Know Your

Know why brake discs are so im­por­tant.


Brake discs are one of the most im­por­tant parts in keep­ing you lot stop­ping safely, brak­ing later, and con­se­quently go­ing faster. With this in mind, we caught up with Adam from Brembo im­porters Bike Torque Racing to learn a bit more about the hum­ble brake disc...

FB: What is the pur­pose of a brake disc?

AJ: To stop you! It is the disc at­tached to the wheel, which works with the brak­ing sys­tem to give you stop­ping power. They took over from the good old fash­ioned drum brakes and there’s a wide range of discs of­fer­ing dif­fer­ent lev­els of per­for­mance.

FB: How does a brake disc work?

AJ: In lay­man’s terms, when you squeeze the brakes, it sends hy­draulic force down through the brake lines into the caliper, caus­ing the brake pads to squeeze to­gether. As the disc is con­nected to the wheel and turns with it, when the pads and disc come into con­tact, the fric­tion works to slow the disc, slow­ing the wheel.

FB: What are the ad­van­tages of af­ter­mar­ket discs?

AJ: Brembo make them 5mm thick, rather than 4.5mm like on most OE discs, which gives a bet­ter heat range. It also de­pends on the man­u­fac­ture, as most OE discs are rea­son­ably good, de­pen­dant on the qual­ity of the steel. You have to re­mem­ber though, no stan­dard disc will be as good as af­ter­mar­ket ones; af­ter all Brembo discs are de­signed as an up­grade. As an ex­am­ple, Brembo ma­te­ri­als are specif­i­cally cre­ated to a cer­tain for­mula for your re­quire­ments rather than be­ing the cheap­est stuff you can buy, with a high iron and car­bon con­tent. This makes the discs more grippy and the fric­tion more ef­fec­tive, which in­creases brak­ing power, while they are thicker to han­dle the heat a lot bet­ter, stay­ing within a big­ger op­er­a­tional range un­der high stress.

FB: And what’s a float­ing disc?

AJ: It ba­si­cally means that the disc is con­structed in two parts, with a fixed cen­tre sec­tion at­tached to the wheel and the outer ro­tor sec­tion that en­gages with the brake pads. Due to the fric­tion a brake disc en­coun­ters se­ri­ous amounts of heat, lead­ing the metal to ex­pand, and by al­low­ing the outer to float sep­a­rately from the mount, it can then ex­pand and shrink with­out con­straint, mean­ing the disc won’t be able to warp. For racing, us­ing float­ing and semi-float­ing discs will be hugely ben­e­fi­cial, and they will also help out if you’re an in­cred­i­bly fast road and track­day rider as well. Fun­nily enough, for the roads Brembo have a disc called the Serie Oro, which has spe­cial anti-vi­bra­tion wash­ers mean­ing you can use them on the road and track with the float­ing ten­den­cies, but you don’t get the noise of the rat­tle like on the top spec racing discs.

FB: How much dif­fer­ent are road- based discs to full- on race discs?

AJ: Re­al­is­ti­cally, with the race prod­uct it’s all about per­for­mance, whereas the road prod­ucts are built for qual­ity, per­for­mance and also prac­ti­cal­ity in mind. At the end of the day the discs are serv­ing a dif­fer­ent pur­pose, so on the Brembo HPK race discs the bob­bins are re­build­able and vi­brate a fair amount, while be­ing slightly thicker to dis­perse the heat even more. This com­pares to a quiet, thin­ner road-go­ing disc that is cheaper, cre­ates less noise but won’t han­dle the heat as well.

FB: Is it easy to tell the dif­fer­ence be­tween the discs if you were putting them back to back? AJ: Of course, it de­pends on the level of the rider and the per­for­mance of the bike, but yes

you should be able to tell the dif­fer­ence straight away. For starters the qual­ity of the steel will give a much greater fic­tion co-ef­fi­ciency and so im­prove the brak­ing power, while of­fer­ing bet­ter heat dis­per­sion for a wider op­er­at­ing win­dow. Es­sen­tially, if you were to put the Serie Oro discs on from stan­dard, you should be able to feel a bet­ter bite un­der heavy brak­ing and be able to use the brakes more in­tensely, ef­fec­tively for longer. This is even more ob­vi­ous if you use a larger disc con­ver­sion kit for a big­ger di­am­e­ter disc, which will of­fer much more brak­ing power thanks to it giv­ing big­ger lever­age.

FB: What’s the score with wavy discs?

AJ: Al­though they look nice, heav­ily-cut wave discs warp at a lower tem­per­a­ture than con­ven­tional discs due to the fact that there is less metal and less sur­face area for heat dis­si­pa­tion. There’s a slight off­set in well-de­signed wavy discs as they cre­ate more tur­bu­lence and air­flow to cool the discs, but Brembo spent a huge amount of money try­ing to de­velop a high-per­for­mance wavy disc when they came in to fash­ion. They aban­doned the whole pro­ject as they just couldn’t make them as ef­fec­tive, and as Brembo are a fiercely tech­ni­cal com­pany, they would not sell a prod­uct that’s in­fe­rior.

FB: What problems do you get with discs?

AJ: One of the main problems we hear about is hav­ing warped discs – al­though most of the time the disc isn’t ac­tu­ally warped.

There’s so much mis­in­for­ma­tion sur­round­ing brake is­sues and discs warp when the op­er­at­ing tem­per­a­ture rises, so much so that the ma­te­rial will dis­tort, and on the road it’s hard to do. A lot of the time it can be some­thing silly like peo­ple just leav­ing their bike over win­ter some­where moist, as if you have sin­tered pads and iron brake discs, the mois­ture can cause the pad and disc to cor­rode – cre­at­ing a pad-like mark on the disc that will cre­ate a jud­der un­der brak­ing. You also need to take into ac­count that brake discs are fairly frag­ile, so make sure they’re taken care off in tran­sit.

Easy on the an­chors, Mar­quez. Honda aren’t made of money.

Char­lie loves per­form­ing the ‘nutt cracker’.

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