Prep for Changing Brake Pad Material

Should I fully sand my rotors if Im changing pad material?

I understand the basics of disc brakes in that a little bit of the pad material imbeds itsself in the rotors as part of the normal process of braking. This would lead me to believe sanding is necessary. The problem is of course that Im a little lazy.

If it matters, I would be coming off EBC Red pads, which they say are a type of organic material, and moving back to the stock Shimano sintered pads.

I originally left the Shimano pads as they were howlingly loud and had ok success with the EBC's. They are starting to wear fast however, and I now have at least 4 brand new sets of the Shimano's laying around, so I figure I'll try them again rather than spending more money.

Frankly I don't think that's necessary. I would suggest simply changing them out for new pads of whatever compound and then breaking them in. Whenever you change brake pads, independent of compound, you must break them in again.

For God's Sake!

Do NOT sand your rotors. Clean them with isopropyl alcohol, wipe dry with a nice clean rag and keep your greasy, KFC-eatin' fingers offa them. Change out the pads, making sure to center them correctly and then go ride your bike.

Well, I know I would need to break in the new pads, but doing that on top of the older material and mixing the 2 is what I was questioning.

The actuall process of breaking in pads is where through application of the brakes the pad material imbeds in the rotor surface gradually getting you up to full braking performance.

What I dont know is: will the new pad material just push out the old with no problem? Or will they mix and decrease braking performance?

It would be highly unusual for the use of one pad material to interfere with the efficacy of another material on a standard metal rotor in such a way as to noticeably affect braking performance, particularly if the rotor were thoroughly cleaned beforehand. That's my opinion. There may be some kind of materials scientist out there who may know about something going on in the meso-scale that I don't who may disagree with what I just said, but I don't think so.

As far as I'm concerned there's no need to do anything to the rotor when switching between different types of pads. I have a set of older Shimano XTs where I switch to the stock metallic pads when riding up at my friends cottage and use organic ones when riding in the city. I just drop the pads in and they work just fine, no need to clean the rotors or pads. I've switched back & forth many times over the years and I've never had any problems.

It would be highly unusual for the use of one pad material to interfere with the efficacy of another material on a standard metal rotor in such a way as to noticeably affect braking performance, particularly if the rotor were thoroughly cleaned beforehand. That's my opinion. There may be some kind of materials scientist out there who may know about something going on in the meso-scale that I don't who may disagree with what I just said, but I don't think so.

All cleaning them with alcohol will do is remove oils, dirt, etc.

IF the previous pad material should in fact be removed to optimize performance, alcohol isn't going to do it.

IF the previous pad material should in fact be removed to optimize performance, alcohol isn't going to do it.

The rotor has micropores in it that may have captured some pad material, maybe several micrograms at most. If you are being told by a manufacturer or dealer someplace that such an infinitesimally small amount of previous material will somehow interfere with the performance of your new brake pads (which it won't), then you probably need to find a new brand of rotor, brake and pad. The bottom line is this: there is no credible reason to believe that removal of previous pad material is necessary unless you have done something highly unusual with your brakes or are using them for some highly unusual application or there is some highly unusual condition that you are not mentioning in this forum.