Speedo discrepancy- anybody else?
#1
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Location: Perth Ontario Canada
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From what I've heard most manufacturers put in a "buffer" on their vehicles, meaning the speedo will show up to 5mph faster than your actual speed. Typically that is why State Troopers give you a 5mph variance. Im not sure if Jag does it, but I will check using my Tom Tom and report back. I put 17"s on my wife's Saab that originally had 15"'s, and much larger tires. Now I am actually going 2MPH faster than what that speedo says according to TomTom, and I think the GPS reading is as accurate as you can get.
#4
From what I've heard most manufacturers put in a "buffer" on their vehicles, meaning the speedo will show up to 5mph faster than your actual speed. Typically that is why State Troopers give you a 5mph variance. Im not sure if Jag does it, but I will check using my Tom Tom and report back. I put 17"s on my wife's Saab that originally had 15"'s, and much larger tires. Now I am actually going 2MPH faster than what that speedo says according to TomTom, and I think the GPS reading is as accurate as you can get.
I drive based on having a 5%error in the speedo reading. Generally, I go 7 mph over the posted limit to account for it.
Mike
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#8
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#9
Manufacturers have been making their speedos optimistic for years. Commonly 30mph was more like 28mph. Remember when a wheel goes over a 'bump' in the road, it will travel slightly further than if the road were flat, same with a depression. So when you do your checking over a measured mile, you need a reasonably flat road. Years ago I bought an ex-coppers BMW bike; its had a special speedo on it, a Jaeger guaranteed 2% accurate.
Leedsman.
n.b. Don't lose any sleep over it!
Leedsman.
n.b. Don't lose any sleep over it!
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#14
You didn't read up on it? The details tell you what's available, including the speed. See: https://www.jaguarforums.com/forum/s...ode#post185626
Last edited by JagV8; 04-16-2010 at 10:20 AM.
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#16
#17
I experimented with the Test Mode today. I can get it into Test Mode. When I tap the trip computer button (the one that I used to set the Trip Mode active)....nothing happens except that the left hand window changes to show the next unit being measured. These are the normal measurements.
What am I doing wrong?
What am I doing wrong?
#18
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Well, some interesting progress. Went for a drive with the panel displaying 'Met Speed' and compared that number to the analog gauge reading and GPS. Probably not the safest thing to do and I should just concentrate on driving instead.
In any case, the ETM number and GPS are very very close, probably within 1-2% but the gauge reading still lags considerably as indicated in my first post.
Is there such a thing as gauge recalibration that can be done by the home mechanic?
In any case, the ETM number and GPS are very very close, probably within 1-2% but the gauge reading still lags considerably as indicated in my first post.
Is there such a thing as gauge recalibration that can be done by the home mechanic?
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