When we made the decision to mount the ADV1 trailer to the rear axle of adventure touring motorcycles to take the weight of your gear off the suspension of the bike, we knew we had set a challenge for ourselves. Historically the number one selling ADV bike on the market doesn’t have a rear axle, it has a huge hole in what they call the final drive unit! I am of course talking about the BMW R1200GS and the R1250GS.
How can we have an axle adapter when there isn’t an axle—only a large hole?
As we pondered this issue, a possible answer began to emerge when we saw some rear hub covers for the GS.
That got us thinking, what if we had a similar sleeve, but with bearings on the end. We began thinking and drawing out possible configurations.
If we could secure a sleeve inside the final drive unit, with bearings on the ends, we could then put an axle through the exact center of the final drive unit hole.
The sleeve and the outside of the bearings would rotate with the BMW’s wheel, but the axle we put through the bearings would not rotate and we could grab onto it with our hitch.
The main issue remaining was how to secure the sleeve in the hole. We studied how the hub covers did it. The o-rings they had in them was a good idea to seal out dirt and water, but it definitely was not enough to keep the sleeve and bearings from rotating or wiggling in the final drive hole. After considering a few ideas, we decided to go with putting fins on the ends of the sleeve, and then making the bearing races perfectly conical, meaning when the axle adapter is tightened up, the race expands the fins the perfect amount to snug it securely in place.
Our prototype worked better than we ever dreamed. We could install the axle adapter in less than 5 minutes with just two 6mm hex wrenches. And we can take off the GS in less than 2 minutes with the same two hex wrenches. And after many, many off-road miles, and the adapter removed from the bike, there was no scratching or marring of the final drive unit. It held perfectly.
The key to the GS axle adapter is the axle itself. It is made of super strong steel and has extremely high tolerances for straightness. That combination means it is not an inexpensive piece of metal.
Our two-armed hitch simply grabs onto the spools, you lock the hitch in place, and away you go!
The hooks that are shown here will be considerably different (much simpler) in our production models.
And that is the story of how the Pasq ADV1’s hitch was made to work with the BMW R1200GS and R1250GS.