So, General Grievous is using a giant mono-wheel thing as a getaway vehicle. The thing is insanely impractical. Such things exist in reality, but have you ever seen one being used for regular commuting? Because there are so many ways for it to fail spectacularly, that's why! We have a modern, industrial society in which we routinely let people jump out of planes, get trampled by bulls, dive inside caves, and surf on 50-foot waves. Yet we still don't let people on to our roads driving monowheels.

Presumably the only reason for Grievous to use such a thing is because he's insanely reckless, and it has some impressive turn of speed that can outrun anything.

Except a giant feathered lizard.

Seriously, in the movie Grievous has a huge head start on Obi-Wan. He's riding this gnarly hi-tech mono-wheel thing, while Obi-Wan is on a lizard. And the lizard catches up. And overtakes.

Presumably it must have a +50 native terrain advantage or something.

Transcript

Obi-Wan: You're not getting away this time.
General Grievous: Ah, the thrill of the chase! Toot the horns! Release the hounds!
[SFX]: Kzrzk
Obi-Wan: I'm chasing you!
General Grievous: The most dangerous game! Exhilarating, is it not?
[SFX]: Kzrzk
Obi-Wan: I leap across.
{Obi-wan jumps on to Grievous's mono wheel}
General Grievous: Youth these days, so impatient. A good panforte takes hours to bake.
Padmé: Grab him!
Obi-Wan: And risk the grappling rules?
GM: You knock the unicycle off balance. <roll>
[SFX]: Kzrzk
GM: Grievous falls off and drops his electro-quarterstaff.
{they fall off}
Obi-Wan: I grab it and keep my distance.
[SFX]: Kzrzk
GM: If you're not going to grapple him, he gets to shoot at you.
[SFX]: Pow! {Grievous shoots at Obi-Wan}
R2-D2: Everybody wins!