Over the past few months, we’ve been
vigorously riding a Whyte 29 C test bike for review in our latest issue
of Enduro Magazine. Whilst the lightweight carbon 29er hardtail is
incredibly quick and has impressed us with its sure-footed stability,
throughout the testing period it hasn’t quite been all apples and roses.
The 29 C is the base model of the 3-tier lineup, and as such features
the basic Elixir 3 hydraulic disc brakes that sit near the lower end of
the Avid range. Despite their no-frills appearance however, these are
actually a great performing brake when setup properly, with heaps of
power and a level of modulation that avoids the ‘bitey’ sensation that
some other brakes can be guilty of.
Although we have plenty of experience with the Elixir range, on our
Whyte test bike the brakes began to develop quite a bit of audible
vibration from both wheels after the first few rides. Despite the
squeaky noises going on, the brakes still performed well enough, but
there was also an ever-so-slight pulsing sensation through the levers
that was pretty dam annoying. The issue we experienced with the brakes
on the Whyte was almost exactly the same that we had with the
Formula R1 brakes
we tested in the previous issue. Although we had some idea of what was
going on, we decided to speak to a handful of different bike shop
mechanics and riders to hear their thoughts on the issue and whether
they had experienced anything similar on their own bikes. On top of
that, we got in touch with both SRAM and Formula to hear their thoughts
on brake noise, what causes it and how best to fix it.
It has to be said firstly that there are quite a few factors that can
cause a noisy disc brake, and that one persons ‘sure-fire fix’ will not
necessarily address the issue that your brakes are experiencing. Here
are some examples of what might be going on:
Contamination: Commonly caused by a wayward squirt
of chain lube or an accidental grab of the rotor with greasy hands,
contamination of your brakes will result in noise of varying levels and
deterioration of overall braking power. In most cases, once the pads and
rotors are contaminated, you’ll likely have to throw them into the bin
and start afresh. A clear indication of contamination is if your front
and rear brakes are providing different levels of stopping force (i.e.
the one with less force is contaminated). However, it is possible for
both to be contaminated at the one time.
Glazed Pads: Caused by excessive heat from sustained
downhill braking, glazing involves your brake pads heating up to a
point where the surface becomes shiny and smooth. This smoothness can
cause a high-pitch whining noise, a lack of overall power and can also
affect the rotor surface too, which will show discolouration like the
pads. This is symptomatic of a setup that is under-gunned for your
weight and/or riding style.
Poor Bed-In: If your new brakes are not correctly
‘bedded-in’ from the start, they can cause noise, poor power and a
‘shuddering’ sensation at the levers. Bedding-in brakes involves
applying a consistent layer of pad material to the rotor surface. It is
the interaction between this layer and the brake pads themselves that
provides you with the friction that slows you down.
Improper Application: Having experienced our fair
share of bike shop time during previous lives, we have found this issue
is a particularly common complaint amongst riders who are using their
MTB for commuting or for lighter duties on bike paths and rail trails.
Disc brakes are designed to operate in some pretty full-on conditions,
and their principle design is to work on friction. Sometimes that
friction results in noise and there’s not a lot you can do about it.
However, the lighter you are, and/or the more ‘gentile’ your riding is,
the less you will be working your disc brakes to their full potential
and the more chance there is for noise to occur.
After some discussion with Dylan Coulson at SRAM’s technical service
centre, DSD, it appeared that our brakes were experiencing the 3rd
issue, caused by improper bed-in. The vibration and shuddering we were
experiencing was due to an inconsistent braking surface on the rotor,
caused by dragging of the brakes during their first few outings. These
microscopic ‘ripples’ along the brake rotor are magnified during hard
braking, resulting in a bloody awful noise and vibration at the levers.

