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Thread: Navigator V vs. Speedometer Difference ???

  1. #1

    Navigator V vs. Speedometer Difference ???

    Greetings. I've noticed that my Navigator V unit consistently displays between 2-4mph faster than the speedometer on the regular / standard display. It may not matter really but was 1). Surprised that the Navigator doesn't seem to be using information sent from the bike for this statistic (as it must for other things, ie. odometer, miles to re-fuel etc., etc.). Is the Navigator figuring out the MPH on its own through its GPS perhaps? 2. Wondering if anyone else has experienced this or could offer insight. Again, I'm not sure its a big enough thing to worry about but perhaps there are other aspects I should be considering and have not thought of. Thanks. Cheers! (BTW: Bike is a s1000xr, 2016)

  2. #2
    Registered User greenwald's Avatar
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    Smile

    Yup - GPS.

    ALL motorcycle speedometers are degraded 3-7% at the time of manufacturing.

    You can research why, as commenting here would be tantamount to "an oil thread!"
    Kevin Greenwald - MSF Lead RiderCoach # 121656 (BRC,SBRC,IS,IME,SMARTrainer)
    Nationally Certified Law Enforcement Motor Officer (Ret.) / IBA Member #34281
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    Liaison 20774's Avatar
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    Welcome to the forum, tzc1999!
    Kurt -- Forum Liaison ---> Resources and Links Thread <---
    '78 R100/7 & '69 R69S & '52 R25/2
    mine-ineye-deatheah-pielayah-jooa-kalayus. oolah-minane-hay-meeriah-kal-oyus-algay-a-thaykin', buddy!

  4. #4
    FUKENGRUVEN SURVIVOR akbeemer's Avatar
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    Quote Originally Posted by greenwald View Post
    Yup - GPS.

    ALL motorcycle speedometers are degraded 3-7% at the time of manufacturing.

    You can research why, as commenting here would be tantamount to "an oil thread!"
    Now wait a darn minute. GPSs do not have oil in them.
    Kevin Huddy
    Tm Pterodactyl MT Outpost

  5. #5
    Back in the Saddle mcmxcivrs's Avatar
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    Both of my bikes and my wife's bike read nearly 10% low compared to my GPSs. My 94 R1100RS was dead on on the speed, but the odometer was high by about 2%.
    Ed Miller, Calgary, AB
    2008 K1200GT, 2009 F800GS
    I can't wait to retire and have a fixed income. The one I have now is always broke.

  6. #6
    Registered User Mark H's Avatar
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    I was thinking the exact same thing on the weekend.

    I was driving in my car, which has a built-in Sat Nave system, and it matches the speed on the Sat Nav to the speed displayed on the cars speedometer.
    On my 2015 R1200GS with the NAV-V I see differences in the displayed speed (My GPS says I'm going slower than the speedometer).
    BMW and/or Garmin have made the choice not to match the two and this may or may not be the best thing, but it is what it is.

    As to why, well at the risk of opening a can of worms, I am of the opinion that a GPS is only so accurate at location (to within a couple of metres/yards at best unless you are military and dropping bombs). As for moving object, possibly less so and fluctuates.
    The speedometer is (as many have said) set to read faster than your actual speed to accommodate a range of factors and still be on the "safe" side.

    Rolling circumference apart from simple accuracy of the equipment is the key factor when it comes to the bikes ability to read speed and distance traveled, because the bike is actually not in truth reading either. As I understand it, it is reading the number of rotations of the wheel. This is very precise, but the variations occur between that measurement and the road surface.
    Mark Hubble
    2015 - R1200GS Black Storm Metallic
    Sydney, AUSTRALIA

  7. #7
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    tzc1999,

    In reply to your first question, how would the bike communicate to the Nav V? I don't believe the nav unit connects to the bike's data bus.

    I find it interesting the your bike's indicated speed is slower than the GPS reading (I'm assuming the GPS is accurate). The accepted practice here in the US is to have the speedometer indicate faster than actual to avoid speeding tickets. I couldn't find a federal regulation on speedometer accuracy for motorcycles, but the SAE standard for electric speedometers, J1226, recommends a calibration within two percent (plus or minus) of the total indicated speed range, or a calibration within four percent with a bias toward reading high. And keep in mind that this is percentage of the maximum value displayed on the speedometer, not a percentage of the actual speed.

    The European Union does have a speedometer standard. Speedometers cannot read slower than actual. For bikes with a maximum speed over 150 kph (93 mph), tests are conducted at 40, 80, and 120 kph and the errors on the fast side cannot exceed 1% + 4 kph. Your BMW should be built to this standard.
    Karl
    2007 R1200ST

  8. #8
    Registered User lkraus's Avatar
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    Quote Originally Posted by kthutchinson View Post
    In reply to your first question, how would the bike communicate to the Nav V? I don't believe the nav unit connects to the bike's data bus.
    Since at least 2005, BMW has provided a three conductor plug that connects to the Nav mount, providing 12VDC power and a speed pulse signal from the ZFE. I cannot say how Garmin actually uses that signal, but it is available for their use.
    Larry
    2006 R1200RT

  9. #9
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    True. But I believe the speed signal is only used by the GPS when there aren't enough satellites in view to determine speed, as when riding through a tunnel.
    Karl
    2007 R1200ST

  10. #10

    Thanks all!

    Quote Originally Posted by kthutchinson View Post
    tzc1999,
    I find it interesting the your bike's indicated speed is slower than the GPS reading (I'm assuming the GPS is accurate).
    Thanks to all for the replies. Its good to know "its not just me". For curiosities sake, I need today to go and make sure I got the direction of the difference the correct way. I wrote the original post from memory (which for me can have its issues) and recalled the GPS being faster than the Bike speedometer. It would make more sense to be the other way around and perhaps I reversed the direction. Regardless, good information to know that these types of differences are, for lack of a better word, "normal".

    Cheers!

  11. #11
    Registered User marcopolo's Avatar
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    I have a Nav V on my 2015 GSA, and have had various Garmin GPSs since 2005 on four different BMWs. In all cases, the bikes' speedometers displayed speeds which were higher than the speeds shown on the GPSs.
    Mark
    2015 R 1200 GS Adventure

  12. #12
    Quote Originally Posted by marcopolo View Post
    I have a Nav V on my 2015 GSA, and have had various Garmin GPSs since 2005 on four different BMWs. In all cases, the bikes' speedometers displayed speeds which were higher than the speeds shown on the GPSs.
    Yup, me too. This is a variation on a theme. When I owned Triumphs there all kinds of threads on speedo being optimistic from 5-10%. That was before the widespread use of GPS. Similar threads were posted for a bunch of major brands. The seemingly unusual thing was the odometer was spot on. There were several gismos sold to adjust the speedo, but in every case if you got the speedo right the odometer changed as well. On my GS the the speedo is so small it's hard to compare it with my Nav V. I've got another post "GPS Speed in Turns" which points out that GPS isn't perfect either.
    Old But Not Dead
    Semper Fi

  13. #13
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    I've had a few motorcycles in the past, and there has always been the complaint that the speedometer is off. Then I bought a Honda NT700V and found the speedometer to be spot on. However, the MPG readout was a joke.

    Something will always not be "perfect". I just adjust the MPH in my mind and ride with the traffic.

    Chris
    Elnathan - 2014 BMW F800GT
    IBA# 49894 True Rounder = 0-20's - Rounder -- to -- 100's+ Red Hot Rounder
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