Sunday, May 11, 2014

Brigitta's Odometer found to be "wonky"

Wonky: A highly technical term used to describe a situation or behavior where the subject is displaying strange behavior.

Yesterday, while tooling around on Brigitta, my '87 R80 Airhead Beemer, I finally realized through more careful observation that the odometer reading was inaccurate.  It was roughly displaying 9.4 miles traveled for every 1.8 miles actually ridden per the tripmeter.

The last known accurate reading is for 102,351 when maintenance was performed on Brigitta's finned exhaust nuts by yours truly on March 30 of this year.  Sigh.  Currently, the odometer was displaying over 8000 miles racked up.....not even close to accurate.  Basically 5600+ miles too much.

The speedometer seems to be working fine (to be again verified via GPS when the roads are clear) and the trip meter seems to be fine.  It's just the odometer, which is after all over 27 years old, that has failed.

As the saying goes, the cheapest thing on a BMW, is the owner.  I am going to hold off on sending the speedometer unit out for repair.  I'll keep track of mileage for service interval purposes by the bicycle computer I installed this morning.

This is the same Vetta C5 Bike computer I'd used on Natasha when her speedometer needle was doing the wild swings during cold weather.

NOTE: For future reference: you must use a value of 1925 when calibrating the bike computer to the front wheel measurement for Brigitta. (From center of front axle to ground)

Warning, BMW Airhead purists....non-BMW compliant mods ahead.  Viewing the pictures will probably offend your sensibilities.

 Vetta C5 installed on handlebar

 Vetta Magnetic Sensor secured to right front brake fitting.

Yes, I know it's ugly, but it works.
Magnet secured to one of Brigitta's front wheel spokes.
A more aesthetic solution to be found....perhaps.

It's snowing outside, so not a good time to go out and test the bike computer's functioning.  I did rotate the tire by hand and was able to spin it as fast as 5 mph per the bike computer so I know it's "seeing" the magnet via the sensor pickup.

Update: 15MAR: I transposed the numbers, it's actually 1925 for my R80's measurements.  The cyclometer works great but I found one limitation that caused me to order a newer one today.  It tops out at 100 kph in terms of displaying current speed.  As Brigitta can do much more, I ordered one that maxes out at 200 kph, well above Brigitta's capacity for speed.  


SonjaM said...

Wonky, is that the same as hinky?

I find your low budget solution very intriguing. In your face Bavarian Motor Werke!

Richard M said...

Hmmm, now is the time to enter the MOA mileage contest ;-)

If the speedo is still working properly, why the bicycle computer? The trip odometer still works so you could just add up the miles every time the tank is filled so you would have the miles when you need it...

Charlie6 said...

To be fair, The unit was made by VDO and lasted over 27 years....not too shabby. The low cost solution(till the speedo and tripmeter break) will do for now and was actually derived from my experience with my '96 Ural Natasha.

Charlie6 said...

Richard, not conscientious enough to remember mileage ridden between fill ups, the computer renders total mileage, which is what I need to schedule periodic maintenance. I am curious to see how accurate mph reading will be when compared against GPS and onboard speedo which has always read about 5mph optimistic

Richard M said...

I heard that some countries prohibit the speedometer from ever reading low but can be 5% high and still be within spec. So manufactuers always err on the high side. Plus, the warranty runs out faster.