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 Farenheit.
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
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.
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.
That is exactly how I was going to define this combination of pad and caliper, grabby! Which I personally like. I've had this same setup on two bikes and loved it on both.
The first setup was on a 748R with the stock master (13x8 or something like that) and steel line. I thought it was great!
Next setup on a makeshift 748RS has the brembo GP radial (19x18) with the same steel line. I like this setup better, as the lever feels better, but the other setup was great too, but I am considered slow
I just bought 4 pad calipers for my racebike, and they came with brembo sintered HH pads [TT2172HH]
are these a racing compound? and are they any good? Or should I be looking to pick up something else? I was running DP RDP pads in my old goldlines.
any feedback, including prefered pads in these calipers would be appreciated.
I have raced on the "stock" pads. They are pretty good, but don't last long. I have also found the EBC's to drag on the rotors a lot and when I can get my hands on them I use Vesrah Super RJL's.
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One Test Is Worth A Thousand Expert Opinions
I have EBC HH pads on my Bimota DB2 with cast iron full floating discs (as on the 900SL etc.) They are excellent in dry conditions, but in rain there's about 1s delivery time on the braking force!
I hardly evere ride in rain so I keep them on. If I used the bike for commuting I would change them for something else. 1s could be the difference between life and death one wet day when meeting a sleepy truck driver!
brembo HH brake pads
Linear Mode
