Am looking for a bike for teenager to take to college and keep outdoors locked to a bike rack. Will bikes such as the Trek (7100/7200/7300) or Raleigh (C30/C40) hold up ok if kept outside throughout the fall - rain, etc., or do they need to be kept indoors or otherwise protected with a tarp or whatever. Thanks. (PS - I'm new to the bike thing, so forgive me if this is a dumb question!)
I don't think it is a dumb question, Tricia. Ideally, a bike would be cleaned and stored inside after each ride. Certain components do not work well with water, ice, etc. The chain is the first thing that comes to mind. Most likely, even if well oiled, the life of the chain will be shortened by the elements. Some of the frames you mention are made of aluminum and are probably quite capable of holding up to the elements, but any steel components are probably going to degrade. Spoke nipples and rims are known to rust and break, especially on the lower cost equipment. That being said, I know there are many bikes that keep on running even after spending their entire lives outside. At minimum, a much more aggressive maintenance cycle would be necessary.
Any of those bikes are OK. My steel bike lived outdoors 24/7 by a coastal town for 2 years with no corrosion.
I use a plastic bag over the saddle to keep it dry. A tarp will be more useful if you leave the bike unattended for any length of time; for daily use it will be too much trouble.
You can protect the frame , spokes and cables (but not the braking surface rims!!) with a few coats of car wax.
Ensure that metal-to-metal contacts are well greased: all threads, seatpost, stem etc.
The best chain lube for outdoor living is probably a wax-based one. This will resist washing off better than liquid oils and will run clean. Modern wax-in-solvents such as White Lightening are easy to apply.
A good bike shop is essential in prepping the final assembly, avoid box-shifters and mail order.
Security may be an issue with a nice-looking bike. Get a solid U lock and a cable.
Nono of those bikes come with the essentials of utility cycling: fenders, luggage rack, lights.