Under reading speedo??

1593 Views 10 Replies 7 Participants Last post by dmcsweeney, May 21, 2012

dmcsweeney

Discussion Starter · May 20, 2012

Hi all,
just wondering if anyone has had an issue with an under reading speedo on a 2.0d? I was driving along a bypass near my house tonite at a steady 100kph, passed a marked traffic car (at a guess travelling at about 55mph). After about 1/2 a mile the blues were on ! I was informed (not very politely) that I was speeding. When I protested my innocence (very politely) I was told my speedo must have been under reading. I've often driven with the sat nav on and noticed that the speedo seemed to over read (by about 3mph at an indicated 75mph - our motorway limit is 120kph - 75mph). Can someone tell me what speed I should see at 2000rpm in 5th? I was grilled at the road side for about 10 minutes, which included being accused of accelerating hard after I'd passed them (aparently they had to drive quite fast to catch me dispite only being about 200m behind me!). So do I have a problem? They wouldn't actually tell me what speed I was 'apparently' doing by the way.
Regards,
Dave

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willc01

· #2 · May 20, 2012

Two questions then, what wheels & tyres do you have on the car and are they the ones the car shipped with or haver they been changed. This can have an effect on the speed reading. The tyre size is plummed into the cars ECU, cetainly affects electronically but not sure if it is the speedo.

I have a free app on my iphone, Dashboard that calculates my speed from GPS, & on a clear day with a strong signal, its pretty accurate to my cars reading.

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lost in france

· #3 · May 20, 2012

The EU regs say that a Speedo cannot under read & can not over read by more than 5%+4kph.

If you claim that your speedo is under reading, a sharp copper could nick you under a Construction & Use regulation.

FWIW my speedo over reads by about 5% against a GPS receiver.

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dmcsweeney

Discussion Starter · #4 · May 20, 2012

Gents,
thanks for your input! The car has it's original wheels and tyres (205/55/R16). Believe me, if I had said I had an under reading speedo these guys would have done me!! They claimed my speedo was incorrect. Fact of the matter is they were trying to get me to admit to speeding (which I was not doing) because they had no physical evidence against me (in Ireland all speeding offences must be backed by a paper printout from the radar gun presented on the roadside, or evidence from a speed camera, which they did not have). How accurate is the Sat Nav method of checking speed?
Regards,
Dave

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lost in france

· #5 · May 20, 2012

dmcsweeney said:
How accurate is the Sat Nav method of checking speed?

SatNav/GPS has an error of about .5 mph (gpsspeed)

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fulman

· #6 · May 20, 2012

Just checked mine - 2006 2.0 d with 17 inch wheels. 2000 rpm with speedometer reading exactly 60 mph in 5th gear.

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ptruman

· #7 · May 21, 2012

Have you got the touchscreen?
If you have, you can get it to show you the vehicle "actual" speed, which will typically be 3mph out from the dash speed (ala your GPS).

The dash SHOULD over read a bit, most cars do.

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Outrunner

· #8 · May 21, 2012

How do you get the speed readout on the cars touchscreen?

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dmcsweeney

Discussion Starter · #9 · May 21, 2012

Gents,
thank you all for your replies! I carried out a few tests yesterday. I don't have an integrated sat nav, so instead I used my portable unit. I reset the trip on both car and sat nav and hit the road. I also had my code reader connected and placed (safely) on the dash. I drove 160 miles, most of it on cruse at 120kph on the motorway. The results were as follows;
1. Average speed on the information centre matched the sat nav.
2. Distance on the information centre read 0.3miles higher than the sat nav (so 0.3 miles over 160 miles)
3. The live speed info on the code reader matched the sat nav most of the time (did drop under by 1mph a few times)
4. The speedo over read by 3mph at a constant 75mph.
5. My speedo over read by approx 2mph against a roadside speed indicator.

I think the results speak for themselves!!

Now for the bad part of the story!! When the plod failed to get me to admit (though I was innocent) to speeding, they hit me for tax. Because I'd been working away from home I hadn't got around to renewing my tax. Not that big a deal as it was only out by 19 days, and generally speaking the authorities here allow one months 'grace' as provided your tax history is clean they accept that you will have to pay that month regardless of when you tax. I taxed the car with 15 minutes of being stopped!! So 650 + 80 fine!! Great!

Now for the even worse part of the story!! I have to pay a token 6o cents every night for parking where I stay in Dublin when I work up there. I parked last night in a designated space, sent the payment text message, received my authorisation text for the next 24 hours, and turned in for the night. This morning at 7am I was greated by a big yellow clamp!

So I got confirmation I was authorised but I still got clamped! A well hidden sign stated that there was a maximum stay of 3 nights in one callender week was pointed out by one of the clamping staff, dispite the fact that the text system authorised me! I can appeal for a refund, but still had to shell out another 120 for now to be released. I paid at 7.20am, the clamper arrived at 7.40am, but the lock wouldn't open!! After it was suggested someone had put glue in the lock, lol, he took out a grinder and started showering my drivers door with sparks. 2 batteries later the chain was still not cut. To cut a long story short the clamp finally gave in at 12.40pm and I set off for work late and alot poorer.

My speedo works fine though!

Regards,
Dave

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Goudy

· #10 · May 21, 2012

For the speeding, you've encountered the worst type of coppers, bored ones!

No sympathy for your tax evasion from me there Ken Dodd!

As for parking, count yourself lucky you don't live with my Mrs here in London, parking tickets fill the glove box of her car, regularly threatened by bailiffs for none payment and I've lost count of the times I've had to break it out of the pound, it's a running joke that there's only a 20% chance the car is where she left it!

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dmcsweeney

Discussion Starter · #11 · May 21, 2012

Goudy said:
For the speeding, you've encountered the worst type of coppers, bored ones!

No sympathy for your tax evasion from me there Ken Dodd!

:lol: Guilty as charged, though the usual 'get it sorted before the end of the month' would have been better!!! While I have huge respect for the law in general there are a few that certainly do have an attitude. Should have offered him a sachet of salt from my other half's stash in the passenger's door for the chip on his shoulder!

Regards,
Dave

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