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How to read your speedo correctly

Discussion in 'Holden Commodore How-To's' started by vnv8driver, Oct 12, 2008.

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  1. jazza15

    jazza15 Jarryd

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    It can't be over, read above. LSD shouldn't mess with your speedo as it is a factory part, if you change the ratio it will. I went from 17's to 15's and didn't notice that much of a difference at all as the diameter of the tyre is still about the same and therefore the speedo's accuracy won't vary.
     
  2. Kurtp

    Kurtp VR Buicks > You ;)

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    Lol, no i havn't changed my diff ratio, though the diff has never sounded to healthy. Winds a bit. I have put larger wheels on it, so can't imagine how bad it was before.
     
  3. stuntmanmike

    stuntmanmike Car wotsit & stuff

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    My speedometer has started to play up. Never had a speeding fine until a week ago when clocked doing 122kph in a 110 zone. Upset about fe*king my untouched demerit points and non-speeding record. Oh well, sh*t happens...
    Anyway, we did a basic test to determine the correct indication of speed on the dash and my speedo reads 12 kph over the speedo output. Grrr!
    Also, the speedo drops to zero and back up every second when I reach "82"kph through to "95"kph.
    I love my VP and am starting to wonder if I should change out the instrument cluster with my spare. Or if I should bite the bullet and buy a VS and start all over again with the upgrades and mods.
    I'd rather not make quota for the highway chops when they could be snaring real crims instead.
    BTW: the diff ratio is factory stock, the rolling stock are 15s with 60 series tyres. I'm guessing the signal to the speedo is the issue somewhere and I'm not an automotive sparky.
    I'll scan the forum for the best threads on this issue unless someone here can shoot a tip or thread link on this topic. Ta
     
  4. schrinky

    schrinky New Member

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    all you guys who think that Victoria has 3kph of leeway, a mate from uni got nabbed doing 63 and got a fine, they only take 2kph off now!
    i have a BT1 with the 2km increment speedo, and i love it, every time i got out west (family live in ballarat) i got under the speed thingo and it says when my speedo is on 100, the shown speed is 100, its great, dad now has a VE SSV and the speedo is horid, i sit behind him on eastlink and his cruise is set at 100 and i have to sit on about 95, taken it to holden, recalibrated it and now it is only 2kph out at 100!
     
  5. SAGuyInNT

    SAGuyInNT Mayhems

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    I have for a long time heard that holden did this to make sure they are not responsible for any speeding tickets and such things. Also with seeing most other cars in manf groups having a similar scale to their own makes and models at least. Looks also to explain why Volvo drivers are always so god damn slow.

    You will see also its not the speedo pin itself that maybe slightly out but how the over all ECU is setup, I have compared my speedo along with the ECU via using a ALDL link. Checked it against GPS and the speedo and the only the GPS had a different reading which i think was around 8% or so. Tested on Stock V6 1992 VP Commodore.

    I know of a few people who simply remove their needle and put it back on at a slightly higher reading which reads correct for their normal speed zones.
     
  6. immortality

    immortality Moderator Staff Member

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    :lock: and banish it to the pages of history just like the OP. full of fail.

    3km/h difference isn't gonna make any difference in the time you arrive at your final destination but may help you get that speeding ticket.:banstick:

    :undead:
     
  7. vn_v6

    vn_v6 Blumpkin

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    my vn is SPOT ON, my gps read 101 and my speedo is on exactly 100, ive got 17 inch rims though, wth stockies it was on like you said around 105
     
  8. Kurtp

    Kurtp VR Buicks > You ;)

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    I got 3 taken off less than a month ago (also figured out what the issue was and speedo is good now)
     
  9. Zeussy

    Zeussy SSM11K

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    Agree'd... :beer chug:

    Have seen this thread around for a while, and still can not see a valid reason why it is open..? :hmmm:


    Do the speed limit - whats on your speedo, if you suspect your speedo is out, get it checked and recalibrated. :banstick:


    The sooner every one realises how peaceful it can be to not worry about how fast you are going, and just enjoy the drive, the better. The amount of "tools" that I see daily make me LOL in real life...:rofl2:
     
  10. helluvabadapple

    helluvabadapple HelluvaBadapple

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    More to do with tyre size I reckon...........
    after having to put different sized tyres I learned this would put my speedo out..............


