We investigate how to use variable data rate in ad hoc TDMA networks and the possible gain in throughput. The use of variable data rate enables the network to adapt to changes in the environment, which is crucial for the ability to guarantee QoS in a mobile network. We study the impact that the routing metric and traffic adaptivity have on the networks ability to utilise variable data rate. Furthermore, we study how the number of data rates to chose from improve the throughput. We also investigate the relative gain in throughput for a system with variable data rate compared to a system with fixed data rate. The study shows that it is of paramount importance to take data rate into consideration when routing, especially when variable data rate is used to add long range low data rate links. We also note that traffic adaptivity plays an important role for the utilisation of variable data rate at the network level. Furthermore, the gain of having a great dynamic in data rates, ie. having many data rates to chose from, is not obvious. The results also show a substantial improvement in throughput when variable data rate is used.