It seems that the vast, vast majority of bikes on campus were bought during freshman year by mommy and daddy at WalMart, and have never been serviced since. Rusted-out bikes are common, and the relevant groundskeeping/police people only remove abandoned bikes twice per year (at the end of Autumn and Spring semesters). Also, there does not seem to be any coherent approach to bike racks: some are long racks, some are upside-down U's cemented into the ground, and there are a few truly eccentric bike racks in the older parts of campus.
By far the biggest gripe that I had was the lack of covered bike parking, especially outside of residence halls. For those poor souls in Owen, Tarkington, and other dorms without elevators, it is not even possible to bring your bike into your tiny room. Even in halls with elevators, there is no place to securely store your bike besides your room. Without covered parking, bikes both cheap and expensive will quickly deteriorate and become unusable without a new chain and other parts. Since replacing such parts on a Walmart bike is not usually possible, these bikes are abandoned, taking valuable space in heavily used locations (like dining courts, lecture halls, and dorms).
In my four years at Purdue, I have only come to discover a few places where one can reliably park their bike at a bike rack with shelter from the elements. If anyone knows of more, please let me know and I'll add it to this list. I do not spend much time in dorm-land or Engineering parts of campus, so it is likely that I have forgotten a few places.
- Beneath the elevated building spanning Wetherill and Brown. There are at least four bike racks, but they can be crowded at times. Similar to the Math building breezeway, rain/snow can fairly easily blow through and still get bikes wet.
- In the Hawkins Hall underground parking ramp. Just to the right upon going down the entrance, there are two bike racks that are a decent distance away from the outside of the garage. This place seems popular with old commuters (saw lots of bikes with 2+ panniers).
- There is some marginal covered parking for bikes in front of Krannert. There is an overhang about 8-10 feet up in the air and some load-bearing pillars. Amongst this are some bike racks. A bike parked there would probably get wet with much wind, though. Another minus is it's proximity to the campus bars; left for too many nights, it would be a likely victim of drunken destruction.