The general rule in our house (and we used to do a lot of high-country back-packing) is the +1 rule. That is, one person out, a 2 person tent, 2 people need a 3 person tent, etc. Even if your bike isn't in the tent with you, your Stuff will be. You'll be glad for the room, in my experience. Leave the kitchen sink at home, and you'll make up the weight.