There's a scraping noise when I brake." Workshop manager Richard from Aachen says he hears this sentence several times a week. When his customers come to have their bikes serviced, the brakes in particular are often at the limit of their functionality - or long past it. The scratching is caused by brake pads that are worn down to the metal base, and metal on metal not only produces this heart-rending noise, it also produces virtually no braking friction. "The nasty thing about brake wear is that the loss of power is gradual and therefore difficult for the driver to notice. Very rarely a part tears or breaks, in 98 per cent of cases you can restore the function by simply replacing wearing parts or aligning the pads."

Bike brake maintenance: recognising the problem

It is all the more understandable that a layman would like to have his braking system checked by a professional from time to time if he uses his bike a lot and regularly on the road, but especially if it is a heavy cargo bike or a fast pedelec. However, the check-up interval is reduced to just a few weeks for these particularly heavily loaded brake systems, and who wants to visit a workshop every two months, especially as they are overloaded anyway and have to charge for such checks. In the following tutorial, we not only want to take away the fear of bikers having to do their own work on the brakes, but above all to sharpen their awareness of when action is required; because, as Master Richard says, the rider only notices the reduction in braking performance little by little.

Colourful system world

Although the market for commercially available brakes is fairly straightforward, there are some systems that require different levels of maintenance. The simplest grouping is rim brakes and disc brakes. Their name indicates the surface on which the braking force is exerted. There are also old-fashioned stamp brakes, which act vertically on the tread of the tyre, but these belong in a museum rather than on the road. A further distinction is the transmission of the braking impulse either by cable (Bowden cable) or by a hydraulic line, which can be recognised in case of doubt by whether or not a small piece of wire is clamped to the brake body. If not, it is a more modern, more efficient and less maintenance-intensive hydraulic brake. For the sake of simplicity, we will divide the tutorial into the two most common types by far: mechanical rim brakes and hydraulic disc brakes, but provide separate tips for the other two combinations.

>> Tips for the maintenance and care of disc brakes

>> 5 tips against squeaking disc brakes

>> Brake know-how: How MTB disc brakes work

>> Braking tips from a pro: "Many bikers brake incorrectly!"

>> How-to: Correct tightening - adjusting the torque on tour

Three basic instructions for working on brakes

• Take your time: The brakes can make or break your health and safety; rushing between the door and the door can even be fatal!
• Oil may be necessary during maintenance, but it must never get onto the brake surfaces or pads. If it does, remove it thoroughly with brake cleaner or a similar solvent. And NO, spray oil of any kind does not help against squeaking brakes.
• The work is worth it: a poorly adjusted and worn brake, even if intact, can increase the stopping distance threefold. With heavy bikes and 25 km/h, this can be 12 to 15 metres more.

Maintenance tips: The rim brake

Little has changed in the technology of mechanical rim brakes over the last 20 years. There are three different types: In the case of caliper brakes, which are mainly installed on sporty bikes, the Bowden cable actuates a type of caliper that squeezes the brake shoes towards the rim. Their advantage is that you need very little lever travel on the brake lever to open and close them, but they are more sensitive to rubbing on the rim. If the brake consists of two elements mounted on the fork blades and a brake cable that splits in a Y-shape above the tyre, it is called a cantilever brake. They are space-saving and can also be operated with little lever travel. Their weakness is their efficiency; you need a lot of force to generate enough braking pressure. V-brakes (pronounced "like") are currently the most commonly used. They also sit on two sockets along the fork, but the cable comes through one of the legs at the side and is clamped on the opposite leg. They are less susceptible to dragging, generate more braking force with less hand power, but require differently geared levers. Mixing the systems is not advisable. The most important aspect of all three variants is the condition and alignment of the brake pads. It is worth briefly checking the brake pads with your eyes and fingers every few weeks:

• All brake pads have grooves or indentations in the braking surface. If the rubber is worn down to such an extent that the surface pressing on the rim is a homogeneous rectangle without these indentations, the brake pad is worn and must be replaced. In the case of pads that are fitted in metal bases (p. 73 above), the pad must still visibly protrude beyond the metal; a new one should be fitted if it is less than 1 mm thick.
• Pull the brake lightly and push the wheel slowly; the dragging brake should not make a scraping noise, otherwise there may be small foreign objects in the rubber that need to be removed with a pointed object. If the pad squeaks or stutters, the brake shoes must be aligned as described below.
• The brake pads should be pressed onto the rim at a right angle, positioned exactly on the braking surface, i.e. neither twisted nor tilted, not touching the tyre and under no circumstances protruding towards the spokes. It may be necessary to realign the pads or brake shoes due to material wear.
• Check the lever travel: Pull the front brake when pushing the wheel in the direction of travel; the wheel should lock before the brake lever has been pulled half way towards the handlebars. Do the same with the rear brake, but push backwards.
• Check pads older than three or four years for elasticity with your fingernail. If you feel plastic rather than rubber when scratching and pressing, the plasticisers are gone and hardened rubber brakes significantly worse, please replace.
• Check the brake flanks, i.e. the surface of the rim on which the brake shoe presses, for dirt, especially oily substances, and if present, remove with a kitchen cleaner, for example. Some rims have a continuous groove along the flanks, which is also an indicator of wear. If the metal is worn down to the deepest point of the groove, you really need a new rim. Without a wear groove, it is difficult to make an assessment; this should be done by a specialist, especially if the surfaces are not smooth and flat, but have grooves and protrusions.

