Cam MTB - the Cambridge Mountain Bikers' Forum

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DISCLAIMER. MOUNTAIN BIKING CAN BE DANGEROUS. YOU JOIN US AT YOUR OWN RISK.

SAFETY BRIEFING.

  • Wear a helmet. Despite recent advances in medical science, brains still cannot be mended nor replaced.
  • Wear gloves or mitts. Hands often hit the ground first. Cuts and grazes invite infection and a hospital visit.
  • Wear eye protection, it only takes a twig or thorn to lose an eye. Crud catchers are a good idea in mucky weather.
  • When downhilling, for your own protection, allow plenty of space behind the rider in front.
  • Bring a bare minimum emergency tool kit and a spare inner tube.
  • Breakdowns are a bore. Plan not to have any by ensuring your bike is in perfect working order.
  • Punctures are also tedious. You can minimise them by fitting latex tubes, slime tubes or running tubeless tyres.

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do brake rotors wear out?

Hi all, no doubt if you have ridden near me, in the last couple of months, as i attempt to stop, you will have been treated to the sound of tortured brakes working badly.

it has got to the point where i have less beaking than my road bike.

i have tried prety much everything! new pads - work for one ride then back to not working.

blead the breakes 3 times now, even to the point of dumping ALL the old fluid, then purging the new oil of air before putting it in the system again. - no joy.

i have removed the breal leaver and cylinder, greased the pistons (with rubber grease) even though they moved freely and evenly. - no joy.

then i changed to a brand new set of Avid Elixr breaks. - slight improvement in performance but still a massive racket under breaking.

this only leaves the rotor to try. using a vernier it measures 1.82mm thickness, the same as a brand new rotor i have. i'm going to order a new rotor as it is the silly Shimano splined fit rather than the 6 bolt that the rest of the world uses.

so has anyone else ever had this problem? A rotor that appears to have NO contamination, dammage or apreciable wear, breaks that appear to be working correctly and fresh pads from different batches and suppliers, but the bike still wont stop?

yes i know i have a rep to live down to, and i habe been putting on a few pounds but this is a serious question and not an excuse, has anyone else experienced this and found a solution?

Pat

Re: do brake rotors wear out?

Hi. Pat
Sounds like you have tried most things. In my experience noise is usually down to contamination of pad or rotor and even if the rotor is a bit worn the pad will soon conform to any wear grooves on the rotor. Alignment is also a possibility-sometimes the loosen caliper, squeeze lever, re-tighten doesn't work that well as the caliper can still twist when tightening due to bolt torque. it may pay to eyeball it all up & tweak it a bit. A dead giveaway for misalignment is if the lever feels spongy or the disc is pushed sideways when the pads contact the rotor. What type of pads do you use-organic tend to wear quickly but sintered take longer to bed in & wear better.Sometimes you can be unlucky & the frame/disc interface has a natural frequency which can be difficult to trace. Are the disc mounting bosses in line & faced-probably not so important with post-mount adaptors used these days.

Re: do brake rotors wear out?

Hi Rick,
thanks for that, i was just logging back in to say a couple of extra bits.

these are the origonal rotors and Shimano XT breaks that are now 3years old, may be significant may be not.

there is a blue hue to the rear Rotor and a few ridges that run the entire way round the face of the rotor, a sign of over heating and general wear?

the rear rotor is 160mm and since i wore out the first set of pads i have always used sintered pads(from superstar mainly) but i'm trying NukeProof ones too.

i have been reading about it on line and it sounds as if people get this as a symptom of bad breaking technique, but only on the big stuff, not on our XC style country.

other suggestions seem to suggest bigger rotors to spread the heat, deglaze the pads (after 1 ride?), use sintered pads (done), learn to break properly (firm breaking and don't drag the brakes), loose weight (ha ha!) and somthing like a fluid bomb - puts more fluid in the system so harder to overheat.

oh well, a new rear rotor and set of brand new XT break set has just turned up from mister Merlin, this bloody well better fix it!

Re: do brake rotors wear out?

Hi Pat,

Hope the new rotor/pads sort it out, otherwise I suspect you are going to break something! However, I'm surprised Pasty has not been along to comment on your mispelling of brakes..braking...etc !

All the best

Pete

Don't buy new rotors just yet. Re: do brake rotors wear out?

Hi Pat don't buy new rotors yet.Usually this is contaminated rotors. Oil gets sort of ground into the steel rotor. The Man from Hope told me to clean mine (rotor) with methylated spirits. This has always cured the problem. I have never worn out a brake rotor. The ones on my Marin were 10 yrs old, and had suffered your symptoms on several occasions. inaccurate WD40 spray after cleaning is the prime cause for me.

Tom R

Don't buy new rotors just yet. Re: do brake rotors wear out?

Hi Tom, thanks for that. that was about the only thing i did not try.
Doh!
new rotor arrived and fitted yesterday!

now you come to mention it, there is a good probability that this could be the main reason for my issues.

i do use WD40 after the occasional times i wash the bike, well i know for the next time i'm tempted to do some tinkering.

after fitting the new rotor i did some further experimentation.

New Avid ElixR on a new rotor worked better but still not as well as i was expecting.

old XT's on the new rotor, about as good as the Avid's. bit disappointing.

new XT's on the new Rotor, flatspot on the tyre on first test

well i will see how it goes tonight in the wilds of the north of Cambridge.