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Now driving an XF Falcon.
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1,042 Posts
Discussion Starter #1
Ok, quick question, how could I find out how accurate my speedometer is?

Living in the speed camera city (aka Melbourne), I want to make sure my speedo is as accurate as possible, in fact I'd prefer for it to read slightly over (so for example read 60km/h when I'm actually doing 59km/h) - I want to at least be able to stay at or under the speed limit when going past those revenue raising machines, oops, I mean road safety devices...
 

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Ford Appreciation Society
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3,666 Posts
Have you tried the speedo check on the side of freeways and H'wys? Over 5 kms, signs posted at the start, and then every km. Check against your odometer.

Also, run your car behind a car who's speedo you trust, and go through various speed zones, noting what speed your car is telling you.

Some Dyno shops can also tell you on the dyno run (or they have on a couple of runs I have had done).
 

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456 Posts
Try using a hand held GPS they are pretty good
 

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Here's how I do mine:

1. get to desired speed on speedo and set cruise control. Try to do thiis on a flat section of road.
2. Cycle your trip computer until you get to the 'average speed' reading and hit reset.
3. After a second you will get a reading which is a pretty good indication of your current speed.

I know that when my speedo is reading 100 I'm doing about 97, when it reads 110 I'm doing about 105. So for me to be doing 110 (say on the way to the Gold Coast) I set my criuse control to 115. Now all those cars don't creep away from, or up to, me!

i know that my friends EBII is rthe same, apparently ford and few other makers set their speedo's this way for a reson. Sounds dumb I know but hey, go figure. Apparently Australia is one of two or three countries in the world that still allows this practice.
 

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Banned
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3,104 Posts
Chase a couple mates, not all of them will have speedos that are out that much....
 

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There are places that accurately test and calibrate speedos, I sometimes work on fire trucks and once a year it goes for a test. I would expect that the police cars also need to be calibrated. Or they give a printout of the speedo reading and actual speed difference
 

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.au member
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2,747 Posts
If you're doing it on an EF/L you can use the Dash Diagnostic mode to find out exactly how fact you're going:

* Turn Smartlock Off, put your keys in the ignition and hold down the odo button. Count to about 12 (keep holding it in).

*Whilst still holding the button in, turn the keys to the 'on' position, but dont start the car. Let go of the button, then push it quickly 3 times, holding it in on the third time. Hold it in until the seatbelt light (in the middle of your teacho) goes out, once it goes out let the button go.

*If you've done it right, the odo should black out for about 5-8 seconds, then start flashing 'FORD' at you. You can now turn the car on.

*Once you're driving push the odo button until you see a '3' in the top left hand corner. At this screen, the bottom row of numbers is the vehicle speed, and it is exact. If your speedo is set right it'll be 3kms out (this is normal factory setting), so 100 on your speedo will equal 97 in your odo doing this test. The top line is engine RPM.

*If you keep cycling through (by pressing the odo button to move to the next screen) you can find battery voltage, fuel tank level etc etc - lots of other things that I cant be bothered writing out. If anyone wants to know the rest I'll post it up later.

*To exit dash diagnostic mode, hold your odo button in for about 3-5 seconds. It should go back to normal after that.

WARNING: If you're driving with Dash Diagnostic mode operating, it is more than likely your engine will stop for half a second or so after around 10 mins of operating in this mode. Your gauges will go back to zero, then they should return to a reading of your current speed/RPM, and the dash will automatically exit diagnostic mode.
 

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847 Posts
Put it on a dyno and get the guy to note what speed your speedo reads for each applicabble speed limit. eg when my speedo says 85 im going 80.
 

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Lamahs approve of manuals
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1,382 Posts
Go to a professional place to get it measured.
Anything that the car is telling you (cruise or diags panel) is subject to the same inaccuracies the speedo itself is - tyres, the speedo gears etc etc.

Personally, I haven't got a great deal of faith in the roadside "calibration" postings, but it might be better than nothing. Oh, and don't trust any of the govt "speed notification" signs that tell you how fast you are travelling on a road - they are notorious for being wrong . . .
 

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Birth, Drift, Death...
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3,039 Posts
any dyno place will be able to tell you, redcliffe dyno does a quick speedo check before the first power run to 'warm up' the dyno or something, they have done it both times i got my car dynoed there.
 

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Ford Member
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103 Posts
I was done apparenty doing 119 when my spedo was reading 104 the cop told me to go to Howard Instruments and get my Speedo recalibrated. I called Howard Instruments the asked my what car I drove I told them an Ea Fairmont Ghia, they then said thats the model with digital spedo. I said yes they then told me they never go out and to save my money and dont bother bringing car in. As for those spedo testers on the Highway they vary dapending on weather conditions I have seen 3 different readings from the same spedo tester on different day. As for using a GPS I have heard of them peing used to calibrate the speed by Instrumentation places.
 

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Can't wait for Winton...
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2,759 Posts
Or drive up the Hume Highway or another road with the km posts on the side, at a constant speed and time how long it takes to do 10 or 20km with a stop watch or even to the second. That is a long enough time that any problem with split second timing accuracy will not have much influence. Then you can work out your speed and compare with the speedo reading. As a general rule, providing you haven't changed gearing, tyre sizes, etc your speedo will most likely be "optimistic" by 3-5km/h at 100km/h. Also to avoid speeding fines don't try to take up any inaccuracy in your speedo or tolerance above the speed limit - that is basically what the wipe off 5 campaign was about.
 
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