speedometer or gps,which is more accurate - BMW Luxury Touring Community
 
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post #1 of 30 Old Jan 13th, 2007, 11:31 pm Thread Starter
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speedometer or gps,which is more accurate

What is more accurate? when my speedometer says 77mph and gps reads 70mph. i then put my gps in my car . when my gps reads 70mph and my car reads 66 mph . why the big difference?
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post #2 of 30 Old Jan 13th, 2007, 11:34 pm
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The GPS is much more accurate. Most speedos run a little high. BMW motorcycles tend to run a little higher than most...

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post #3 of 30 Old Jan 14th, 2007, 12:29 am
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The GPS every time with this proviso. Level road, straight, no sky obstructions. To be honest, the satellite sampling rate is so frequent, it's as good as it gets.

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post #4 of 30 Old Jan 14th, 2007, 5:18 am
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When does 100 = 90? Only on an LT. Possibly you are new to the LT. The speedometer is notoriously inaccurate, but at least consistent. Unless you have done "the speedo modification", you need to subtract approximately 10% from your indicated speedo reading to get the correct MPH. God love those quirky little german engineers, they just can't seem to make an accurate speedometer for the LT. Just one more thing that bonds us together as a community.

Steve
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post #5 of 30 Old Jan 14th, 2007, 6:00 am
 
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I've owned 8 other street bikes that were not a BMW, and ALL of them had just as inaccurate of a speedometer as my LT (before I did the 'speedo correction' mod to it). I just think that most riders through the years were not aware of how badly their bike's speedos were off. But now that we have a GPS mounted to the bike, the error is revealed like never before.
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post #6 of 30 Old Jan 14th, 2007, 6:50 am Thread Starter
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Quote:
Originally Posted by xenia
64

When does 100 = 90? Only on an LT. Possibly you are new to the LT. The speedometer is notoriously inaccurate, but at least consistent. Unless you have done "the speedo modification", you need to subtract approximately 10% from your indicated speedo reading to get the correct MPH. God love those quirky little german engineers, they just can't seem to make an accurate speedometer for the LT. Just one more thing that bonds us together as a community.

Steve
2004 LT
i am new to the community,bought a 2002 LT a couple of months back and absolutly love it. don't think it gets any better than this bike. smooth as a caddy and corners like my supra.
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post #7 of 30 Old Jan 14th, 2007, 11:52 am
 
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Quote:
Originally Posted by dodk64
i am new to the community,bought a 2002 LT a couple of months back and absolutly love it. don't think it gets any better than this bike. smooth as a caddy and corners like my supra.
Smooth as a caddy?! Now I KNOW you meant to say, "smooth as a 7 series" . . . didn't you?!
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post #8 of 30 Old Jan 14th, 2007, 3:55 pm
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Quote:
Originally Posted by messenger13
Smooth as a caddy?! Now I KNOW you meant to say, "smooth as a 7 series" . . . didn't you?!
Exactly! When my co-workers say my bike is the Cadillac of motorcycles, I always correct them with "No, it's the BMW of motorcycles"

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post #9 of 30 Old Jan 14th, 2007, 4:12 pm
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Had a guy in the gas station say "BMW, now that's a cadallac."................
I said "better than that, it's a BMW."

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post #10 of 30 Old Jan 14th, 2007, 7:09 pm
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Quote:
Originally Posted by STARFIGHTER
Had a guy in the gas station say "BMW, now that's a cadallac."................
I said "better than that, it's a BMW."
My favorite: "BMW? BMW? When did BMW start making motorcycles?

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post #11 of 30 Old Jan 14th, 2007, 9:15 pm Thread Starter
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Quote:
Originally Posted by messenger13
Smooth as a caddy?! Now I KNOW you meant to say, "smooth as a 7 series" . . . didn't you?!
can't afford either ,so i guess smooth as a 7 series it is.
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post #12 of 30 Old Jul 9th, 2008, 4:24 am
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Re: speedometer or gps,which is more accurate

Getting back to the original question - the GPS is almost 100% accurate. Almost because there is a deliberate built in constantly moving position error of about 20 meters as I understand it. So in absolute terms the calculated speed shown would be out, but probably only by a decimal point.

