R55 speedo off by 2+mph... fixable?
2nd Gear
Joined: Jan 2009
Posts: 67
Likes: 0
From: Columbus, Georgia
I'm going to stir the puddin here but keep in mind, this is what I do for a living...
First off, lets keep in mind that when someone says, "Well Officer, my GPS said my speed was ___" and implies that their Garmin GPS is more accurate than a speedometer just because it has the little three lettered acronym in front of it does not make it the standard for horizontal accuracy. GPS comes in several different grades. Survey grade, mapping grade, navigational grade, recreational grade, and my favorite- Walmart grade. I use survey grade and mapping grade GPS, and LIDAR at work everyday and the differences are significant even under "ideal data collection conditions". Since Garmin's, which are navigational grade units (and don't post process mind you) lets just leave it at that. To put it in prospective, my $5K mapping grade Trimble GeoXH is lucky to get horizontal accuracy of less than 5 feet without post processing. After post processing I may get decimeter quality if I rub my head and tummy at the same time. My Garmin unit in my car is between 20-40 feet innacurate on the horizontal so that should give everyone an idea of its ability of capturing your movement accuracy, i.e. speedo comparisions. Besides, ever seen a statement of positional accuracy on the side of a Garmin box? Nope!
Anyway here's a really good tutorial from Trimble for ya'll to read:
http://www.trimble.com/gps%5Ftutorial/howgps.aspx
First off, lets keep in mind that when someone says, "Well Officer, my GPS said my speed was ___" and implies that their Garmin GPS is more accurate than a speedometer just because it has the little three lettered acronym in front of it does not make it the standard for horizontal accuracy. GPS comes in several different grades. Survey grade, mapping grade, navigational grade, recreational grade, and my favorite- Walmart grade. I use survey grade and mapping grade GPS, and LIDAR at work everyday and the differences are significant even under "ideal data collection conditions". Since Garmin's, which are navigational grade units (and don't post process mind you) lets just leave it at that. To put it in prospective, my $5K mapping grade Trimble GeoXH is lucky to get horizontal accuracy of less than 5 feet without post processing. After post processing I may get decimeter quality if I rub my head and tummy at the same time. My Garmin unit in my car is between 20-40 feet innacurate on the horizontal so that should give everyone an idea of its ability of capturing your movement accuracy, i.e. speedo comparisions. Besides, ever seen a statement of positional accuracy on the side of a Garmin box? Nope!
Anyway here's a really good tutorial from Trimble for ya'll to read:
http://www.trimble.com/gps%5Ftutorial/howgps.aspx
6th Gear
Joined: Feb 2012
Posts: 2,264
Likes: 31
From: wisconsin, usa
I'm going to stir the puddin here but keep in mind, this is what I do for a living...
First off, lets keep in mind that when someone says, "Well Officer, my GPS said my speed was ___" and implies that their Garmin GPS is more accurate than a speedometer just because it has the little three lettered acronym in front of it does not make it the standard for horizontal accuracy. GPS comes in several different grades. Survey grade, mapping grade, navigational grade, recreational grade, and my favorite- Walmart grade. I use survey grade and mapping grade GPS, and LIDAR at work everyday and the differences are significant even under "ideal data collection conditions". Since Garmin's, which are navigational grade units (and don't post process mind you) lets just leave it at that. To put it in prospective, my $5K mapping grade Trimble GeoXH is lucky to get horizontal accuracy of less than 5 feet without post processing. After post processing I may get decimeter quality if I rub my head and tummy at the same time. My Garmin unit in my car is between 20-40 feet innacurate on the horizontal so that should give everyone an idea of its ability of capturing your movement accuracy, i.e. speedo comparisions. Besides, ever seen a statement of positional accuracy on the side of a Garmin box? Nope!
