As others have said, the trail will suffer from mountain bikes. The water bars and rock steps are not designed to handle mountain bike traffic and will erode as a result. I've already fixed up damage as a result of bikers on this and other trails.
Since I contributed a large amount of time building that trail, I really don't want to go back and do it again. Please don't ride bikes on the Carriage Road. No exceptions, no early morning rides, no bikes. It's tresspassing on private land and it's wrong.
Skiing and snow mobiling, which might seem like they would cause damage, actually have little or no effect on the soil. If you could bike down on top of the snowcover I personally wouldn't have a problem, but I don't think it would be much fun.
If you must bike, find places where it is legal and welcome. They are out there, enjoy.
-dave-