The steps that we will take you through today are part of a process
that essentially ‘resets’ the rotor and pad surface so that you can
begin bedding-in the pads as if the brakes were new again. What needs to
be said here is that depending on how badly the brakes have been
bedded-in in the first place, you may actually have to replace both the
rotors and pads, which is what both Avid and Formula recommend. We would
also recommend this if you’re guilty of a short temper or are not
renowned for amazing mechanical abilities amongst your mates. Of course,
if your brakes are contaminated, this process has limited effectiveness
depending on how bad the contamination is. Unless you are 100% sure on
the issue you’re experiencing, this may be the point where your local
qualified bicycle mechanic will be better equipped to fix the issue and
get you back out on the trails. We shouldn’t need to note how important
brakes are whilst riding off road, but if you’re not sure – hand your
steed over to the experts!
In order to carry out this procedure, you’ll need some
bicycle/automotive disc brake cleaner, some clean lint-free rags,
gloves, Wet ‘n’ Dry sandpaper, and the necessary Torx/Hex keys to remove
your rotors and pads. A clean work surface is essential, along with
ventilation.
Step 1. Remove the Disc Rotors from the wheels.
Step 2. Remove the brake pads.
Step 3. Clean both brake rotors by blasting with disc brake cleaner
Step 4. Using a small wooden block, wrap around the sandpaper so that
you have a flat surface to work with.
Step 5. Begin rubbing the brake track of the rotor with the
sandpaper, making
a circular pattern and applying a medium-firm
pressure. You should be able
to see a visible change in the surface
(below). After sanding, give the rotor
surface a blast with disc brake
cleaner to ensure all contaminants are removed.
Note the difference in the rotor surface on the left (after) and the right (before).
Step 6. Now to clean the pads. Blast the brake pads with disc brake
cleaner,
then rub the pad surface along a clean rag to remove any
contaminants off the surface.
Step 7. Using a clean piece of sandpaper, rub each pad in a circular
motion
in order to remove any microscopic patterns on the surface. After
this step,
give each pad another blast with disc brake cleaner, wipe
along a clean rag
and allow to dry.
Step 8. Mount the rotors back onto the hubs and fit the pads back
into the brake callipers. Ensure all hardware and mounting bolts are
torqued and tight.
Step 9. Bedding In.
Depending on the brake manufacturer, this process can vary from brand to
brand. If you speak to mechanics, there will likely be a range of
techniques to accomplish this task properly, but the fundamental thing
to remember is that you want to apply an even and smooth layer of brake
pad material to the rotor surface. Here is a fairly standard
step-by-step procedure that you can carry out with your freshly reset
brake rotors/pads. This process is also the same if you have brand new
brakes.
- Find yourself a long stretch of road, and better yet a nice long downhill road.
- Ride up to a moderate speed of around 20km/h
- Apply both brakes firmly till you are at a walking pace, but DO NOT COME TO A STOP
- Continue riding up to speed and repeat steps (2) and (3) approximately 20 times
- Continue riding, but this time at a quicker pace of around 30km/h
- Apply both brakes firmly till you are at a walking pace, but DO NOT COME TO A STOP
- Continue riding up to speed and repeat steps (5) and (6) approximately 10 times
This procedure should allow for the brakes to heat up sufficiently to
ensure that pad material is evenly displaced onto the rotor surface.
During the process, you should feel a notable increase in braking power
by the end. In addition to the above, here are some further tips:
- Do not overcook the brakes in the bed-in process (by going too fast), otherwise you’ll simply glaze the pads.
- Do not ‘drag’ the brakes or be overly gentle about it, as that is
another way to develop an overly smooth pad surface that will create
noise.
- Avoid trying to bed-in brakes on your very first ride off-road.
- If the noise or vibration begins to return during the bed-in process,
then unfortunately your brake rotors & pads will likely need
replacing, though you can attempt the entire rotor/pad reset process
again if you have the patience.
For the most part, we’ve found the above process to be very
effective. You should note that if you bed-in brakes properly from day
one, you should have quiet, smooth and strong braking with minimal
issues. Reseting the pad/rotor surface should only be necessary if you
haven’t managed the bed-in process correctly.
For the full details on the process that SRAM recommends, check it out here:
Avid Brake Bed-in Theory-3. And for Formula brakes, head on to their website
here.