Any tips floating around here on when brake pads can be decontaminated, and when they can’t? We frequently find ourselves at the shop doing the song and dance of trying to avoid throwing away brake pads with lots of life left on them, in order to get rid of awful brake howl. Hit the pads with some sandpaper and isopropyl alcohol, maybe the same for the rotors. Sometimes it works, sometimes it doesn’t. Often, it doesn’t seem to make a difference whether the pads are organic or metal, SRAM or Shimano.
Is there logic to when it’s even worth the time to try to save pads and rotors? If pads must be tossed in the trash bin, is it likely that rotors can always be salvaged? Can metal be often saved, organic not?(this is a notion we’ve heard lots but can’t confirm) It would make sense that rotors wouldn’t be permanently contaminated unlike a thick pad, but some frustrating repairs can sometimes make us want to throw our hands in the air and pads/rotors into the trash. Surely ya’ll can relate to all of the dozens of wasted minutes of cleaning/sanding/gingerly re-bedding in brakes only to find brake howl at the end of a sweaty summer test ride.
I feel your pain here @user14
What I now do is the following on all disc pads and rotors when I am not immediately replacing them due to excessing, or close to the limit, wear.
Pads
I first rub the brake compound against a small piece of sanding mesh (think sandpaper with holes in). I prefer sanding mesh as the material that comes off the pad goes through the mesh onto the bench rather that clogging it up like it does with normal sandpaper.
I then spray both the pads with iso propyl alcohol (IPA) and rub them together. While the pads are still a bit wet, I’ll rub the braking surface onto a clean rag or blue tissue. I repeat this a few times until no more brown/black liquid comes off the pads. Pads are then left to air dry.
Rotors
I take them off the wheels, spray them with IPA and wipe them. Once dry, I mark the rotors on both sides with a marker pen. I then run a 80 grit sanding disc, attached to a cordless dremmel at low speed, around the rotor braking surface , starting at the pen mark, to scuff them up. This takes very little material off the rotor. I then wipe the rotors again with IPA and leave them to dry.
Pads and rotors are then refitted and bedded in.
If the brakes are still noisy, I’ll remove the pads to find they are shiny and glazed over. Pads like this go straight in the (metal recycling) bin. I’m spending no more time on them. I’ve tried cleaning and sanding pads again, but it never works and is a waste of time.
Rotors would then get another wipe over with IPA, new pads (also washed with IPA as above) fitted and in nearly all cases the noise is gone and brakes are powerful after a bed in.
Brush the rotors with this stuff…then walk the bike, using the brakes in an on-off manner for 30-50m. Then walk it back, lightly dragging the brakes. FInally get on the bike and drag the brakes a bit and then do a few hard brakes.
While not a permanent solution, it will eliminate the howling. Cheap and effective.
I used to use Squeal Out for bike discs, but The PInk Stuff is WAY cheaper and just as effective.
Have you tried SwissStop Brake Silencer? It’s a sort of metallic spray paint for disc pads. Give them a good clean, then spray it on, let it dry for about 20 minutes, and it usually does the trick. My understanding is that it works by temporarily increasing the friction between the pad and disc, giving you the chance to bed the pad back in again before it completely wears off. I’ve used it in the workshop on fairly badly contaminated pads, with probably 90% success rate. It doesn’t work quite so well on glazed-over cooked pads, but often they’re a sign of a bigger issue (rider error/140mm rotors)
This is a really smart system, and I could see it being useful on some rotors that come out of the box with a near mirror polish (like newer cheaper Shimano rotors do).
However, I do think it’s an inefficient use of time in a busy workshop, and it’ll abrade into the little bit of material rotors have (e.g: a new Shimano setup is 1.8 mm, and recommended replacement is 1.5 mm).
@WCS_Alex appreciate the nice thorough response, and the thoughts echo what was written in the awesome Shimano Bleed Procedure document. I mentioned your idea of the 80 grit Dremel bit to the other guys at the shop, and they cringed slightly at using that tiny bit, trying to scuff up the rotor and maintain a nice flush surface. Is this really preferred to using some sandpaper…i reckon say around 80 grit? We love an excuse to bust out some power tools, but the dremel bits seems woefully inadequate in the surface area dept. Really cool idea, and maybe we can be enlightened.
@VeloBouf thanks for the tip on the Pink Stuff. One of our guys stumbled upon the Squeal Out stuff via some online forum months back and we quickly got a tub from Amazon to try it out . Again, inconsistent results for us. Plus, if we’re going to charge customers for this work (always working on a fair labor rate for this…), we want to feel that it’s permanent and not just a temp fix. Nothing more frustrating than people having to drive their bike back to our shop for a fix they didn’t get the first go-round…
@James_Heath I need to check into SwissStop. Haven’t heard of this, but like the SquealOut, I’m always a little skeptical of these fixes. Your mention of glazed over pads is a really good one, and one that we should look deeper into. Admittedly, I’d say we don’t fully understand glazed pads around here, but can also say that we do have lots of extremely sustained and steep descents which might lead to glazed pads, regardless of the pad material used?
