Hi all,
I just did a trip to Moz and out of idle curiosity compared the speedo reading with a GPS. When the speedo reads 120, GPS reads 100 which is a massive difference. Thought I might have undersized wheels/tyres, but am running on Bridgestone Dueler AT's 31x10.5R15 LT which seems to be ok.
Checked the Haynes manual and found a wiring diagram which shows a "vehicle speed sensor". Does anyone know where this is hidden on a 1995 GLS 4.2 and is it something that can be fixed/calibrated ?
Mike Meyer
Speedo Accuracy
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Mike Meyer
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Grootseun
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Re: Speedo Accuracy
Mike your vehicle speed sensor sits on the gearbox , final drive shaft - its normally a megnetic pick up type sensor and the only way you can change or calibrate that is by changing the physical gear on it and this is a lot of trail and error work go to control instruments or VR2 Instruments and they can calibrate the gauge itself
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Re: Speedo Accuracy
Mike, before you do anything, check what the error is on the trip counter compared to the GPS.
However, I do suspect that the speedo is calibrated for the alternative wheel size of 7.50/16 (the old split-rim Marie biscuits seen on landies and cruisers of 20 years ago), which was the standard size in many markets and has an OD of about 33", as compared with your 31"
My car on 33" wheels shows 130 at a true 120 but the trip is just about spot on.
The speedo can be re-calibrated as Driko says. This is done by re-painting the face with the markings at the correct places, but there is not much that can be done about the trip counter. I would just get to know it and live with it.
However, I do suspect that the speedo is calibrated for the alternative wheel size of 7.50/16 (the old split-rim Marie biscuits seen on landies and cruisers of 20 years ago), which was the standard size in many markets and has an OD of about 33", as compared with your 31"
My car on 33" wheels shows 130 at a true 120 but the trip is just about spot on.
The speedo can be re-calibrated as Driko says. This is done by re-painting the face with the markings at the correct places, but there is not much that can be done about the trip counter. I would just get to know it and live with it.
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tour de frans
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Re: Speedo Accuracy
Agree with Peter, Also remember the manufacturer build a vehicle with a 10% over read for the speedo. With that 10% over read the odo are spot on.
The 10% differance, its law. Fitting bigger wheels with make the Speedo more true, but the odo will read less kms.
Rdgs.
The 10% differance, its law. Fitting bigger wheels with make the Speedo more true, but the odo will read less kms.
Rdgs.
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Mike Meyer
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Re: Speedo Accuracy
Thanks Guys,
I will do the odo vs gps check and then decide what to do after that - maybe just live with it. Once I know what the error is at 60/80/100 I can work around the problem.
I will do the odo vs gps check and then decide what to do after that - maybe just live with it. Once I know what the error is at 60/80/100 I can work around the problem.
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Kagiso II
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Re: Speedo Accuracy
Latest SA 4x4 also has informative article on this issue ... worth the read.
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Grant
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Re: Speedo Accuracy
Mike,
I experienced the same on my Troll. Now I have 285/75/16'S and the speedo is 100%. I still only travel at 100 km/hr, but have to be carefoll in the 80 & 60 km zones.
I experienced the same on my Troll. Now I have 285/75/16'S and the speedo is 100%. I still only travel at 100 km/hr, but have to be carefoll in the 80 & 60 km zones.
V8 Power
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ChristoSlang
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Re: Speedo Accuracy
Yep, 33" tyres on my Patrol and the speedo error is less than 5%...
Christo (the snake man)
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Re: Speedo Accuracy
What is the difference on the distance?
Herrie op Safari/Patrollie
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1983 Safari
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ChristoSlang
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Re: Speedo Accuracy
Never been bothered to check 
Christo (the snake man)
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1998 4.2 GL Patrol (Chuck Norris)
2007 350Z twin-turbo coupe (Batmobile)
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