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The speedo reads 5 mph slower than you're travelling?

I've owned eight BMWs and all of the speedos read about 5% faster than actual speed.

If you Google motorcycle instrument repair, some alternatives are listed. Personally if it's working otherwise, I'd save the money and convert in my head.
 

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Yes, purchase an "authorities" version speedometer and install it. I was able to find a used one with fewer miles than my bike and then used a small AC motor to match up the miles before the install. Did take me a week at 96 MPH indicated to get the miles right, though.
 

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Discussion Starter · #6 ·
I have to do 70 by the speedo to actually be going 65, and it is across the board. In other words when I want to do 45, I need to be reading 50 on the speedometer. I've had bikes that were a couple mph off but never one this far off.

As to the suggestion of using the GPS? Well I was getting passed a LOT, so I looked at my GPS and noticed the problem, however being this far off throws everything out to include avg speed, mpg, etc... so I kinda want it fixed. The bike is still under warranty so maybe I need to call a dealership and see what they say?
 

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Teach said:
I have to do 70 by the speedo to actually be going 65, and it is across the board. In other words when I want to do 45, I need to be reading 50 on the speedometer. I've had bikes that were a couple mph off but never one this far off.
?
That makes more sense, your speedo is reading 5mph fast at a given speed. Every BMW I have ever heard of does that to some degree. If the bike is under warranty you can see what is an acceptable margin of error. On my wife's VW, they replaced the instrument cluster because the clock was slow by a few minutes per month.
 

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The speedometer reading higher than you are actually traveling has come up a lot in the various BMW bike forums. It seems to be a consious decision by BMW. Knowing how the Germans run things my guess is there is probably a law or rule with penalties for selling vehicles with speedometers that read lower than you are traveling. My guess is BMW purposely makes them read higher to make sure they don't sell one that reads lower. Lawyers and lawsuits may also be involved.

I know both my LT and my RT are off about 4mph at 75mph compared to the GPS speed.

Bruce
 

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I suspect that, as with BMW/MINI autos, the accurate speed is known internally by the various control modules (BMK, KOMBI...) but the Mothership has instructed Siemens to introduce an optimistic "adjustment" to disuade litigants from involving AG in their proceedings. Think of it as "defensive programming".

Using the right software tools ( ;) ) and a D-Can cable, any recent BMW/MINI auto can have its settings changed to display the accurate speed in the HUD computer's display. What's interesting, however, is that this setting change DOES NOT change the actual (analog) speedometer display! A lot of effort has been spent examining trace files to find a way to change the analog speedometer adjustment in the Siemens code, but members of the BMW and MINI coding communities have not turned-up anything workable.

So, rest assured that the accurate speed is "known" to your bike, but AG's "prudence" prevents you from seeing it. Nothing is wrong here...move along...no animals were harmed...

Note: The coding information presented above is openly available to anyone at a number of BMW/MINI coding forums on the InterTubes and is, therefore, general knowledge. My presenting this information in this forum in no way is meant to imply that MOI have actually performed ANY of the coding actions above...especially while waiting to take-off on the runway. So There! ;)
 

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Buchnerb said:
The speedometer reading higher than you are actually traveling has come up a lot in the various BMW bike forums. It seems to be a consious decision by BMW. Knowing how the Germans run things my guess is there is probably a law or rule with penalties for selling vehicles with speedometers that read lower than you are traveling. My guess is BMW purposely makes them read higher to make sure they don't sell one that reads lower....
Bruce
I think You hit the nail on the head!
All motorized vehicles have a slightly optimistic speedometer over here, most probably for the reasons mentioned above.
 

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Must be a BMW thing. My 318 reads 2.3 to 2.5 MPH faster. The odometer is accurate. This is built into the design. I have not checked mt RT yet but I'm sure it is off a little.
 

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Gaby said:
All motorized vehicles have a slightly optimistic speedometer over here, most probably for the reasons mentioned above.
That has always been the case in my experience until recently.

My Triumph Scrambler speedo reads 1-2% faster than actual speed below 100 km/h, is dead on at 100 and actually reads 1-2% slower than actual speed about 120. Our Ford Escape is just about dead on throughout the range, as well.

I'm so used to doing an indicated 5 over the limit to get actual speed, I have to keep telling myself their speedos are accurate.
 

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deanwoolsey said:
Yes, purchase an "authorities" version speedometer and install it. I was able to find a used one with fewer miles than my bike and then used a small AC motor to match up the miles before the install. Did take me a week at 96 MPH indicated to get the miles right, though.
I ride a '99 RT-P, so I do have the "authorities" version of the speedometer, and I find it is accurate to within 1% to the GPS speed indicated on my phone... just like the RT-P brochure claims...
 

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Buchnerb said:
The speedometer reading higher than you are actually traveling has come up a lot in the various BMW bike forums. It seems to be a consious decision by BMW.
There's no "seems to be" about it, it's fact.

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Well that's probably why I haven't gotten a ticket when traveling in rural communities with zealous cops and radar/laser. If the speedo is showing 60 and I'm only doing 55, which is the speed limit, I'm good. If I'm doing 65 and the speedo is 5mph off, I'm doing 60 and maybe the cops are giving me 5mph. Win/Win I guess.
 

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Most motorcycle speedometers are off between 5 and 10 percent. So 60 is really 54, 70 is really 63, etc. I believe they make them that way intentionally. There are laws in the U.S. which regulate all this but I don't know what they say about it all, but I assure you that the authorities version speedometers are indeed accurate within 1 or 2 percent. That's impressive for a mechanical speedo since they are nothing more than a bar magnet on the end of the drive cable which induces a field in the base of the needle which has a metal bar mounted on a clock spring attached to the shaft. The older LTs which appear to have an analog output are actually digital and have no cable. Mine (a 2000) has been modified and is within 1 percent. The newer ones cannot be fixed as far as I know. I do not know if the newer RTs are a mechanical drive or are electronic but it's easy to tell. If you have a hub drive assembly on the front wheel and a cable leading to the speedo, it's mechanical.
 

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deanwoolsey said:
{snip}...The newer ones cannot be fixed as far as I know. I do not know if the newer RTs are a mechanical drive or are electronic but it's easy to tell. If you have a hub drive assembly on the front wheel and a cable leading to the speedo, it's mechanical.
Per my earlier post, the speedometer error is purposefully introduced by the bike's software; the analog speedometer in the newer RTs is controlled by a computer that makes this adjusted reading. Efforts at correcting the analog gauge through software software settings on other BMW/MINI control modules has not been successful.

However, the intentional speed inaccuracy should be consistent across the range of speeds and, thus, is easily predicted by the rider.
 
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