Nitron have designed and developed a series of disc and bell designs for the Lotus owner who requires the ultimate braking set-up.
Discs essentially take the kinetic energy of the vehicle and utilising friction turn this into heat energy stored inside the disc. This energy then needs to be dissipated sufficiently before the next amount of kinetic energy needs to be absorbed. Ventilating the disc internally with vanes helps, these vanes are often curved to assist with airflow from the inside of the spinning disc through to the outside edge. The greater the airflow, the faster the disc will cool. The heating and cooling process is called the thermal cycle, and it is important to have a disc of sufficient mass (weight) to be able to absorb all the heat required and cool down again within the capacity of the disc. If the disc is too light, the disc will get too hot, then cool down again, then get too hot again, and so on until the disc cracks because the thermal cycle exceeded the capacity of the disc. A heavier disc will absorb the same amount of energy and not get so hot, thereby reducing the thermal cycle, and the disc will last. All too often light discs are mistakenly chosen, and they will fail prematurely, usually warping before cracking. Discs are oddly one area of un-sprung mass that does need to have weight to some degree.
However, the part of the disc that needs to have mass is the part that comes into contact with the pads, rather than the central mounting bell part of the disc. This is why the bell part of the disc is often aluminium (which is not only light but dissipates heat extremely well). The problem with aluminium is that when heated, it expands at a greater rate than steel. When the bell is rigidly bolted to the disc, the differential rate of expansion can cause issues like warping and cracking. Allowing the two metals to slide against each other alleviates this. This is why serious racing discs allow the disc to float on the driving bell. This type of disc location also allows the disc to self centre, which will reduce pad knock-off (where the pads are pushed away from the disc by the disc not running true).
Nitron offer several fully floating disc and bell combinations utilising the best materials available. Our disc kits utilise a bobbin drive system, where a series of Titanium bobbins are bolted to the disc and then the aluminium bell has a number of slots machined into it where the bobbins slide as the bell expands. The bells are machined from 7075-T6 aluminium and then hard anodised to provide a super stiff bell with a very hard and durable coating. The bells are then laser etched with their details. The following sizes are available:
• 304mm OD x 25.4mm thick 12 bobbin drive
• 295mm OD x 25.4mm thick 12 bobbin drive
• 290mm OD x 25.4mm thick 8 bobbin drive
Note: the 290mm disc can be used with the standard hand-brake caliper on the rear. All discs can be used as front or rear discs on cars with 4 bolts on a 100mm PCD, i.e. Elise S2 onwards.