Rim brakes Bicycle brake

1 rim brakes

1.1 advantages , disadvantages
1.2 brake pads
1.3 self-assisting characteristics

rim brakes

rim brakes called because braking force applied friction pads rim of rotating wheel, slowing , bicycle. brake pads can made of leather, rubber or cork , mounted in metal shoes . rim brakes typically actuated lever mounted on handlebar.

advantages , disadvantages

aluminium rim worn-out v-brakes. outer wall worn through , wheel dangerously weakened. disadvantage of rim brakes.

rim brakes inexpensive, light, mechanically simple, easy maintain, , powerful. however, perform relatively poorly when rims wet, , brake unevenly if rims warped. because rims can carry debris ground brake pads, rim brakes more prone clogging mud or snow disc brakes (where braking surfaces higher ground), particularly when riding on unpaved surfaces. low price , ease of maintenance of rim brakes makes them popular in low- mid-price commuter bikes, disadvantages alleviated unchallenging conditions. light weight of rim brakes makes them desirable in road racing bicycles.

rim brakes require regular maintenance. brake pads wear down , have replaced. , before wear out completely, position may need adjusted wear. because motion of brakes not horizontal, pads may lose centering wear, causing pads wear unevenly. on longer time , use, rims become worn. rims should checked wear periodically can fail catastrophically if braking surface becomes worn. wear accelerated wet , muddy conditions. rim brakes require rims straight (not out-of-round or warped). if rim has pronounced wobble, braking force may intermittent or uneven, , pads may rub rims when brake not applied.

during braking, friction surfaces (brake pads , rims) experience thermal heating. in normal use not problem, brakes applied limited force , short time, heat dissipates surrounding air. however, on heavily laden bike on long descent, heat energy may added more can dissipate causing heat build-up, may damage components , cause brake failure.

a ceramic coating rims available may reduce wear , can improve both wet , dry braking. may reduce heat transfer inside of rims because thermal insulator.

brake pads

brake pads available numerous shapes , materials. many consist of replaceable rubber pad held on mounting, or brake shoe, post or bolt on attach brake. made 1 piece attachment directly molded in pad lower production costs; brake pads of cartridge type held in place metal split pin or threaded grub screw , can replaced without moving brake shoe alignment rim. rubber can softer more braking force less lever effort, or harder longer life. many pad designs have rectangular shape; others longer , curved match radius of rim. larger pads not provide more braking force, wear more (in relation thickness), can thinner. in general, brake can fitted variety of pads, long mounting compatible. carbon fiber rims may more sensitive damage incorrectly-matched brake pads, , must use non-abrasive cork pads.

ceramic-coated rims should used special pads because of heat build-up @ pad-rim interface; standard pads can leave glaze on ceramic braking surface, reducing inherent roughness , leading severe drop in wet-weather braking performance.

self-assisting characteristics

if front brake mounted behind fork so-called self-assisting effect occurs. friction force between brake shoe , rim creates bending moment presses shoe stronger on rim leading amplified brake force. self-assist reduces input force needed apply brake. disadvantage might brake fade - non-linear relation between actuation force , brake force.