First remember the rider can control the speed using hand signals – see other FAQ.  Here is a rough guide on how fast you should drive for different disciplines.
• Skier on 2 skis? 34kph for Juniors and 37kph for Adults
• Trick Skier? 26kph
• Slalom skier? 40 – 43 kph
• Kneeboarding? 32kph (Beginner 16-24kph),
• Wakeboarding – 28-35 kph (Beginner 25-29kph)
KPH > MPH
20 > 12
25 > 15
30 > 18
35 > 22
40 > 25
45 > 28
Above all else do not frighten people. Riders may not be able to let you know that you are driving too fast. Edge on the side of caution so as not to put people off – but remember too slow can be just as bad as too fast.
Adjust your speed according to the conditions and ability of your rider. Have fun, be safe.