HOW TO SERVICE YOUR BRAKES
Brakes are a pretty damn important component on every bike so it makes sense to sort them out. In the first of our step-by-step tutorials, we take a look at the best ways of stripping, cleaning and bleeding your brakes. So grab a brew, pick a comfy seat and soak in this essential wisdom…
1 Tooling up
Before you start servicing your brakes you should kick things off by trying to identify any problems, so get your bike on a paddock stand and give the wheel a good spin, making sure there’s nothing untoward or any horrible noises. Ideally the wheel should spin relatively freely and be accompanied by a consistent noise as the pads brush lightly on the discs. Having done this, it pays to look your bike’s braking system over and identify what tools you’ll need for the removal of the calipers and other parts so you’re ready to get cracking with the service.
2 Caliper removal
Most bikes’ brakes are different but your practice for servicing them is best started by cracking off any pad holding pins, assuming they’re not the ‘R-clip’ type. This will make life easier once you’ve unbolted the caliper, as stiff pins can prove a nightmare to uncrack on a loose caliper. At this point you can go the whole hog and remove the pad pins fully, along with the pads and any spring plates while the caliper is still bolted to the fork leg. Alternatively, unbolt the caliper and remove the above items. As tempting as it is, once the caliper’s removed, don’t leave it to swing on the brake line as this might cause damage to the line or your bike; use a bungie to hang it to the bike when it’s not in your hand.
3 Get scrubbing
Depending on how long it’s been since they were last serviced, chances are the calipers and their components will be in need of a good clean. There are lots of brake cleaning products on the market, so you shouldn’t struggle to get your hands on one. The same goes for the good old toothbrush, which is the perfect tool for scrubbing off dirt and grime. Never, ever use anything like a wire brush, as you’ll risk the performance of the dust seals. Spray generous amounts of cleaner, use lots of elbow grease and have a clean cloth to hand to wipe away the dirt you’re scrubbing off. Principally, it’s the internals of the caliper that you should be most concerned about gleaming up, especially the pistons, but there’s no harm in tidying the outside while you’re at it.
4 Pumping pistons
You can buy a pair of piston pliers online. They allow you to turn the pistons in the calipers without harming them, so you can access their hidden side. It’s important to give the pistons a good clean, so I’d recommend you get a pair. Using normal pliers or anything else will compromise the outer surface finish of the pistons, so don’t even think about it. There are two seals per piston in a typical caliper; a dust seal (nearest the surface), and an oil seal behind it. Both need to be in top condition to create a thorough seal against the piston, so don’t risk compromising them. You’ll want to clean as much of the pistons as possible, but if you try to pump them out you’ll risk the pistons popping out. It’s best to get a piece of soft wood slightly thinner than the thickness of the pads so you can squeeze the brake lever and pump the pistons out a bit further.
Take your time and look to see which pistons move freest and which are most stuck; the hope is that all pistons operate equally. With the pistons further exposed, give them a bit more of a clean and inspect the state of the dust seals. If they’re furry or look like they are bulging out from their recess, you’ve got a problem as it suggests there is corrosion behind the seal that will need cleaning out. To do so you’ll need to drain out all of the fluid in the system so you can remove the piston and extract the corrosion from the recess. You’ll also need to fit a new seal.
5 Greasing up
Assuming the seals are okay now’s your chance to give the dust seals a bit of a lube so the pistons can move freely. Make sure you use a rubber-friendly grease, such as Silkolene’s Red Rubber Grease (never use copper slip). The aim is to try and work the grease into the dust seal, so get your fingers stuck in and manipulate the matter as much as possible into the area. It’s not an easy job, but the gains are well worth the effort. The next part of the process is to push all the pistons back into the caliper so the grease is carried with them. You might be able to use your fingers to do this, but there are specific tools on the market that push all pistons back in sync and save you the hard work. If you are pushing them back in manually, be mindful that as one piston goes in, another might be forced out; don’t let that happen. Lastly, you’ll want to wipe away any excess grease from the moving of the pistons. If you’ve got lube all over the caliper, it’s a good idea to wash the item again with brake cleaner for good measure.
