Before I attack drilled brake discs I first want to say I am voicing my opinion and my experiences, your opinion and experiences may be different.
Drilled brake discs always form cracks around the holes. Sometime the holes are small and insignificant but they can also develop into something larger which can mean you have to replace your brake discs.
The best way to put a stress point in something is to drill a hole in it and brake discs are no different.
If you are fitting drilled brake discs on your race car then drilled brake discs may be fine, you are only go to use the brake discs for a single race until you dispose of them, if you want a longer lasting brake disc and you still want the benefits of being able to evacuate the brake pads gasses then grooved brake discs are the way to go. Modern race cars are using drilled brake discs more than ever.
You can still find drilled brake discs of performance cars, I have no idea why, I can only assume they are there for the looks and pandering to customers who think 80s technologies is still cutting edge.
If you want a long lasting brake disc that gives the benefits of a drilled brake disc, grooved brake discs are what you are looking for.
You can find a range of grooved brake discs on the Street & Circuit website. We have grooved brake discs from Stoptech & EBC.
How much of a difference do grooved brake discs make?
If you are looking for that extra couple of tenths of a lap, then the difference can be huge, especially over a long race.
On a road car, the difference is not so much.
For a grooved brake disc to start to work the gassing of the brake pad must be so much that it is reducing the coefficient of friction between the brake pad and the brake disc. For this to happen your brake pads must be of the highest quality ie even though the brakes are at extreme temperatures, it is not the brake pad that is reducing in performance but the surface interface between the brake disc and the brake pad.
In short, before you fit grooved brake discs, you brake pads need to be of high quality.
Sure you can fit grooved brake discs with normal brake pads but normal brake pads literally evaporate at extreme temperatures, grooved brake discs are only going to make wear even worse.
For grooved brake discs to work your brake fluid also needs to be of high quality. Grooved brake discs only work at extreme temperatures and for the brakes to work at extreme temperatures your brake fluid should not be boiling. If you are using normal DOT4 brake fluid it will boil under extreme conditions.
In other words, your car should be fitted with high quality performance brake pads and high quality and fresh (ie one year old maximum, especially if you are hard on your brakes) DOT5.1 brake fluid before you think about going to grooved brake discs.
Having said all that, grooved brake discs will give your brakes a little bit of extra bite in normal driving but you can get the same braking power by simply pushing the brake pedal harder.
You fit performance brake parts to your car because you are identifying weaknesses in the braking system and addressing them.
In 99% of case, the weak links in a braking system is as follows with the weakest link listed first.
1. Brake pads.
2. Brake fluid
3, Brake discs
4. Brake hoses (you can move this up a slot or two if you car is more than 10 years old)
It is pointless fitting performance brake discs if there is weaker point earlier in the chain.
Fitting grooved brake discs to a car with OE replacement brake pads is akin to fitting a bigger anchor to a ship because the anchor chain keeps breaking.
Street & Circuit is a dealer of Ferodo Racing performance brake pads, EBC performance brake pads and Roesch carbon fibre performance brake pads.
For a street car occasionally driven on track a set of Ferodo Racing brake pads in connection with a set of Brembo Group N brake discs and DOT5.1 brake fluid will extract 90% of the potential out of your car’s braking system.
If you are still looking for big gains after this then you are in the hunt for a big brake kit which will be a big step forward in power but it also comes with it’s own drawbacks.