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NSW [Sep 25, 2016] Learn how to maintain disk brakes (NSW)

Discussion in 'NSW' started by imagineero, Sep 21, 2016.

Learn how to maintain disk brakes
Start Date: Sep 25, 2016 09:00
End Date: Sep 25, 2016 11:00
Time Zone: Australia/Sydney +10:00 AEST

Rosehill TBA
Rosehill Racecourse

Posted By: imagineero

Confirmed Attendees: 0
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  1. Will be servicing the disk brakes on my bike this Sunday, most people don't realise that brakes can be serviced and performance significantly improved for virtually nothing. As mechanics replace brake pads they generally push the pistons back into the calipers without cleaning them which causes the accumulated road grime to start seizing the piston in the seals. The end result is wooden brakes with no feel and no power, its not unusual on 6 piston brakes for only 2 or 3 of the pistons to be doing the work while the others are seized leaving terrifying brakes. Bikes like this are frightening to ride, you squeeze and squeeze and get very little braking then suddenly another piston becomes unseized and you lockup.

    The other possible result of partially seized calipers is that they can cause pad rubbing during normal riding. Free pistons normally move towards the disk when you brake, then when you release the brake lever they retract slightly. Seized pistons sometimes don't retract - they leave the pad rubbing on the disk which makes an annoying sound.

    On this DIY day you're welcome to bring your own bike along and watch/learn how to perform the task and repeat it on your own bike with assistance. All tools required are provided, just turn up with your bike and be ready to get your hands dirty. You're also welcome just to watch if you'd like to learn how to do it for the future, but you'll be expected to give someone else a hand if doing so. All types of bikes with disk brakes can be done, anything from old single piston bikes up to the most modern sport bikes with DCBS 6 pot calipers. It's a great time to change your pads if they need changing also - in which case bring new pads!

    Kicking off at 9:30, expecting to take 2-3 hours at a relaxed pace. Event will be cancelled if raining. Numbers limited to 10 otherwise it just gets a bit out of hand.
    • Like Like x 7
    • Winner Winner x 5
  2. Disc brakes...And you don't service the discs, you service the callipers. If you want to teach people about things, you should know those things yourself.

    It is extremely rare for pistons to seize on the out application stroke, you can't compress a liquid, and heavy force at the lever/pedal amounts to much more hydraulic force than is needed to move even the most stubborn of pistons. The real problem is with the brake pads dragging on the disc when the sticky pistons don't release when there is no force on the lever/pedal.
    • Agree Agree x 1
  3. Thanks for the spelling lesson tweet ;-)

    I disagree about it being extremely rare for pistons to seize on the out stroke. In my experience it's extremely common, by the second or third set of brake pads it's almost a certainty that some of the pistons will require more force to move than others. Brakes aren't an off/on item where we go from zero pressure to 2000psi, we are looking for feel. On most bikes that are 5 years old or more, typically only a few of the Pistons are doing most of the work until you are at lockup stage. You lose a lot of feel and control. From my experience, a service brings most bikes of that age or older from wooden to eye popping. It's well worth the time and very noticeable the difference it makes. It's the first thing I do on every bike I buy.
    • Like Like x 1
  4. what an excellent way to encourage someone to help others for free!
    • Like Like x 1
  5. What an excellent way to encourage the blind to lead the blind...for free.
    • Dislike Dislike x 3
    • Agree Agree x 1
  6. ^ jesus get over yourself, its not a fcuking spelling competition
    • Dislike Dislike x 2
    • Agree Agree x 1
  7. And the aim of the post wasn't to fcuking spell check, but you probably couldn't read any of the words with more than 4 letters...
    • Agree Agree x 1
  8. jmcjmc
    Ummm, I don't think its spelled that way guys o_O

    (too early for making the funny. Sorry, not sorry...O:))
    • Funny Funny x 6
  9. Well done imagineero on the offer. I don't know what sort of service you intend doing whether just a piston clean or a full service of new seals & fluids but your offer to show people is in the right spirit. The problem I see would be the person without much mechanical knowledge attempting a task on such an important item as brakes and getting it wrong.

    You're being bloody picky Tweet because the guy said disk/c brakes and not callipers. I think even the dumbest person would have understood what he meant. BTW ... when I service my callipers I also have the facilities to service the rotors when they need a light grind.
    • Agree Agree x 2
  10. when i first read it i thought you wrote, your being Prick Tweet. i would of had to agree with that too.
    poor blokes just trying to help people out ffs...
    • Agree Agree x 2
  11. Thats great thanks for the info on breaks.
    • Funny Funny x 2
  12. Woops sorry that was brakes.
    • Funny Funny x 5
  13. While you are at it cleaning the caliper pistons... please take the time to show how to clean and free up floating disc rotors.
    Alot of rider say their front brakes pulse and my disc are warped... try cleaning the brake rotor bobbins first.

