I heard it wears off after a few rides but it is still not gripping firmly. Is there any solution for this? I also saw using rubbing alcohol. Is that sufficient?
I mistakenly put WD40 for my disc brakes and now pads not anchoring as well as before. Any solution?
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16Why'd you violate the engineer's rule? WD-40 is for if it doesn't move and you want it to. You should have used duck tape: That's for when it moves and you don't want it to.– davidbakCommented Feb 4, 2021 at 4:47
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@davidbak good suggestion, the duct tape gives excellent stopping force. Unfortunately I then had to use WD-40 to get moving again, and then when I tried to apply new duct tape to brake at the bottom of the hill it wouldn't stick...– leftaroundaboutCommented Feb 4, 2021 at 15:20
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What is 'duck' tape?– Lamar LatrellCommented Feb 4, 2021 at 17:46
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3There is a Duck brand of duct tape. So when someone says "Duck" tape it's kind of like saying "Kleenex" when you mean "facial tissues". (Unless you're a sick duck, and wrap birds in strips of adhesive - in which case, shame on you!)– Duncan CCommented Feb 4, 2021 at 18:51
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2...and ample people who will tell you that "duct" is the misnomer, as the fabric tape was originally made from the stuff called cottton duck, and is distinct from the tape properly used on ducts.– CCTOCommented Feb 4, 2021 at 19:00
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4 Answers
Disc brake pads are very sensitive to contamination. You can clean the disc rotors with rubbing alcohol, but that's about it. Anything else will contaminate the pads.
You may not be able to restore the pads. The easiest and surest thing would be to replace the pads.
If you want to try to restore the pads, get some "drywall sanding screen", remove the old pads, use the screen to remove the contaminated layer from the pads, and reinstall them.
Make sure to clean the rotors with rubbing alcohol before reinstalling the cleaned pads/installing new pads so no contaminant gets onto the restored/new pads.
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2If you've reached the point of giving up, I'd think baking them in a hot (400F+/200C+) oven for 30-45 minutes would work if the alcohol or other cleaner doesn't. Heck, if that doesn't work, put 'em into an old cast iron skillet, put the skillet with the pads in it into the oven, and turn on the "self clean" cycle. The skillet is just in case the pads do something untoward like melt in your oven. (That's also a great way to get old seasoning off a cast iron skillet so you can re-season it - and no, you don't need the brake pads to do that...) Commented Feb 3, 2021 at 23:04
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8@Andrew Henle A blowtorch is much easier and less destructive towards your oven’s food safety rating. Don’t heat the pads up until they begin to undergo fusion of course. Just enough to boil all of the oil off. Commented Feb 4, 2021 at 7:18
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1Acetone will clean it - just don't get it on anything else but the metal. It will eat the paint and any plastic it touches.– J...Commented Feb 4, 2021 at 16:08
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1For goodness sake do not put brake pads in a food skillet. (Unless you're prepared to throw out the skillet afterwords) The pads could well give off toxins, and WD-40 itself is pretty toxic if inhaled or taken internally.– Duncan CCommented Feb 4, 2021 at 18:53
Brakleen or another automotive brake cleaner will work. It is stronger than alcohol and should have no problem removing w40 and most other lubes.
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1Except brakleen leaves a residue on its own. I had little success using it with my disc brakes Commented Feb 4, 2021 at 21:33
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1I haven't used Brakleen specifically, but every automotive brake cleaner I have used dries clean with zero residue. I would recommend using them outside though.– MikeyCCommented Feb 6, 2021 at 17:28
Soak the pads in gasoline then light them on fire.
Don't laugh, I've done it and it worked.
Be prepared both to 1. safely extinguish the fire (can't use water!) and 2. throw out the pads if you ruin them.
You need only a tiny bit of gasoline both to 1. burn off the contaminants, or 2. start a major fire. The fire will go out when the gasoline is consumed.
Clean the rotors separately since the contaminated pads probably made them slick too. Use alcohol or other suitable solvent, not gasoline.
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From my experience, having contaminated my pads a few times with hydraulic mineral oil due to sloppy brake bleeding or installation, what does the trick is simply thoroughly repeating the bedding-in process. Bedding-in is the procedure of getting brand new brakes to work properly (which they do not do out of the factory, on brand new bikes) by repeatedly braking hard to a stop from a reasonably high speed. This deposits some pad material on the rotor, providing much more friction than if the pad were in contact with bare steel of a new rotor, and also removes any contaminants from the surface of the new pad, which is why you generally have to bed in new pads a little, even when used with old rotors.
When the pad is seriously contaminated, you have to do this process quite rigorously. I get about this by climbing a sizeable hill with a road to descend down (this is more practical than doing it off road, even if you are on an MTB). The descent should ideally be steep enough to easily get you to sufficient speed (say 30 to 40 km/h, or less if safety is an issue and you don't mind doing more repetitions) and long enough that you can accelerate and decelerate several times, because you don't want to repeat the climb a zillion times. Last time I remember doing this it took me about 20 braking stints, or three descents, but then the brakes were fine (incidentally, it took me MUCH more to bed in brand new, clean, uncontaminated metallic pads after I replaced organic ones, so pad material can definitely influence how much bedding-in you might have to do). Of course, it helps if you clean the pads with isopropyl alcohol and sanding paper beforehand, as mentioned in the other answers.
