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New mechanical disc brakes will not brake?

Old 03-24-23, 05:46 PM
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New mechanical disc brakes will not brake?

HELLO to all. I have a problem with mechanical disc brakes. I accidentally sprayed WD 40 on my brakes and could no longer brake. I tried cleaning with a spray designed for cleaning car disc brakes, but there is no success. I bought new brake disc rotors and new pads. Before I installed, I also cleaned them with that spray nicely, and installed new brakes. However, the same problem. Although I drove for several days, and tried to burn them in, since I heard that with new brakes you have to remove that layer from above in order for them to grip well, but the same problem is still there. Even the new brakes will not grip and brake as well as before. Where could that WD 40 spray have ended up and where did I go wrong so the brakes won't brake well? They just slide when I brake, I have to brake really hard for them to catch and lock the wheel. And the front brake doesn't even lock when I brake. What do you think could be the problem?
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Old 03-24-23, 06:08 PM
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Try using new parts that you haven't sprayed with anything.
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Old 03-24-23, 07:21 PM
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The rotors can be cleaned with brake cleaner or rubbing alcohol but never put anything on the brake pads. Most likely the WD-40 ended up contaminating the new brake pads.
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Old 03-24-23, 08:30 PM
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Get SA XL Drum brakes.
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Old 03-25-23, 02:46 AM
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Maybe I wasnt clear.
I did buy new rotors and new pads. Installed it, but brakes wont break strong as before, it slides...
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Old 03-25-23, 05:23 AM
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[QUOTE=MrLovato;22839589] I bought new brake disc rotors and new pads. Before I installed, I also cleaned them with that spray nicely, and installed new brakes. /QUOTE]

Originally Posted by Kontact
Try using new parts that you haven't sprayed with anything.
Yep
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Old 03-25-23, 07:10 AM
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Spraying anything with any lube properties around brakes of any kind is contra indicated.
Rotors can be cleaned but the pads are porous and will have absorbed the material rendering them unusable or nearly so.
Remove brake pads from calipers, spray inside the calipers with brake cleaner to remove all traces of the lube.
Throw away the pads...sucks but you should have known better and pay the foolish tax.
Install new brake pads.
Thoroughly clean the rotors with brake cleaner.
Install wheels and you should be okay.
Don't spray anything with lube properties around your brakes...ever !
If this doesn't work bring it to a local shop where they likely know more than you and will repair the damage you have wrought.
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Old 03-25-23, 07:23 AM
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Originally Posted by Kai Winters
Spraying anything with any lube properties around brakes of any kind is contra indicated.
Rotors can be cleaned but the pads are porous and will have absorbed the material rendering them unusable or nearly so.
Remove brake pads from calipers, spray inside the calipers with brake cleaner to remove all traces of the lube.
Throw away the pads...sucks but you should have known better and pay the foolish tax.
Install new brake pads.
Thoroughly clean the rotors with brake cleaner.
Install wheels and you should be okay.
Don't spray anything with lube properties around your brakes...ever !
If this doesn't work bring it to a local shop where they likely know more than you and will repair the damage you have wrought.
Thank you. I didnt clean inside brake. I just bought new rotor and pads. I will clean now inside brake, where clip is, and then see how it is.
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Old 03-25-23, 07:30 AM
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you’ve described a good portion of mechanical / cable actuated disc brakes - but could just need more time to ‘bed in’ the new pads / rotors ... it is fairly common for new pads / rotors to require some time before good / full braking is available

( can find the proper procedure to bed in pads on the internets )

also a few things to check -

ensure no lubricant remains on caliper - especially inside portion ... this contamination / lubricant could get on the pads ... (and squealing could then also be a future problem)

check pads for contamination / lubricant - might be a good idea to hit them with light application of isopropyl alcohol or similar ... maybe also lightly sand face of pads if they appear to be contaminated or glazed

check caliper position - ensure caliper is centered over rotor

check pad adjustment to ensure pad(s) are in proper position

then cable adjustment

also could be due to the pads - what brand / type pads ? some pads provide greater braking than other pads

Last edited by t2p; 03-25-23 at 07:35 AM.
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Old 03-25-23, 07:40 AM
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If the pads are resin and they get contaminated, they cannot be cleaned and will need to be replaced.

