Thanks @180º and @raven24 for commenting and sharing your experiences. It is definitely more plausible that different tracks will have different behavior, and it's also plausible that the track/vehicle conditions change throughout the day.Yes, I worked in attractions. I never worked Matterhorn, but I did receive some training on the ride. We learned the more weight the bobsleds carry, the faster they go. We also learned that as the bobsleds continue to move and go throughout the day, the faster they go by nighttime. I tested the weight factor and Infound it to be true. Before the single bobsleds we have now, I had my sister ride in the same bobsled I was in. We then rode separately and they definitely went slower. The same thing happened during my grad nite some years ago. A bunch of us got on Matterhorn and that puppy was going so fast I thought I was going to fall out.
Something else to note, the right side of the ride has a longer track, but is slower than the left side, which has a shorter track but is faster
That said, the claim that the weight of a ride vehicle changes the velocity, especially to the extent that heavier vehicles go faster, although intuitive, is actually a very suspect claim. I've mentioned that the physics of attractions like this makes this claim suspect, but I don't think I've stated how strong a conclusion that is. You can easily see that the mass of a vehicle can not change the velocity through a straightforward calculation, put simply gravity powered rollercoasters must obey energy conservation. Intuitive notions about acceleration and momentum come from that calculation. Where mass does enter into it is in the structural and material properties, but there are multiple reasons why this can only lead to heavier vehicles being slower.