The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Weshawk on October 01, 2007, 12:49:34 PM
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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...
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I'm thinking that all dual-shock R65s used the same gear ratio so they should all have the proper level of inaccuracy! ;)
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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).
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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.
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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)
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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
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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.
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...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??
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I just checked my '79 - it has a W1276 and a 31/9 (3.44) final drive. It is a 120mph speedo.
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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. :-/
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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...
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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.
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Mine became spot on after it went to PaloAlto.
TTFN,
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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
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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 :-(
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There are currently 2 R65 rear drives for sale on Ebay.
One is a 31/9 ratio, taken from an '80 model R65, being sold by what appears to be an honest merchant.
http://tinyurl.com/yw4qm8
The other is a 32/9, taken from an '82, and is being touted as a "low geared, sidecar drive", by a seller with a long history of strong reputability and knowledge on Ebay and in the BMW community.
http://tinyurl.com/2yr8da
Anyone have more knowledge of this?? Is the 32/9 really that much lower, or designed for sidecar duty? Would it net much difference, as most of us seem to have 32/9 rear drives?
My own '84 is a 32/9, and I'd love to give up a little off-the-line grunt for lower rpm at highway speeds.
Is it a realistic expectation to create a better freeway flier from a simple swap?
Thanks for any more help or info ;)
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I think the seller is saying that because R65s are geared lower than the bigger bikes. A person with an R100 who wanted to use a sidecar with it might like that final drive to lower his gear ratio. If you want higher gear ratio you would want to get a final drive off of one of the bigger BMWs, though I think the R100GS are also geared lower. I don't know their ratio.
I can't find the numbers on mine but I presume it is the original.
Are you going to bid on that one, as I wouldn't mind picking up a spare if it goes cheap?
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Nah, Ed, I'm not bidding, help yourself, and good luck!
Still can't help but wonder what effect a taller ratio, be it the 31/9 or something else, would have on the R65's highway capabilities... :-?
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I can get almost to redline in 5th gear on mine, on a really long very slightly up hill stretch not far from where I live. I think that with a taller rear end I just wouldn't be able to wind it out as much. I doubt it would be any faster. I figure it must be rolling around 105 or so at those rpms; my speedometer would only read 85 though. :-[