Like a brand new car, they should tighten all the cables and check the
major bearings (cranks, pedals, hubs, headset) for either looseness or
tightness or lubricant depletion. If the bike's been in wet weather
also check the chain for squeeking and relubricate if necessary.
In the old days, many new bikes came with "Tight" bearings, e.g. hubs.
After 100 mi or more the cups would "press in" to the races and the
bearings would develop some play and require re-adjustment. That's
one of the origins of the "30 day checkup" offered by many shops.
All products experience an "infant mortality" period near the
beginning of life and a "wear out" period near the end of life. The
goal of the mechanic is to look for such problems developing and
either fix or replace any malfunctioning parts before they fail
completely. Modern parts probably don't have much in the way of
infant mortality. However, for a TREK 1200 the mechanics should know
what the design flaws are and he/she should look in these areas ...
- Don Gillies
San Diego, CA