Bike + rack in the rain?
 

I recently purchased a trailer-type bike rack from Thule after saving up for quite a while.
After installing the rack, it just dawned on my that maybe I should get a cover for the bikes in case of rain. What's the convention? When it rains while you have your bike hung on the bike rack, do you let them get soaked? Do you cover them?

If you mean cover them while actually driving, then no - a cover will act as a huge sail putting all kind of weird stress on the rack. The bikes can handle the rain - just dry them, lube the chain and you should be good to go.

Just let them get wet. Relube the chain if necessary.

If your seat absorbs water, you may want to put a plastic bag over that.

I cover the seat and handlebars with plastic bags. The rest of the bike is fine.

Just do what you'd do if you've been out on your bikes in the rain.
I use a carrier bag for my bike seat but only because it's ancient and needs it.

Thanks for the responses. I usually don't go out to bike on a rainy day, so I didn't realize it's not even a serious problem.

I just cover the seats with plastic bags on our bikes. They'll be fine in the rain, other than getting a bit dirty; no biggie.

I'm not sure about the rack but my two month old Thule has some visible, light surface rust around bolts or "rivets." Not sure what to make of that but I'm not happy about it.

What everybody else said. I have three steel bikes that sat on a patio two blocks from the Pacific Ocean for about two years, salty mist on them nearly every day, and while they did develop some superficial rust, nothing significant happened (they'd been Frame Savered, which probably helped). My racks, a Thule and a Yakima, got light rust on some of the fasteners and rivets, but that's all. I'd rather there were no rust at all, but indoor storage wasn't possible.
Coating exposed parts with wax or clear nail polish might have helped. Fresh water, from rain or stream crossings, shouldn't be a problem. My mountain bike has been completely submerged three or four times without damage.

Have you noticed any issues cropping up from the rusted fasteners/rivets?

I have, in the past, during foul months where road salt is used, covered the drive train, front & rear gears and chain with plastic bags and taped them on. there are some days during the fall/winter/spring in NE where the roads are just nasty especially if there's rain & road spray. it's so much easier to protect the gear and chain than to clean them. during summer months / clean road months where there just may be rain and mild road spray I cover nothing. the only exception would be if I were to bring my bike that has a the leather saddle, then that would get some paper towels and 3 platsic bags firmly attached!