross the traffic (not waiting for the lights to change... Only really funny as there was no accident... :zip:

I've seen a victorian running too slow (40kms/hr on a 60kms/hrs zone - and no its not schools zone), didnt give signal and shoulder check when change lane (almost get hit my car which located just next to his back door), went to the trem line (yep only 1 trem line in Sydney CBD and he still cant avoid id) etc etc...

also I have a fight with a QLDers which beeping and flashing lights behind me eventhough I have already ran 65kms/hr on a 60zone. Then we are side by side on the red light, he swears a lot to me (cant here what he said) and then I pretend to took off, then he took off while the light still red... then you kno what happened: a big tyre screech and a big bang, then a big laugh from me... (hope he still alive though :p).

I think this is as a result of different law on diff states... but then again, they have to start removing the trem line in Melb or adding more trems in other states, etc etc... :p

aaronng
03-01-2008, 12:40 PM
Who is with me that this information should:
A: Be the same across the country
B: Be made readily available for everyone, so that it out rules the heresay.
C: All rigts, resposibiltities etc of the driver be made clear, as this all seems to be a grey area.
D: Rights and responsibilities in an accident, eg what information you need to give/receive, who is at fault in what situation, eg someone backing out of their driveway (very grey)

I am saying that the AUSTRALIAN government should make available ONE book, containing all laws about speeding, drink driving, modifying, hooning, etc.
I cannot get a straight answer on the "hoon" laws here, it seems that if i accidentally squeek my wheels at the lights (even for 1 sec) they can potentially impound my car, given a grumpy enough cop!!

It is way too grey and i believe that information about this could make the roads far safer than they are now.

How many times have you guys been beeped or roadraged for not indicating in a zip merge, because some old man does not have any idea about the proper laws!!

Sorry, maybe should have been a new rant thread!!
It is controlled by the state government, not the federal government. Even if the federal government wanted to do it the one-book way and the state governments didn't agree, then it wouldn't go ahead. That's why you have different licenses for each state, different rules and different P plate rules as well.

Kiz_EG6
03-01-2008, 12:49 PM
It is controlled by the state government, not the federal government. Even if the federal government wanted to do it the one-book way and the state governments didn't agree, then it wouldn't go ahead. That's why you have different licenses for each state, different rules and different P plate rules as well.

I know, but just because something IS one way doesn't mean it
SHOULD be.
I am saying that it should be a country wide thing, what is the point of having it state to state? It just doesn't make sense, we are one country, we share the same currency and most other laws, whay is the road state, not federal?!!
I would be interested to see if the USA has 50 different sets of laws, one for each state, what a nightmare!

aaronng
03-01-2008, 12:52 PM
I know, but just because something IS one way doesn't mean it
SHOULD be.
I am saying that it should be a country wide thing, what is the point of having it state to state? It just doesn't make sense, we are one country, we share the same currency and most other laws, whay is the road state, not federal?!!
I would be interested to see if the USA has 50 different sets of laws, one for each state, what a nightmare!

You have to go back in history and see that each state was run separately because they started as separate colonies.
Yes, USA has 50 sets of laws although many of the laws overlap. Some states allow guns, others don't.

Kiz_EG6
03-01-2008, 12:55 PM
You have to go back in history and see that each state was run as if it was its own country.
Yes, USA has 50 sets of laws although many of the laws overlap. Some states allow guns, others don't.

Yeah, but that was horse and cart days :p

I know what you are saying though, guess i'll neva get my PERFECT workl ;)

JP.87
03-01-2008, 08:28 PM
ye.. da speedo on my honda civic 07 FD1 reads 3km difference higher than my gps.
gonna get it checked out for my first service.
~

Psy
03-01-2008, 08:50 PM
Man a GPS is far from accurate. Despite the speedometer basing it on the actual speed. Gps is basing it on how fast the signal sends and recieves.

I was driving to Canberra once and was going 110Km on a normal speedometer, not digital... and the TomTom GPS was showing 105km..

Bayani
04-01-2008, 01:14 AM
Not really, Psy.

GPS Readings are based on Point-to-Point readings over a specified period.

Meaning the only time it is truely accurate is when you are travelling on level ground dead straight.
However, the difference in displayed and actual are minimal and only start becoming apparent at high speed.

Also, your 'evidence' that a GPS unit is not accurate is flawed.

As stated earlier; and dicated by legislation; Speedometers are allowed to under-read by a particular percentage (also sometimes with the addition of a few km's).

Your speedometer may very well be out. Illegally, if so, as your speedometer could be under-reading.

Of course. You may have just been travelling on a slant.

one4spl
04-01-2008, 06:56 AM
GPS, in general, is very accurate as for the GPS to find your position it needs very accurate timing abilities. It’s very easy for the GPS to calculate your real speed by taking a sample of where you are now, and where you were exactly a second ago and measure the distance in-between. The GPS is aware of all three axis, and can therefore calculate that distance regardless of the incline of the road you are on.

