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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: ronbuell on November 30, 2014, 10:38:42 PM
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I"m checking to see if mine is off. I was running indicated 45 on one stretch of road and everyone was passing me. So I ran up to indicated 50 to keep up. Engine was running 3500 at indicated 50.
Is that what it should be, or is my speedo in error?
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Unless someone has adjusted the calibration, by design(or not......) from BMW the speedo is off by roughly 10% to the high side.
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I've never heard of a BMW motorcycle speedometer being accurate. All three of mine (82 RT, 91 LT, 04RT) read higher then actual.
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Mines actually pretty accurate according to the iphone speedo -- get yourself one of those free apps.
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It's also easy to adjust the speedo to correct the problem. Search the site for Karamba.
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Its not that easy to adjust the speedo, I have just done mine, you have to remove the speedo from the instrument cluster to do it and that is the hard part. It was worth it , where I live, Scotland, there are many small towns with speed monitoring signs they both tell you how fast your going and either tell you to slow down or if your actually under the speed limit thank you. My speedo is now reading exactly the same as these signs, but are they accurate?. Now i wonder about the odometer accuracy. On my r80 I made my speedo more accurate by changing the final drive ratio, I had stripped the crown wheel gears so I needed a replacement any way, I ended up putting a slightly higher ratio which made the oddo read 5 % under but the speedo was fairly accurate. Just something to play with when you a few hours to spare.
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I've used an iphone speedometer app to double check my bike's speedo reading. The app is called (surprisingly enough) Speedometer and is free from the Apple Appstore. I fastened the iphone to the handlebars and rode at various speeds, comparing the instruments to the iphone. I'm not sure how accurate GPS-derived speeds are but it was close enough for my purposes.
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I've used an iphone speedometer app to double check my bike's speedo reading. The app is called (surprisingly enough) Speedometer and is free from the Apple Appstore. I fastened the iphone to the handlebars and rode at various speeds, comparing the instruments to the iphone. I'm not sure how accurate GPS-derived speeds are but it was close enough for my purposes.
Similar here, I've compared mine(post adjustment) to 2 different Garmin units and am within 2mph. Both units are also spot on with speedometers in my vehicles.
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There are plenty of apps for speedometers. I use GPS speedometer on Android. GPS cannot provide good instantaneous speed. So be sure to ride at a constant speed for 30 seconds or more (the longer the better) before recording the difference.
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Your speedo is in error, but that is the way BMW makes them. Took my K75RT out for a ride today and checked the speedometer. At 3500rpm my calibrated speedometer indicated approximately 48mph while my Garmin gps indicated 47mph.
My speedometer has had the "soldering iron" calibration done to it. It was calibrated last summer to read approximately 1-2mph high which is a safety margin. The correct setting as I recall is 44mph at 3600 cycles(60cycle house current X 60seconds/minute).
Since my speedometer should have read a bit lower at 3500rpm, I am suspecting that my tach may have been reading a bit low and the engine was turning faster than my tach indicated, possibly due to the temperature. It was around 32-35 degrees F this morning when I did the check.
In any event, at 3500rpm in 5th gear with a 32:10 final drive you should be doing an actual 42-43mph and reading something like 47 or 48 on your speedometer. If you needed to run 50mph at 3500rpm to keep up with traffic in a 45mph zone I would say it sounds like yours is running correctly for an uncalibrated factory speedo.
Rule of thumb is to subtract 10% of the speedometer reading to get your actual speed.