Home > Technical (L322) > Speedometer about 2 MPH fast |
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lschwarcz Member Since: 18 May 2019 Location: Hillsboro, OR, USA Posts: 273 |
Hi Everyone,
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28th Jan 2021 12:56am |
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TJRL Member Since: 07 Sep 2019 Location: Reading Posts: 198 |
As noted by Ian, an over-read is normal over here.
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28th Jan 2021 6:46am |
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p38arover Member Since: 16 Dec 2015 Location: Western Sydney Posts: 1534 |
Same in Oz, cars can read up to 10% high but can’t read low.
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28th Jan 2021 9:14am |
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ur20v Member Since: 19 Feb 2019 Location: None Posts: 634 |
Speedos are a mechanical device (not GPS) It’s done to allow for tyre wear, and differences between rolling radius of tyre brands etc... a speedo cannot legally under read speed in most countries in the world so they run up to 10% fast so it cannot be used as a reason for speeding. This is the same for all manufacturers and vehicles on the road.
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28th Jan 2021 9:59am |
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steptoe Member Since: 23 Jul 2012 Location: london Posts: 382 |
There's a legal reason why not just your speedo, but all speedos over read............ so you can't use the excuse of a speedo over reading and blame the manufacturer if you're ever caught speeding.
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28th Jan 2021 10:02am |
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bishbosh10 Member Since: 25 Apr 2013 Location: North Somerset Posts: 344 |
How are you measuring "actual" speed"?
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28th Jan 2021 12:15pm |
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lschwarcz Member Since: 18 May 2019 Location: Hillsboro, OR, USA Posts: 273 |
I've read a LOT of really good replies here.
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29th Jan 2021 12:28am |
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TJRL Member Since: 07 Sep 2019 Location: Reading Posts: 198 |
Larry, my wife has had company cars for many years now; BMW, Merc, Merc, and now Audi. All of them read exactly 2 mph too high on the speedometer but were almost perfect on the navigation / GPS systems. My last new car was a 2005 Audi A3 (sold in 2019 when I got my FF) and it too was just the same as were my 2001, 2008, 2014, 2015, 2018 and 2020 BMW motorbikes.
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29th Jan 2021 10:12am |
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ur20v Member Since: 19 Feb 2019 Location: None Posts: 634 |
When I mentioned the Speedo is a mechanical device it’s was a general comment and I meant it is ‘driven’ off a gear or reluctor wheel /hall sensor as the sensor which is ‘driven’ off the transmission, diff or drive shafts and the dash cluster is electronic. To be fully electronic it would need to be a GPS device.
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29th Jan 2021 3:47pm |
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lschwarcz Member Since: 18 May 2019 Location: Hillsboro, OR, USA Posts: 273 |
ur20v,
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29th Jan 2021 5:23pm |
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Bl4ckD0g Member Since: 16 Feb 2020 Location: 127.0.0.1 Posts: 1322 |
If you have the digital dash then you can adjust the speedo “accuracy” if you like. As mentioned, there are too many variables for it to be 100% accurate for 100% of the time.
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29th Jan 2021 7:41pm |
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steptoe Member Since: 23 Jul 2012 Location: london Posts: 382 |
If you know the speedo reads 2mph faster then why not just deduct it in your head when driving... or is that too difficult 😄. To be honest I only look at the big numbers, 20,30,40 etc etc , 2mph doesn’t even register in my thoughts as I wouldn’t notice a 2mph difference. |
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30th Jan 2021 12:06pm |
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lschwarcz Member Since: 18 May 2019 Location: Hillsboro, OR, USA Posts: 273 |
Hi steptoe,
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30th Jan 2021 5:16pm |
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TJRL Member Since: 07 Sep 2019 Location: Reading Posts: 198 |
All true, but does not address the OP's original questions. I thought that all vehicles from all manufactures over read a bit (at least by 2%) in order to meet the legal requirement to never under-read. I am quite content that my cars and bikes over-read 2mph, but have to say I am intrigued that the OP's recent vehicles dd not seem to. 2010 Range Rover TDV8 Baltic Blue Autobiography (2011 MY) - SOLD 1960 Land Rover SII SWB SW 2020 BMW R1250 RT LE 2021 Triton ST-125 (Monkey Bike) |
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30th Jan 2021 5:34pm |
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