How-to: Front disc brake calliper servicing

Since the arrival of the Haynes manual, I’ve not thought it overly necessary to keep posting how-to’s, unless I were undertaking an undocumented procedure. Performing a partial strip down and service of the front brake calliper is one such procedure. I do this every 2’500 miles, as I ride during winter when the calliper and its components are extremely vulnerable to road salt. If left unchecked, the brake will bind, internal components will seize and sorting out that mess will be complicated and possibly expensive. A stitch in time saves nine and all that…

Warning: The brakes are a life-and-death part of your bike! Don’t tinker with them unless you have the technical competence to do so! If in doubt, seek professional help. Some of the chemicals used are quite nasty – protective gloves should be worn and the area should be well ventilated. As always, I take no responsibility whatsoever for anything terrible that may result by following what I’ve written. This article is to be treated as an account of my own personal experiences.

What this procedure involves is essentially removing the pads, detaching the calliper, partially disassembling it, cleaning everything up, paying particular attention to the more vulnerable parts, inspecting these parts for corrosion, wear and damage, applying the correct greases in the correct places and putting it all back together again. It takes about 1/2 an hour to do this.

Here are the tools I use:

  • Torque wrench
  • Breaker bar
  • 8mm and 12mm sockets
  • Toothbrush (not one you currently use on your teeth!)
  • Red rubber grease
  • Loctite 243 (blue).
  • Copper grease
  • Brake cleaner
  • 240 grit wet and dry paper
  • Newspaper and kitchen towels

To start, the brake pads are removed first. I first push the calliper inwards towards the disc with the palm of my hand so that the pads can be removed more easily.

Next, the pad retaining pin is removed with the 8mm socket:

Now the pads may fall out, or they may have to be pulled out. Here they are, nice and filthy. Now is the time to check how much friction material you have left. In my case, I have a good few thousand miles left out of these – might need to change them at the next service:

From the perspective of facing the the front of the motorcycle, the pad on the left faces the left side of the disc and the pad on the right (with the hook on its end) faces the right side of the disc. The friction material should be at least 2mm thick and evenly worn (not thicker at one end of each pad than the other and the same thickness on both pads. It should not be cracked or show any signs of damage (chunks missing etc). If in doubt, pads should replaced.

Put the pads somewhere safe – we don’t want them to get contaminated with dirt, grease etc. Next, remove the bolt that holds the brake hose to the mud guard with the 8mm socket:

Now that the brake hose is free, we can remove the calliper. It’s held to the front fork by two bolts. Time for the 12mm socket and breaker bar:

Note that Honda specify these bolts as being ‘ALOC’ and state that they should be replaced when you remove them. From what I can tell, they come from the factory with a thread locking compound, which I simply replace with blue Loctite 243 (non-permanent, chemical resistant – designed to hold the bolt in position but can be undone with hand tools). They may also be stretched and weakened when tightened, hence only having one use. I have reused these many times and have never encountered problems. I do not believe that they are torqued up tight enough to make them stretch (30Nm). I have also amusingly found that some people say that ALOC stands for Add Loctite Or Crash!

Now the calliper can be gently released. It is okay to let it hang on the hose if you’re careful not to suddenly drop it. Some folks use a bungee and hang it from the handlebar, taking the stress off the hose. Now we can split the calliper – the gold part (calliper body) separates from the black part (mounting bracket):

Depending on the condition of the calliper, considerable force may be needed to pull the two components apart. They could be seized together if the calliper has been neglected over a long period of time.

Once you separate the calliper from the bracket, you can also remove the pad spring (which might fall out anyway). Here are the spring and bracket – dirty, with remnants of grease on the slider pins:

Now our attention turns to the calliper itself. Observe the two round pistons and black rubber boots – filthy!

We need to do some cleaning. So, time to pump out the pistons. This needs to be done very carefully. Pull the brake lever and the pistons should move outwards. If only one piston moves, hold it down with your thumb and keep pumping, slowly and carefully, so that the other one moves out. Keep a careful eye on the brake fluid level in your master cylinder. DO NOT let it drop below the lower limit marker or you may get air into the system (this is bad!). We’re aiming to get both pistons about halfway out, so that we can clean them properly. You can do them one at a time if you wish.

Here’s what we get when they’re pumped out:

Now it’s time to clean everything up. Pay particular attention to the pistons and rubber boots. I use Wurth Brake And Chain Cleaner with my trusty old toothbrush and kitchen towel (which is very slightly abrasive, so well suited for this job) Wurth Brake And Chain Cleaner is safe on rubber components. Other brake cleaners may not be. If in doubt, you can use pure brake fluid, but be sure to rinse everything thoroughly with water when you’re finished as brake fluid will strip paint!

And when you’ve cleaned everything up, inspect the pistons carefully for pitting and corrosion. If they’re pitted, they can damage their seals and you could get a brake fluid leak which could be catastrophic. They will need to be replaced, along with the seals (which consist of two inner fluid seals and two outer dust seals). Check the rubber boots for any swelling, cracks or other damage and also replace them if needed. My calliper above is okay.

