Bike brakes.
They give riders control, confidence, and safety.
But guess what else they are?
The most confusing part of the bicycle...
which in itself is confusing, because they're so important.
For many of us,
the mystery begins with our first bike experience,
trying to stop by dragging our feet on the ground.
Then, we're using our feet by pedaling backwards.
Then, we're using our hands,
left for the front brake, right for the rear.
I don't think so. If you're in England,
it's left hand for the back brake.
Now, look at all of these variables.
There's brake type,
riding conditions, rider weight,
hand size, hand strength,
finger length, riding style,
rotor temperature, air temperature,
pad wear, pad compound,
fluid temperature, pad temperature...
I can't keep up.
It's confusing and overwhelming.
With so many variables,
many riders don't know whether they have the right brakes,
or even where to begin...
but that's why we're here,
to start the demystification process,
with a little help from the science.
It is extremely true
that the brakes are such a huge part of the bike,
and it is such a starting point,
and it doesn't matter, you know, what category it is.
We design a bike for an intended rider.
It has an intended purpose.
It has somebody that you're after,
but you don't know if that's actually how they're riding.
It's like, "What kind of terrain are you riding?
How long are you gonna ride there?
Are you going to go ride in the mud in the winter?"
Whether or not they have their levers inboard
20 millimeters, 25 millimeters...
Okay, he knows what he's talking about,
but he's getting into brake setup,
and while setup is crucial, that's episode two.
This is about understanding the right brake system
with the right specs
for where you ride and how you ride.
But first there's a few main factors
that influence any brake's performance,
no matter its features...
Oh yeah, and for the record,
we're just talking about hydraulic disc brakes here.
Sure, there are still other brake types out there,
such as mechanical discs and rim brakes,
but they're increasingly rare.
Hydraulic disc brakes are the undisputed champion.
To understand the basics of the hydraulic system,
when a rider pulls the brake lever,
it pushes brake fluid through the line
to a number of pistons in the caliper.
That pushes the pads against the rotor.
That's right.
High tech.
So, in selecting a brake for your bike,
depending on the kind of riding you're going to do,
you might think about how fast you ride,
how steep the terrain is that you ride,
things like how aggressively you ride,
and how frequently you want to maintain your bike.
Truthfully answering these questions
will help you determine your optimal setup.
Mountain bikers debate pretty much everything,
and the fluid that goes in their brakes
is one of those debates.
Yeah, so in pretty much every brake on the planet,
you'll find DOT fluid,
but then also in bicycle disc brakes,
you'll find mineral oil in some of them.
Beyond simple tests,
like comparing the boiling points of each fluid,
which are almost identical,
it's been impossible to compare,
because no one's done it scientifically,
but recently, one brand
wanted to definitively know the differences,
and engineered two versions of exactly the same brake system
to run on mineral oil or DOT fluid.
They removed from the equation
the variables of caliper and lever design,
allowing them to compare fluid types
on a level playing field for the first time,
apples to apples,
and this is what they found.
With mineral oil,
you can basically leave it for long periods of time
with little or no maintenance,
and it's not really going to change.
As the saying goes, and the science shows,
oil and water just don't mix.
The lower maintenance of a mineral oil brake
is optimal for people
who don't ride in a competitive context,
or whose bike goes long periods of time
without getting ridden.
With DOT fluid, you're getting the broadest band performance
across a range of temperature,
so if you charge hard and do a lot of steep riding,
and you're looking to go as fast as possible,
then DOT is going to be your choice.
DOT fluid brakes require higher maintenance
because the fluid absorbs water over time,
so in order to restore the performance to its peak,
you're going to have to periodically change the fluid.
When we set out to make a mineral oil brake,
instead of only just changing the fluid,
we also had to change all of the seals
throughout the brake,
and through a lot of extensive testing,
discovered that the seals used in a mineral oil brake
are not quite as high-performing
as the seals that we can use in a DOT brake,
especially in very cold and very high temperatures.
When you pull the brakes,
your caliper pistons are displaced out
and make contact with the rotor,
and when you let go, those rubber seals
that seal the pistons in the caliper
are what pull the pistons back to their home position,
so that rubber is basically acting as a spring.
Rubber is a viscoelastic material,
so the speed at which it moves
is going to change with temperature.
The rubber compounds that are compatible with DOT fluid
offer better performance
because they have a broader temperature operating window
relative to mineral oil compatible rubbers.
For those of us who don't understand
the material properties of mineral oil brake seals,
we caught up with pro athlete Yoann Barelli
for a different perspective.
Ooh, yeah.
