Adventure Maui is a tour company that will prove to you that there are few things like the bike trip down Haleakala. If you go early in the morning, dress in layers. If you go in the afternoon then you should dress accordingly. The top of the crater is pretty chilly most of the time. The sunrise, if you’re a morning person, is amazing as is the sunset if you’re not a morning person. Making it up to the top before sunrise requires that you get up well before the sun and get into the van for the long ride up to the rim. You must be a capable rider. If you haven’t ridden in a long time, then riding down the side of a steep volcano isn’t a good refresher course. It’s fun, but it can be dangerous if you aren’t used to biking. The best advice is to get back on a bike and do some up and down hill biking before you come to Maui to reorient yourself with the sport.