A sidecar question on behalf of someone else.  

Recently someone I know decided to consider a sidecar build with an Earles Fork front end and has the choice of using either a K100 set up or a K1100 as the moto.  As there is a mix of both types on the forum, I decided to ask as to what are both the advantages and disadvantages of one over the other.  

The idea is not how to build one but any peculiarities relating to one over the other.  For instance, the two different types of final drive and which would be the preferred one and any potential problems that need to be overcome.   

The initial plan is to build one up in anticipation of attending the OCR in two years time at Mt. Augustus.  The bike is not being designed as an off road version but for normal road usage.  The owner has many miles of K100RS experience in the past.

When Paralever appeared, sidecar builders were afraid of its ability to cope with specific stress of sidecar riding. EML, for instance, choosed to eliminate the articulation by turning it rigid. Some were also concerns by the rigidit of the cast swingarm.
But eventually...nothing happened.
My sidecar K1 has 230 000 kms of tough use on tough roads, with a large 175 65 14 tyre on a 6 inches wide rim. Not any problem with the paralever, despite it was often ridden in a road rallye rythm!
I don't have any problem either with my R1100RT sidecar, which shares the same final drive and almost the same swingarm (except shock fittings ).

So monolever or paralever, there's no issue.
The monolever offers only one advantage: you'll get more choice of final ratios. That's all.
But as you usually mount small diameter car wheels, it's not even a big deal, as you can adjust the ratio by changing the rim diameter and tyre height instead of final drive.

Agreed that Mono or Paralever choice is not a deal breaker as far as strength and integrity go. Ex-local sidecar manufacturer DMC used mostly Paralever for decades with minimal issues. When the small pivot bearings of a Paralever inevitably fail, there are several plain bushing choices as drop-in replacements for the BMW-only supplied bearing.

Thanks for the replies, and I shall pass on the info.  

Always a sensible reply, jbt.