6 Pads and pins
With the caliper cleaned and the seals lubed, your attention then turns to the pads, pins and plates you removed from it. The pins need to be super smooth so the pads can slide effortlessly on them, so they need to be debris free. Scotch pad is a great product for cleaning the pins up which you can scrub with your hands, or an easier option is to hold the pin in the jaws of a drill and then power it round against the Scotch pad. Once clean, give the pins a good inspection, making sure they’re not pitted or bent, as both will compromise the performance of your braking. If needed, replace them altogether. Use brake cleaner and a toothbrush to clean the spring plate, and the same for the backs of the pads. Now’s a good time to inspect the face of the pads and make sure that they’ve been wearing evenly (top, bottom and sides), have plenty of meat left on them (by referring to the inset wear markers) and are not glazed. If the surface of the pad material is glazed you can use a course sand paper to burr them up.
7 Back together
Now you’ve got everything shiny and functioning properly, it’s time for reassembly. Because you’ve pushed the pistons all the way back, it will prove easy to get the pads in place. Because most bikes’ brakes are different, it’s best to refer to your owner’s manual if you can’t remember how the pins and spring plates locate. Some spring plates, like the one on this CBR600, double up as a retaining spring so it’s essential they locate perfectly. Don’t be overly focused on screwing the pins in to the
specified torque setting, as it’s easiest to do this once the calipers are mounted back on the bike, which is the job you’ll do next. Make sure the pads are flush to the relevant internal walls of the caliper so the disc can slot effortlessly between the face of them.
8 Righty-tighty
It’s now time to tighten the caliper back to the fork leg, torqueing it up to the manufacturer’s specification. If you’re unlikely to remove the caliper before its next service, it’s advisable to use some Loctite so there’s no risk of the bolts dropping out over time. Race and trackday bikes are less likely to go down this route as the calipers are fitted and removed far too regularly. What’s most important, regardless of how often the calipers are fitted or removed, is the mounting bolts are correctly secured. You can then torque up the caliper pins to the necessary specification, before pumping the front brake lever to push the pads out to meet the disc(s).
9 Time to flush
Now that the calipers have been serviced you’ll want to change the brake fluid too. A lot of brake fluid is hygroscopic, which means it absorbs water from the air. That’s not a good thing because water boils easier than oil and can mean you end up with a spongy brake.
Air in the system, through weak joints, is another issue you’ll want to avoid. A good way of ensuring you’ve got neither in your system is to flush through fresh brake fluid. Another sign of oil fatigue is its colour, which is usually caused by contamination of brake dust getting past the seals and into the system – you don’t want that. Start by preparing the correct tools you’ll need for the job, including a simple catch bottle to contain the waste fluid.
10 Out with the old
Most modern bikes use a round, plastic container to house their oil, but on this CBR the oil’s located inside an aluminium housing, secured by two screws (that are easy to round off). Carefully undo the screws and remove the cap of the reservoir to expose the plastic guide and rubber diaphragm within. You’ll now have access to the fluid, which you’ll need to extract from the system to make room for fresh fluid. You can do this by pumping it out through the calipers’ bleed nipples, or by using a syringe to extract it quickly and easily directly from the reservoir.
11 Fresh and flowing
Once you’ve made some room for fresh fluid in the reservoir, start to pour in the new fluid. You’ll then be in a position to start pumping the fresh fluid through the system, for which you’ll need a clear rubber hose to fit over the bleed nipple on the caliper, with the opposite end aimed into a receptacle. Unlock the bleed nipple by a quarter turn and pump the brake lever to make the fluid flow. Do this one pump at a time, making sure you’ve closed the bleed nipple again before releasing the brake lever, so no air or fluid can be drawn back up the line. This is a
MAKE SURE THERE ARE NO LEAKS, THAT THE WHEEL SPINS FREELY AND THAT THE LEVER FEELS FIRM.
pretty time consuming process, but it’s important to take your time and do it properly, one caliper at a time. Make sure to keep an eye on the level of fluid in the reservoir, as this will drop down with every pump; never let it run dry or you’ll suck air into the system. It’ll typically take three full reservoirs of fluid to flush a caliper through with new fluid. Once you’ve completed the procedure on one side, do the same on the next, before going back to the first side and pumping through another fill for good measure.
12 Job done
The closing stage is to clean the diaphragm and carefully replace it along with the reservoir lid and any of its internals, making sure the fluid level is sat at the correct level on the unit’s guides. At this point you’d be wise to inspect the lines and make sure there are no leaks, that the wheel spins freely and that the lever feels firm and consistent with every squeeze. If you’ve spilled any brake fluid on your calipers, make sure to wash it off with brake cleaner. It never harms to double check all your bolts again either, so get stuck in and do the rounds before patting yourself on the back and admiring your handiwork.