Unimog Club UK

I have been thinking about putting some weight over the back wheels.  The isometrically mounted thing you mentioned in another thread has me thinking though.  If I want to strap my spare wheel over the back axle, how do I do it?  Conventionally I would just bolt a frame between the chassis rails and away you go.  I will have to crawl under my radio box and have a closer look at the pivot mount.