There are two main types of brake pads; organic and sintered. Organic pads tend to feature materials like Kevlar and other natural materials, all of which get bound together in a special resin. Sintered pads, on the other hand, are metal based. Copper and alloys form the majority of the pad's make-up, producing a material that has a higher ceiling temperature and a lesser wear rate than an organic pad.
Motorcycle brake pads vary according to the application they're intended for. Just like motorcycle tires are speed rated, motorcycle brake pads are friction rated. Take HH for instance. You'll typically find that reference on a sintered brake pad and it determines that the product has twice the friction rate of a single H brake pad. This would suggest it would be better suited to a higher performance machine, or a heavier dissertation of energy to slow it down.
Within sintered and organic brake pads, most manufacturers have several different options of product, tiered towards their usage. At the top end of brake pads technology are race-spec brake pads. As well as a compound better suited to a higher initial bite and faster deceleration, they feature special backing plates designed to withstand the extreme forces they're submitted to. Every type of brake pad will have an optimum working temperature. Exceed that range and you'll experience brake fade, as the brake pads allow too much heat through to the calipers boiling the brake fluid in turn. Aide from race-spec pads, working temperature is achieved almost instantly on application of the brakes. The challenge then is to control that temperature with the special cooling technologies which get factored into the brake pad design.
How do they attach the compound to the backing plates? There are various methods, but the most common ways are as follows: Organic brake pads plates feature recesses that the resin compound flows into during the manufacturing process, creating a mechanical lock. The addition of special adhesives also actively strengthens the bonding of the two components. Sintered brake pads are a little more difficult to attach, due to the higher demands required from them. They use a number of pips cast into the backing plates to protrude into the sintered compound being forced onto the plate; a bit like steel reinforcement in concrete.
Why is it important to bed brake pads in? Depending on the scenario, the importance varies. If you're talking new pads on new discs, the bedding in process is essential to allow the correct heat process to take place. Too much heat could damage the discs or glaze the brake pads over. The bedding in process also allows for a special film to be transferred from the pads to the disc, creating a better coupling of the two components. And in turn performance. It's important to note you should never use old brake pads on new discs. However, you can use new brake pads on old discs. Although this will also require a running in process of gentle braking for the first 100 kilometers of use, so that the new brake pads can bed into the shapes and grooves of the discs.
How does rain water affect brake pad performance? Brake pads depend on heat to perform, so the application of water hinders their initial performance. It's something that's always been an issue, but new technologies for both brake discs and brake pads have massively enhanced braking performances in the wet. Brakes will always work in the wet but their consistency will be compromised as a result. There is no quick fix...
How does brake pad thickness affect performance? The thicker the brake pads, the harder it is for heat to reach into the calipers. If pads are too thin, excessive heat could be transferred to the calipers, boiling the brake fluid and even melting the rubber seals; which could lead to complete brake failure. This is why it is important to inspect your brake pads on a regular basis and change them if they are under the manufacturer's recommended thickness.
Why are some compounds slotted? Slotting compounds provides a number of different benefits. It helps with the dissipation of heat and also with the dispersion of water, when braking in the wet. Slotted compounds also de-stress the brake pads, by reducing the overall area of the compound's width. This improves brake pad duration and helps to prevent any potential failures. The longer something is, often the easier it is to brake under force.