Why do power dumpers have different sized wheels?

Question

Regarding power dumpers like this motorized 4x4 wheelbarrow:

The front wheels are larger than the back wheels, which I think is unusual for wheeled machines. What is the reason behind that? I don't see any space issues at the back that would force smaller wheels.

For what it's worth, all four wheels are driven simultaneously via chains. I don't think there's any sort of differential or anything like that. Although I don't have much knowledge of mechanics.

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Is it because there is much more weight at the front when the dumper is loaded, and the larger wheels spread out the load on the ground, improving traction? (less traction needed at rear)

Answer 1

Yes, and also the bigger wheel won't get trapped in small potholes and will be more stable hitting bumps, preventing the dumper from tipping over or to the side.

They can climb up bigger obstacles usually found in construction sites too.

Answer 2

As you've hinted at,the rear wheels carry a much smaller load.

But more importantly, the rear wheels are sort of optional. If you encounter an obstacle that the rear wheels can't negotiate, it's relatively easy to just lift on the handles to help them roll over it, or even just carry them over it if really necessary. You already need to do that to dump it, and (at least with the ones I've seen) to steer. It's rather more difficult to do the same with the front wheels. Obviously you'd rather not do it all the time, but doing it once in a while isn't a big deal.