No calliper leek, pads keep getting contaminated

JW599

This is really annoying me!

I fitted a new front rotor (when from 160 to 180) massive brake squeal after fitting. Suprised me as I've contaminated pads in my early days of home maintenance so I'm a bit over the top making sure I'm wearing gloves and clean everything with isopropyl wipes.

Whenever I clean the bike I also take the wheels off and wrap the callipers in small bags.

Fitted a fresh set of pads, and cleaned rotor again. Extra careful with new pads and bedded in gently. I also corrected the pistons before fitting as these were not coming out evenly.

At this point all working perfectly, front brake started to feel really good nice and quiet.

Left bike in the garage over the weekend, this morning performance of front brake dramatically reduced and again become very noisy. Really bizarre.

I've checked the front calliper and can't find any leaks, it also wasn't that long ago when everything was re-tightened, had a minor leak at the lever that has been fixed.

Brake lever still feels nice and firm.

I can try fitting the old 160 rotor back but worried about wrecking more pads!

kajjal

When cleaning the rotors make sure you clean the tops as well as the face the pads hit, these can pickup all kinds of stuff that is rapidly put back on the pads.

Also check inside the callipers thoroughly as they often have ridges or gaps where things can get trapped to escape onto the pads or rotors later.

The Rookie

Doesn't need to be contaminated at all to squeal.

Bedding in shouldn't be gentle, quite the opposite, maybe that's your problem!

swod1

Are you sure the calipers are centered? could be off slightly to the disc causing it to make noise.

Is the new front disc one of them floating rotor types I've had issues with these before and gone back to the ordinary all metal ones.

JW599

Ah, getting this issue all over again.

- Checked oil, was nice a full coming out of the top cap when un-screwing
- Cleaned pistons, re-checked and were nice and even
- Replaced pads
- Re-aligned caliper
- Bedded in with some high speed stops (including 30mph+ downhill stops)
- The front brake was running quiet and felt great

Very gradually brake bite reduced over a couple of rides
Bike left in garage for a week
Next ride it began to squeel under heavy braking
This week it I can play it like a violin.

swod1 wrote:

Is the new front disc one of them floating rotor types I've had issues with these before and gone back to the ordinary all metal ones.

Rotor is a basic Shimano one - RT-66, brake is Deore M615 with resin pads.

bobbydigital

The resin pads in my experience are evil and I never use them. If I buy any brakes from ebay normally m165 m785 style I will buy metal based pads, even unbranded ebay jobbies, they bite on the first pull and give constant braking even when wet.

Resins get dashed in to a envelope and sent to the trash.

The Rookie

Resin pads soak up humidity very readily which can make them squeal, or the Shimano glaze rather easily and again that makes them squeal, key to both is to use only firm braking and not ‘sissy’ braking them.

jimmysplash

I have exactly the same problem with my Shimano M446 groupset. I clean the rear rotor, pads are relatively new. Squeals like a pig and the performance completely useless. Check pads and they are contaminated. Rotor is contaminated. And there is no leak. Local bike shop mechanic (knowledgeable geezer) reckons there is an ingrained layer of oil on the rotor thus causing the problem. He explained in scientific mechanic speak.don't know any different and believe him. Haven't bought a new rotor yet but will keep you informed. It is utterly frustrating.

The Rookie

Cleaning resin pads is a waste of time, it’s soaked right in and after you clean the surface it will come out again, I think your mechanic is spouting pseudo scientific BS.

swod1

The Rookie wrote:

Cleaning resin pads is a waste of time, it’s soaked right in and after you clean the surface it will come out again, I think your mechanic is spouting pseudo scientific BS.

Yes had nothing but hassle with shimano resin pads, found uberbike semi metallic to be a good all rounder for the uk weather for where i ride.

Currently have race matrix pads in as they were out of stock at the time i ordered.

steve_sordy

Oil does not soak into metal discs. The only metal components that have that capability are those made from compressed powdered components by a process known as sintering. Brake discs for bikes are not sintered.

I once had a similar problem that drove me mad. What was worse it was intermittent. It turned out to be my daughter's old bike that had been leaning on my bike. It had a leak from the brake lever and was dripping onto my calipers! It only takes one drop.

Are you shielding the discs when you lube the rest of the bike?

There is a method that can be successful to clean brake pads. It is only worth doing if you don't have time to buy a fresh pair. The method is known as the "disco inferno". Put the pads on a concrete surface and soak them brake disc cleaner, or iso-propyl alcohol (IPA). Then get yourself a blowlamp and burn the bejasus out the pads. Put the flame on to the pads until the edges of the pads glow red. There will be a lot of black smoke at first as all the contamination burns off. Allow the pads to cool (the metal backing will be HOT!) Put some 80-100 grit sandpaper on a flat surface and rub the pads over the surface in a circular motion until the pad surface is smooth and clean. Job done. It has worked for me, but it is not a guaranteed surefire winner. You will need to bed in the pads again.

veronese68

JW599 wrote:

Very gradually brake bite reduced over a couple of rides.

This makes me wonder if you are glazing the brake. You've put a bigger rotor on so you don't need to brake as hard, this could cause glazing. Try braking harder than normal a few times and see if the braking improves, might also help the squealing.
I tend to glaze the rear brake on my commuter as I tend to use it gently to adjust speed, I notice it as performance gets worse. Using it harder every now and then helps.
Worth giving it a go as it's free.

swod1

Veronese68 wrote:

JW599 wrote:

Very gradually brake bite reduced over a couple of rides.

This makes me wonder if you are glazing the brake. You've put a bigger rotor on so you don't need to brake as hard, this could cause glazing. Try braking harder than normal a few times and see if the braking improves, might also help the squealing.
I tend to glaze the rear brake on my commuter as I tend to use it gently to adjust speed, I notice it as performance gets worse. Using it harder every now and then helps.
Worth giving it a go as it's free.

This i also thought of, you can easily glaze resin pads if your not careful when bedding them in.

Are the discs for resin only pads as they might have too much of a shine on them as i have in the past taken a piece of wet n dry and roughed up the disc surface which has helped in my experience.

to avoid brake problems i now avoid shimano pads or any resin pads and have been fine ever since.

JW599

Hopefully.... It now seems to be sorted.

I bit the bullet and decided to start all over. Replaced rotor and pads. I was given a tip not to keep the brakes applied when dismounting the bike/stopped for the first few rides with fresh pads as it might cause the brake material not to set evenly.

Instead of the problem getting worse when leaving the bike for a few days, it seems to get improved.

The bike is kept in an old garage that gets hit by alot of direct sun to a window, maybe the recent UK weather had something to do with it.

I also found that I had a lazy piston.

After a couple of weeks the front brake feels better than any brake I've had getting more firmer. Almost went OTB this morning!