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Wales
by Joske Vermeule, September 1
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Forums39
Topics49,915
Posts838,214
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Jun 14th, 2026
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Joined: Apr 2013
Posts: 1,370 Likes: 11
Has a lot to Say!
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Has a lot to Say!
Joined: Apr 2013
Posts: 1,370 Likes: 11 |
My dealer told me it can be tweeked but not how. As it is tied to the front wheel it will change over time as the tire wears down.
Use your GPS and trust that. Your mileage may vary.
I, personally, use the tachometer as my bible. That is far more important than how fast I'm going.
What's your mileage? Who cares. Is it practical? See #1. What happens when it rains? You get wet.
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Joined: Nov 2013
Posts: 1,947
Talk Morgan Enthusiast
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Talk Morgan Enthusiast
Joined: Nov 2013
Posts: 1,947 |
Legally speedos have to read high. In Europe they can be up to 10% out. Mine over reads 10% at 30 getting a bit closer at higher speeds.
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Joined: May 2014
Posts: 5,442 Likes: 133
Black Rat Charter Member
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Black Rat Charter Member
Joined: May 2014
Posts: 5,442 Likes: 133 |
On my new M3W, the spedo is off ~10%, perhaps closer to 8%, reading high. An indicated 45 is closer to 40. Based on this older thread, this is a somewhat common issue.
Has anyone successfully re-calibrated the spedo or is there a known way to get it closer to accurate? This is because in the UK it is illegal to supply a vehicle where the speedo under reads, therefore all manufacturers build in a 10 % safeguard. On the Trads it is possible to re program the same thing may apply to the M3W. Do a search on speedos as somewhere on here it tells you how to do it.
Keith
2013 narrow bodied + 4 Ruby.
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Joined: Jan 2016
Posts: 625
Talk Morgan Regular
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Talk Morgan Regular
Joined: Jan 2016
Posts: 625 |
Does this help ? http://www.caigauge.com/documents//product-instructions/spedometers/speedometers/pil042-460-435.pdfThey all read high though as others have said for legal reasons, just live with it. ( except my Lotus Elise that read 6 k lower than I was going, very dodgy in Victoria and South Australia where they use speeding fines to finance the politicians perks  )
Cheers John
2011 4/4 - "Elrond"
2007 Elfin C3 Clubman - “Gimli”
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Joined: Jun 2016
Posts: 439 Likes: 3
Learner Plates Off!
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Learner Plates Off!
Joined: Jun 2016
Posts: 439 Likes: 3 |
Thanks! Well, it might work, if I could get it into that mode. When I press the reset (indicator stalk button) and turn on the ignition, I get a "UNIT" or a "WARN" display. The UNIT seems to set 12H or 24H, presumably for the clock, and the "WARN" cycles through three digits, initially set to 000. Assume it may have some un-documented speed warning function? But in any case, I haven't been able to get "SET PPU" to appear. If I could, it would be a simple matter to re-set it to get it closer it would seem...
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Joined: Feb 2016
Posts: 8,704 Likes: 416
Needs to Get Out More!
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Needs to Get Out More!
Joined: Feb 2016
Posts: 8,704 Likes: 416 |
The linked document suggests a dedicated trip reset button needs to be used. The M3W doesn't have one 
Richard
2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone
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Joined: Jun 2012
Posts: 2,243 Likes: 73
Talk Morgan Expert
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Talk Morgan Expert
Joined: Jun 2012
Posts: 2,243 Likes: 73 |
The speedo adjustment is a function that is part of the locked ECU I think. The S&S manual mentions a calibration adjustment but that is in relation to the ECU history rather than the speedo signal, not sure if it corrects the speedo as well. It should be a simple case of putting the correct numbers into the ECU, if you could. Has anyone with an unlocked ECU tried doing this? I have had 3 Lotus cars with a similar system that have all read perfectly (unlike Uther), not +8% as the M3W does. It's a calibration issue that could be easily resolved. I wouldn't mind a +1% error but +8% is just bad.
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Joined: Jun 2016
Posts: 439 Likes: 3
Learner Plates Off!
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Learner Plates Off!
Joined: Jun 2016
Posts: 439 Likes: 3 |
Is there any reason to believe the speedo is controlled by the ECU? Based on the document posted, it would seem that the speedo is totally independent, but apparently a different model than the one the document was written for...
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Joined: Feb 2012
Posts: 5,659 Likes: 10
Charter Member
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Charter Member
Joined: Feb 2012
Posts: 5,659 Likes: 10 |
It's a common problem I beleive but only with plus errors. I have not heard of negative errors.
Martin (Deano)
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Joined: Jun 2012
Posts: 2,243 Likes: 73
Talk Morgan Expert
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Talk Morgan Expert
Joined: Jun 2012
Posts: 2,243 Likes: 73 |
You are correct truckin-on, reading up on it in the S&S manual again, it seems the speed sensor on the wheel sends the signal to the speedometer and that sends a signal to the ECU, not the other way around, as I thought. The ECU can be calibrated to the signal it gets for it's data recording but this will not change the indicated speed.
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