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Speedo accuracy #689459
18/02/21 03:34 PM
18/02/21 03:34 PM
Joined: Jan 2020
Posts: 20
Selby N. Yorkshire
C
Colin725 Offline OP
New to Talk Morgan
Colin725  Offline OP
New to Talk Morgan
C

Joined: Jan 2020
Posts: 20
Selby N. Yorkshire
Having checked my speedo against a portable sat nav reading, I am horrified to see it is way out.
At true 30mph it is showing 39mph and gets progressively worse.
Is this common with Morgans, mine is a 1995 plus 4, and any suggestions as to the possibility of getting it recalibrated or is it a replacement job.

Re: Speedo accuracy [Re: Colin725] #689463
18/02/21 03:59 PM
18/02/21 03:59 PM
Joined: Feb 2020
Posts: 256
Cotswolds
Treesurveyor Offline
Learner Plates Off!
Treesurveyor  Offline
Learner Plates Off!

Joined: Feb 2020
Posts: 256
Cotswolds
Curiously, my speedo was regularly 5mph-9mph out (under reading) against sat nav. When I replaced my tyres, all 4, I found it back to parity at low to midrange speeds, and 2-3mph under at motorway speed.


"DOT" 35th Anniversary Edition Plus 8- family owned from new. Rolls Royce Pewter.
06 Saab 93
Re: Speedo accuracy [Re: Treesurveyor] #689473
18/02/21 04:13 PM
18/02/21 04:13 PM
Joined: Jan 2020
Posts: 20
Selby N. Yorkshire
C
Colin725 Offline OP
New to Talk Morgan
Colin725  Offline OP
New to Talk Morgan
C

Joined: Jan 2020
Posts: 20
Selby N. Yorkshire
I bought it with full set of new tyres fitted so nothing to compare previously.

Re: Speedo accuracy [Re: Colin725] #689495
18/02/21 05:04 PM
18/02/21 05:04 PM
Joined: Jul 2007
Posts: 25,577
Cheltenham, Glos. UK
Graham, G4FUJ Offline
Salty Sea Dog
Graham, G4FUJ  Offline
Salty Sea Dog
Member of the Inner Circle

Joined: Jul 2007
Posts: 25,577
Cheltenham, Glos. UK
It's not legal Colin.


Graham (G4FUJ)

D8921 L44FOR '93 4/4 Giallo Fly 2 seat smile
'90 LR 90 SW
'06 Saab 9-3 Convertible
Re: Speedo accuracy [Re: Colin725] #689500
18/02/21 05:08 PM
18/02/21 05:08 PM
Joined: Aug 2013
Posts: 13,868
Salisbury, UK
Peter J Offline
Formerly known as Aldermog
Peter J  Offline
Formerly known as Aldermog
Member of the Inner Circle

Joined: Aug 2013
Posts: 13,868
Salisbury, UK
Originally Posted by Colin725
Having checked my speedo against a portable sat nav reading, I am horrified to see it is way out.
At true 30mph it is showing 39mph and gets progressively worse.
Is this common with Morgans, mine is a 1995 plus 4, and any suggestions as to the possibility of getting it recalibrated or is it a replacement job.


At least you are very unlikely to get caught speeding, if you go by the speedo reading!
But you might be pulled for causing an obstruction.

I suspect someone has fitted tyres with a different profile, so effectively changing the wheel size and altering the speedo drive gearing.
You don't mention the model and the wheel/tyre size fitted.


Peter,
V8s are best....
Tarka the 'Otter Mog....2014 Plus 8
AMG C63 Estate.


Re: Speedo accuracy [Re: Colin725] #689546
18/02/21 07:40 PM
18/02/21 07:40 PM
Joined: Jul 2013
Posts: 3,171
West Sussex, UK
Chris99 Offline
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Chris99  Offline
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Joined: Jul 2013
Posts: 3,171
West Sussex, UK
Construction and use regulations allow a speedo tolerance of -0% to +10% so all speedos should overread. To accommodate manufacturing tolerances most are towards the 10% error but 39mph at 30mph is outside the limit.


Red Leader drive
Re: Speedo accuracy [Re: Chris99] #689557
18/02/21 08:19 PM
18/02/21 08:19 PM
Joined: Jan 2009
Posts: 5,144
howard Offline
Charter Member
howard  Offline
Charter Member

Joined: Jan 2009
Posts: 5,144
Originally Posted by Chris99
Construction and use regulations allow a speedo tolerance of -0% to +10% so all speedos should overread. To accommodate manufacturing tolerances most are towards the 10% error but 39mph at 30mph is outside the limit.


True but since its never checked by officialdom, that doesnt matter.

I would be a bit cautious comparing with a satnav because they arent htat accurate on speeds paricularly if unudlations and hills are involved. Their speed calculation is the distance between two calculated points on the geoid and the time difference. That said the satnav wont be 30% out or anything like it. Check wheel and tyre sizes. Check if the speedo has been replaced - does wonders for resale value sometimes!

Re: Speedo accuracy [Re: Colin725] #689560
18/02/21 08:35 PM
18/02/21 08:35 PM
Joined: Aug 2010
Posts: 3,624
Costock, South Nottinghamshire...
Paul F Offline
Talk Morgan Addict
Paul F  Offline
Talk Morgan Addict

Joined: Aug 2010
Posts: 3,624
Costock, South Nottinghamshire...
If the speedo is digitally calibrated, another possibility is that someone has inadvertently changed the calibration number.

I cannot remember the numbers or the button sequence required to display the number - hopefully someone will be along soon who knows what they are talking about.


Paul
Costock, UK
2014 4/4 Rolls Royce Garnet Red
Disco 4
Teddy - 17h1 Irish Draught cross
Re: Speedo accuracy [Re: Chris99] #689571
18/02/21 09:36 PM
18/02/21 09:36 PM
Joined: Feb 2016
Posts: 3,688
East Harling, Norfolk UK
RichardV6 Offline
Talk Morgan Addict
RichardV6  Offline
Talk Morgan Addict

Joined: Feb 2016
Posts: 3,688
East Harling, Norfolk UK
Originally Posted by Chris99
Construction and use regulations allow a speedo tolerance of -0% to +10% so all speedos should overread. To accommodate manufacturing tolerances most are towards the 10% error but 39mph at 30mph is outside the limit.

The law allows more than that Chris, it's up to 110% + 6.25 mph over read in the range 25 to 70 mph. A cars speedo could legallly be indicating 50.25 mph when actually travelling at 40 mph doh


Richard

2018 Roadster - Red/Magnolia - "Morton"
1966 Land Rover series 2a SWB
1960 Velocette Venom
Re: Speedo accuracy [Re: Colin725] #689607
19/02/21 08:46 AM
19/02/21 08:46 AM
Joined: Jul 2007
Posts: 19,655
Suffolk
John V6 Offline
Member of the Inner Circle
John V6  Offline
Member of the Inner Circle

Joined: Jul 2007
Posts: 19,655
Suffolk
Sadly mine under reads by c 10%. MMC say it is legal, hence my GPS speedo. I know the GPS has faults but that combined with rpm & gearing is helpful


JohnV6
2014 Brooklands Edition Roadster "Brookland's Belle" #5 of 50
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