Sheldon Brown's Bicycle Technical Info
by Sheldon Brown; John Allen · sheldonbrown.com
The late mechanic Sheldon Brown's technical site, now maintained by John Allen. It has articles on brakes, drivetrains, gearing, wheelbuilding, cup-and-cone bearings and frames, plus a beginners' section and a detailed glossary. It explains why parts work and how standards fit together, not just the steps. That makes it the best free resource for diagnosis and compatibility questions, and on older bikes it covers what Park Tool does not. It is especially strong on older and mixed-standard parts and compatibility.
More resources on Bicycle Repair & Maintenance
The Bicycle Wheel (3rd Edition)
Jobst Brandt's engineering account of how a spoked wheel carries load through spoke tension, followed by a practical method for lacing, tensioning, truing, dishing and stress-relieving wheels. It is the theory behind why truing and tension balance matter. This is the advanced step for the topic's wheel-truing strand. No free source explains wheel mechanics as rigorously, and his stress-relieving method is standard practice.
RJ The Bike Guy
A home mechanic's YouTube channel of full-length, uncut repairs on everyday, department-store and older bikes. It covers freewheel removal, cup-and-cone hub and bottom-bracket overhauls, brake and derailleur adjustment, and cheap tool alternatives, and shows the mistakes and fixes along the way.
Zinn & the Art of Road Bike Maintenance, 6th Edition
This is the one print manual worth owning alongside the free web references. Lennard Zinn's illustrated workshop manual, over 450 pages. It covers tools, flat repair, tubeless setup, mechanical and electronic shifting, rim and disc brakes, wheel truing, bearing overhauls, internal cable routing and troubleshooting. It uses exploded-parts diagrams and step-by-step procedures throughout. It follows a sequenced curriculum, with a coherent structure the component-indexed websites lack.
Park Tool Repair Help
Park Tool's free library of about 190 step-by-step repair articles, most with video. It is organized by component: brakes, derailleurs, chains, bottom brackets, headsets, hubs, wheels and tires. It runs from basic adjustments to shop-level procedures such as frame and brake-mount facing. This is the default reference on r/bikewrench and in shops. It gives procedure-level instructions with torque specs and diagnostics for every major component, all free.