Unimog Club UK

An indicated fifty on your speedo and the 405 Mitas tyres I would check it against a sat nav but you could have high ratio hubs @ 2800 you should be able to get about 56 mph. If your speedo is showing a low speed and your sat shows your doing 60 + you've got high ratio diffs !!! Does it only rev to 2400 ?
Regarding your mitas check the speed rating it should be g and load rating 136.
Moose