[Beginner] Brakes squeals like a piggy...

[erickza]

Hi,

 

Sorry if this question is going to offend people as a noob question but I am getting desperate. I bought a Giant Revel 0 two years ago - http://www.giant-bicycles.com/en-za/bikes/model/revel.29er/12798/59411/#specifications - after my wife talked me into starting MTB. Loving the bike and got it at a good deal.

 

We ride here in Durban particularly Giba Gorge for those that know the area. Anyway long story short after my first service the brakes have never been the same. At the first service they claimed they cleaned the pads as they were "contaminated". They could not explain with what. I got home and test rode the bike and there was NO breaks. The levers came all the way back to the handlebar. Phoned the owner of the shop and he told me to bring back. Took it back they now changed the pads and bleed the brakes. Test rode it at the shop and was great. After first visit to MTB park, back the square one. Phoned the owner and got the impression he was not really interested and said the brakes will come back and the squeaking will get better. It didn't.

 

Take bikes to shop number two for a full service and mentioned the long story about brakes. They assured me they will get this sorted. Picked bikes up and test ride felt good. Sadly I did not ride my wife's bike but back to that later. After two ride my rear brakes is squealing badly, embarrassingly badly. Also I cannot get it to lock not matter how much pressure I apply. My wife's bike is so bad she struggles to stop quickly and both front and rear brakes squeal badly.

 

Now is there anything I can do at home to look into the problem. I have never really worked with hydraulic brakes before so I am a bit nervous to start tinkering. But is there perhaps something I can check myself? Or adjust or clean? I'd love the brakes not to squeal number 1 and 2 to be a bit more reactive.

 

Is there perhaps some guides?

 

Thanks in advance, I am getting a bit frustrated.

 

[nox1111]

Go to Midas and get some Wynns Brake cleaner (i think its about R70) - take the pads out, and the wheels off and spray the pads on the braking surface - a couple of times - dirt should run off them, then cover your wheels with news paper that just the disc (rotors) are open and spray them two or three times.  re-assemble and see if its still does it.  Braking performance should also be better.

[nox1111]

I've had an issue before with el-cheapo pads hardeing up when heated over and over - and they started making the most awkward squealing sounds - replacing the pads was all that worked then.

[jules1976]

had this issue as well LBS advised that alignment could be off.

 

after last service back break realigned and all sorted.

 

will also investigate the Wynns brake cleaner option.

[nox1111]

alignment is super easy fix - take a #5 allen key and loosen your caliper bolts - the ones that prevent it from moving side to side - only one or two turns.  Squeeze your brake a couple of times and release, squeeze it a last time and this time hold it - tighten the bolts whilst holding the lever down. release and spin, if it spins freely - it should be good, if not, do it again.

edit: spelling

[Mojoman]

Its up to you how much you want to fiddle but I have held the brake pads over a gas flame for just a few seconds, let them cool then take some sand paper and sand down the top of the pad a little until clean pad material shows. You can also lightly sand the rotors on their contact surfaces (circular sanding motion, both sides of the plate, dont use a very coarse paper) and then go for a ride and get a little speed up (on a flat section) and then make several sharp braking actions. I have used this on my cheap Tektro brakes and sometimes I just buff up the pads on the XT brakes on my other bike. For some reason the Tektro brakes seem to suffer from glazing on their pads, the XT ones seem to not have too much of an issue.

[CdT85]

I had this issue with my Avid Elixir 5's after a bleed/service. Washed the pads in boiling hot water and sunlight liquid, put them in the oven for half an hour to dry, problem solved. 

 

I can suggest Nox1111 advise as well. The break cleaner will do the trick as well.

[David Marshall]

I feel your frustration!  You have two problems 1) functionality. 2) Noise.

 

Looking at 1) first - 'cause we all like to stop time.  Check your lever operation.  There should be some free travel and then the lever should stop before reaching the bar.  The feel should be consistent when you repeat the action. You should not get the brake to "improve" on subsequent activations.  You may feel that the front feels slightly firmer than the rear but this is normal as there is more oil in the rear line.  If you are happy that the levers are fine time to go to the caliper.  Remove the wheel and brake pads and and check out the pistons.  Hold a suitable sized block between the pistons ( to check that they don't move too far out - I use two cone spanners or a tire iron) and then gently operate the lever and see if both pistons move a similar amount.  If one moves more than the other you can clean and lube the pistons by activating the lever so that the pistons come out more than normal (still keep the tire iron between them and you may need to hold in the one that moves easier to get the sticky one out). NB  Make sure that niether of the pistons comes right out.  Clean with a Q tip and some degreaser,  when dry lube with hydraulic oil and gently press the pistons back into position.  Use Dot fluid to lube if your brakes use brake fluid.