    Take a large diameter bolt and nut that fits the hole of the rotor bobbin and some large washers.
    Put a washer on the bolt put it through the hole of the rotor bobbin put on another washer and then the nut.
    Put on some nitrile gloves and spray the bobbin with brake cleaner then tighten the nut to clamp onto the bobbin... now just turn the nut clockwise so that the bobbin begins to spin... the bobbin is tight but will spin. spray some more the clear out the muck in the gap between the bobbin and hub while spinning the bobbin.
    Do all you rotor bobbins to free the disc.
    • Informative Informative x 3
    • Like Like x 1
  14. Clean the bobbins by all means, although I use an easy out & slow speed drill in reverse. Another cause of pulsing is the variation in rotor thickness. I've reconditioned rotors with as much as .004" variation. Even with .001" variation the high spot will bind. I don't know if the cause is a manufacturing fault or material hard spots but sitting at traffic lights with the front brakes on is not a good idea.
  15. Thanks for the tip! I've not done anything more than add a drop of 3 in 1 to these in past. That's certainly an idea I'll be using in future.
  16. Well done mate, you can also check out the delboys garage YouTube channel for bike maintenance tips, at the moment he's doing a street fighter build so you will have to probably search back a few episodes.
    Be excellent to each other.
  17. For those that are wondering about the process, there's nothing mystical about it. A short run down;

    After removing one caliper and the pads, take the top off the master cylinder (otherwise risk damage to it when pressure builds) and ensure there's enough fluid, protect bodywork as necessary. Pump out first piston and get to work cleaning. I use fresh clean brake fluid to clean with and it works just fine with no risk of damaging seals. A toothbrush gets most of the work done, and if you have a stubborn grime ring (many do) then soft tools like padlepop sticks and disposable plastic knives are used to scrape it off without damage to the pistons.

    One a single piston caliper it ends there. On a multi piston you need to seat the now clean piston and ease the next one out. Depending on how many pistons you have and the arrangement (all activated by one master or split into different masters) some combination of clamps, wedges/chocks and pieces of flat bar restrains the pistons you are not working on allowing you to unseize the frozen ones. On 6 pot calipers you sometimes cant get access to the piston near the caliper in which case rotate them with pliers with the jaws protected by plastic to prevent scratching. Once all pistons are reseated (sometimes necessitating removal of fluid from master cylinder) a wipe down with clean rags and re-assemble then move on to next caliper.

    Once all reassembled, attached a bleed hose to each nipple in turn, some bikes have a set order for bleeding, and flush and replace the fluid with new. Old fluid takes on water which causes corrosion internally on pistons, and loses some of its feel and heat resistance. Top up fluid as required and refit master cylinder lid. Clean disks and calipers with brake cleaner and go for a short ride to wear the brakes in.

    It's pretty straightforward and less complicated than it sounds, on a small bike one one or two pot brakes the whole job can be done in under an hour, on a large bike with 3 sets of 6 pot calipers and combined braking it takes a few hours but its no harder. The difference is immediate and very noticeable. I find that on most older bikes this procedure has never been done, people simply force the pistons back in and replace pads each time. So if you're bike is 10+ years old you get a huge benefit from this, bringing your brakes back to new. I sold my beemer last wee and added a 2002 ST1300 to the stable which is suffering severely from wooden brake syndrome, from my experience of doing this to a lot of bikes you get a lot of feel back.

    I find that on many bikes only a few pistons are doing the work. The effect of this is that you get very little lever travel, the lever feels hard. Because the cylinder displaces a set volume of fluid and only a few pistons are moving, they move a lot for a small amount of lever pull. The breaks are not very effective and it feels like you need to pull quite hard to get good breaking. The seized pistons let go unpredictably, they all require different levels of pressure to get moving and when you squeeze really hard they suddenly pop, making braking unpredictable. With all pistons free to move and requiring the same amount of pressure to get going, plus fresh fluid, the brakes once again have "feel". You get a little more lever travel which gives you more control, and the amount of braking is linear compared to the amount of lever travel. Since the fluid is acting on many pistons, the amount of effort required is reduced also. I've ridden some bikes that needed a full four finger handful of brakes to pull up, but once cleaned and maintained two fingers is enough to controllably and predictably apply any amount of stopping power required.

    The trick mentioned Giggit adds another level for floaters and sounds well worth doing.

    None of this is especially hard to do, but can be a little frightening if you've never worked on your own bike. Or maybe you just don't have the right tools. Different bikes might be using bolts, allen keys, torx heads, or some combination, then you also need some bleed hose, hand tools, clamps etc. Everything is on hand, so it's a good opportunity to either do this to your own bike or learn how its done so you can do it at a later date.

    Some people say "I'd only trust my brakes to a mechanic", but I've not ever found a mechanic who services brakes, they simply replace. If your calipers are seized they fit new calipers. My brakes are one of the few things I wouldn't trust to a mechanic!
    • Agree Agree x 1
    • Informative Informative x 1
  18. With zero interest and the possibility of light rain tomorrow I'm cancelling the event.
  19. A mobile mechanic we use to use would make new pistons out of stainless rod for my quad as they operate in a fairly harsh environment, never had a problem with them seizing afterwards
  20. Never use 3 in 1 or WD or penetrating oil for this. It'll help free the bobbin in the first instance but attracts and retains dirt/grit straight away - so you'll be back to square one in no time. A liberal spray of brake cleaner is the way to go.
    GigittGigitt 's description is the way to go. Check out youtube for this - heaps of good vids to show the way.

    A nice easy maintenance trick to keep on top of things.
    • Agree Agree x 2