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Registered
Join Date: Aug 2004
Location: Baton Rouge
Posts: 1,039
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Speedometer or GPS
What is more accurate when flying down the highway? Speedometer or the GPS? There is a consistent difference of 4 mph between the 2. The GPS registers slower than the truck.
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11-24-2012, 10:49 AM
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Back in the saddle again
Join Date: Oct 2001
Location: Central TX west of Houston
Posts: 56,135
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GPS should be more accurate. It's VERY common for analog Speedos to be off, usually reading high. And when they are off, it's by a percentage, so it may be off by 4 mph at 60, but then would only be off by 2 mph at 30.
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11-24-2012, 11:09 AM
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Registered Abuser
Join Date: Jul 2007
Location: Southwest Montana
Posts: 2,738
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GPS Is going to be the most accurate. Most of my cars speedos are 2-5 Mph Off.
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MT 930 1987 930 - Gone but not forgotten A man with priorities so far out of whack doesn't deserve such a fine automobile. I would rather wake up in the middle of nowhere than in any city on earth - Steve McQueen американский |
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11-24-2012, 11:13 AM
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I'm with Bill
Join Date: Jun 2005
Location: Scottsville Va
Posts: 24,186
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I used my GPS to determine how off each car is. Funny thing is my old Dodge truck that uses a cable is dead on.
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Electrical problems on a pick-up will do that to a guy- 1990C4S |
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11-24-2012, 12:10 PM
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If you are running non stock tires it can throw the spedo off I think. GPS should be more accurate.
Bernie P |
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11-24-2012, 03:04 PM
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I'm with Bill
Join Date: Jun 2005
Location: Scottsville Va
Posts: 24,186
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Quote:
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Electrical problems on a pick-up will do that to a guy- 1990C4S |
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11-24-2012, 03:32 PM
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canna change law physics
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GPS will be more accurate, And many times, it is the Speedo guage that is wrong. I had the speed sensor on my BMW from the ODB-II port, and it matched the GPS. The speedo on the dash read high.
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James The pessimist complains about the wind; the optimist expects it to change; the engineer adjusts the sails.- William Arthur Ward (1921-1994) Red-beard for President, 2020 |
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11-24-2012, 05:19 PM
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Remember that your GPS receiver is also averaging quite a bit. To get a good reading, find a straight stretch of highway and hold constant speed for ~1/2 mile.
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11-24-2012, 05:27 PM
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"A machine you build yourself is a vote for a different way of life. There are things you have to earn with your hands." |
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11-25-2012, 05:47 AM
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Location: Baton Rouge
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just standard size tires
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11-25-2012, 06:43 AM
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Location: Maryland
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Quote:
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1996 FJ80. |
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11-25-2012, 07:18 AM
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Senior Member
Join Date: Jun 2000
Location: N. Phoenix AZ USA
Posts: 28,943
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If I am really concerned I take two GPS units and take a drive with them. Consistantly the GPS units are nuts on while the speedo is the one that is off...
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2013 Jag XF, 2002 Dodge Ram 2500 Cummins (the workhorse), 1992 Jaguar XJ S-3 V-12 VDP (one of only 100 examples made), 1969 Jaguar XJ (been in the family since new), 1985 911 Targa backdated to 1973 RS specs with a 3.6 shoehorned in the back, 1959 Austin Healey Sprite (former SCCA H-Prod), 1995 BMW R1100RSL, 1971 & '72 BMW R75/5 "Toaster," Ural Tourist w/sidecar, 1949 Aeronca Sedan / QB |
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11-25-2012, 07:35 AM
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Join Date: Dec 2001
Location: Ky, USA
Posts: 1,128
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GPS is the defacto standard of speed measurement. Unless you are rapidly changing your speed, it is dead on.
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11-25-2012, 03:30 PM
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Join Date: Jan 2007
Location: Australia
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Went a through a speed trap that shows your speed. My GPS read 112kmh, so did the speed trap. My speedo show 98kmh. So I guess if you use the cars speedo, 9/10 times you won't get nabbed speeding.
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In Heaven… the mechanics are German, the chefs are French, the police are British, the lovers are Italian and everything is organized by the Swiss. In Hell…the mechanics are French, the police are German, the chefs are British, the lovers are Swiss and everything is organized by the Italians. |
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11-25-2012, 06:12 PM
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Join Date: Jun 2000
Location: bottom left corner of the world
Posts: 22,765
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I changed my speedo to a kms one and it reads about 10% too fast. Whereas the old one, a mph one was correct. I think Fishcop is using my old one on his car as he was driving off his rev counter.
We have friendly speed traps (ones that show you how fast you are going without a big ugly cop writing you a ticket) so I know exactly how the 911 and the Corolla read. Interestingly both are wrong by the same percentage. |
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11-25-2012, 07:38 PM
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1970/1982 Porsche 914-6/911SC 2.7 RS
