Your brake pads are one of the most crucial components on your bike; Small yet far more technically complex than you might think.
They determine just how effective your braking system will work across a wide range of dry, wet and often slippery conditions.
Unfortunately, brake pads are a consumable component that undergoes wear and tear and have to be replaced over time to maintain peek performance. The vast majority of rim brake pads supplied on fully assembled bikes are fairly standard in composition. Different colors, indentation patterns and size make very little difference to performance. The compounds and additives that make up the pad (including metallic additives) do.
There are multiple choices to be made when designing a superior pad. Balancing durability, speed modulation, rim material type and of course price can all make a huge difference to your ride and stopping.
SO WHAT ARE PADS MADE OF?
Generalizing, cheap brake pad makers use either processed rubber or forms of resin, which provide adequate and silent braking under normal loads. These pads generally have shorter lifespan, especially under wet conditions.
Semi-metallic pads use a combination of synthetics and different proportions of various metallic particles for the pad compound.
Metallic disc pads use sintered steel with no synthetic additives. They transfer quite high frictional loads to your disc rotors which results in higher heat load and surface wear.
You will also see “Ceramic pads” in the market which sound very exotic and usually cost more. They are made using a mixture of clay and porcelain with copper filaments used as a binding agent.
SO WHY ALL THE DIFFERENT TYPES?
The biggest issue every brake pad type has to overcome is heat dissipation. The friction of braking largely converts your kinetic energy (speed) into thermal energy (heat). Standing wave oscillations within the pad (brake squeal) is actually also dissipating a tiny bit of sound energy. Any pad that cannot effectively dissipate the heat it generates will not perform well for very long before it starts to degrade.
There are numerous cases where excessive rim pad heat has caused delamination of carbon clincher rims leading to catastrophic rim failure, often at high speed. In other cases tires have been blown off the rim and steel disc rotors have warped, causing massive vibration and loss of stopping power.
The other major issue is to ensure that the interaction between the brake pad compound and the braking surface is compatible with many different types of rim materials – aluminum, alloys such as scandium and composites. Incompatibility leads to premature wear and may, at worst, lead to partial or complete brake failure.
The disadvantage with ceramic as a brake pad material is that it doesn’t dissipate heat well; causing the other components on your bike’s braking system to warp. Selecting a brake pad will come ultimately down to the buyer’s personal preference.
TO WEAR OR WEAR OUT?
All brake pads eventually wear down and need to be replaced due to frictional surfaces forces generating heat which ‘ablates’ the pad surface. Engineers formulate their pads to ensure pad wear characteristics that do not significantly damage or degrade the rim brake surface by comparison.
Unfortunately high-performance stopping power usually comes at a price: excessive pad wear and short lifespan (which is great for the manufacturer’s profits).
Nex-Gen’s material specialists have developed the world’s leading all-weather pad performance without sacrificing pad lifespan or rim degradation.
Comparing the wear of 3 leading pad brands during 1000 cycles from 30 kph to zero, Nex-gen pads measured half the wear of the Campagnolo Carbon pads and would last approximately 20 times longer, given identical conditions, as a leading European brand. Full test data results in the table below.
TEST DATA FOR THE TECHNICALLY-MINDED
The maximum temperatures generated at the pad/rim surface during a long, steep descent at high speed can easily exceed 200°C / 392°F (also depending on the rim material). This potential maximum heat load significantly exceeds what is known as the glass transition temperature or Tg of most epoxy carbon rims leading to thermally induced mechanical failure.
As of writing only one or two major composite rim manufacturers can effectively handle such high heat loads using proprietary Resin formulations which resist thermal damage.
A pad specifically designed for composite rims will work effectively on an alloy rim, but since the compound is generally designed for higher temperatures, the braking will not be optimal. However, a pad designed for alloy rims when used on carbon will wear faster and deposit pad material on the rim as the pad disintegrates in the higher heat-load environment. Composites are very poor thermal conductors whereas alloy rims are very efficient thermal conductors.
That’s also the main disadvantage with ceramic as a brake pad material – Despite the exotic sounding name it doesn’t dissipate heat well (Ceramic tiles on the space shuttle heat shield); causing the other components on your bike’s braking system to potentially exceed their thermal design limits.
Each test repeated over 10 cycles and results averaged.
Wheel: Reynolds Aero Carbon.
Ambient temperature 24°C/ 75.2°F.
Tire: Maxxis High Road 25C.
Tire pressure: 100 PSI / 6.9 BAR.