Bearing Systems used in Bicycles — ETC Awards Limited Apprenticeship Assessment Qualification Motor Vehicle & Transport Revision
This subtopic covers the fundamental principles and practical applications of bearing systems in bicycles, focusing on their role in reducing friction betw
Topic Synopsis
This subtopic covers the fundamental principles and practical applications of bearing systems in bicycles, focusing on their role in reducing friction between rotating components such as hubs, bottom brackets, and headsets. It explores the distinctions between cup-and-cone, cartridge, and sealed bearings, guiding learners through identification, failure diagnosis, replacement selection, and precise fitting and adjustment. Mastery of this area is essential for ensuring safe, efficient bicycle operation and long-term reliability.
Key Concepts & Core Principles
- Safety checks: Always perform a thorough safety inspection (e.g., brake function, tyre pressure, frame integrity) before any repair or after completing work.
- Tool identification and use: Know the specific tools for each task, such as cone spanners for hub adjustments, chain whip for cassette removal, and torque wrenches for critical bolts.
- Wheel truing: Understand how to correct lateral and radial wobbles using a truing stand and spoke wrench, ensuring the wheel runs true and round.
- Brake and gear adjustment: Master the principles of cable tension, limit screws, and pad alignment for rim and disc brakes, as well as derailleur indexing for smooth shifting.
- Drivetrain maintenance: Learn to clean, lubricate, and replace chains, cassettes, and chainrings, recognising wear indicators like chain stretch and shark-tooth sprockets.
Exam Tips & Revision Strategies
- When asked to identify bearing types, always note the presence of a cage, adjustable cone, or integrated seals as distinguishing features.
- For failure mode questions, structure your answer around contamination, lubrication breakdown, mechanical overload, and normal wear.
- In practical assessments, double-check bearing orientation and press-fit tolerances before installation to avoid frame damage.
- Use the ‘finger-tight plus quarter-turn back’ technique for cup-and-cone adjustment, then verify by spinning the wheel to feel for smoothness and play.
Common Misconceptions & Mistakes to Avoid
- Confusing sealed cartridge bearings with loose ball cup-and-cone systems, leading to incorrect service procedures.
- Neglecting to inspect bearing races for damage such as pitting or brinelling before installing new balls or cartridges.
- Selecting a replacement bearing with incorrect dimensions or insufficient sealing for the intended riding conditions.
- Overtightening adjustable bearings, causing excessive preload that leads to rapid wear and increased rolling resistance.
Examiner Marking Points
- Award credit for accurately identifying bearing types (e.g., cup-and-cone, cartridge) from physical components or diagrams, with justification.
- Award credit for diagnosing common failure modes such as pitting, spalling, contamination, or excessive play through tactile and visual inspection.
- Award credit for selecting the correct replacement bearing by measuring internal/external diameters, width, and verifying load/ speed ratings where applicable.
- Award credit for demonstrating the correct procedure to fit and adjust a bearing system, including setting preload to eliminate play without binding.