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Author [ES] [CA] [PL] [PT] [IT] [DE] [FR] [NL] [DK] [NO] [GR] [TR] Topic: How accurate/inaccurate is the speedo?  (Read 6047 times)

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Offline GS TRV

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How accurate/inaccurate is the speedo?
« on: September 19, 2012, 07:26:27 PM »
When I first demo'd a CT i had a hunch that the speedo was wildly over-reading. After taking delivery of my own I can concur and after letting my brother have a go he is convinced it over reads too.  My estimate is 10-15 mph.

Can anyone confirm this? I suppose I won't really know until I get my gps fitted but I'm convinced its a fair margin. Certainly way more than the digital speedo of my S1000RR that I traded in.

Any thoughts?

Trev

Offline scotsy

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Re: How accurate/inaccurate is the speedo?
« Reply #1 on: September 19, 2012, 07:53:14 PM »
According to my GPS its a full 10% fast which is about normal for jap stuff (inc cars)

stick the 'turned on' gps in your jacket pocket and check the highest speed recorded on a short ride and compare it with the speedo reading you attained afterwards (did it on an aeroplane once and got 540mph  :156:)

Offline grahew

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Re: How accurate/inaccurate is the speedo?
« Reply #2 on: September 19, 2012, 08:40:30 PM »
*Originally Posted by GS TRV [+]
When I first demo'd a CT i had a hunch that the speedo was wildly over-reading. After taking delivery of my own I can concur and after letting my brother have a go he is convinced it over reads too.  My estimate is 10-15 mph.

Can anyone confirm this? I suppose I won't really know until I get my gps fitted but I'm convinced its a fair margin. Certainly way more than the digital speedo of my S1000RR that I traded in.

Any thoughts?

Trev

I was told many years ago all speedo's run approx 10% over so when you get pulled for speeding you have no excuss :159:

Offline thetrecker

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Re: How accurate/inaccurate is the speedo?
« Reply #3 on: September 19, 2012, 09:07:42 PM »
Is this a daft question... or how come GPS is automatically assumed to be pin point accurate? speedo's were always considered 10% out as grahew said and a speed trap will give a few mph over and above to allow for this otherwise if it was accurate a lot more tickets would be issued. if satellite is tracking the bike from space, is there not a delay differential to consider.  Tyre wear is more pronounced on a bike than a car so it would vary over 5000miles anyway so i bet the designers take a mean average of the wheel and tyre diameter and set the speedo to this
Thetrecker. Sometimes your the bug and sometimes your the windshield.

Offline Mika

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Re: How accurate/inaccurate is the speedo?
« Reply #4 on: September 19, 2012, 09:13:14 PM »
Speedometers are allowed by law to have up to a 10% error.

Most manufaturers build a higher reading in to them to stop people speeding and also to help with fuel consumption.

Certainly I think BMW don't use the full 10% as my GS always seemed to be reasonably accurate

Offline GS TRV

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Re: How accurate/inaccurate is the speedo?
« Reply #5 on: September 19, 2012, 09:58:23 PM »
Are u sure?it feels WAY more than 10%!

Offline Mika

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Re: How accurate/inaccurate is the speedo?
« Reply #6 on: September 20, 2012, 12:57:14 AM »
Comes under Road Vehicle (Construction and Use) Regs 1986

10% is the maximum that a manufacturer is allowed to use in a speedo, if it's more than that then there is a problem with the bike.
« Last Edit: September 20, 2012, 07:13:03 AM by Mika »

Offline revenue

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Re: How accurate/inaccurate is the speedo?
« Reply #7 on: September 20, 2012, 06:01:24 AM »
Just done a test, this will also depend upon your tyres and how worn they as this affects the rolling radius of the tyre as well ! mine has done 3500 km
50 Kmph shown speedo GPS showing 47 Kmph
100Kmph on speedo GPS showing 94 Kph

So approx 6.5% over actual speed  :028:

 


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