Now we clean the bracket and pad spring:

With the bracket, we have to pay close attention to the two slider pins, making sure they’re not pitted/corroded or damaged at all. Light wear to the paint is okay.

Let’s grease everything up. Apply red rubber grease to the slider pins and smear a thin layer around both pistons to protect against corrosion:

Red rubber grease is safe to use on or around rubber components, and it should not affect brake fluid either.

Now push both pistons all the way back in with your thumbs (or use a block of wood for leverage if thumb pressure is not enough) and reassemble the calliper by pushing both parts back together, ensuring that the rubber boots ‘hop’ over the lips on the bracket’s slider pins. You may need to syphon out some brake fluid from the master cylinder if you’ve ever topped it up in the past. Personally, I have never found the need to.

Next, re-mount the assembly back on the fork, remembering to clean up the mounting bolt threads and adding one drop of Loctite to each Torque them up to 30Nm:

Don’t forget the pads! Roughen up the friction material with some wet and dry paper, then clean them up with some brake cleaner:

Clean up the pad retaining pin (if it’s severely corroded or damaged, replace it), apply some red rubber grease to the o-ring and put some copper grease on the screw threads, as well as on the backs of the brake pads. Be extremely careful not to get any on the friction material! Applying copper grease to the pads will help protect the pistons from corrosion and can also prevent the brakes squealing when they’re used.

Now re-install the pads, starting with the right hand pad, remembering that its ‘hook’ must go over the lug of the bracket:

Next, reinstall the pad pin, making sure it passes through the holes at the bottom of both pads – torque it to 17Nm:

Finally, re-fix the hose retaining bracket to the mud guard – torque to 10Nm.

Now the brake can be tested for binding. Pump the lever until it becomes firm. Spin the front wheel by hand, it should turn relatively freely with little resistance. With a hard push I can get 1 to 2 turns from it. The pads will rub on the disc a little, which is normal. Spin the wheel again, applying the brake before it stops. Then, try to spin the wheel a final time – it should turn in the same way as it did when you first spun it. If the wheel is very difficult to turn, the calliper probably has a lot of internal corrosion and the seals will most likely need to be replaced. But if you follow this procedure at every service interval, that won’t happen for a very long time (17’500 miles for me and counting)!

Advertisements

31 thoughts on “How-to: Front disc brake calliper servicing

  1. i change the pads every 3000 km is cheap now for me 41000km with my cbf125 I burn 2.1 litres per 100km with 3ml aceton every 1 litre 95 octane fuel

    fanis fz6 from greece ( my other bike is yamaha fz6)

  2. Hi. I have 1700 miles on my 2010 CBF125 about 250 miles of which are my own. Last two rides I noticed the front brakes seem to have much less power. Though the still stop the bike I’d describe them as softer and without the bite I remember. Could they be worn already?

    • Your bike is 2 years old, so it’s time to change the brake fluid. I get 8’000-10’000 miles out of a set of pads so I doubt they’re worn, but it’s easy enough to check – shine a torch between the calliper/disc and have a good look; you should still see enough meat on the pads. Remove them if you want to do a more thorough inspection.

      • Thanks for the info – just had a look and there’s plenty of pad there. So its probably the fluid – didn’t know it aged so quickly. I’m new to bike maintainance but I want to do as much as I can myself. Did an oil change and chain adjustment recently so would like to try the brake fluid change too. Thanks again.

  3. Hello
    I think this is a great site, well done.
    I have a all black one year old CBF 125
    I just dont understand one of your stages on the brake pad removal (its driving me crazy) I wonder if you could describe in more laymens terms please, its right at the beginning ” I first push the caliper inwards with the palm of my hand so that the pads can be removed more easily”
    This is done before any pins are removed. I for the life of me dont know what you mean.
    Would you be so kind as to explain to me please?
    Thankyou
    Keep up the good work
    Regards
    Dave

  4. Do you mind me asking where you order your parts for the bike from?
    I came off mine a few days ago and need to get a new fairing and wing mirror.

    Thanks,
    James

    • Usually from eBay (there are a lot of breakers – they often only list a few parts so it’s best to contact them directly and ask for specifics) or Lings if I can’t find them there and the part needs to be brand new and OEM.

  5. Hello, I’m a proud owner of a CBF125 too! Passed my bike test back in 1990 and have had a good few bigger bikes since then but there summat thats ‘lovely’ about nipping through commuter traffic on a little bike but with the experience that comes from 22+ yrs riding, most other riders think yer ‘L’ plate has fallen off until they catch up with you at the next set of lights (!) and see a full beardy growth and and the aged features of a grey long-haired almost 50 yr old hippy 🙂 Like you, I do about 9-10,000 miles a year just commuting up to London from Kent everyday and rack up the miles pretty quickly. Regarding the front caliper I find its a great ‘cheat’ to have a spare on the shelf in the garage!!! No really, buy a spare off eBay for a whatever you think is a fair price and service it at your leisure…. then when the time comes in darkest winter you can just swap over the caliper and service/refurb the other when the whim takes you.

    Top tip that I reckon.

    I did 104,000 miles on my last bike, a Kawasaki W650 I owned from new.

