Drive Channel on YouTube have done a video comparing the original/stock brakes on a BMW F30. (I have embedded it at the bottom)
They measured the stopping distance of the car from 50mph and compared the difference to different performance brake parts.
They tried the following:
1. stock setup, stock brake pads, stock brake discs,
2. the stock brake discs with performance brake pads,
3. performance brake pads with performance brake discs and finally a
4. big brake kit.
Now dont get me wrong, I am all about testing performance car parts but only when the test is meaningful.
And testing different brake parts on a car stopping from 50mph is meaning-less.
The stock brake pads and stock brake discs are more than capable of triggering the ABS from 50mph, which means the limit on stopping distance is the tires and not the brakes.
Stopping from 50mph is traction limited, not brake component limited.
You can watch the video to see the results but suffice to say, if the test car was in good condition at the start of the test, all other things being equal, the car should have stopped in exactly the same distance for all of the tests.
Again, stopping from 50mph to zero is traction limited. It is not brake pad limited, or brake disc limited. The tires are dictating how far the car travels when braking from 50mph.
Having said all that, I am not saying that the parts Drive Channel tested would not make the car perform better, they will, but only under more extreme circumstances.
Let me put it another way. If I was driving an F30 BMW 328i and the car was not able to trigger the ABS all the way from 50mph to zero, I would be taking the car back to BMW so they could fix it. The car would be unsafe to drive.
So how did Drive Channel come up with such massively better numbers for the performance brake pads over the standard brake pads?
I do not know for sure but I can guess.
1. The cars braking system was desperately in need of a service for the first test. I imagine the brake fluid was well past its best.
2. Driver Channel were not comparing like with like. As well as the brake fluid being old I would also say the temperature of the brakes at the start of the two tests (stock brake pads vs performance brake pads) was vastly different.
3. They changed the brake fluid when they changed to performance brake pads.
What Drive should have done.
1. Definitely, 100%, higher speeds for the tests. BMW is famous for having below par brakes, but even a 50mph test is not going to fade them.
2. The start line should have been two of three corners earlier and the braking measured in the same place. Some people are going to say that puts too many variables into the test, the driver might go through the corners at different speeds or braked in different places.
But they would be wrong.
A decent driver can consistently lap a 90 second track within two or three tenths of a second. Two extra corners in the test is not going to make more than a tenth or two of a second difference. What we are trying to do here is simply put more temperature into the brakes at the start of the braking event.
3. They should have strapped a performance meter on the car. For not much money you can build graphs showing how the braking G varied as the car slowed down. It would have given a much better idea of where in the braking zone the difference was being made and also how much difference was between products and runs. It goes without saying this same software can spit out the stopping distance at the same time. No need to resort to a tape measure……
If there is one thing the casual observer can take away from Drives brake test video it is this. Fresh brake fluid is essential if you want your brakes to perform the way they were intended to. So many times we see people changing their brake pads without changing the brake fluid. This is a huge mistake and possibly even dangerous. The average driver will probably not even realise their brake fluid needs changing until it is to late. ie the brake pedal has gone to the floor and still the car is not able to trigger its ABS.
Again. The test was a nice idea but it was fatally flawed. It smacks of some non drivers putting together a test that would be understandable to the lowest common denominator ie Jane Public who has not interest in cars and would never watch this video, let alone but a set of performance brake pads. What Drive should have done is catered to their audience and put something in the test to mentally chew over.
However, one good thing the test did show in the best possible way, is the danger of driving a car whose brake system is in need of a service.
Here is the video