It wasn't until Shimano developed their "V-brake" (known generically as the side-pull cantilever or the direct pull brake) that a viable alternative to the traditional cantilever was available. The table below shows these two 520 characteristics through time.These data should be of use to people who plan to buy a vintage 520.These were considered powerful enough to stop a heavily loaded bike going downhill.The sidepull brakes of the time were considered less capable for such extreme duty.This information was provided mostly by visitors to this site.This page also includes suggestions for estimating the current value of a Vintage Trek.
The TX900 was the early top-of-the-line frameset, dating from 1976 to mid 1978.
They are: Tom Adams, , Mark Agree, Don Allgire, Peter Berger, Wayne Bingham, Alan Burnett, Larry Black, Dave Breitlow, Ed Brown, Colin Campbell, Dan Carlsson, Mark Carter, Andrew Chadwick, Chris Clement, Bill Clements, Chris Cleveland, John Colt, Nels Cone, Robert Cooke, Mark Crabtree, Julia De Grace, Kris Echert, Taryn Echert, Anita Edens, Dave Evans, David Feldman, Ivan Feldman, Erik Frey, Tim Fricker, Cory Fry, Rich Ferguson, Marsha Gill, Don Gillies, Dickey Greer, John Hallows, Lyle Hanson, D.
Hansen, Keith Hatfull, Mitch Hawker, Sean Hickey, George Hoechst, Bill Howard, Jim Jack, Jennings Kilgore, Michael Johnson, John Keller, Steve Kurt, Jeff Kwapil, JP Lacy, Kevin Maher, Dave Mann, Steve Mann, Tom Marshall (T-mar), Tom Meara, Michael Mc Cullough, Marty Meison, Lou Miranda, Dale Mizer, Greg Mooncalf, Mike Marro, Kirt Murray, George Nenni, Larry Osborn, Dennis Pieper, Andy Poplawski, Chas. Roberts, Brandon Rouse, Roger Sacilotto, John Satory, Paul Schleck, Travis Sherwood, Dan Shindelar, Bruce Squires, Dave Staublin, Jay St.
This longevity and popularity has raised the value of this bike over similarly-priced vintage Treks of the period.
Two parameters are specially important to the 520 over the years: chainstay length (as pointed out by Robert Cooke) and the type of brakes used.