KPH to MPH conversion

[Oinkoink]

Perhaps someone that has done this might be able to help out.  Will I have to change the speedo only or the speedo and drive too?  Checked a few online parts guides but don't see where it shows US and Euro parts where different.  Maybe just showing US spec bikes only.  

[dirtrider]

3 hours ago, Oinkoink said:

Perhaps someone that has done this might be able to help out.  Will I have to change the speedo only or the speedo and drive too?  Checked a few online parts guides but don't see where it shows US and Euro parts where different.  Maybe just showing US spec bikes only.  

Morning Oinkoink

 

What motorcycle year & model are you working with? 

[Oinkoink]

Yeah that might help!  It's a 1995 R 1100RS

[dirtrider]

34 minutes ago, Oinkoink said:

Yeah that might help!  It's a 1995 R 1100RS

Morning Oinkoink

 

Those early 1100RS bikes are (or at least  can be) different. My speedometer usage chart doesn't include the early 1100RS so that is no help. It should be the same as BMW used (at least as far as I know)  the same speedometer cable RPM for all the speedometer heads. None (MPH or KPH) were that accurate anyway.  

 

About all I can suggest is to try a MPH speedometer head the see how close your speedometer reads at hi-way speeds.

 

Even with the correct parts BMW was very cautious back in those days to keep the actual  speed showing on the speedometer well over what the vehicle was actually traveling as by law it couldn't ever read lower. (even with different tires or tire wear)

 

Believe it or not the spec BMW used was-- (  the maximum amount the motorcycle speedometer could read higher than actual road speed was 10% of the vehicle’s actual speed plus 2.4 mph )

 

That equates to--  if the actual vehicle speed is 55 mph then  (55 x 10% = 5.5mph), so that 10% (5.5 mph) + the  (2.4 mph) = 7.9 mph, so permissible speedometer  displayed speed could be  from 55 to 62.5 mph & still be considered within specifications..

 

Once you know what your speedometer error is we can probably track down the correct (or closer anyhow)  drive/driven gears to get it closer. 

 

Some of my old 1100 R bikes were off well over 10mph at freeeway speeds so once GPS devices became available that is all I have used for a speedometer as I usually push the limits  pretty far so like to know exactly how fast I am actually going.