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Wales
by Joske Vermeule, September 1
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Forums39
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Jun 14th, 2026
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Joined: Mar 2009
Posts: 3,825 Likes: 69
Talk Morgan Addict
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Talk Morgan Addict
Joined: Mar 2009
Posts: 3,825 Likes: 69 |
Is gps mph measurement truly accurate?
Nick
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Joined: Jul 2011
Posts: 1,948
Talk Morgan Enthusiast
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Talk Morgan Enthusiast
Joined: Jul 2011
Posts: 1,948 |
Is gps mph measurement truly accurate?
Nick It will be much more accurate than a car's speedometer - assuming a 'modern' GPS unit with a good fix onto multiple satellites. Inaccuracies arise with gradient, since GPS horizontal position fixes are more accurate than their vertical altitude fix. GPS will therefore tend to understate distance and speed if driving up or down a gradient. Fag-packet Pythagoras shows that a 4% slope will cause a GPS error of <0.1% and the error only becomes significant (ie greater than 1%) when the gradient is steeper than 15%.
Stuart
"There's no skill substitute like cubic inches."
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Joined: Jul 2011
Posts: 152
L - Learner Plates On
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L - Learner Plates On
Joined: Jul 2011
Posts: 152 |
Jay
If I install a 4.1.1 diff, what revs would I be at in fifth gear at 60mph/100kph?
Jeff
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Joined: Apr 2008
Posts: 12,260 Likes: 319
Scruffy Oik Member of the Inner Circle
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Scruffy Oik Member of the Inner Circle
Joined: Apr 2008
Posts: 12,260 Likes: 319 |
Without knowing the rolling radius/effective circumference of the wheel, and the drive ratio of the 5th gear, that's an impossible question to answer. If you do know them, then it's simple maths.
Tim H.
1986 4/4 VVTi Sport, 2002 LR Defender, 2022 Mini Cooper SE
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Joined: Feb 2011
Posts: 14,009
Member of the Inner Circle
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Member of the Inner Circle
Joined: Feb 2011
Posts: 14,009 |
Jay
If I install a 4.1.1 diff, what revs would I be at in fifth gear at 60mph/100kph?
Jeff It was a while ago I had the 4/4 Jeff. All my workings out re rpm/ speed have all gone. It certainly didn't feel like it was over revving.
Jays
Former Morgan owner. Gone but hopefully not forgotten!
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Joined: Aug 2014
Posts: 265
Learner Plates Off!
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Learner Plates Off!
Joined: Aug 2014
Posts: 265 |
Jay
If I install a 4.1.1 diff, what revs would I be at in fifth gear at 60mph/100kph?
Jeff Around 2600 with the Mazda gearbox.
Looking for another Morgan!
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Joined: Jul 2011
Posts: 152
L - Learner Plates On
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L - Learner Plates On
Joined: Jul 2011
Posts: 152 |
Guys
Thank you
2600 feels about right.
Tempted with throttle bodies but I think I'm resolved to go the diff route
When finances permit
Jeff
4/4
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Joined: Aug 2014
Posts: 5,587
Charter Member
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Charter Member
Joined: Aug 2014
Posts: 5,587 |
TB's are well worth it , and they look fantastic too !
Geneva 2016 plus 8' The Green Godess' 4 side exits .
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Joined: Mar 2014
Posts: 688
Talk Morgan Regular
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Talk Morgan Regular
Joined: Mar 2014
Posts: 688 |
Porsche 981 Spyder
V8 Speedster ( 5 years)
4/4 Competition spec (5 years)
4/4 4str Kent ( 10 years)
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Joined: Apr 2012
Posts: 1,653
Talk Morgan Enthusiast
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OP
Talk Morgan Enthusiast
Joined: Apr 2012
Posts: 1,653 |
Guys,
TBs are amazing but it is a lot of money.
2022 Plus Four, 2023 Super Three, Range Rover Vogue SDV8 and Triking T3.
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