    I intend on doing at least double that on my little CBF!!!

    Nice blog BTW, good info.

    Best

    Dave.

  6. Thanks CBF Rider, i now have some nice clean smooth front brakes. The fluid level on mine is only just above minimum, as it was when i rode it out the shop, so to be on the safe side I cleaned and greased one piston at a time pushing it back in so the fluid level didnt drop to low. Its probably just me but although its normal, it niggles me that the pads slightly rub the disc when the lever is out. I can get 2.5 spins of the wheel if i spin hard, which is fine, but somehow it seems like a design flaw or something, but then again, disc brake are pretty damn effective so its all good.

      • Hi, I’m the very proud owner of a Honda125cbf. I’ve obtained some very good tips from your web site. I intend to do all the servicing and jobs on my bike now the warranty is running out and to save money.
        When you carry out a service yourself at the correct time do you fill in the service book or leave blank. With not having a dealer stamp? What is the best option for re-sale afterwards?

      • For Curly,

        I plan to run this thing into the ground so not going to sell it on, but I do document everything – I fill in one of my service check-lists every time and staple to it any receipts for bits and pieces bought, oil, plugs, everything. If I were buying second hand, I’d trust a fist full of those rather than a book full of dealer stamps.

  7. Having followed step-by-step instructions I have just changed pads @ 10,000 miles now I find I have no brake when I have re assembled rechecked assembly seems ok bled brake no good took to bits again one piston seems to move more than the other despite both being free could a master cylinder seal have been damaged.
    I feel this could be the case and your advice should point out loosen the bleed nipple amply prior to pushing back assembly.

    • if you were replaceing the pads opening the bleed nipple as well as removeing the reservoir cap and adding new dot4 fluid would certainly be adviseable, however there is a warning before the demo explaining that if you have neither the skills or aptitude to complete the task then leave it to a professional

      • Finally got the chance to reply… No idea why you’d touch the bleed nipple at all unless you’re changing fluid or some air got into the system because you weren’t careful and let the master cylinder level drop too low. As I said, seek professional advice and help if you’re at all unsure, and treat my posts as an account of my experiences which may help you understand the workings of this bike a bit better.

  8. Pingback: [Ownership Thread]: Honda 125 Stunner CBF - Page 52

  9. i hav completed 13000 kms on my stunner cbf..it seems as if disc brakes are bit weaker than before….they arent as effective as they were earlier..giv me some suggestions…and my brake oil indicator is is far below minimum…will refilling brake oil strengthen my brakes??
    where will i find this specific brake oil??is there some name for it??and how to refill it??
    in wait of ur reply..

  10. I have been told to change my brake disc for every time I change brake pads, as they wear together – is this really the case?? I have enough material left on my disc, so why change it?? Your help would be appreciated. Thanks!!

  11. I bought a used cbf 125 a couple of months ago and when changing the front tire noticed that the calliper was very stiff and decided to give it a service. I could not remove the calliper from the mounting bracket as it seemed to have completely seized up. The pistons seemed to have seized but I did manage to remove them allowing me to replace the rubber seals which turned out to be in desperate need.
    I then replaced the break pads with a new set and put everything back together. It all seemed to be working well until I took it for a test ride. I got a few miles and then it started to make a loud knocking sound from what sounds like the Calliper. I have taken it back off checked it over and replaced it several times trying to find where i have gone wrong but everything other that the bracket being seized on seems fine. There are a couple of marks on the pistons themselves but they a sliding in and out fine, not leaking any fluid and like I said now have new seals.
    Any ideas what could be causing this? It sounds like maybe the break pads are loose but I don’t see how this could be the case?
    Would appreciate any help as I only got to ride for a week after passing my CBT before having nothing but problems keeping me off the road!

    • Update; I replaced the calliper with a used one I bought off ebay which appears to be in very good condition and I am still having the same problem 😦 this time I decided to take it for a little ride anyway to see if it eased up and also so I could get a friend to listen and see if he could see anything while I was riding.
      Whilst out I noticed I could feel a slight wobble from through my handlebars. I also noticed that at times the noise did seem to stop but could not recognise any pattern to when or why.. it did seem to happen less often when accelerating? I got my friend to have a listen and he said it was definitely coming from the from wheel and it looked like the calliper was being knocked/rattling but when I get off and look everything seems tight and I cant find anything loose..
      Its turning out to be a nightmare.. I am now thinking maybe its a warped disk? I don’t see how this could have happened but after changing the calliper I cant think what else it could be.
      I just want to ride my bike!! 😦

  12. Hello, I just went through a change in both brake fluid and pads. I did not roughen up the new pads. The systems looks as if it is free of air. But. Now the wheel is a little hard to turn. With my hand I can give it a maximum of 3/4 of a free turn. The new brake pads seem to be in touch with the brake disc. After I push the caliper with my hand, it seems to be a little better. So is it because of new pads?? Is it going back to normal after the new pads are being settled? Or is it something else I should check?

  13. What brake pads would you buy for a 2010 cbf? There are a couple of different variations out there and not certain on which ones to buy.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s