Brakes are the most important upgrade if you want to track a roadcar, but Hyundai’s done the job for you on the i30N.

YOU MIGHT THINK that increasing power is the first thing you’d do if you want to take your sportscar to the track, but that’s just not the case. Your first investment should be driver training, and then after that, your first car modification should be the brakes…unless you own an i30N.
The weakness with standard brakes is not stopping power. Even from high speed, the average sportscar can generate enough braking power such that the tyre traction is the limit of braking, not the power of the brakes – unless you run very grippy track tyres. For most sportscars, the actual problem with the standard brakes is heat dissipation.
At any given speed a car has kinetic energy, and at a lower speed it has less energy, so the act of deceleration means the car must convert some kinetic energy into another form of energy. For cars, the brakes convert kinetic energy into heat energy. But the braking system cannot take unlimited amounts of heat, so it needs to constantly get rid of the heat in the same way a car’s engine needs to get rid of the heat it generates, and humans sweat to get rid of their heat.
Aside from upgrading the actual stopping power of the i30N with calipers which more strongly grip the pads to the rotors compared to a standard i30, Hyundai also have a range of measures to improve heat dissipation:
  • Thicker and high-temperate brake pads – the thicker the pad, the longer it lasts and the better able it is to soak up heat. A special compound is used (a “track/street” compound) so the pad can tolerate higher temperatures than standard – the usual tradeoff for that is cost, brake dust and noise although I didn’t notice any such issues on my i30 Fastback N test;
  • Cooling air to front wheelarches – a duct which pipes fresh, cool air from the front of the car directly into the innards of the wheel well which is where the heat builds up from the brakes, tyres and engine;
  • Hot air removal system – fast moving air routed past the front wheel which draws out heated air from the wheelarch.
Here’s a video explaining them all in more detail, including just how much more energy is used on track than road:

These are exactly the upgrades which we’d recommend for a typical sportscar owner wanting to do trackdays, so it’s good to see Hyundai ahead of the game. This is why we say the i30N is a true motorsports car, not just a sportscar. And our track test proved that, unusually for a stock vehicle, the brakes don’t fade after track use. About the only other change we’d recommend is use of high-performance brake fluid with a higher boiling point than standard, which is sold as either DOT 4 high-temp, or DOT 5.1.
So in practice, Hyundai’s efforts have paid off. We track-tested the i30 Fastback N at Phillip Island, and the brakes were fine even after numerous hotlaps two-up. We then drove to Canberra and double-entered the car at the N Festival where it did a lot of lapping, again mostly two-up, then drove home to Melbourne. Despite all that use the stock brakes were fine, and the only other stock cars I can think of that would handle that sort of work would be specialised sportscars such as Lotuses and Porsches which are hardly in the same class as the much cheaper Hyundai derived from a standard hatch.
If you do overheat your brakes then one of two things will happen. Either the brake pedal will go soft or hard, neither of which is desirable when you’re topping out in third gear approaching a 180-degree hairpin.  If the brake fluid overheats, it will boil and bubble, so air will get in the fluid. Brake fluid is not compressible, so there’s a direct link between your foot pressing the pedal and the calipers clamping the pads to the rotors. Air is compressible, so when air gets in the fluid your foot pressing the brake pedal just compresses the air, and doesn’t do much for clamping the pads to the rotors.
It is also possible for the brake pads to overheat and disintegrate, or glaze over. This means that the friction between the pad and the rotor is decreased, so while the pads may be clamped hard against the rotor, there’s so little friction there’s not much braking. 
Failing brakes is extremely dangerous, so let’s hope more carmarkers follow Hyundai’s lead, and deliver sportscars that can turn more than a few laps before retiring with overheated brakes!

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