Is an expression usually applied to describe the friction material durability. It is generally perceived that a HARD BRAKE PAD is one that is more suitable for race conditions.
This however is an expression more than a real hardness change especially because in modern day brake pad manufacture pads are not made harder to prolong life or to gain performance.
Brake pad hardness has been used as this general terms because there has been no standard way in which brake pad manufacturers could describe their different products.
It is true however that some brake pads are physically harder than others and when measuring the surface hardness in real terms there is a vast range of hardness across the world wide range of brake pads.
Performance and race type brakes, generally referred to as hard usually contain a large proportion of steel fibers and these can be abrasive and very damaging to the brake rotor. It is this meaning for the term brake pad hardness that disc or rotor manufacturers refer to when grouping brake pad hardness. Rotor manufacturers are trying to say that hard or very abrasive pads may damage their rotors and are not normally recommended for street driving.
However some manufacturers have managed to produce sport and race brake pads that do not use, or use very little steel fibre and are not mechanically hard at all. These are the families of Aramid fiber based brake pads using modern day fibers such as Dupont Kevlar or Twaron. Kevlar of course is six times as strong as steel when used in a matrix form and is far less abrasive than steel fibers so it is an excellent, although expensive, binding fiber that can be used to replace steel fiber.
The basic properties of a sport or race brake pad need to be its higher friction level, plus its ability to handle higher temperatures of sport and race braking plus its wear life ability. If all of these can be achieved without the need for brake pad hardness to be a mechanical hardness then you have a perfect situation.
It is becoming more and more accepted that NAO or non asbestos organic pads made with Aramid fibers are far less abrasive on brake discs and most aftermarket brake discs or rotors work well with them.
So if you are looking for a harder brake pad and by that you mean you want a sport or race pad that grips well and can handle heat plus lasts well enough in track driving then an Aramid fiber, Kevlar or similar brake pad base would be the right choice
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