From forgeworld (and an old thread) these are Imerpial vehicles.
The first speed is tactical, then on road, then the epic speed and an attempt to rationalise it
Conqueror 24kph/34kph/30cm (commonly agreed, can be explained by not needing to halt to fire?)
Destroyer 36kph/50kph/ ? 25cm?
Exterminator 24kph/40kph/ ? 25cm? (a higher speed here would be one reason to take it)
Leman Russ 21kph/35kph/20cm
Vanquisher 19kph/32kph/20cm
Thunderer 22kph/32kph/ ? 25cm? (could up speed with same arguement as demolisher)
Executioner 18kph/30kph/20cm (same bracket)
Demolisher 17kph/28kph/20cm (maybe the russ spends more time firing its gun)
Salamander scout 68kph/100kph/35cm
Salamander command 55kph/70kph/30cm
Chimera 55kph/70kph/30cm
Hydra 35kph/50kph/30cm (drives really fast
)Medusa 35kph/60kph/ ? 25cm?
Manticore 45kph/60kph/20cm (I reckon the slower Epic speed is to account for reloading!)
Basilisk 21kph/35kph/20cm
Trojan 60kph/80kph/30cm (in same bracket as Chimera)
Atlas 20kph/34kph/20cm (in same bracket as Russ)
Baneblade 18kph/25kph/15cm (all SHTs must have a harder time finding cover as they advance!)
Shadowsword 18kph/25kph/15cm
Stormblade 18kph/25kph/15cm
Stormsword 18kph/25kph/15cm
