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Motorcycle Brake Pads

October 27, 2016

Motorcycle Brake Pads

Brake Pads –

There is almost a bewildering array of motorcycle brake pads compounds with each manufacturer (except cheap Chinese pads) warranting the benefits of each compound but these will break down into the three basic types which we will come to in a minute. Firstly lets start with my own experiences of the cheap Chinese options. I like to save a penny like any other, so when I saw on eBay a complete set of pads for my Honda XR650L for $9 bucks, I thought, “Well they can’t be that bad?!?” Well these uneducated pads (I like to call them this because  they appear to have no qualification and have never passed any tests!) and I applied these to my motorcycle, I am old now and don’t go screaming around so I thought these would work, I allowed the first 100 or so miles in hoping they would ‘bed in’ but much to my disappointment, after one hundred miles they still didn’t stop me! Ah well I thought, they must be running a harder compound, so I persevered and gave them another 100 miles – no difference! After yet another 90 or so miles, I gave up and threw them in the trash and yes I was throwing my money away, but they were garbage.  Not saying they will be the same but that was my experience and I won’t do it again.

Your motorcycle brake pads started life in the hands of a friction material formulator, most likely a chemist by degree. Chemists select the composition of a brake pad by choosing from a fixed list of compounds that fall into 4 categories. Fibers, such as fiberglass, kevlar, arimid, stainless steel,  aluminum and copper maintain the heat stability of the pad. These fibers have various binding strengths and can be organic or metallic. Friction Modifiers such as graphite adjust the friction level and fine tune the performance characteristics of the pad at specific cold and hot temperatures. Fillers take up dead space in the pad. These are generally organic materials with some low frictional effect such as sawdust, glass and rubber. Finally, Resins are used to hold the elements of the brake pad together so they don't crumble apart.

Every motorcycle disc brake pad that I've ever seen has been manufactured using an Integral Molding (IM) process. Bascially, the pad formulation (sort of like a cake mix) is pressed in a mold against the steel backing plate using adhesives and mechanical locking.

Most high performance pads are positive moulded. This means that only one pad is pressed in the mould at a time. Some motorcycle brake pad manufacturers who use mass production equipment will flash mold their pads. This means that the mould creates a whole tray of pads, all pressed at the same time. In general a positive mould pad is more durable and has a high sheer strength because the full force of the manufacturing press is applied to one pad at a time. After the pad has been moulded is moulded into a puck and bonded to the steel backing plate, it is usually cured in an industrial oven to slowly remove the moisture that remains in the pad compound.

IMPORTANT – We only recommend brands tested by the German Testing Institute  TUV – Why? Because firstly this is an expensive test for manufacturers to pass, so they won’t be testing any product without toughly developing and testing prior to the test and secondly the Germans are very thorough!   

The Chase Test, better known as the SAE J866A test procedure, provides a uniform means of identification that may be used to describe the initial frictional characteristic of any brake lining. The Chase Test is used to assign a two character code (e.g. EE, FF, GG, HH, etc) to a specific friction formulation. These characters represent the coefficient of friction when a 1" square piece of friction material is subjected to varying conditions of load, temperature, pressure and rubbing speed on a test apparatus known as the Chase machine.

The coefficient of friction measured by the Chase test describes the relationship between the two forces acting on the friction material. A clamping force is exerted on the friction material, resulting in a frictional or resistance force. A low coefficient of friction means that very little of the clamping force is transferred into resistance force. On the other hand, a high coefficient of friction means that given the same level of clamping force, a higher resistance force is generated by the brake pad.

For example, a pad that carries an HH code has a normal coefficient of friction of 0.55 or higher, and a hot coefficient of friction of 0.55 or higher. The first letter of the code represents the normal friction coefficient. This is defined as the the average of four test data points measured at 200, 250, 300 and 400 degrees Fahrenheit.

The second letter of the code represents the hot friction coefficient based on a fade and recovery test. We all should know what brake fade is. If you've ever had to use the front brake extensively and found that its effectiveness quickly diminished, that's fade. Recovery is basically the period where the brakes are gradually cooling off. The hot friction coefficient is defined as the average of 10 data points located at 400 and 300F. on the first recovery cycle of the pad; 450, 500, 550, 600 and 650F. on the second fade cycle; and 500, 400, and 300F on the second recovery cycle.

The range of friction coefficients assigned to each code letter are as follows: C = less than 0.15. D= 0.15 to 0.25. E= 0.25 to 0.35. F= 0.35 to 0.45. G= 0.45 to 0.55, and H= over 0.55.

If H is the highest coefficient of friction, then why aren't all pads manufactured and rated to a HH specification? Well, while a HH pad might be ideal for high performance or track day riding, it could be too "grabby" or aggressive for those of you who spend your time commuting. Similarly, some "racing" brake pads are unsuitable for the casual Sunday canyon ride because they never reach their ideal operating temperature, much like racing tires, in these relatively gentle conditions.

 

The Three Basic types of pads –

Organic - These contain no metal content and usually made up from materials such as rubber, glass and Kevlar in a heat resistant resin. For general use these are actually our recommended motorcycle brake pads being both the quietest option and give a long rotor life and they are the least aggressive. They also produce a great ‘feel’ as they very progressive Pro’s: Great feedback, less expensive and long rotor life Cons: Can fade with aggressive use/riding and can have a shorter service life.

Semi-Metallic - These pads are the compromise between the organic’s and fully sintered pads offering and improved fade resistance over the organic and increased durability by containing between 20 – 40 % metallic materials into the compound. Pro’s: Increased service life and durability and good for the majority of road riding motorcycles and still better on rotors than fully sintered pads. Cons: Similar prices to Sintered but not the full performances in fade resistance.

Sintered-   Is made of powered metals usually bronze and copper using extreme heat and pressure to apply them to backing plates. Being the hardest compounds, they work better once they have heated up but have an excellent coefficient of friction and heat dissipation making suited for extreme aggressive use and racing. Pro’s: Highest friction rating combined with longevity Con’s: More expensive and more abrasive to the rotor’s. Also can take time to warm up to optimum performance and greater noise.






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