    Sizing Your Tyres


    You have 3 options when it comes to replacing your tyres:
    1.Replace your existing worn tyre with an identical or similar tyre
    2.Change to a premium tyre, using your existing wheel rims
    3.Change to a premium tyre with entirely new wheels - a package deal (eg. a progression might be from a 205/65 R15 to a 215/60 R16)
    For those of you who have chosen option 3, this tool calculates the new overall tyre diameter and will let you know the number of revs/mile for both your existing tyre and the possible alternative(s). For a legal fitment, the difference in overall tyre diameter between your existing tyre and your replacement must be within +15/-15 mm in most states*.

    * Queensland permits +15/-26 mm.
    (this is from [url=http://www.carbonblack.com.au/car-tyres/tyre-sizes/sizing-your-tyres.aspx

    Hope this makes sense to others who believe it's their speedo....or a bad radar!!!!!
     
  11. justincredible

    justincredible New Member

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    I know this is an old thread but I thought I would still have a say.
    As said earlier in this thread, its not about speeding or getting there faster, but rather about driving style. If you have ethe choice between doing 100 or doing 96 on the same road, why would you want to do 96; especially when other cars are passing you 4km/h faster (still within legal speed limits). By saying this, I don't beleive you should use your 2km/h grace by driving at 102 coz its there for a reason. If you drive at 102 and for whatever reason go to 103 you may get done (assuming there is only 2km/h grace) whereas if you were driving at 100 and went up by the same 1km/h you would be still safe.
    Also i believe that if your in reasonable traffic and everyone is going a few ks over the limit, go with the flow. Just remember the happy snapping camera is most likely to get the first car in the bunch and if its quick maybe another unobstructed vehicle. A copper won't even bother.
     
  12. TMM

    TMM OEM+

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    After i got the digital speedo enabled, my VY agrees 100% with every GPS i've used. Funny that. It probably also helps that the rolling radius of the VY berlina1/2, calais1 and s-pak1 is larger then the other models. I'm running 225/55R16 which theoretically should've made it over read even more then standard.

    Berlina (16") - 215/60R16 - 332mm
    S-pak1, calais1 (16") - 225/55R16 - 326mm
    Exec (15") - 195/65R15 - 317mm
    S-pak2, calais2, VX SS etc (17") - 235/45R17 - 321mm
    VY SS etc (18") - 235/40R18 - 322mm
     
    Last edited: Jun 25, 2010
  13. Apple5

    Apple5 New Member

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    I have a VF SV6 Stock standard. Just travelled from Mt Gambier to Sydney. Used my GPS program on the trip. Both the odometer and the gps were so close, 0.3%, the difference was negligible.
    The speedo on the other hand was excruciating. Now, sitting in a car for 12 hours is bad enough, but almost 13 just sucks.
    In Victoria, they had the speed recognition near Wodonga. 115 speedo indicated gave 110 on the VIC speed test unit.
    In NSW, a different story. They have 5 seperate Km posts marked. Now the average Joe Blogs would read the speed test and start the trip meter at the end he would see he has travelled exactly 5 km which would give the assumption the speedo is correct.
    Knowing there was a speedo problem, and having a first instance verification with the GPS I decided to time the interval for the 5km.
    Flashing past a sign@ 115km per hour gave me an average of 32.5 seconds per km (5 readings using the iphone timer) It was not very accurate but short of placing infra red beams at each mile post, it was a second verification.
    Placing a speedo adjustment device in the circuit will not cut it because you have 4 digital outputs , The analogue speedo, the digital speedo, the HUD and the odb2 output which all read from the same calculation which is inside the computer after the odometer and it is correct.
    How can that figure be calibrated???
    This also gives other questions of calibration. Instantaneous fuel economy is one.
     
