I think so too. But I have not found a way to confirm it with theories and/or formulas.
I don't think you have a "pure" physics question.
1) Same rider, same road, same time, same high crosswind.
2) 2 identical motorcycles with one exception: 1st motorcycle has stock tires (130/70/17 rear, 110/70/17 front.) 2nd motorcyle has upgraded wider tires, same brand, same rubber compound, same thread, same shape (140/70/17 rear, 120/70/17 front.)
Question: Which motorcycle can be ridden faster (remember same rider) in crosswind. In other words: Do larger surface tire contact help at all in crosswind for a motorcycle.
edit - also, does this really change with speed of the cycle? A cycle will tip over in a crosswind standing still. Maybe going faster actually increases the stability, as the wheels are acting as gyros, and you have more inertial force. I think that needs to be determined first.
First, as Westernskies points out, the tires are not just wider they are different diameters. I think that if you want a "physics" answer, you need to phrase it as a "physics" question.
You seem to be making some assumptions in your approach:
Do larger surface tire contact ....
Wider tires may have two different effects. Which one is more important to a crosswind?
1) they might give better traction, in which case they would be able to take a higher (crosswind) force before skidding out sideways. (Although, I seem to recall that in theory, tire width does not affect traction, as a wider tire has fewer PSI, and it all balances - in practice, this is not true because tires and roads are not perfect surfaces, this is why I say it might not be a physics question, but a real world question).
2) A wider tire would make the cycle less prone to 'tipping' - so if the major problem with a cross wind is that the force causes the cycle to tip over, then a wider tire may help, regardless of traction being better/worse/same.
So I think you have more of a 'real world' question, and the first thing I would want to know is whether tire 'grab' is the limiting factor in a cross wind force, or tire width (stability), or maybe something else?
Now that I re-read it, I'm not even sure what the question is. If the crosswind isn't actually pushing the cycle to some limit, I doubt the tire width has anything to do with speed. Would one cycle/tire combo be faster with no crosswind? I'm confused what you are looking for, and that may explain why you got no response from the physics forum.
-ERD50