Traditional speedometers are only accurate at one speed. Above that they normally under-read and below it over-read. And that's when the tyres are brand new. any other time and the ratio is out.

In speed limits I always set the cruise by reference to the GPS.

Kevin.
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post #13 of 30 Old Jul 9th, 2008, 7:16 am
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Re: speedometer or gps,which is more accurate

I'm former LEO and have checked my GPS against the RADAR unit I use( No Flaming Please). It was pretty much dead on with the radar.

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post #14 of 30 Old Jul 9th, 2008, 12:38 pm
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Cool Re: speedometer or gps,which is more accurate

I never look at my speedo anymore - my GPS is the unit that gives me the best chance of not falling prey to a performance award.

Denny
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post #15 of 30 Old Jul 9th, 2008, 2:00 pm
 
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Re: speedometer or gps,which is more accurate

And all this time I thought the LEO's were just being nice to me.
On every bike I've owned, the speedo has been off by as much as 10%. the faster I go, the worse it gets.
Happy to use the GPS now, but I also know I no longer have an excuse...
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post #16 of 30 Old Jul 9th, 2008, 2:07 pm
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Re: speedometer or gps,which is more accurate

I agree GPS always although the reaction time to changes to speed is kinda slow. Checked my 2009 LT last weekend and speedo was off (fast) by about 4 mph at any where from 50 to 70 mph. Also checked the odometer and was only off by 1/10th of a mile after 40 miles traveled. Can't get much better. Don't assume that speedo error also means odometer error in all cases. Heck my 2006 BMW M Roadster is almost 4 mph fast at 70 mph while my GMC SUV is perfect. Must be a German thing I guess. Of the dozen or so bikes I've owned over the years my 2002 Road King is the only one that had an accurate speedo. Probably less than 1 mph error at 70 mph. Go figure, the least technically sophisticated motorcycle on the planet!

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post #17 of 30 Old Jul 9th, 2008, 2:32 pm
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Re: speedometer or gps,which is more accurate

After I mounted my GPS, my riding buddies all asked what was my hurry. “Why are we running 80 mph?” They all doubted me when I told them we were only running 73.6 mph. It took a while but they all run 80 on their speedos now.

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post #18 of 30 Old Jul 11th, 2008, 1:17 am
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Re: speedometer or gps,which is more accurate

Yep all those speedo's are inaccurate. I'm off by about 4 mph. It's complicated to make a speedo that is accurate all the time, without constant calibaration.
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post #19 of 30 Old Jul 11th, 2008, 1:31 am
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Re: speedometer or gps,which is more accurate

Quote:
Originally Posted by Caveno
Yep all those speedo's are inaccurate. I'm off by about 4 mph. It's complicated to make a speedo that is accurate all the time, without constant calibaration.

Maybe wrong here, but I was under the impression that the over read was a requirement. At least it is a requirement not to under read, so a small margin is built in?

Almost every speedometer I have checked is 10% over.

Just pussin' through.
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post #20 of 30 Old Jul 11th, 2008, 4:32 am
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Re: speedometer or gps,which is more accurate

Quote:
Originally Posted by rab1967
I'm former LEO and have checked my GPS against the RADAR unit I use( No Flaming Please). It was pretty much dead on with the radar.
Ditto on that.

Just wondering. If the speedo are off, show slower speed, then how come some of you still get nailed for speeding?????????hmmmmmmmmmm

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post #21 of 30 Old Jul 11th, 2008, 7:33 am
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Re: speedometer or gps,which is more accurate

Lark touched on this a few back....If the speedos are off ~10%....does that mean the odometer and trip meter are off ~the same amount? Would like to know to get a better idea of my MPG on my 2004LT. My comp. says I get ~40-41 which kind of stinks. I am an "easy cruiser" type of rider with the wind screen down most of the time. If my trip meter is accurate I then get 46 MPG or so....