Clean the rotors well with alcohol before the new pads touch those rotors.
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Old 03-25-23, 11:28 AM
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If you need to ever clean a brake use isopropyl alcohol beyond that don't use sprays on a bike nothing should ever need to be sprayed on a bike if you need to use a spray use it on a rag and then use the rag on the bike. However with brakes use clean stuff don't use rags especially ones cleaned in diesel or anything like that. I would just use a clean paper towel and isopropyl alcohol. Brakes do not need to be lubricated with anything and if they do it is specific stuff and would never be done with pads or rotor installed and you don't want any sort of lubrication or oil anywhere near the braking surfaces so those would get cleaned with isopropyl alcohol and a clean paper towel.

If you have metal pads and rotors and a fire resistant surface and understand fire and burning things you can clean pads and rotors by soaking them with isopropyl and setting them on fire. This is quite dangerous and one must be careful when doing it. It may not work in every situation and you may still need to replace stuff.

WD-40 for those who still aren't aware is a water displacer and not really useful for many things on bikes aside from maybe helping after you have cleaned your chain. You will still need to properly lubricate it with a proper bike lube which the WD-40 Company does make under their Bike products line but that is separate from WD-40 the product.
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Old 03-25-23, 12:08 PM
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Troll.
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Old 03-26-23, 06:52 AM
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Originally Posted by GamblerGORD53
Troll.
Sigh...curmudgeony Dwarf, not a troll...get is right...
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Old 05-17-23, 04:56 PM
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Originally Posted by GamblerGORD53
Get SA XL Drum brakes.
Honestly, I wouldn't go down a hill with drum brakes.
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Old 05-20-23, 05:52 AM
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Originally Posted by satrain18
Honestly, I wouldn't go down a hill with drum brakes.
Sounds like you've never ridden a bike with good drum brakes (Shimano Rollerbrakes are NOT good drum brakes). They definitely feel different, but they will stop you just the same.
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Old 08-20-23, 10:35 AM
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Originally Posted by grumpus
Sounds like you've never ridden a bike with good drum brakes (Shimano Rollerbrakes are NOT good drum brakes). They definitely feel different, but they will stop you just the same.
You do know that drum brakes have little to no modulation whatsoever.
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Old 08-20-23, 11:28 AM
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Originally Posted by MrLovato
Thank you. I didnt clean inside brake. I just bought new rotor and pads. I will clean now inside brake, where clip is, and then see how it is.
You said you sprayed the new rotor and pads. Don't spray the rotor and pads with anything.
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Old 08-20-23, 05:54 PM
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i have two uses for brake cleaner.. getting massive buildups of brake dust out of automotive brakes BEFORE i replace most of the parts, and as a PENETRANT to break down rust/corrosion.
it PENETRATES the permeable brake pads, dragging any oils in with it.

clean the disc with isopropyl alcohol.... and soaking the pads in it, in a jar, overnight might help too... if not, you'll be buying new pads.
Organic/Resin pads hold onto oils the most... Sintered Metallic pads usually clean out better.

PS.. you are not alone... i see this mistake fairly often... chain lube on brakes is the leading mistake... one bike i recently saved from the scrappers had BOTH DISCS slathered with that "chain lube" that turns into a rock-like crust when mixed with road grime... I Still haven't found anyone that will admit to what that stupid swill is....there was over 1/4" buildup on the rear dropouts and on the Bottom Bracket area... it took about a half gallon of Gasoline and a VERY stiff parts brush to remove it..some got Chipped loose... like pressure flaking flint arrowheads.... SMH.

Last edited by maddog34; 08-20-23 at 05:57 PM.
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Old 08-21-23, 08:53 AM
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Originally Posted by satrain18
You do know that drum brakes have little to no modulation whatsoever.
The response is different because of the self-servo action of the leading shoe. If you're relying on rapid variations in braking force, on the limits of tyre adhesion, then drum brakes probably aren't appropriate, but for touring and utility bikes they're plenty good enough, and have the advantage of being fairly effectively shielded from the environment.
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Old 09-08-23, 10:48 PM
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Originally Posted by grumpus
but for touring and utility bikes they're plenty good enough
For Dutch utility bikes, they're good enough, since they're usually ridden only in flat areas.
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Old 09-08-23, 10:56 PM
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Originally Posted by satrain18
For Dutch utility bikes, they're good enough, since they're usually ridden only in flat areas.
Troll.
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Old 09-11-23, 01:20 PM
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Originally Posted by satrain18
For Dutch utility bikes, they're good enough, since they're usually ridden only in flat areas.
Many traditional Dutch bikes have only a coaster brake, and it doesn't seem to be a problem in their native environment which is flat and mostly segregated from motor traffic. Coaster brakes are not good drum brakes. My utility bike has to cope with hills and motor traffic, so a Dutch bike would not be a good fit.
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