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Author Topic: Spedo accuracy  (Read 1459 times)

Offline Pesky jones

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Spedo accuracy
« on: April 14, 2015, 02:04:12 pm »
Say you're going 80mph, does anyone know if your're actually going 80? Or less?

Offline Matthewsimone

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« Last Edit: April 14, 2015, 02:50:23 pm by Matthewsimone »
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Offline StuF

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Re: Spedo accuracy
« Reply #2 on: April 14, 2015, 02:51:24 pm »
My digital speedo reads 80 mph where my analogue gauge shows around 72/74mph  when on the motorway
Digital one is more accurate I guess!

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Offline xjay1337

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Re: Spedo accuracy
« Reply #3 on: April 14, 2015, 03:01:27 pm »
Say you're going 80mph, does anyone know if your're actually going 80? Or less?


My dash says 80 my Polar MFD which is wheel speed sensor says 75

Offline lukemk5gti

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Re: Spedo accuracy
« Reply #4 on: April 14, 2015, 03:13:53 pm »
I've always wondered this after seeing one of those speed digital display signs showing a different speed to what I'm doing.

At least by the looks of that link you're actually travelling slower than your speedo shows.

I might have cruise control on at 100km/hr in a 100km/hr zone and when I see a speed camera I still hit the breaks on occasion thinking what if the speedo is wrong!!

Offline xjay1337

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Re: Spedo accuracy
« Reply #5 on: April 14, 2015, 03:36:02 pm »
The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

Offline usmangti

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Re: Spedo accuracy
« Reply #6 on: April 14, 2015, 05:04:09 pm »
The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

Is it also true that a camera or speed gun can only catch you above the speed limit after 10% plus 2mph? Ie in a 30 would have to be driving at least 35mph?

Offline xjay1337

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Re: Spedo accuracy
« Reply #7 on: April 14, 2015, 05:24:15 pm »
CPS recommend only pursuing cases where the speed is 10% + 2.
You can (technically) be done for doing 1mph over the speed limit. But practically it won't happen.

Offline andyR43

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Re: Spedo accuracy
« Reply #8 on: April 14, 2015, 07:18:50 pm »
The European regulation, ECE-R 39, states that the speed indicated must never be lower than the true speed or higher by more than one-tenth of true speed plus four kilometers per hour (79.5 mph at a true 70).

You will never be going faster than your displayed speed.

Is it also true that a camera or speed gun can only catch you above the speed limit after 10% plus 2mph? Ie in a 30 would have to be driving at least 35mph?

I had to attend a speed awareness course for travelling at 33mph in a 30mph zone. Caught by a camera van, just after pulling away from traffic lights and the road merging from 2 lanes into 1 so filtering into the traffic!!!


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