Steve
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post #22 of 30 Old Jul 11th, 2008, 10:09 am
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Re: speedometer or gps,which is more accurate

Quote:
Originally Posted by loser
Lark touched on this a few back....If the speedos are off ~10%....does that mean the odometer and trip meter are off ~the same amount? Would like to know to get a better idea of my MPG on my 2004LT. My comp. says I get ~40-41 which kind of stinks. I am an "easy cruiser" type of rider with the wind screen down most of the time. If my trip meter is accurate I then get 46 MPG or so....

Steve
Found this over in the FAQ section under the HoW forum. Common issues question. HTH.
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post #23 of 30 Old Jul 11th, 2008, 2:22 pm
 
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Re: speedometer or gps,which is more accurate

My Volkswagon Jetta is 2MPH off according to my gps...
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post #24 of 30 Old Jul 11th, 2008, 2:56 pm
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Re: speedometer or gps,which is more accurate

Have a 94 K1100LT & noticed i was being passed by everybody if i kept the spedo @ the posted limit. Had a buddy who is a LEO clock me at various speeds. The actual speed was exactly 10 percent lower than the speed indicated on the spedo, so now I compensate, & keep getting smacked on the helmet by co-pilot/ navagator/photographer...ok shewhomustbeobeyed who forgets about me having to do so. Don't have a GPS.
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post #25 of 30 Old Jul 11th, 2008, 11:13 pm
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Re: speedometer or gps,which is more accurate

On my 05' LT the speedo is off by 3-4mph up to about 90 then a little more but not much. The odo is accurate with the GPS (2820) and if I am say going 75 and press the BC to see my speed (reseting the average speed) it agrees with the GPS not the speedo! I know that when my GPS read 127mph the speedo looked like it was reading about 135mph.

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post #26 of 30 Old Jul 12th, 2008, 8:25 am
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Re: speedometer or gps,which is more accurate

Quote:
Originally Posted by DaveDragon

GPS Trip Computer from Ride-About 2008

I think the GPS speed is more accurate.

Anybody wanna race?
On my StreetPilot III, I have a maximum speed of 595mph .

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post #27 of 30 Old Jul 12th, 2008, 11:03 am
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Re: speedometer or gps,which is more accurate

Quote:
Posted by Dave Dragon

If your riding an LT, the speedo is easy to fix. It needs a single zero ohm jumper.
What's a zero ohm jumper ? Never seen one marked zero ?

Where would a guy go to get himself one of those ?

Would it be cooled by liquid Nitrogen ? Or liquid Helium ?

Now I've heard you can get close, But that Zero figure is awfull hard to obtain.

Just pokin at ya.

John

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post #28 of 30 Old Jul 12th, 2008, 11:50 am
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Re: speedometer or gps,which is more accurate

Quote:
Originally Posted by JPSpen
What's a zero ohm jumper ? Never seen one marked zero ?

Where would a guy go to get himself one of those ?

Now I've heard you can get close, But that Zero figure is awfull hard to obtain.
A zero ohm jumper is a component generally known as a "Zerohm". It is electronically just a piece of wire, but it is in the body of a resistor. The idea is to make it easy for automatic insertion machines to fit wire links.

They can be obtained from any component supplier.

Just pussin' through.
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post #29 of 30 Old Jul 12th, 2008, 7:12 pm
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Re: speedometer or gps,which is more accurate

the gps should be more accurate. I had a harley electraglide with gps, a lt with gps and now a rt, all seem about 3 miles per hour off.
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post #30 of 30 Old Jul 13th, 2008, 2:29 am
 
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Re: speedometer or gps,which is more accurate

My speedometer is off 10% and the odo is off 4%, both high. About all I use my Street Pilot III for anymore is as a speedo.
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