|   Louises' power loss? | bladteth
Jan 11, 2002 3:42 PM | | Hi,
I've recently switched front brake pads with the rear and outer with
inner in my Louises. Before that I brushed them in soapy water,
cleaned dry (the same with rotors) and grinded using sandpaper. Then
I put everything back together and set up brakes as described on MC
homepage. Yes, the modulation is even better than before, but my
Louises lost some of their stopping power. I've got the strange
feeling, like the pads are not grasping the rotors but rather slide
on them. What could have gone wrong? Do they have to brake-in for a
second time?
TIA,
bladteth |
| Yep................. | Mike T.®
Jan 11, 2002 4:06 PM | | ......Louise has to be bedded in all over again. It won't take long.
Mike T. (mcm #717) |
| I'm just curious... | bladteth
Jan 11, 2002 4:33 PM | | ... what is happening to pads, their surfaces or anything else during
the brake-in period. Why don't rim brakes have to go through this?
bladteth |
| Good question and................. | Mike T.®
Jan 11, 2002 6:00 PM | | .....even thought the "how" has been asked many times, I don't remember seeing the "why" question asked.
Pads and rotors need to be conditioned to each other and this is done by a transfer of material from one to the other that "burnishes" or polishes the surfaces, especially the rotor. The high spots are worn off the microscopically rough surface leaving a polished surface with the pad mated to its contours perfectly.
This is why when you sand the pads you have to repeat the process over again.
If the brakes are used too heavily, the surface of the pad can melt and the molten stuff glazes over when it cools. This then has to be removed before the optimum coefficient of friction can be had.
As I'm not a physicist all the above is subject to scientific explanations.
I would imagine rim brakes are totally different as the braking materials - rims and pads - are far softer than their disc brake counterparts.
Mike T. (mcm #717) |
| Good question and................. | MPU
Jan 12, 2002 2:30 AM | | I think that if you change the pads rear-front or in-out the pads are not touching the rotor with all surface. I doubt that the caliper can be set so that there is no difference in pad wear. That's why it takes some time to bed the pads again. The differences in caliper positions can be very, very small but they all count. |
| My point of view | bladteth
Jan 12, 2002 2:31 AM | | Your explanation seems nice but as I recall from lessons of physics,
the smoother the surface, the lower the coefficient of friction.
I see it in this way: when the surface is more rough and the braking
force applied is relatively small, the contact between pads and rotor
is smaller - only the higher spots engage. More braking force makes
the contacting surface greater. When it is smooth (after bedding) the
lever-brake force ratio is therefore lower but so is the modulation.
This would explain, why it doesn't apply to rim brakes (the pads are,
as you mentioned, much softer) and gives an answer to my question -
since I grinded my pads, they once again need a break-in period. How
do you find this theory? |
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