 

Now you can look at the discs and pads. Make sure the pads have some life in them and are in reasonable condition. You would be surprised at how many bikes i have in needing "bleeding" when it is just that the pads are worn!  You can give the pads a good wash with detergent and give them a light sanding on water paper.  Move the pads in a figure of eight motion over the paper to keep them level.   Treat the discs the in the same way but I use a bench mounted belt sander to de glaze the discs if they are scoured and badly marked.  Re assemble and make sure the caliper is correctly adjusted to the disc.  After such a treatment give the pads and discs time to settle in by using the brakes sparingly for the first few minutes of braking.  If after all this you still have squealing brakes you might have to look at pads with a different compound.  Hope this helps.

[JXV]

It seems your brake pads are getting recontaminated. you mention adequate test rides at the shops followed by deterioration.

 

How are you cleaning your bike and with what?

any other possible sources of contamination....eg. oil from a car exhaust spraying over the discs when travelling or while stored in garage? riding through oily puddles? spraying Q20 or other oil on derailleur to lube it with overspray onto brakes? excessively lubing the chain?

[erickza]

Just a special thanks to nox1111 for the break cleaner tip. Managed to service my wife and my bike on Saturday and we did our first MTB event on Sunday. Breaks were quiet as a sleeping baby.

 

nox1111 I owe you a beer!

[erickza]

Sorry another question while we talking about brakes, if I want them to bite better must I just increase the mineral oil?

[JXV]

Sorry another question while we talking about brakes, if I want them to bite better must I just increase the mineral oil?

What brakes are they exactly? Checked the thread and cannot find this info.

 

Some brakes have adjustments for reach and so-called 'free-stroke' You can use this to fine tune to an extent but if the brakes have air in them the adjustments will just frustrate you.

 

If the levers have a spongy feel or if they get stronger after pumping a few times then they have air in and must be bled correctly. I have seen many cases where a rider paid to have brakes bled and they still had some air in them.

 

BTW - brake cleaner : the Shimano XT manual says the seals are not compatible with this.

[porqui]

erickza - google and youtube is your friend.

 

There is TONS of stuff on the www which shows/explains how to go about it in detail.

If you are the handy type of guy it's pretty straightforward (You do not have to be an expert anything)

[erickza]

Sorry Porqui, I will do that. I received some great advice that worked I was hoping I could get a nod in the right direction. I guess you can't win them all :-)

[nox1111]

hey, I have a basic tip - in no way a bike shop fix, but you can do it at home, and it takes only about 15minutes for both brakes.

 

What you can try - on top of your brake reservoir topcap - it should specify the oil that you need to use - make sure that you get this.

 

Get your wife to assist - its always easier to help hold things, when you dont have a bikestand. 

Then - and this is not the best, but have worked for me. set your brake lever straight on your bar, so that the reservoir is upright - and the fluid level.

 

Here's the tricky bit - you want your cable almost straight vertical -  you need to get the caliper away from the lever vertically, with no kinks or big bends in the line, stand on a table with the bike and hang the caliper.  Then tap the line lightly, with something hard - like a butter knife's back end - loads of times - almost a vibration more than individual taps - what this does is - it gets any air bubbles in the line to loosen up and travel upwards to the reservoir.

 

tap it for 20 seconds, take a break, and again for 20 seconds. if there's air in the line, there should be tiny bubbles in the reservoir coming from where the brake hose is connected.

 

Let your wife place the caliper on the rotor - don't have to bolt it on, but the pads need to be spaced, and then slowly pump your lever - as is with the reservoir open. 

 

Repeat this proces (let the caliper hang, tap with hard object, hold on rotor pump slowly) 2 or 3 times and then top up the reservoir with the oil as recommended and button everything up.

 

As I said - not perfect, but have sorted out weak brakes for me in the past - as air is more often than not the culprit in weaker brakes. 

[arendoog]

I just rode with my squealing avids  CR for 3 years and replaced them with XT,S .I actually miss the avid cr ,s .They worked as well or even better than the XT,s and now nobody knows I am coming down the mountain anymore