Ahh.
Well, what's often missed
when talking about brakes and temperature,
it's the seal material and its ability to manage heat.
Take the drain plug seal in my bath, for example.
If it was made of the oil-proof seal material
required in mineral oil brakes,
and there was a heat source near it
capable of reaching temperatures of 500 degrees,
just like rotors and pads can hit,
it could cause the bath plug to lose its squeeze,
start to melt, and ultimately leak,
and that's definitely not good.
Wait, are you saying that the difference
in which brake fluid performs best
comes down to the seal material required?
Yeah. That's the science.
And speaking of science,
mineral oil sounds like something you'd take a bath in,
but it's not safe to touch your skin,
or safe for the fish on the other side of this drain.
It's a chemical,
and it needs to be treated like one,
just like DOT fluid.
That is some interesting science.
Lots of riders believe
the inconsistent bite point at the lever
is a result of reaching a brake fluid's boiling point.
With mineral oil brakes, it all comes down
to the performance of the seal rubber.
Demystifying brakes also requires consideration
of piston count at the caliper.
Larger-diameter pistons have more surface area
to press the pad against the rotor.
A bigger pad means more of the pad material
is responsible for creating all of that good friction.
To explore this further,
we got in touch with the folks at Enduro MTB,
who run the Garda test,
a lab test designed to push brakes
to the brink of performance.
When we do testing in a laboratory,
for, let's say, a brake group test,
of course, we have certain protocols
with expertise from us,
but we always reach out to different brands,
different brake engineers
to have the lab data ready
when we are testing on the field,
but the important thing is that those test riders,
they don't have the data,
but once we discuss the products,
we have the data available, and can validate certain things,
or the amount of pistons, the pad material,
the rotor size,
they definitely can be a really good indicator
on the character of the brake.
Rotors directly impact the amount of friction
a brake caliper is able to create
between the pads and the rotor.
The more friction, the more stopping power,
and a larger rotor both adds mechanical advantage
because of a larger brake surface area
and the ability to keep brakes running
at their right temperature.
Rotor size is another one that we go 'round and 'round on,
and the how to pair it to that intent on the bike.
I mean, take the SB130,
we spec 180s on that because we feel like
that's a good all-around, all-mountain bike,
but then we kinda expand it to the SB130 Lunch Ride kit,
where we are spec'ing bigger tires, bigger rotors,
bigger brakes, even,
and that bike is meant to be pushed even harder
compared to the standard SB130 spec.
If you look at the difference between a 180 rotor to a 200,
it's about a 14% difference in stopping power.
Imagine 14% less arm pump,
or being able to stop in 14% shorter distance.
That could mean making the turn...
or not.
While we can generally say
that bigger rotors bring more control,
that's actually not always the case.
[Patterson] So a rider is running large rotors
but isn't braking hard enough, often enough, or long enough,
or maybe isn't heavy enough
to create enough friction
to build up the right amount of heat
in the pad/rotor interface.
Well, that's the key.
As the temperature of a brake pad increases,
so does the amount of friction it can produce.
That means a rotor that's running too cool
isn't going to heat up the brake pad
enough to reach its full power.
In this case, a smaller rotor can actually be more powerful.
There's a point where the temperature gets too hot
and decreases the pad's ability to create friction.
In this case, a bigger rotor can help.
Either way, though, the right-size rotor is critical.
People always talk about power
because it's a fascinating thing,
but as important as the power is its control.
The most natural thing for a brake
is to produce heat.
Why? Because friction causes heat.
That's a good thing.
Yeah, for sure. Heat's definitely not the enemy.
You need heat.
If you don't have heat, it's not going to work.
How do you know?
Well, it turns out
that paying attention to the color of your rotors
can help you know a lot.
If you have brown markings on the spokes of your brake,
that generally means
that the brake is dissipating heat down the spoke
like it's intended to do.
If you have a purple or a rainbow kinda tinge
down the spokes or on the braking track,
generally that means that your brake is getting too hot,
so in that instance, you could, you know,
try changing pad compounds,
you could try going up in rotor size,
or sometimes they do cook,
and that's part of maintaining a mountain bike, basically.
Whatever it takes to take the mystery out of brakes
is worth it,
because they're too important
for us to continue relying solely on hearsay,
opinion, and guesswork.
Better brakes make better riders.
No question.
[Evie Richards] I literally couldn't race as fast as I do,
or have as much fun as I do,
unless my brakes were set up perfectly.
My mechanic, he gets sick of me.
Look at him.
-That's a good point, actually. -That is a good point.