The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: MR.E on August 05, 2011, 04:00:10 PM

Title: speedos - not the swimming kind
Post by: MR.E on August 05, 2011, 04:00:10 PM

Hello

I've removed the speedo from the BMW (1981 r65).
Is there a way to fit a speedo with a smaller connection screw on the back of the  unit, the BMW one seems large compared to my other bikes is there a step down you can buy?

Cheers
Hope it makes sense

Title: Re: speedos - not the swimming kind
Post by: Rob Valdez 79 R65 on August 05, 2011, 04:27:48 PM

I've never heard of one, but you could probably have a machine shop make you one - at a very high price.
Then you have to worry about conflict with all of the other cables and bracketry.

I guess you are doing away with the dash panel?
If not, will this substitute speedometer have the same display diameter to fill the hole?
Will this substitute have the correct ratio to go with your final drive?

Title: Re: speedos - not the swimming kind
Post by: MR.E on August 19, 2011, 04:11:46 PM

Hello again

managed to get a cable made & fit a smaller mechanical speedo to the bike BUT then i find out theres a ratio thing on speedos & it's why my speedos well out of sync.

SO, any ideas what an R65 ratio is or where i can find a small (60mm) mechanical speedo?

Thanks for your help

Title: Re: speedos - not the swimming kind
Post by: Barry on August 19, 2011, 05:26:17 PM

The speedo ratio printed on the face of Airhead speedos is the number of cable revolutions for 1 mile traveled and therefore the correct ratio depends on which final drive you have.

Info in this previous thread

http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1300201693/7#7

Title: Re: speedos - not the swimming kind
Post by: nhmaf on August 19, 2011, 09:32:46 PM

IF you're going with aftermarket speedometers, the easiest solution is to get the kind that uses a magnetic sensor pickup on the front wheel (like a bicycle).  The Vapor, and many other units work this way, and you can reprogram it to properly match the circumference of whatever front wheel/tire combo you are running

Title: Re: speedos - not the swimming kind
Post by: MR.E on August 20, 2011, 02:35:31 PM

cheers for the replies,
i fit the Vapour to my WR work really well BUT would like to keep the mechanical style to the bike.

thanks

just looking at my bmw speedo now, at the bottow of the face it says - W 1276 - is that the ratio??

Title: Re: speedos - not the swimming kind
Post by: Barry on August 20, 2011, 03:19:23 PM

Quote

just looking at my bmw speedo now, at the bottow of the face it says - W 1276 - is that the ratio??  

Yes.

It's the correct ratio for a 3.44 final drive.

Title: Re: speedos - not the swimming kind
Post by: MR.E on August 20, 2011, 03:22:45 PM

ok, i've no idea what i'm looking for do i need a 1:276 ratio speedo then??

Thanks very much

Title: Re: speedos - not the swimming kind
Post by: nhmaf on August 20, 2011, 03:51:03 PM

The "W1276" number means the speedometer is geared to  1276 revolutions of its input = 1 mile, and conversely, 1276 revolutions per minute = 60 MPH, though many of these BMW speedos tend to always read a bit higher, by 3%-5% on average, for the speed indication, they are generally very accurate for distance (odometer) when working properly.

Since the speedometer is inferring your road speed by the number of revolutions of the drive shaft, different final drive ratios require different speedometer ratios.   If you had a 3.56:1 final drive (32/9 stamping) you'd need a "W1318" speedo.   If you had a 3.0:1 (33/11 stamping) you'd need a "W1112" speedometer

The speedometer seller should be able to tell you the turns-per-mile or turns-per-kilometer for any unit they are selling.

Title: Re: speedos - not the swimming kind
Post by: NorR65 on August 20, 2011, 04:24:30 PM

May be this speedo:

http://www.mmb-messtechnik.de/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=122&category_id=4&option=com_virtuemart&Itemid=9&lang=en