Originally Posted by
biker128pedal
Note if you upgrade to a new 700c wheelset you may have to change out to longer each brakes to reach the rim or get adapters to shift the pads down. I did the former on a lower end same vintage model Trek my son has now. If you are keeping the bike it may be worth it for new tires. Also if the current rims rims are worn get new 700c rims and build.
There's a good chance that the stock brake calipers that came with the bike/27" wheels should work just fine with the 700C wheels, with some vertical adjustment to the brake pads. The Bead Seat Diameter of the 27" wheels and 700C wheels are about 630mm and 622mm, respectively (and a difference of 8mm). You need to adjust the brake pads by 4mm, approx.
Can confirm that the same stock brake calipers worked for both 27" and 700C wheels, on my vintage Schwinn, with a bit of vertical adjustment.