Deciphering Speedometers

[RoadsNV]

I have a 1980 r65. The speedometer does not work. I am shopping for a replacement. underneath the trip odo is km/h and MPH under that. Below that on most every speedometer is a "W" with a decimal number. On mine, it is W 1.138. I have seen various others with W 1.xxxx but I am not sure what this number means, or if it even pertains to compatibility to register the correct speed. This W number is on factory and aftermarket speedometers. I figured it would just have to come off a bike with the same diameter tires.
Anyone have any information on this W number, or information on where to get parts to fix mine, or where to send mine for repair? Or maybe you have one lying around to send my way?

[schrader7032]

The "W" number indicates how many times the speedometer cable turns per mile...so for 1.138 it will turn 1138 times per mile. It is tied to the final drive ratio which should be stopped near the fill plug on the drive shaft. While the tire diameter figures in as well, typically the diameter of tires are going to be about the same.

As for your W 1.138, I cannot find that number referenced on this page:

https://bmwmotorcycletech.info/ringgears.htm

Do you mean 1.318? If it is 1.318, then your final drive is likely 32/9 or 3.56.

I've seen some people mention Joe's Speedometer in Reseda, California as well as Overseas Speedometer in Austin, TX.

[srankin]

While I have not had work done by him, he was very polite and professional to help me with an issue, here is another link. As far as I know, he is still around and working.

Terryvira@hotmail.com

St.

[RoadsNV]

Do you mean 1.318? If it is 1.318, then your final drive is likely 32/9 or 3.56.

I think it has a decimal, but I am not positive. It is old and I am older
I only assumed a decimal since the aftermaket ones that are more clearly visible seem to have one, as do some of the old ones on eBay.
Thank you so much for this info! I was looking at a couple on eBay out of different model airheads. Mine only registers 80mph. I'm wondering if the others
(they have slightly larger W numbers) will still work because they register 120-140mph. I'd hate to throw away $300-$400 just to find out

[schrader7032]

I had read that the 85 mph speedos were actually more accurate! If the "W" number is not the correct one for the final drive on your bike, the speedometer won't read as actual and will be off. If you know how much is it off, etc., you can still use it. Hopefully it is not off in the direction that is more attractive to law enforcement!

[RoadsNV]

Guys, thanks for the links and recommendations. I found a few speedo internal gears finally. I am a little apprehensive about taking mine apart though.
I guess I'll contact these folks and price it out whether I take it on myself or put it in someone else's hands.

[Darryl.Richman]

You might note that the way numbers are written in Germany (and much of Europe) is backwards from how we write them in the US. The period is used as a thousands separator, and the comma is used as a decimal point. So, a W number of 1.138 actually means 1,138 (one thousand one hundred and thirty eight). This is why it takes 1138 revolutions to go 1 km.

Note also that W indicates turns for whatever the base unit of the speedometer is. A kmh speedometer is turns per km, an mph speedometer is turns per mile.

[srankin]

Is it the speedometer part that is not working or the odometer? The odometer is all gear driven and prone to fail. there are articles in various places as to how to repair the most common failure.

As for the speedometer part, I would caution taking the spring behind the needle apart or letting it get unwound. I had a speedometer issue years ago and had a log chat with Terry Vera as to how things work. That spring has to be wound just right to calibrate the speed as well as to prevent the needle bouncing. It is fussy to adjust.

I I had a 85mph unit I sacrificed to learn kind of how things work. it can be fussy to get things back together. Good luck. St.

[wa1nca]

Thanks Darryl
Never understood what the W meant

Always best to use a GPS apt on your cell phone to get the correct speed

correct working speedometer with errors,mismatched speedometer,transmission,rear end,rear tire
will all effect a correct indicated speed