Minibot Design Insufficiency (Contact Pressure Based)

[FirebearBenD]

My team has a fairly basic minibot design - a couple plates of metal, a couple traditional wheels designed to move up the pole, and a motor. We're thinking we don't have a terrible design idea, as we can get the minibot to move up the pole at a decent rate if we press the minibot against the pole. However, without a human hand, we aren't seeming to get enough contact pressure between the wheels and the pole for the minibot to climb effectively. Naturally, adding weight (our first idea) would slow the minibot down too much and make it above the 15 lb weight limit, so we were wondering if there were other methods that could get us the necessary contact pressure.