Forum bmwbike.com

In regard to mounting a sidecar, an original BMW manual for R50, 60, 69S states that the 50 and 60 require a gear ratio change but that the R69S does not. Did I read that correctly? There is much discourse on this subject on the internet but to a layman it is confusing. Some say yes, some say no. I also have read the R69S came from the factory with gear ratio set for sidecar use. So: specific to the R69S -- is it necessary, or not, to change gear ratio when mounting a sidecar? Thanks.

Let me broaden this query to include the R50. And -- if gear change is necessary on either the R50 or R69S -- what kind of $$ are we talking about and how easy is that to have done, i.e., parts readily available?

I emailed the Steib sidecar manufacturers in Germany in pursuit of an answer to my question. I would think they know what they're talking about. Here is their response:

"thanks for your message.
For using a 1960´s BMW with sidecar I would recommend models R50,R50/2,R60,R60/2.
R69S was produced for more sporty riding.

In reality I use my 600cc BMW without sidecar ratio, because I´m riding less than 1000km a year.
If you plan to go 2000km or more a year, better use a sidecar ratio.
For 500cc models I would recommend STEIB models S350 or S500,
for 600cc you can mount all STEIB models."

Dave, obviously the higher you gear the outfit the more strain it puts on everything getting off the mark. It's like taking off in 2nd gear if geared too high. If the rear spline isn't in good condition this problem will multiply along with others. Obviously if you only do 500k's per year there'll be less wear on everything.
From my experience if you ride an outfit fast or often all needs to be in good condition or it'll wear out exponentially faster.
I am building similar at present, good luck.
Trevor