    Last edited: Jul 23, 2018
  14. vc commodore

    vc commodore Well-Known Member

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    Brilliant thread dig after 8 years.

    At the end of the day, sit on your cars speedometre reading and you shouldn't get pinged...If other turkeys want to wizz pass you to get to their destination quicker, good luck to them.....No skin off my nose
     
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  15. Apple5

    Apple5 New Member

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    Cant win with you admins ..... If I open a new thread, you would tell me there has been one for years. ;)
    Point being I had a VN and a VS and they were both spot on the mark. I dont speed but I sit on the speed limit. Especially on long journeys. After reviewing the various products available. None suit because they all work off the pulses from the gearbox. If I change that with a "calibrator" then it will change my odometer reading which already correct.
    Besides, noticed those who own older model cars have one speed and newer models have another speed.
    Governments/ manufacturers do not think through their decisions very well. I wonder why they complain road rage is on the rise. Then have half the cars wanting to do the speed limit and the others wanting to do the real speed limit.
    Then we have the people who just "roll over". If the government provides, then its all ok.
    In this day and age, we should have more accuracy, not less.
    PS, it was a good thread read.
     
  16. krusing

    krusing Member

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    I have a similar situation with my VE with different speedometer readings, I have the Digital display and when I am sitting on the Hume highway at 100 km/h, the analogue speedo is on about 109 +/- 1km/h.
    Where I have a Navman GPS and it will display 107 km/h, and I have another GPS device [a GPS speed detection device ;)] that also reads 107 km/h, so I would safely say, the Speedometer in my car is 3k's my favour ;)
    I was also in Wodonga last week and passed under those gantries, and they are an "Advisory Only" guide, where there was one the Geelong freeway, and that was the same as my both GPS displays, so not to draw attention to my self, I travel at the digital display speed, and haven't had to pay any voluntary tax's.
    Don't get me wrong, I am not a lane or road hog, I just like to get to where I am going safely and efficiently. ;)
     
  17. immortality

    immortality Moderator Staff Member

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    I can't believe this thread is still going, it's got to be the most useless thread in this section(someone should lock it).....:mad:

    Factory speedo calibration is set a few Km/h faster than actual to safe you from yourself. All manufacturers do it. End of story.

    Changing your wheels to something other than what was fitted from new will also alter your speedo reading (who knew right?).....
     
  18. immortality

    immortality Moderator Staff Member

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    Australian Speedo accuracy standards
    Australian Design Rule 18 sets out the accuracy standards for vehicle speedos.

    Until July 2006 this rule specified an accuracy of +/- 10 percent of the vehicle’s true speed when the vehicle was travelling above 40km/h.

    That is, at a true vehicle speed of 100km/h the speedo could indicate between 90km/h and 110km/h.

    An odometer accuracy of +/- 4 percent was also a requirement.

    From July 1 2006 a new standard began its phase in and by 1 July 2007 all new vehicles had to comply. The new standard requires that:

    • The speedo must not indicate a speed less than the vehicle’s true speed or a speed greater than the vehicle’s true speed by an amount more than 10 percent plus 4 km/h.
    • Odometer accuracy is no longer defined.
    What this means:
    • For a vehicle travelling at a true speed of 100km/h, the speedo must read between 100km/h and 114km/h. The effect of this is that many drivers will find that at 100km/h they are driving up to 14km/h below the speed limit if they rely on the vehicle’s speedo.
    • The speedo must always read 'safe', meaning the vehicle must not travel faster than the speed indicated by the speedo.
    This change was made to align Australian vehicle rules with those already in place in Europe. It applies to all Australian motor vehicles except mopeds.
    Dealers will generally not attempt to correct speedo error unless it exceeds the legal requirements.
    https://www.racq.com.au/cars-and-driving/safety-on-the-road/driving-safely/speedo-accuracy
     
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