BMW K1200, K1300, and K1600 Forum banner
41 - 52 of 52 Posts

·
Registered
Joined
·
148 Posts
To carry @Beech post one step further, I always have my rotors media blasted when changing brake pads compounds. Any road Racer will tell you this can make a critical difference in breaking performance.

Disc brakes work by smearing some of the brake pad compound onto the brake rotor itself. Think of the carbon / carbon brakes used in high performance racing, carbon brake pads with carbon rotors. Having one brake compound in the brake pad and a different brake compound smeared on the rotor will produce less effective braking.

It's difficult to appreciate how much brake pad compound is actually on the rotor until you have them media blasted. After blasting even a well used rotor will look completely flat, with no grooves or ridges in the rotor surface.

Media blasting will also ensure you get an even distribution of pad compound around the rotor. This will help prevent high spots that eventually lead to warping of the rotor and pulsating at the lever.
 

·
Registered
Joined
·
13 Posts
I looked at Brembo, and EBC, but for not much more settled on OEM, I got 30k miles on the previous set, and I`ve always found them to have more than enough stopping power and easy on the disc`s.
Disc`s are expensive.

Good Luck.
 

·
Registered
Joined
·
520 Posts
Discussion Starter · #43 ·
I have the a set of brembo HH pads on my bike. They are more powerful than the stock pads, but they eat the rotors and mess with the ABS. By that I mean when the ABS is activated, it repeatedly lifts the rear wheel off the ground even with a loaded top box with every pulse of the ABS. Very annoying, looks stupid and squidly to others and can be dangerous, so I’m going to change them to either stock or carbon lorraine.
I should have trusted my instincts on this (ALWAYS go OEM). Dammit. You’re right, the HH pads mess with the ABS, and obviously the ABS would have been extensively tested with OEM pads, and not aftermarket.

Dammit.

[update]

I just checked bobsbmw and it seems the front pads they sell are sintered metal.

P/N: 34 11 8534183
 

·
Registered
Joined
·
520 Posts
Discussion Starter · #45 ·
I don’t understand how a pad change “messes with” the ABS, causing stoppies that are absent with OEM pads. Can anybody straighten me out on that?
If I slam on the front brake, it immediately activates the ABS and it takes like half a second to actually deploy.

This is kind of scary.
 

·
Registered
Joined
·
256 Posts
Of course it does because you’re either on the point of locking a wheel or the sensors have detected a speed differential between front and rear wheels. That is not a function of the brake pads but you ‘slamming’ on the brakes. That will happen with any brake pad.
 

·
Registered
Joined
·
520 Posts
Discussion Starter · #47 ·
Of course it does because you’re either on the point of locking a wheel or the sensors have detected a speed differential between front and rear wheels. That is not a function of the brake pads but you ‘slamming’ on the brakes. That will happen with any brake pad.
My old pads didn't do this.
 

·
Registered
Joined
·
256 Posts
Yes. Some pads don’t start to work to their fullest until warm. Not all the compounds have the same efficiency at all temperatures. Track compounds have a very high hot friction coefficient, but only after they reach temperatures like 660°F – 840°F as opposed to street compounds, which are designed to work best at around 570°F and if used on the track will suffer from fading. In any event once the wheels are on the point of lockup the ABS will behave as you described regardless of the type of pads you have
 

·
Registered
Joined
·
19 Posts
As others have noted, different pad materials create different brake feel and different operating temperature ranges. Performance Friction used to have some neat graphs on their site that showed the torque/pressure curves of their various pad compounds. A very steep graph with brake torque rising very rapidly with modest early brake pressure would be described as “high initial bite” while another compound might show a much more progressive onset of brake torque with peak braking force being achieved with a higher lever/line pressure. Interestingly, the absolute peak brake torque of both pads could be very close to identical. It’s just how they got there that differed. There were also temperature/torque graphs that showed the temp at which the pads achieved maximum torque as well as the drop-off in torque as the temperature increased. So you could visualize how the pads might behave as temps increased. Some pads “hung on” to peak torque to some very high temps, then dropped-off suddenly. Others might start losing torque at a lower temp, but drop off more gradually.

If I had to guess, I’d say Fastdaddy nailed it: the new pads have a much higher initial torque rise (more “initial bite”) and your previously developed technique for how fast you pull the lever simply creates much more brake torque much quicker, resulting in ABS activation.

Also guessing, I’d say it’s possible this much higher initial braking force may be enough to create a stoppie that is sensed by the ABS as a wheel speed difference causing it to activate whether the front wheel is locking up or not.
 

·
Registered
Joined
·
42 Posts
I don’t understand how a pad change “messes with” the ABS, causing stoppies that are absent with OEM pads. Can anybody straighten me out on that?
The after market pads, particularly HH compound have much greater grip and much higher initial bite than the stock pads. So when ABS is engaged, it pulses the brakes on and off very fast at maximum pressure. So with warm tires, it lifts the rear wheel off the ground 6-12 inches with each pulse. The system is balanced for the stock pads, so grippier pads will cause the above issue. Kind of like the ASC does with the front end if you hold the throttle open, front wheel comes up, system kicks in and front wheel comes down. Very annoying. And potentially dangerous.
 

·
Registered
Joined
·
19 Posts
I understand how pads with higher initial bite could cause a lever yanker to perform a stoppie he wasn’t planning on. And I can understand that the ABS might activate in that scenario due to wheel speed difference. But somebody’s gonna have to show me a video of the back tire rising and falling at the same frequency of the ABS before I buy that aspect of this discussion.

Additionally, I think some folks are giving the ABS and ASC systems credit for being able to sense the pitch change associated with wheelies and stoppies when it’s really just very quick reaction to front/rear wheel speed deltas. You need an Inertial Management/Inertial Reference system like on the modern literbikes to sense and control a wheelie or a stoppie. The OEM ABS is exceptionally effective and it may be the case that it is so exquisitely synchronized with OEM BMW pads that a pad change can incite stoppies that didn’t used to happen even with 4-fingered yank technique brake application. But whatever intervention happens in either direction - wheelie or stoppie - happens because of wheel speed differences that either system perceives as a loss of traction because 1 of the wheels is in the air.

I’m happy to be corrected if there’s actually a crude 2-axis IMU buried in these bikes that I don’t know about.
 
41 - 52 of 52 Posts
Top