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Offline Tigercat

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SPEEDO CHECK
« on: March 19, 2013, 02:17:03 PM »
Did a speedometer check on the way in this morning.  As is typical of past Triumphs, the speedo is optimistic.  Using my Garmin GPS, the speedo reads 1 MPH fast at 35 MPH and the error increases with speed.  At 70 the speedo is reading 3 - 4 MPH fast.  Not all that surprising I guess.  Anyone else wonder why they can build electronic fuel injection that maintains a perfect fuel/air ratio but can't seem to build accurate speedometers?

Cheers,
 :306:

Offline Robmcg

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Re: SPEEDO CHECK
« Reply #1 on: March 19, 2013, 09:33:32 PM »
They can build them accurately.  :187:
 It's the bloody do good Governments, trying to "stop the creep" over the speed limit.

Here in Australia, a Speedometer must read optimistic, up to 10%, or the company will cop a very heavy fine.  :172:

Our wonderful governments, dragging us back to the time of Lucas electronics. ( Prince of darkness)

What you did is best, I check all my speedos with 3 different GPS systems and then recalibrate my brain, so that when I look at the speedo, I know fairly accurately, how far over the speed limit I am.

Offline ThickBrit

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Re: SPEEDO CHECK
« Reply #2 on: March 20, 2013, 11:03:03 PM »
And (digital) ones that don't work when the temp drops below 4 degrees C! Drives me nuts.

Offline Berber

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Re: SPEEDO CHECK
« Reply #3 on: March 21, 2013, 05:56:55 PM »
Yes the lack of digital early morning is a pain. At least Triuph admits it knows about it and is looking at a fix.
'The farther one travels, the less one knows.......'

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Offline Chaos

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Re: SPEEDO CHECK
« Reply #4 on: March 22, 2013, 08:20:02 AM »
Mines out by 5mph at 70 according to the sat nav. The sat nav is always on and the only instrument that use :821:
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Offline Cide1

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Re: SPEEDO CHECK
« Reply #5 on: August 15, 2013, 01:40:17 PM »
Digging up a 5 month old thread, but I figured it is better than making a new one...

My speedo feels like it reports way faster than actual.  I'm thinking it may be off as much as 10 MPH at 70 MPH.

I'm ordering a GPS, but it's not here yet, so I don't have anything for comparison.

My Yamaha's are also off by a similar amount, I don't understand why they don't build the things to report accurately. 

Online john348

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Re: SPEEDO CHECK
« Reply #6 on: August 15, 2013, 01:53:10 PM »
I think the law is something like 10% over 0% under so to be on the safe side (variances in tyre size etc.) the manufacturers go for something like 5% over read.  In fact on the sprint when I cahanged the gearing to 18 tooth front the TuneEcu package asked what the gearing was (it knew about 18 front) and "How much over read do I want".  I put 0 and it is now very accurate.  I do not know if the TT has this (I am sure it will have) but more importantly can you get at it with the new law restirctive ECUs.  I have dealer tool but haven't tried it yet.

Offline CoJaW

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Re: SPEEDO CHECK
« Reply #7 on: August 15, 2013, 01:58:09 PM »
Speedometers rely on the rotation of the wheels to represent speed. (Unlike satnavs!)  Tyre wear, pressure and loading affect the rotational speed of the wheels for a given road speed. The law says the speedo must never under read, so manufacturers design  the speedo to over read in normal circumstances so that it doesn't under read in extreme circumstances!

 :087: