Speedometer error
Thread Starter
|
Freshman User
Joined: Aug 2011
Posts: 31
Likes: 0
From: Oho
Speedometer error
Gave my "96 Aero" a road test from home in Ohio to North Carolina last week.
Drove approximately 1400 hundred miles.
I was using my Garmin GPS and noticed that the incdicated speed on the speedometer was 5 mph less than that on the dashboard dial. Also the odmoter was gaing approximately .1 (one tenth) per mile. If this has been the case since the van was new it has about 9K less than what was on it when I purchased it a month ago.
Any ideas on why the speedometer is not givig the correct speed?
The original tire size was 215/75 but the tires on the van now are 215/70. I doubt if this minor difference in diameter would cause a 5 mph error.
Can the speedometer error be corrected?
Drove approximately 1400 hundred miles.
I was using my Garmin GPS and noticed that the incdicated speed on the speedometer was 5 mph less than that on the dashboard dial. Also the odmoter was gaing approximately .1 (one tenth) per mile. If this has been the case since the van was new it has about 9K less than what was on it when I purchased it a month ago.
Any ideas on why the speedometer is not givig the correct speed?
The original tire size was 215/75 but the tires on the van now are 215/70. I doubt if this minor difference in diameter would cause a 5 mph error.
Can the speedometer error be corrected?
Postmaster
Joined: Oct 2009
Posts: 3,432
Likes: 7
I disagree with you completely Jose. The Garmin is accurate, in fact GPS speedometer technology is the most accurate, with radar and laser based systems coming in second.
All Aerostars are off because the speedometer is actually calibrated for a larger tire than Aerostars ever came with stock.
How do I know its the speedometer thats the issue? Well, Garmin is not the only one that indicates you are going slower than the speedometer indicates. All other GPS units do it too (Tomtom, Maggellan, Apple Maps, Google Maps, Motion X, etc.) Ground based systems like the speed warning signs, cops, etc. confirm the same thing.
All Aerostars are off because the speedometer is actually calibrated for a larger tire than Aerostars ever came with stock.
How do I know its the speedometer thats the issue? Well, Garmin is not the only one that indicates you are going slower than the speedometer indicates. All other GPS units do it too (Tomtom, Maggellan, Apple Maps, Google Maps, Motion X, etc.) Ground based systems like the speed warning signs, cops, etc. confirm the same thing.
Thread Starter
|
Freshman User
Joined: Aug 2011
Posts: 31
Likes: 0
From: Oho
Agree with Khan
I took my Garmin out in my other Aerostar, the 96 with (4)EWD, my Chevy Impala and my Chevy Malibu. The Garmin was spot on accurate with the speedometers in these three vehicles. The Garmin is dead accurate, the speedo in the my 2WD Aero is off.
I also noticed since posting the vehicle was originally supplied with 215/75 tires but now has the lower and wider profile 215/70 size. Wonder what this difference makes?
Regards
Steve
I also noticed since posting the vehicle was originally supplied with 215/75 tires but now has the lower and wider profile 215/70 size. Wonder what this difference makes?
Regards
Steve
Lead Driver
Joined: Sep 2003
Posts: 7,015
Likes: 208
From: SoCal
The nominal difference is about 3.3%, but the actual difference could be more or less. It's very unlikely for two tire makes/models with the same size designation to be actually the same size. For one thing, the width designation is the nominal width of the tire at its widest point.
Fleet Mechanic
Joined: Apr 2003
Posts: 1,460
Likes: 6
From: Florida
I did a test yesterday:
two vehicles going 70 mph each, both reading 70 mph at the speedo, both with same size tires, both "stabilized" at 70mph on the road, both with different GPS, (one a Cellular Phone GPS, one with my Garmin), both GPS with same destination address, both of us connected via cellular phone; Upon reaching and maintaining 70mph speedo speed for one minute, then reading the GPS speed, one GPS showed 69 mph, the other showed 71 in RED.
Neither GPS showed 70mph.
so which was the accurate reading if two vehicles are showing 70 mph at the speedo?
does it really matter?
two vehicles going 70 mph each, both reading 70 mph at the speedo, both with same size tires, both "stabilized" at 70mph on the road, both with different GPS, (one a Cellular Phone GPS, one with my Garmin), both GPS with same destination address, both of us connected via cellular phone; Upon reaching and maintaining 70mph speedo speed for one minute, then reading the GPS speed, one GPS showed 69 mph, the other showed 71 in RED.
Neither GPS showed 70mph.
so which was the accurate reading if two vehicles are showing 70 mph at the speedo?
does it really matter?
Thread
Thread Starter
Forum
Replies
Last Post
