Which MPH is acurate - GPS or Speedo?

c-lapier said:
Many posts have pegged the speedo error at 7%. I checked the odometer against mile markers on I-75 for 200mi from the Mackinaw bridge and it was 2.25% over.
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Odometer and speedometer are not necessarily tied together as many with GPSs can testify.
 
c-lapier said:
Many posts have pegged the speedo error at 7%. I checked the odometer against mile markers on I-75 for 200mi from the Mackinaw bridge and it was 2.25% over.
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I've clocked the odo at 2% off.

Curt
 
So if Honda can offer a "calibrated Speedo with 2 mph increments" for the LEO's-why can't we have the same accuracy?? They have proven that they can offer true speed readings. they chose not to.

We should demand better-
HONDA Give me an acurate Speedo!
 
RibsST1300 said:
So if Honda can offer a "calibrated Speedo with 2 mph increments" for the LEO's-why can't we have the same accuracy?? They have proven that they can offer true speed readings. they chose not to.

We should demand better-
HONDA Give me an acurate Speedo!
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+1 on that.

I wonder if it's possible to buy a LEO speedo and install it on the public ST?
 
I think someone posted a table before, showing the difference between the speedo readout and the actual speed at various speeds. I don't remember exactly what the numbers showed, but what I took away from that post was a general sense of how to "discount" the speed shown on the speedo. If it says 75, I know I'm doing close to 70, probably a bit less. If it says 85 I know I;m doing about 78.5. When it shows 90 I know I'm in the low 80s.

That's all I really need to know. Does it matter whether I'm going 77 or 78? Although I ride with a gps and gather all relevant info in its trip computer, I rarely have it display my speed in real time.

What I have done is check my speed against my customary riding speeds indicated on the speedo so I get a feel for reading the speedo and adjusting it downward.

I do believe that as between the gps and the speedo, it's a no-brainer: The gps is far more accurate.
 
crazykz said:
Yes, as soon as everyone has come to the understanding that I am always right we'll all get along much better. :D

Actually this has been an issue for me but I don't care if the bike is right since I run GPS. For me I did to have accurate information for rallies so I've done a bit of comparisons to check this. YMMV

Curt
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I would never question "THE CURT MAN " in the sense of being right or wrong he might put a hex on one of my farkles. :eek:
 
RideOn said:
My Garmin 2610 reads 65 mph when my ST1100 speedometer reads 60 mph. Seems like a pretty big difference. Which should I believe? I tend to believe the Garmin.
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My F250 speedo matches my Garmin and my Toyota Sienna but not the ST so I believe the Garmin.
 
Just 2 days ago, by speedo I was travleing at 70 when Zumo said I was going 65. Huge difference in my opinion! I know I will lawyer up if I get pulled over for speeding.
 
Brighteyesue said:
Just 2 days ago, by speedo I was travleing at 70 when Zumo said I was going 65. Huge difference in my opinion! I know I will lawyer up if I get pulled over for speeding.
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7.1428571428571428571428571428571%

Thanks for the data point Sue. ;) Just proving me right. :crackup :D

Curt
 
Brighteyesue said:
I like the pecan waffle - yummylicious. Hey man, I was just thinkin of you :D
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Well I am on the minds of many women so that's no surprise. Of course most of them are behind bars with a different motive than what you might normally think. :rolleyes:

Curt
 
7% error at 120 indicated would be 112 by GPS.
 
BigBlackST said:
Our commercially available GPS units have a built in INACCURACY of at least 5%. This, coupled with the variables of weather, terrain and cover, can make the speed readings off considerably.
Motorcycle speedos have never been known for being very accurate (and I have no idea why they aren't)- with some being off by as much as 10%.

Best way to get a 'read' on accuracy- do a measured mile at 60 mph indicated (on either the speedo or the GPS)- then you'll know for certain.
Your watch should be pretty accurate, unless it's a Rolex (which is always off by the same amount- it's built in to the things!)

I was traveling back to my home from Washington when I was stopped in Virginia for a suspected radar device seen on the dash by a State Police officer.
It was a handheld Garmin III.
The officer was quite familiar with these things and asked if he could take a look at it.
He immediatley paged to the 'history' one- and noticed that my recorded Top Speed was 694 MPH.
"Care to tell me where you did this one, sir?" he asked.
"Not on any roads around here, sir." was my answer.

[I'd taken a flight in the jump seat on a fighter jet during a demo - and flicked the unit on when we were about to hit Mach out over the Atlantic somewhere!]
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i'd like to see your support for the contention that commercially available GPS is off by at least 5%. +/- .01% is closer to it given a few miles to average.

Max Speed is often very inaccurate - I have seen several of my units register Max Speeds in cars, sailboats, and on motorcycles in the 300 and 400 mpg range but those are 'snapshots' and with units today updating once per second the average over any appreciable time/distance is quite accurate. Even the ancient Garmin III was accurate to .01 knot in a steady state (read your manual) and that was old pre-WAAS DGPS technology.
 
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