To answer this question in a single word, YES! They are better and hence there is a reason why they are used. They are a bit more premium compared to the other regular discs in terms of the cost, but then in the longer run when we see how they are actually better, you will understand the reason why. The reason for this is all in the physics of it. The transfer and conversion of energy is what is the cause of this. Now one can always argue that petal discs look cooler and they add an extra aesthetic value to the entire thing and yes, they are not completely wrong, but after all, when it comes to bikes and its safety mechanisms, it is really more about performance against looks. So now to answer the question, if petal discs are any better than regular discs; yes they are better and this is why.In disc brakes, the motorcycle is moving along and it has some energy that is rotating the wheels and the disc of the bike. Now when you want to stop the bike, you need to apply some outside force to it. Now for this when you pull the brake lever, the brake pads rub against the disc and the friction stops the discs which are connected to the wheels and hence the bike comes to a halt.
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Now all that energy that the bike has when in motion is all converted to heat energy at the discs. We have learnt in physics in school, “Energy can neither be created nor destroyed; it is only transformed from one type to another.” Similarly there is heat energy created and this causes the disc of the bike to heat up. Now if the disc heats up the lot, the metal it is made up of will not be able to handle all the stress put on it and hence for that reason the disc needs to cool soon. That means transfer of the heat energy to the atmosphere due to air cooling and that in turn means more amount of surface area required to get more amount of air in contact with the disc to rapidly cool it.
This is the same principle and technique used in air cooled engines where the engines are given fins on top to increase the overall surface area of the engines such that they can be quickly cooled up. The same way tea cools down a lot quicker in a saucer than in the cup. It is simple physics. So the only way to increase the surface area of discs is by somehow increasing contact patch and that is exactly why petals are given on the discs.You can notice that not all discs are given petals. Some discs are the usual round ones while only some get petals and there is a good reason for it. The reason petals are given is if the disc is expected to undergo heavy braking forces and has to dissipate a lot of heat a lot quickly or else if the disc is of a smaller size and the area is not enough to handle to heat dissipation rate.
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So to safely conclude, yes, petal discs are better than regular discs but only when there is a real need for it, else it is a complete waste to say the least. But if we do consider for a long term thing, then yes, even though the regular discs are enough for the bike, if you do happen to use petal discs on it, it will definitely last quite a lot more than the regular discs and will seldom give issues with braking even in extreme heat situations.
By: Pratik Patole