Speedometer

[Weshawk]

Thank you in advance for replies...  I'm finally getting around to searching for a used speedometer for my 79' R65.  The current one has been broken for some time now, so on my nerves.  

To top it off, the main cover to the instrument panel split on the side, so I need to replace that part as well.

Here's my question: I keep seeing a few used ones on ebay and and want to get advice on how important it is to have the ratio or whatever is listed on the face of the speedo that shows the type (i.e. W = 1276).  I'm sure it is a must, but maybe I can get away w/ it not completly matching.

Regards...

[Justin B.]

I'm thinking that all dual-shock R65s used the same gear ratio so they should all have the proper level of inaccuracy!

[nhmaf]

IF for whatever reason the ratio numbers aren't visible on the speedometer, at least if the seller
can accurately tell you just what bike it came off from (and it was a dual shock R65) you should be fine.
If it came off an R75, R80 or R100 - each of these had different final drive ratios (none matching the
R65) and the speedometer / odometer could read 10% - 25% low.   I think that the proper R65
speedometers generally read about 5% fast, on average, though the odometers are usually very close).

[Weshawk]

The one that I'm watching on ebay is w = 1318 and mine is w = 1276.  I guess I'm not fully understanding what this means, but it sounds like the miles per hour will be off by the difference in numbers w/ the two above?  Sorry, if I sound like a dummy.

Thanks for the response too.  Again, I love this site.  Regards.  

[Semper Gumby]

Hi Weshawk

Hmm. I don't get it either.  My 1980 (should be the same as yours) has a W1318 speedo with a 32/9 final drive.  What's you final drive ratio?  (Just infront of the drive shaft filler nut on the forward part of the final drive where it mates to the drive shaft)

[NC Steve]

Hmmmm, I got curious and just checked the speedo on my '84, and it's also a W1276.
The final dive ratio remains as 32/9

Weshank, your '79 speedo is a 120 mph unit, right, as is the '84.
Could the W1318 be the 85 mph speedo, that was out in '80 (?) thru '82 or '83 (?): no claims of trivia knowledge here!


ps: I may have answered my own question (or not).
Is this the speedo you're eyeballing on Ebay? If so, it's indeed a w1318, and also the 85 mph unit.
Are there any accuracy issues with using the 2 units interchangeably?

http://cgi.ebay.com/ebaymotors/1981-BMW-R65-ORIGINAL-SPEEDOMETER-NO-RESERVE-AUCTION_W0QQitemZ250170485250QQihZ015QQcategoryZ50465QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Bob_Roller]

I checked RealOEM.com, and this is what I found with the part numbers for the speedometers, W=1276 speedometer is for use with a 3.44 final drive, the W=1318 speedometer is for use with a 3.56 final drive.

[NC Steve]

...and 3.56 = 32/9, while 3.44 = 31/9. Yet, I've seen 3 '84s with 1276/120 mph speedos, and (I assume) the standard 32/9 rear ends, contrary to RealOEM.

Interesting, but what does it all mean, especially accuracy-wise?  :-/
And if there are actually different rear-end ratios between the early and late models, what effects are there on performance, longevity, etc??

[Rob Valdez 79 R65]

I just checked my '79 - it has a W1276 and a 31/9 (3.44) final drive.  It is a 120mph speedo.

[nhmaf]

I re-checked my 82 R65LS - it has the W 1318 speedo (85 mph) and has the 32/9 (3.56) rear end.

If BMW actually went back to using the 3.44 rear ends in '84 or later when the 120 mph speedometers came back,
I suppose that might make some sense to switching back to the 1276 speedometers which were used with 3.44 rear ends.

Or, perhaps a number of folks knowingly put on the 3.44 rear ends to get a little bit more top speed or less RPMs
at cruising speeds (65-70 mph) ?  

All else being equal (tire/wheel diameter, etc.) a 3.44 compared to 3.56 rear end is a ratio of .9663, so the
speed/distance error of using one instead of the other speedometer for the rear end could mean an error
of a little under 4%.   Now, maybe some people found that their W1318 speedos were reading about 5% fast, and made
a switch to the 1276 to compensate ?

Hmmmm. :-/

[Weshawk]

I think this is getting somewhere.  I'm going to check tonight to see what my rear is reading.  It sounds like it will be 31/9, which means that the 1318 won't work.    

Unless someone else can say it doesn't matter.  I'm also thinking that there could be a chance that the person I bought the bike from replaced the speedometer w/ a new one that didn't match.  I guess before I starting thinking that though, I need to check my rear ratio.

Man, this is complicated.  Well worth it though and I'm actually learning something.

Thanks again...

[Rob Valdez 79 R65]

I just checked my '79 - it has a W1276 and a 31/9 (3.44) final drive.  It is a 120mph speedo.

Mine reads well over 5% fast.  Closer to 10%.

I always heard that the 85mph speedos were pretty close to accurate.

[Semper Gumby]

Mine became spot on after it went to PaloAlto.

TTFN,

[trolle]

Just to add to the confusion: The kmph speedometer on my '84 has a w=781 (781 times 1.632 equals 1276) and the final end ration is 32:9. As far as I know both speedometer and final end are factory fitted.

It reads 5% fast

greetings from a windy, sunny and cold north

[mjbickford]

I re-checked my 82 R65LS - it has the W 1318 speedo (85 mph) and has the 32/9 (3.56) rear end.

If BMW actually went back to using the 3.44 rear ends in '84 or later when the 120 mph speedometers came back,
I suppose that might make some sense to switching back to the 1276 speedometers which were used with 3.44 rear ends.

Or, perhaps a number of folks knowingly put on the 3.44 rear ends to get a little bit more top speed or less RPMs
at cruising speeds (65-70 mph) ?  

All else being equal (tire/wheel diameter, etc.) a 3.44 compared to 3.56 rear end is a ratio of .9663, so the
speed/distance error of using one instead of the other speedometer for the rear end could mean an error
of a little under 4%.   Now, maybe some people found that their W1318 speedos were reading about 5% fast, and made
a switch to the 1276 to compensate ?

Hmmmm. :-/

this is the benefit of the 79 speedos (120 mph)  i have one on my 82, and it is more accurate... almost dead on according to the ploice radrs i have encountered :-(