I would like to start commuting one or two days a week. My commute one way is 18 miles. Because of recent ankle surgery I have been doing trainer rides to help get back some of my bike fitness. I would like to work up to being able to do all 38 miles of the commute. I would begin by doing a bike bus commute. It's 5.4 miles from my house to the bus stop. As I get more fit I ride a bit further to the next bus stop before geting on the bus. Buses here have racks on the front. I have a carbon road bike, a hard tail mountain bike and a single speed crusier. I would like to use the carbon bike because I can get places faster. Would puting the carbon bike on the front bus rack add a bunch of wear and tear to the bike? Would it get bumped around alot? OR should I put slicks on my Mountain bike and use it to start? Or buy a cheaper al road bike?

Thanks FunBikeLady