Disc brakes are one of the most significant advances in mountain bike history. It only takes a spin around the block on a bike equipped with old-school cantilevers to be reminded of how lucky we are to have the stopping power and control that modern disc brakes offer. We asked Fabien Barel, Brake Authority's R&D manager (as well as two time Downhill World Champ), about how disc brake pads are made.
What are disc brake pads typically made of?Brake pads can be divided in two main categories: organic and metallic sintered. The materials which compose the compound are merged together during the manufacturing process thanks to a binder. This binder is in resin for the organic pads, or in metal for the metallic sintered pads. The sintered pads are lot more resistant to high temperature whereas the resin has a tendency to melt and burn which results in a drop in the braking performances at high speed. Plus, the sintered pads last longer.
How are they made? Can you explain what “sintered” means? STEP 1: Powder mixing
Sintered pads are manufactured using powders.
The friction product contains at least 10 different constituents (copper, bronze, iron, ceramic, graphite…).
Each of these constituents has a key role when the pad is in contact with the rotor (comfort, noise, performance).
STEP 2: COMPRESSION
Once mixed, the constituents become a friction mix which is then compressed using a tool that gives it its definitive shape.
STEP 3: HEATING AND SINTERING
Next, the result is placed on a metallic base and placed in a high temperature oven.
That’s the sintering process: one constituent of the mix melts and attaches the compound to the base..
STEP 4: FINISHING
The pad is finally rectified, checked and packed.
Sintering = technology that allows the transformation of metallic powders into metallic compounds.
Most riders are familiar with how hot rotors and calipers can get after a long downhill. What types of temperatures have you seen during testing? What is the effect of high temperatures on braking performance?We've seen temperatures of 125 °C recorded with the laser captor during the DH testing sessions.
Extreme heat during braking can cause what riders typically call 'fading.' This is the drop in braking performance that will cause a longer braking distance.
What is “bed in”? Why is this important? When they’re new, rotors and pads have a slightly rough surface, which decreases the braking performance. That’s why bed-in is always necessary to get the optimal performance from the brake system. The bed-in period allows any roughness to disappear in order to have pads and rotors perfectly flat. Therefore, the contact surface between the compound and the rotor is maximum and braking is more efficient.
What makes one pad better for XC while another one is better suited for DH? In our R&D lab, we put together different compounds for different uses. In fact, for each use we have a specific pad. It’s important to choose the right pads depending on your discipline. If you just ride along with your MTB, there's no need to get pads for DH racing for example, as they’re designed to be efficient at high speed - they'll still work at slower speeds, but that's not their intended purpose. That’s why we’ve developed the Ceramic, oriented towards DH racing, and the Burly, which is more suitable for leisure or “non professional” use.
I personally like to know what company I can trust to know what their talking about....
What is just said here is that for once this article brings knowledge to the reader, not ONLY advertisement. As an example, the sintering process is quite a technical stuff and was well explained, also there were no add in each answer as we are used to.
If you compare this article with the one about bushings you'll get the idea. At the end of barel's interview he is mentionning in one sentence what the brand he works for is making and who it is for. To my mind, it's enough and more effective thant someone repeating again and again he is better than others without really proving it.
1.poor setup
2.poor setup
3. poor setup
also? poor maintenance regime
cleaning bike with aggressive "muck-off" products contaminating disc rotors and disc brake pads, getting overspray from aerosol chain lube, suspension spray or bike polish onto rotors and pads. Leaking hose connectors or damaged hoses getting DOT or Mineral oil onto rotors and pads.
most disc brake systems when setup properly (caliper alignment over rotor, bedding in process) and maintained properly, will cause little problem, and very little noise or vibration (admittedly some bike frames have resonance issues with certain brake systems)
I have lost track of the number of mountain bikes and hybrids bikes with disc brakes coming in for service with terrible setup and filthy rotors / pads
complaining of "needing bleeding", "lack of power", "too much noise", when what it needs is initial proper setup, cleaning, bedding in process and regular maintenance (often nothing more than cleaning brakes after bike wash or heavy riding, with disc brake cleaner and then wiping off with lint-free rag, doing increasingly harder stops on road until noise abates)
Also it would be good to know which constituent metals do what.
too true. Hmm vegetable extract... tasty tasty vegetable extract. I often enjoy some delicious vegetable extract soda.
After that you are looking at contamination.
Fabien is right with bedding in to a small degree but bedding in is about starting with clean, non contaminated rotors and moving some pad material onto the rotor.
This is why you usually use clean water to don it, it helps prevent contaminants getting onto the rotor.
Rotors are not flat as flat polished surfaces have never been known for making good friction contact areas.
A little like a car (well a lot actually) brake rotors are not waterproof, if you have a contaminated rotor with brake fluid (which is corrosive) then you have to change the rotor also to stop the squealing and increase brake performance.
Another cause could be that when you fitted you rotor you did not clean the mating surface between the rotor and the hub, or this surface is damaged/not even. You can get anti vibration plates that fit over 2 rotor bolts at a time, never know if they work or not though.
To properly bed them in when new, do a bunch of hard stops when they are new, but don't stop all the way. Sram says do 15, wait for rotor to cool down, then do some more.
Buy feeler gauges, the ones that look like swiss army knife. Loosen Caliperbolts. Stick feeler gauges on both sides of disc and calipers. Pull brake. Tighten bolts. Your brakepads should be aligned.
If that did not work you now have narrowed it down to contamination or glazing or overheated disc. Glazed pads can often recover after sanding them a bit. Contamination: Replace pads and disc. Overheated and warped disc. Replace.
Disc quality and longevity have worsened over the past two years. Our 3 month old 200 Avid Discs wear quicker than before.
I have rotors where there is no rescue.
I have seen a good mechanic change everything but the rotor and the issue remains....
Check for leaks
Change pads and rotor if you have real concerns.
I like the idea of using a laser temperature sensor... lol (might want to read the manual)
The worst is broke. Broke really limits your ability to go fast. But it works in the wet and dry.
if your thinking of going to a bike park in europe (30 degrees), what king of pads would you take? sintered? FAIL
for avid, formula, even pre 2011 shimano
only resin in the trial pads.. but there are no other options for that,. .