Speedometer accuracy 2021 R1250RT

Having problems with the BMW Navigator V VI or the TFT display?
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Speedometer accuracy 2021 R1250RT

Post by THE_Beemrider »

Good evening, I’ve had my new 2021 R1250RT for a few weeks now and I’m loving it. My last ride was a K1600GT and previous to that I had 2 K1600GTLs. With the 1600s I never looked at the speedometer to see how fast I was going, I looked at the GPS for the true speed. With each BMW I’ve owned (5 of them before my current RT),I verified that the speedometer was reading around 7% slower than actual. For example with an indicated speed of 100kph, the gps showed the true speed to be 97.  When I asked about this I was told it was a deliberate strategy by BMW … probably BMW lawyers …for some stupid reason.

Anyway, anybody know if that is also the case with the new RT? (Probably) anybody know if there is a way to get the true speed from the phone supplied GPS?

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Re: Speedometer accuracy 2021 R1250RT

Post by Casbar »

Don't think they read low due to lawyers. All vehicles normally indicated speed is lower than actual unless you have a calibrated speedo like on Police Bikes. The reasoning is you can't then blame the speedo if you are speeding as its reading low. GPS is also not foolproof either, by the way it samples speed, although probably a lot more accurate than the speedo on the vehicle.
Hors Piste
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Re: Speedometer accuracy 2021 R1250RT

Post by Hors Piste »

I'm guessing that you are in the US, where for some reason folk appear to be obsessed with speedometer accuracy.  If you're not, please forgive me.

Speedometer accuracy is governed by regulation. See for example http://www.fleetco.co.za/index.php/information/speedo-accuracy

One of the main requirements is that "The indicated speed must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading."

Hence manufacturers (not just BMW!) have tended to err on the side of caution and speedo's are set to under-read.  As technology has improved (speed no longer determined by a gear attached to the front wheel for example) they have tended to become more accurate.

As far as I know it is not possible at present to see the GPS speed on the TFT.
Last edited by Hors Piste on Fri Aug 27, 2021 8:24 am, edited 1 time in total.
Peter Baker
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Re: Speedometer accuracy 2021 R1250RT

Post by Peter Baker »

Generally speaking the speedos I have had on BMWs over the last 10 years have got more accurate, my first K1600GT over read and at 70mph true GPS they would show 75 - roughly speaking, my R1200RT was similar.  However my K1300S was much more optimistic:-) showing at least 10% over!  The most recent bikes R1250RT and Gen 2 XR are more accurate...  Manufacturers cannot "afford" to get it wrong so my assumption is they error on the side of caution and as technology has improved they have been able to reduce the margins...  Just my view!  Peter
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Re: Speedometer accuracy 2021 R1250RT

Post by jackronner »

In the US there used to be speed-checks signs in a series of measured miles where you could time a minute at 60mph.  On long tours I have to admit I love the cruise control.  With so many cars now with cruise, it seems there are many fewer eejits who speed up, slow down, speed up ad nauseum, making for a safer and calmer  riding experience ("Pick a speed, goddammit!!).  But I sometimes find myself making driving/passing choices based on the desire to not have to disengage the cruise - a kind of inertial navigation.  Not always the best choices.  Tech giveth and taketh away.

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