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ncsonderman

Actual vs. Speedo indicated?

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ncsonderman

I haven't hooked up a GPS to the GSA yet and wonder if someone can share what my actual speed is at different speeds vs. my speedo? I know on my RT that I am only travelling 72 when my speedo lies and says I'm doing 80.

 

Thanks for the help. Better safe than pulled over :/

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Tri750

I forget the formula that BMW used to use. It was something like 3 or 5 percent plus 2 miles an hour.

If you say 7 mph optimistic, your likely right there.

 

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dirtrider
I haven't hooked up a GPS to the GSA yet and wonder if someone can share what my actual speed is at different speeds vs. my speedo? I know on my RT that I am only travelling 72 when my speedo lies and says I'm doing 80.

 

 

Morning Joe

 

Motorcycle speedometer indicated speed is a difficult thing to pin down.

 

The basic US & European rule is that the vehicle's (actual) travel speed should never be higher than the (speedometer) indicated speed. That is a tough thing to always assure as tire diameter, tire type, tire wear, tire temperature, tire pressure, load on the tire, & tire construction all play a role in how the speedometer reads the tire distance traveled per revolution.

 

Then on the GS, GS-A there are so many tire types & lug depths that trying to predict the speedometer accuracy is a guess at best.

 

Assuming the BMW GS, GS-A doesn't get a different speedometer calibration for US import it probably runs under the (UNECE) regulations of indicated speed should not be more than 110% of actual speed + 4 km/h.

 

Most late model BMW GS,GS-A speedometers that I have had my GPS on run about 5+mph fast @50mph & a little over 10+mph fast at 100 mph.

 

My Hexhead GS-A OEM speedometer runs about 7mph fast at 60mph & close to 15mph fast at 100 mph with worn TKC80's on it.

 

To really know what your bike is doing you need to run a timed mile, or use a (good) GPS on a flat level road running with the tire type/brand , air pressure, & load you want to calibrate to.

 

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Haynes

It's not a linear error.

Speedo 60km/hr, GPS 56km/hr.

Speedo 100km/hr, GPS 94km/hr.

Speedo 120km/hr, GPS 114km/hr.

 

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Huzband

My '08 RT was slightly worse than my current '07 GSA.

 

This is a shot of my speedo in west Tx on my 50cc. Cruise was set at 88mph by GPS.

 

%2708%20Trip%20009-M.jpg

 

I don't have a corresponding shot of the GSA speedo, but I have noticed it's much closer to the GPS than the RT was. I found last Thu on I=95 coming home from Kissimmee an indicated 82 gave me a dead on 80 GPS reading.

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ncsonderman

Thanks gentlemen! This bike is smoother than the RT but catches the wind more. I look forward to many adventures on it. I've got to convince some friends that it isn't too pretty to take off road

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ThomasJ

"This is a shot of my speedo in west Tx on my 50cc. Cruise was set at 88mph by GPS."

 

80 mph on a 50cc? that's something I would like to see! :grin:

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Huzband
"This is a shot of my speedo in west Tx on my 50cc. Cruise was set at 88mph by GPS."

 

80 mph on a 50cc? that's something I would like to see! :grin:

 

:rofl:

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dirtrider
"This is a shot of my speedo in west Tx on my 50cc. Cruise was set at 88mph by GPS."

 

80 mph on a 50cc? that's something I would like to see! :grin:

 

:rofl:

 

Afternoon Huzband

 

That would be the Iron Butt 50CC Quest not a 50cc motorcycle.

 

http://www.ironbutt.com/ridecerts/getdocument.cfm?DocID=4

Edited by dirtrider

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Huzband
"This is a shot of my speedo in west Tx on my 50cc. Cruise was set at 88mph by GPS."

 

80 mph on a 50cc? that's something I would like to see! :grin:

 

:rofl:

 

Afternoon Huzband

 

That would be the Iron Butt 50CC Quest not a 50cc motorcycle.

 

http://www.ironbutt.com/ridecerts/getdocument.cfm?DocID=4

 

Yeah, yeah. Splitting grammatical hairs. ThomasJ was obviously cracking wise at my expense, & I'm still laughing about it. :grin:

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lkchris

For sure in the Airheads and early K eras, BMW produced Service Bulletins describing "Speedometer Advance." In both versions I have, they hasten to note that the odometer is accurate.

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