Space Exploration Vehicle model?

Top Gear (UK) did a road test with Captain Slow, James May with these vehicles.

Josh Gates got a chance to drive one on his show, Expedition unknown.

I wonder why are the wheels/tires so small? Are we planning on exploring a giant salt flat planet somewhere?

Or maybe one with an existing road infrastructure?

Greg

I wonder why are the wheels/tires so small?

Well, potential bodies for exploration are all significantly less than 1G.

Moon is 0.15G (1/6); Mars is 1/3 (.037G).

So, you can get acceptably low ground pressures with significantly smaller contact surfaces.

There's a corollary issue that you also need to have enough ground pressure to actually have traction in extraterrestrial locations.  Which is complicated as you want the vehicle to have as little mass as possible, just to decrease the tare weight to have to lift.

Let's say the Earth weight of the thing is 100KG, on Mars it's only 37KG, for 4 wheels that's only 9.25kg each; for 6, it's 6.16KG each.  If the contact patch is 10x10cm would only be ±62grams per square cm.

A "springy" tire is handy as it's less complicated than suspension equipment, which is middling important for human drivers/occupants.  So, tires are better than rollers (torsion bar geometry is complicated in low-G environments, too.)

Those may be test wheels only for use in 1g gravity and the wheels will be different for lower gravity planets. I think the original lunar rovers didn’t have exactly the same metal mesh wheels for earth testing, as the ones used on the moon.

The aboce is an excellent point.

My quick search did not turn up a lot of details on the earth-bound rover trainer.