Grooved brake discs, the truth is you probably do not need them
On cost/benefit ratio grooved brake discs probably offer the lowest bang for buck of any car modification. The truth is a good quality set of direct replacement brake discs will give you 95% of the stopping power available in your braking system.
If you are chasing tenths of a second then sure, you need grooved brake discs but for everyone else the money is better off spent elsewhere.
A set of grooved brake discs are is the range of 3 times more expensive than a set of plain replacement brake discs and not to forget than grooved brake discs are a service item which means you’re not going to be buying just one set.
The money is better off being spent on a set of camshafts, a better exhaust, better air filter, piggyback engine management, driving course, track day, better tyres etc etc. It is a long list because grooved brake discs are a very expensive disposable service item.
Basically, on the list of priorities of things that make a car go faster, grooved brake discs are pretty far down the list.
If I have not talked you out of buying a set of grooved brake discs by now…
What do Grooved Brake discs actually do?
When your brake discs and brake pads are hot, the brake pads will release a small amount of gas, this gas can form a layer between the brake disc and the brake pad massively reducing the friction between the two surfaces. This is brake fade.
Grooved brake discs reduce brake fade by giving this gas somewhere to go. Instead of the gas being trapped between the brake pad and the brake disc the gas is forced into the grooves leaving a cleaner surface between the brake disc and the brake pad maintaining the friction between the two surfaces.
The shape that these grooves is not written in stone which is why you can see so many designs but they all do the same job.
As the grooves pass under the surface of the brake pad the gas follows the path of least resistance and fills up the void that makes the groove.
As technology has moved forward there is less and less need for grooved brake discs on road cars
10 or 20 years ago brake pads would gas more than their modern day equivalents, which meant grooved brake discs had a bigger effect on overall braking power.
Modern brake pads gas considerably less and for this reason it is only at the ragged edge where grooves come into play. You are very rarely going to need the grooves on the road but as I said at the start, in a competitive environment every tenth counts which is why race cars always use grooved brake discs unless the rules specify discs of the same design as fitted to the car from the factory.
Save the money that you would have spent on a set of grooved brake discs for something that offers a bigger bang for buck and that means probably any performance part you can think off.