That reminds me of one thing, the guy on that group trip that had one said that on steep gravel uphills he could have a traction problem because so much of the weight was on his four wheels that were not driven, only one wheel was part of the drive train and it did not have as much weight on it as most two wheel bikes have on their rear wheel.

But he could climb any hill because there was no minimum speed that he needed to stay upright.