Brake Wear
Have you ever wondered where all the brake dust gathered on your wheel rims goes?
The answer could well be your lungs.
Brakes reduce vehicle speeds by using friction to convert kinetic energy to thermal energy. This process involves abrasion of the brake lining and rotors or pad and discs, which produces debris and particles. Brake wear contributions are generally predominant at road junctions, motorway exits and other locations where braking regularly occurs. During its lifetime, 80% of the brake’s friction material will wear off (Garg et al., 2000). Westerlund (2001) estimated that the total wear of brake linings used in passenger cars, goods vehicles and buses as 45,000, 7600 and 3330 kg per year respectively. Research carried out inside a motorway tunnel in Hatfield, Hertfordshire, UK has estimated that brake wear contributes 11% to the total particle concentrations (For more information see Research).
Brake wear emissions are also a heath concern due to the types of emissions they release. Although brake material is no longer made of asbestos, modern brake materials contain heavy metals and carcinogenic compounds such as antimony. Compounds and materials found in brakes include: lead sulphide, phenol formaldehyde resins, polycyclic aromatic hydrocarbons, aluminium, calcium carbonate, barium and antimony sulphate, kaolinite clays, graphite, silica, magnesium and chromium oxides, zirconium, Ziron, Molyddenite, carbon black, cashew dust, rubber, glass, Kevlar, ceramic, potassium titanate fibres, chromite as well as other metal powders (Garg et al., 2000; Kennedy and Gadd, 2003; Sanders et al., 2003; Chen and Stachowiak, 2004; Weiss et al., 2006). Brake wear particles also pollute soil and watercourses situated close to roads.
Brake wear emissions are affected by a number of factors, selections of which are given below:
- Late braking and braking hard increases emissions due to increased force on the brake pad or disk.
- Maintenance- leaks and misalignments are not only dangerous but increase wear of the brake material.
- Vehicle loads-heavy loads increase the wear rates due to a greater force being exerted onto the brake material.
Find out how you could reduce your non-exhaust emissions