Reziko

Hi. So two weeks ago I sprayed dw40 on my bike brakes. Both of them stopped working. Then mechanic changed something. Now it works,but it sounds awful. What should I do?

Outrider1

Reapply WD-40?

bwilli88 

WD40 is to reduce friction, your brakes work by friction.
Change both the pads and the rotor.

Crankycrank

As mentioned above, never use a lubricant on your brake pads or discs. Hopefully your mechanic thoroughly cleaned your discs before installing new pads. Here are some videos that explain various reasons and fixes for squeaking brakes. how to stop bicycle disc brakes from squeaking - YouTube You could also go back to your mechanic and have him/her try to sort it out and probably no charge as it should be working properly when it leaves the shop. Also, sometimes new pads just need some time to bed in and will stop squealing on their own but shouldn't take more than several rides.

pdlamb

A. Be happy you have working brakes.

B. Wash both sides of the discs with hot, soapy/Dawn.

C. Find a mud puddle, splash some muddy water on the discs, ride around hitting the brakes.

dedhed

interesting most posters are assuming discs.

Crankycrank

Dang it, good point. I'm guilty of that.

dedhed

Considering what is there to lube on a caliper/rotor unlike rim brake pivots.

grumpus

Assuming rim brakes, clean the brake tracks on the rims thoroughly with detergent and a scouring pad, or a solvent like isopropyl alcohol.
If it's disc brakes clean the rotors in the same way.
If that doesn't help come back for more advice, and tell us what sort of brakes.

cyccommute 

Well at least you learned not to spray lubricant onto parts of your bike that depend on friction. Assuming rim brakes, your squealing is probably due to pad alignment. The pads should be “toed in” which means that the front of the pad hits the rim first. Flat or toe out pads will cause the pad to vibrate or “chatter” which is what we call the squealing.

If the brakes are disc, you likely have a contaminated rotor which contaminates the pads. The rotors need cleaning with mineral spirits followed by acetone or denatured alcohol. The pads, even if they are new, are beyond hope. You’ll need new pads as well.

Take the bike back to the mechanic and have them figure out the problem. That’s why you pay a mechanic for.

Andrew R Stewart 

Back when I started working on bikes I used WD40 for rim cleaning. I did this on, perhaps, hundreds of bikes. I can't remember any brake system function "failures" from this cleaning (and cleaning includes wiping off after spraying, no way would I just load up the brakes with a partial lube and do nothing else...). I should include that I consider braking noise/squeal happening during slowing down not as a failure, just an annoyance. At some point after I began working at the area's better shop the boss caught a fellow wrench doing this cleaning and reamed him an extra hole. Not wanting to be on the receiving end of the boss's reprimanding I stopped, mostly. Since I will still use a bench top spray lube sometimes for cleaning but will follow up with a solvent on rag wipe off of the brake tracks.

I also caught the assumption of a disk brake. So many here made that same mistake that I went back a few times to reread the op to see if I was the one that missed the info. Having done the same myself, in other threads before, I wasn't going to say anything unless the need grew.

To the OP's problem- Many things can contribute to a system not functioning. To be able to give best advise I would want to know the condition of the current parts (corrosion in pivots or cables, brake pad glazing or hardened from age, caliper pivot adjustment, cable and casing routing as well as the part of the brake system that many don't consider so, the brake track on the rim (assuming rim brakes). With so little info at this point I don't see that we can tell the OP what's really going on. For now the best we can do is offer possibilities and speculations. Perhaps if we knew more about what the bike shop actually did we might have better "aim". The one possibility that I think of is that the brake pads were replaced and not aligned or tweaked for minimal noise. But this is a shot in a nearly dark room. Andy

choddo

Intentionally spraying wd40 on a brake (surface?) is pretty wild. I remember at school maybe doing bike proficiency a teacher asking what we’d put oil on and I said the brakes (meaning the pivots) and they laughed at me. As a kid that was a bit galling.

I don’t toe in pads on side pull caliper brakes or v-brakes and never get any squealing unless it’s raining maybe, but I’ve had to do it on rubbish cantis to try to reduce it.

I’d try some isopropyl alcohol on whatever it was you put that stuff on and put new pads in unless the mechanic did that.

veganbikes

Never use actual WD-40 on a bike, there just isn't a need, it is a water displacer (hence the WD) and has some carrier lubricant in it but not enough to work on a chain or anything like that but enough to contaminate pads and rotors and other braking surfaces should you be using disc brakes. Clean everything well with isopropyl alcohol and a paper towel or some other clean cloth that is not a rag or at least not a shop rag which can be cleaned in diesel. That is at least a start.

Like Andrew R Stewart said we are all kind of shooting in the dark but cleaning everything first will at least get somewhere.

Jay Turberville

"Sounds awful" somehow gets most people thinking that way. :^)

Andrew R Stewart 

Sure, for those who never had rim brakes squeal. Or never rode them. One of the challenges with not knowing stuff is that often one doesn't even know they don't. Just ask Donald Rumsfeld Andy

wheelreason

LOL, "You stop with the brakes you have, not the brakes you wish you had"...

Iride01 

Welcome to BF.

Where exactly on the brakes did you spray the WD-40? In what way were they not working? Are the cable pulled rim or disc brakes. Or are they hydraulic disc brakes?

If you sprayed the WD-40 on a rusty cable or rusty pivot point on the calipers to free them up, then you also likely got some overspray on the pads and rim or rotor. All that definitely needs to be cleaned off and the pads changed. Though for rim brakes, I have just cleaned them good and endured the squalling noise for a month or more and they finally went back to being silent.

ScottCommutes

Embrace the horrible sound. It makes people notice when you have to brake to get around them.

daniell

Rim brake squeal serves as my horn.

GamblerGORD53

Don't feed the TROLL.

sweeks

- Marvin, the Paranoid Android

(EDIT: a Hitchhiker's Guide to the Galaxy reference)

wheelreason

In all seriouslness, I have the front cantis set up so they squeal loudly on purpose (long 2 tone pads), makes the MUP rides almost bearable....