Brake shoe Drum brake

brake shoes typically made of 2 pieces of steel welded together. friction material either riveted lining table or attached adhesive. crescent-shaped piece called web , contains holes , slots in different shapes return springs, hold-down hardware, parking brake linkage , self-adjusting components. application force of wheel cylinder applied through web lining table , brake lining. edge of lining table has 3 “v -shaped notches or tabs on each side called nibs. nibs rest against support pads of backing plate shoes installed. each brake assembly has 2 shoes, primary , secondary. primary shoe located toward front of vehicle , has lining positioned differently secondary shoe. quite often, 2 shoes interchangeable, close inspection variation important.

brake shoe assembly

linings must resistant heat , wear , have high friction coefficient unaffected fluctuations in temperature , humidity. materials make brake shoe include, friction modifiers (which can include graphite , cashew nut shells), powdered metal such lead, zinc, brass, aluminium , other metals resist heat fade, binders, curing agents , fillers such rubber chips reduce brake noise.

in uk 2 common grades of brake shoe material used available. don 202 high friction material did not require brake power servo. disadvantage lining prone fading on steep hills (calculate kilowatts dissipated one-ton car descending 15% hill @ constant 60 mph) harder lining, famous vg95 produced required brake servo. other snag parking brake fail annual mot test unless high friction linings installed test.