Anyway here's a really good tutorial from Trimble for ya'll to read:
http://www.trimble.com/gps%5Ftutorial/howgps.aspx
First off, lets keep in mind that when someone says, "Well Officer, my GPS said my speed was ___" and implies that their Garmin GPS is more accurate than a speedometer just because it has the little three lettered acronym in front of it does not make it the standard for horizontal accuracy. GPS comes in several different grades. Survey grade, mapping grade, navigational grade, recreational grade, and my favorite- Walmart grade. I use survey grade and mapping grade GPS, and LIDAR at work everyday and the differences are significant even under "ideal data collection conditions". Since Garmin's, which are navigational grade units (and don't post process mind you) lets just leave it at that. To put it in prospective, my $5K mapping grade Trimble GeoXH is lucky to get horizontal accuracy of less than 5 feet without post processing. After post processing I may get decimeter quality if I rub my head and tummy at the same time. My Garmin unit in my car is between 20-40 feet innacurate on the horizontal so that should give everyone an idea of its ability of capturing your movement accuracy, i.e. speedo comparisions. Besides, ever seen a statement of positional accuracy on the side of a Garmin box? Nope!
Anyway here's a really good tutorial from Trimble for ya'll to read:
http://www.trimble.com/gps%5Ftutorial/howgps.aspx
i have also double checked using a stopwatch and mileposts on the i-state, again repeatable and consistant
scott
2nd Gear
Joined: Apr 2012
Posts: 115
Likes: 7
From: Dallas area TEXAS
My concern in that in my 2013 Clubman Non-S with 175/65 R15's. my Speed on the speedo is 75 and my GPS speed it 68. When you complain to Mini they say it is in spec and that they are aware of it.
Now, if the speedo is off and is reading 5+% off, then aren't they ripping you off on 5% of you warranty? You are getting less than the 36k mile warranty.
I am upgrading to 215/45 R17's with new wheels, but it won't get the speedo correct.
I was looking for a programs to fix this, but haven't found one.
Update- even with the 215/45 R17 the speedo is still off about 2 mph. A lot better than before with the 175/65 R 15's.
Now, if the speedo is off and is reading 5+% off, then aren't they ripping you off on 5% of you warranty? You are getting less than the 36k mile warranty.
I am upgrading to 215/45 R17's with new wheels, but it won't get the speedo correct.
I was looking for a programs to fix this, but haven't found one.
Update- even with the 215/45 R17 the speedo is still off about 2 mph. A lot better than before with the 175/65 R 15's.
Last edited by Smoothmove; Aug 8, 2013 at 10:59 AM. Reason: update
3rd Gear
Joined: May 2013
Posts: 155
Likes: 0
The speed displayed in your is designed to read slightly over your actual speed by design. This allows for tire diameter differences and keeps them in compliance with DOT regs. The spec if I remember correctly is 10% +2mph. Now as far as odometer accuracy I've always found it to be spot on. Our vehicle come with several tires sizes available. If you stand a 15, 16,17 inch oem tire next to each other you will realize why this buffer has been build in, not too mention diameter changes as a tire wears.
2nd Gear
Joined: Jul 2013
Posts: 80
Likes: 2
From: Duanesburg, NY
It is interesting that my MINI and my wife's KIA both read fast by ~3 mph at highway speed based on my gps and escort radar detector. The gps and radar detector read the same within a small variability. Sometimes one is slightly higher, then the other. My old car was 2 to 3 mph slow at highway speed. That is 5 to 6 mph difference between cars! I'm trying hard to retrain myself. Of course, most of the time I look at my radar detector...
6th Gear
Joined: Apr 2013
Posts: 1,894
Likes: 8
From: Philly PA
Well, how is it inaccurate? Are you running out of fuel while it still shows 3 carrots?
Two things to keep in mind about the Mini.
Fuel rate (available distance), is based off of a combination of driving habits (foot the floor VS Granny style..) AND fuel quantity in the tank.
Fuel is calculated in the tank based off of TWO floats.. one on each side of a saddle style tank. Hard corners with low fuel will confuse things a bit.
I don't wait to the last red carrot of death before I get fuel.. that's not healthy for fuel pumps in any brand of car.. Gasoline is a coolant and lubricant for the pump. I fill up at the second to the last carrot.
I know the Scangauge has a setting where it can monitor fuel volume.. I've never used it but it could be helpful in trying to pinpoint an issue.
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