Ultimately, I think we definitely need to stop doing more than 1 round of cleaning pads/rotors in repairs. If it doesn’t work the first time, ain’t no way it’s going to get better, even if we swear that sometimes we get improvement the 2nd time. It also appears that the consensus is that the rotor (assuming not excessively worn) should never really be replaced. Simply sanded, IPA’d, reinstalled, and rebedded.
@Gila.Monster I’ve probably given you a wrong steer on the bit I am using. A much better description is an small 80 grit flap wheel (see photo).
I’m using verg light pressure (less than hand sanding I’d think) and only doing one full scuff of the rotor on both sides, using the pen mark as the start end point.
Takes <1 minute to do both sides of the rotor and takes off very little material.
Hi- Is it possible to post the ‘Shimano Bleed Procedure document’?
Also, somewhere on Discord someone posted about cleaning disc rotors with UFO clean. (I think they submerged the rotor for a few minutes.). Has this approach been more widely adopted? And could I substitute Silca’s chain stripper for the same purpose?
I’ve personally avoided using UFO drivetrain cleaner anywhere near brake rotors or pads. The instructions on the back of the pack specifically call out not to use on pads but would like to hear feedback from others that do use this product for rotor cleaning.
I have a 3d print file for a conical washer to align a centerlock rotor on my rotary table that uses a M6 center bolt. I came across this same video a while back and liked the idea, but It seemed weird to me to go through the trouble of using a drill press and rotary table and not take the extra step to make sure the rotor is centered on the bolt. I’m happy to share it if anyone else decides to go down this rabbit hole. It certainly works well, but I’m not sure its worth the effort compared to other sanding techniques if they are done carefully. Its certainly not worth the investment in tools if you don’t already own them. Also, I like the marker approach @wcs_alex mentioned above.
Quick demo of what I do to the rotor, as mentioned above very light pressure.
These are rotors out of the bin btw, hence why they are excessively scored on the braking surface
The Silca brake and drivetrain cleaner was effective in silencing my squealing rear Shimano Dura-Ace brake the last couple of times. I just spray onto the rotor and into the brake caliper, and wait about 5 minutes before rinsing them off with water.
We have used virtually all the solutions out there in our shop. Most techniques and products give unpredictable results which is frustrating and time consuming. Several months ago we started using the Silca rotor decontamination spray and have had very good results. Clean the rotors, sand the pads. It’s a bit pricy but give the results we are sticking with it. Use it in a well ventilated save, it stinks.
Thats the stuff. I mis-spoke the name since I wasn’t near it. Use it as directed. Light spray hanging the rotor off of a hook from a spoke or something. As it dries contaminants will turn red. Whip it clean with a clean rag/ towel. Rinse in clean water. Put the rotor back on with the sanded pads and go through the bed in process. We use a Sinter machine. Hope this helps.
Swapped my old SRAM rival calipers for Hope RX4+’s, only to realise the wheels had originally been supplied with the 15mm endcaps on the hubs instead of 12mm - PSA check your endcaps when new, massive rabbit hole chasing that down. Anyway, that all got fixed but the brakes still howl. I’ve tried everything, including Hope’s exhaustive list of preliminary checks - piston balancing etc. I tried the Silca brake cleaner as above, worked for one ride, then the noise came back. Tried the pink stuff miracle cleaner today. Same again. Used all the tips in @Dave_Rome’s excellent threaded article for bedding in brakes. Still no dice. The noise seems to appear with moderate quick breaking, at speed its fine breaking gradually hard is ok too, until coming to a stop, and just before stopping the noise kicks in, or if I grab brake quickly. I’m a bit of a hope fan and have several sets on my MTB’s, including the 4 piston E4’s and haven’t had this trouble.
I did re-use rotors from the SRAM calipers (hope road rotors),but they had swissstop organic pads and I’ve been using the hope/galfer red pads, so I thought the compound would be a close enough match. Was reluctant to throw out the brand new pads and try another set and even more reluctant to get new rotors, but I’m at a loss, is there anything else worth trying? Bike is a Cotic Escapade and Cotic insist the frames are faced at the disc tabs, and they look like they are, but I couldn’t say for sure.
I’ve cleaned sanded, and re-bedded and rebalanced these damn brakes more than anyone really should, should I just get new rotors and pads?
