Can disc rotors become 'infected' and lose braking power?

[sage]

Didn't ever think so, but am starting to wonder - constant changes to brake pads later (3rd set now across both my bikes) and I'm finding that roughly 2-3 rides later the pads squeal and lose their braking power.

 

Tried every remedy I've received (light sanding, copper paste, burning in petrol etc) but no way to get the brake pad performance back.

 

Now my thoughts are turning to the discs themselves..

 

Here's my theory: the cheap plastic spray bottle that over the years has housed my bike degreaser (or the degreaser itself?) has somehow gotten something right into the metal of the rotors themselves...plasticisers coming out?

 

Got a new set of rotors recently, put new pads on and they are fine and holding as expected.

Changed the rotors back to use the old 'infected' ones..and bamn, brakes squeal and lose power after 2-3 rides again.

 

Anyone ever had something like this?

[Mojoman]

Personally I can't see steel rotors absorbing chemicals from your degreaser. Out of interest what brakes, rotos and pads are they? After you have scuffed up the pad and rotorsn do you bed them in a bit?

[brad890]

I had something similar, pads kept getting contaminated and squealing like a stuck pig, turned out that the callipers themselves where leaking a little brake fluid causing the problem.

 

but in your case you say changing rotors works, then it must be something to do with the rotors, because if it were contamination changing rotors wouldnt have an effect.

 

i'm interested to hear the answer to your question

[Dirtbreath]

Interesting.

 

Are your new rotors the same make? Wondering if the thickness of a rotor affects where the pads rest and after excessive wear they sit where there is just enough friction to squeel.

[Big H*]

Try Norton to disinfect the virus

[Ysterperd]

Not so much infected as contaminated with oil based solvents like chain cleaner spray etc which somehow stay on rotors. Need to clean them with surgical alcohol and do pads as well then bake pads in oven at high heat, dont burn as this can cause further contamination of pads.

 

Also chech thickness of rotors, most rotors need to be replaced if the thichness is less than 1,75mm.

[braailegend]

I lost a few disc brakes to this, throw everything away and start over. If oil/lubricant got into the calliper its a lost case. I tried everything, from diesel, spirits, cooking it in the oven,burning, degreaser etc. You'll just end up spending more money

[sage]

Thanks - good inputs...

 

Yes, had some trouble with the calipers leaking...new seals and one new caliper was required (dirt seems to get in everywhere eventually, but that's MTB)

 

None of the rotors were old and below thickness - some were only 2 months old.

 

I've a couple of wheelsets, and all rotors were a mixture of XT, XTR and XT Ice-tech

 

From what I can see above my choices are

a) fresh start with new rotors and pads expensive!

b - surgical alcohol treatments (such a solvent has no additives)

 

This whole thing has been a bit of a bummer...I've lost a bit of confidence on the bike as I cant trust the brake stopping power...amazing how that slows one up and you go conservative..

Edited October 14, 2012 by sage

[Johan Bornman]

I think your discs are glazed. A light sanding won't solve the problem. The material is tough and a hard sanding with 80-grit emery paper is what they need. They have to end up with a satin finish, no shine at all. This cannot be done on the bike.

 

At the same time, lightly sand your pads and then gently break in your "new" brakes. A violent first stop will void your hard work.

 

I've written about this before. Perhaps if you search for "brake fade" in my posts, you'll come across the post again. It explains it all.

[Cassie]

JB - that sounds feasible.

 

As an aside...THE ONLY CLEANING i give my brakes...is a once over with the hose pipe - running water (just to get rid of mud, dust, small grit) - then the rotors get a wipe with an acetone rag, just to remove any accidental spillage of degreaser etc that might have ended up on the rotors from my conventional cleaning practices...

 

Then...new pads always need to be "broken in" as per JB instructions....I wet the system with water ...then go bloody fast down the road and GENTLY featrher the brakes till they are dry... works everytime!

 

Finally - i only use resin pads on a matched resin rotor (Shimano DEORE XT)....and four yeras later - only have used 3 sets of pads....mud - water - dust - you name it, i ride it!!

[sage]

Good advice...many thanks!