BRAKES YOUR QUES­TIONS AN­SWERED

This month we ask Dan New­ton, boss of PB Brakes, your ques­tions about brakes.

Performance Vauxhall - - VAUX TECH - WorDS Midge

di­rec­tion as we found this doesn’t de­crease the strength as much with­out af­fect­ing the func­tion. Braided hoses com­prise of a Te­flon in­ner wall, with strands of stain­less steel braided on the out­side for in­creased dura­bil­ity. One ad­van­tage is that they ex­pand less than your OEM rub­ber hoses, which al­lows you a firmer brake pedal. A firmer brake pedal means more feed­back and ul­ti­mately bet­ter brak­ing. The other big ad­van­tage is safety – They’re al­most bul­let­proof! Use­ful if you have prob­lems with peo­ple sab­o­tag­ing your brake lines as you sleep. Gly­col-based brake fluid is hy­dro­scopic which means that it loves to ab­sorb mois­ture, which is al­ways go­ing to find a way into the brake sys­tem via mi­cro pores in the cap, lines and seals. This is a bad thing since it dra­mat­i­cally re­duces the boil­ing tem­per­a­ture of the brake fluid – 3 per­cent wa­ter in DOT4 fluid can re­duce the boil­ing point by up to 50 per­cent! That’s dan­ger­ous be­cause bub­bles are com­press­ible, which causes at best a spongy pedal feel, and in ex­treme cases it may go all the way to the floor with­out ac­tu­ally stop­ping the car! One word – Torque! When you in­crease the di­am­e­ter of the disc, the amount of brak­ing torque also ex­po­nen­tially in­creases. So in the­ory the big­ger the disc, the faster you’ll stop. How­ever, there is a limit to how big you can go. You’re lim­ited by how much grip your tyres al­low, once your discs are over a cer­tain size you’ll brake so hard that the ABS will ini­ti­ate in or­der to pre­vent the tyres from los­ing trac­tion, and what­ever gains you made are out the win­dow. Brake pads can also be a lim­it­ing fac­tor as your bog-stan­dard street com­pound will just melt if sub­jected to more torque than it can han­dle. You also need to con­sider that brake discs are fairly heavy items, and in­creas­ing the weight that each wheel needs to ro­tate is go­ing to have an ef­fect on your ac­cel­er­a­tion. This max­i­mum rec­om­mend size of discs de­pends on the car, but gen­er­ally speak­ing, heav­ier cars re­quire larger discs for ef­fec­tive brak­ing, and lighter cars can get away with run­ning smaller discs. It all comes down to cost re­ally. Your bog-stan­dard OEM discs are usu­ally cast in one solid piece as this is most cost ef­fec­tive way to man­u­fac­ture them. One-piece discs are fine for nor­mal use and the odd spir­ited drive, but push them too hard or take them on the track and they will fade within a cou­ple of laps at race speed. When you’re fly­ing down the straight at 130mph and you hit the brake pedal, the last thing you want is for it to sink right down to the floor be­cause of fade. One so­lu­tion is to up­grade to a set of two-piece discs with bil­let alu­minium cen­tre caps. The con­tact area be­tween the ac­tual disc and cen­tre cap is min­i­mal, which greatly

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