The ONLY way for a GPS to be as inaccurate as a speedo is for it to be designed with an error, and as there’s no ADRs telling the GPS makers to make them inaccurate then I don’t see why they would be.

Look at GPS-based race timing equipment like http://www.driftbox.com/. They have been shown to be at least as good as the best track-based timing equipment for many years.

JaCe
07-01-2008, 09:13 PM
^ I compare my speedo to my GPS sometimes and always note that it's out; but the gap varies... although that's probably due to me not holding the speed exactly constant in city driving.


I have tested my odometer/tripmeter using the signs on the freeway, and I can tell you that Joele's concern is REAL. :)

Since when were highway/freeway signs spot on though? I really doubt the distances they post are an exact figure- it's probably even rounded by an immaterial amount!

Joele
08-01-2008, 07:45 AM
Since when were highway/freeway signs spot on though? I really doubt the distances they post are an exact figure- it's probably even rounded by an immaterial amount!

Some hwy's have odometer checks though and they have a sign every KM
- Reset here
- 1 KM
- 2 KM
- 3 KM
- 4 KM
- 5 KM

Even over 5 KM I noticed a difference..

aaronng
08-01-2008, 08:17 AM
Some hwy's have odometer checks though and they have a sign every KM
- Reset here
- 1 KM
- 2 KM
- 3 KM
- 4 KM
- 5 KM

Even over 5 KM I noticed a difference..

I find a difference even after 1km!

aaronng
08-01-2008, 08:19 AM
Since when were highway/freeway signs spot on though? I really doubt the distances they post are an exact figure- it's probably even rounded by an immaterial amount!

If you don't trust the signs, do you trust those speed check speed cameras? I've used those and got 105 when travelling at an indicated 110.

spiderman
08-01-2008, 08:31 AM
I have a 07 Sports and have taken it back to Honda twice and the second time demanded they fix it....they did not....

The first time they said there was nothing wrong cause my wife took it in and all they did was put the comp on it. The second time they went for a drive with me and yes it was out by 7KM at every speed...

Honda Australia said they were protecting there customers....bullshit....

just now i drive 117 when doing 110km etc...

got to say though its the only issue i have had with my car touch wood...
and i have done 40000 kms in it

aaronng
08-01-2008, 08:41 AM
I have a 07 Sports and have taken it back to Honda twice and the second time demanded they fix it....they did not....

The first time they said there was nothing wrong cause my wife took it in and all they did was put the comp on it. The second time they went for a drive with me and yes it was out by 7KM at every speed...

Honda Australia said they were protecting there customers....bullshit....

just now i drive 117 when doing 110km etc...

got to say though its the only issue i have had with my car touch wood...
and i have done 40000 kms in it
Is it out by 7km/h even at 40km/h? Doing 110 at an indicated 117 is normal. But doing 33 at an indicated 40 is not.

Joele
08-01-2008, 02:46 PM
I find a difference even after 1km!

I do too to be honest and obviously as you go past each check point it gets slowly worse and 100% unmistakable by the 5km mark..

clayton4115
08-01-2008, 03:36 PM
can someone explain to me how does one use those highway km signs?

- Reset here
- 1 KM
- 2 KM
- 3 KM
- 4 KM
- 5 KM

what are they for?

Bayani
09-01-2008, 11:19 PM
They are used to check your ODOMETER.

The DISTANCE you travel.
You will have a reset button located near your odometer.

Press your Reset Button when you pass the 'reset here' sign.

When you reach 1,000m you should be passing the 1 KM sign.
At 2,000m you should be passing the 2 KM Sign.

Essentially it is to keep drivers occupied with something to do; whilst at the same time being useful.

Stop. Revive. Survive!

Bayani
09-01-2008, 11:23 PM
Is it out by 7km/h even at 40km/h? Doing 110 at an indicated 117 is normal. But doing 33 at an indicated 40 is not.

Is it a Digital Gauge, Arrong? I'm not familar.

buddah51au
12-01-2008, 07:56 PM
Speedo tolerance by all manufactures, be it a Mini, a Mercedes or a Ferrari is +/- 10%. Personally i would prefer a speedo that reads slightly above actual speed the way cameras are hidden every where. Play it safe & set cruise contol 5% above a posted speed limit and you should never receive any unwelcome mail.

Havocwreaker
05-02-2008, 10:47 PM
Does anyone know of a way to calibrate the speedo such that it shows your actual speed?

disappointed
06-02-2008, 09:36 AM
Does anyone know of a way to calibrate the speedo such that it shows your actual speed?

Can't be done with any reliability, because of your tyres. The difference between a new set of tyres and a worn set of tyres and the inflation pressures of the tyres makes it infinetly variable, thus impossible.

Havocwreaker
06-02-2008, 11:19 AM
The speedo is calibrated to over read by 6%. I perhaps should have posed my question as is there a way to reduce this over reading? So that I'll say you're doing 101...instead of 106 when you're actually doing 100.