Outdated system: the coaster brake

If you miss the classic coaster brake here, not only is it quite difficult to maintain because you have to open the brake drum and remove the rear wheel, it is also weak and outdated. Many people swear by it out of habit, but if the bike has an additional rim brake at the rear, it is better to use it, you react almost a second faster and the power can be dosed much more precisely. Important: In an ideal full braking manoeuvre, the front wheel provides around 85% of the total braking power, so you should always decelerate both wheels, i.e. maintain both brakes. It is an absolute myth that you are more likely to take off with the rear wheel if you only brake at the front instead of with both systems!

Worn rim brakes? What to do now

The diagnosis of brake wear is therefore not difficult, and to be honest, the steps that can be taken by the layman are not more difficult either. Anyone can really take five basic measures.

Adjust brake play

If you can pull the brake lever very far towards the handlebars until the braking effect kicks in, you can fix this in 15 seconds. On each brake lever of Canti and V-brakes, the cable exits the lever through a kind of nut (illustration on the right). It consists of two parts that have to be screwed out of the lever by one or two turns with a normal right-hand thread. This brings the brake pads slightly closer to the rim without the lever being pulled. Check briefly whether the brake now "grabs" early enough or even grinds. Now adjust the distance to the rim by turning it in and out so that the latter is not the case. Important: Then turn the narrow of the two nuts on the brake lever side back again without turning the adjusting nut back in. This secures the desired setting. If the thread of the adjusting nut is not sufficient to set the desired position of the pad, screw the nut back in completely, press the two brake callipers against the rim by hand and release the clamping of the cable on the brake. This is best done by two people. Now pull the loosened cable tight, i.e. clamp it a little further up again. Tip: Place a beer mat between the brake pad and the rim, then the distance will fit exactly later! Tighten the cable properly and check it for tightness by briefly pulling the brake to the maximum. Incidentally, mechanical disc brakes are adjusted in exactly the same way, except that they react more sensitively to every turn of the brake lever. The adjusting nut is also rarely located on the brake body and not on the lever.

Align coverings

This step is deliberately placed second, as it is incredibly simple if the brake clearance is correct. The brake pads are each secured in the leg with an Allen screw. Loosen these only slightly, the base or brake shoe can now be moved. Place one hand on the brake lever and hold the pad with the other so that it is exactly vertical and only points at the braking surface of the rim. If you now pull and hold the brake lever slowly and firmly, you only need to tighten the Allen screw on the base and the pad is perfectly aligned. Perfectionists can place a double-folded sheet of paper between the rim and the rear third (in the direction of travel) so that the pad is minimally bevelled; this often prevents squeaking. Repeat on all brake pads on the wheel and briefly check the play again. With hydraulic rim brakes, the pad is firmly seated in the plunger, which is pressed out by the fluid. Its alignment and position is therefore adjusted by slightly loosening the complete brake cylinder, which is mounted on the fork or additionally on an inverted "U". Here too, the brake is applied in the correct alignment and the retaining screw is tightened again.

Replace pads

If the pads are used up as described above, you should take them to the shop to buy new ones. On some brakes, the pad and base are one component and are replaced including the fixing screw, on others you can remove the pads in their installed state and replace them with new ones, there are two different lengths here, so the sample can be important as a template.

The pads are secured with a screw or split pin; without this, the old pads can be pushed out to the rear with a flat-blade screwdriver. If you have to remove the metal bases, it is important to remember that the open side for inserting the new rubbers must always face the rear in the direction of travel, otherwise they will fly out at the first brake application!

Oiling

If you are working on the bike anyway, you can also maintain smooth running. Two drops of thin oil on the contact points between the frame or fork and brakes - where parts move against each other - are sufficient. No oil should get onto the pads or rim. With a little skill, you can also oil the cables without removing them. All you have to do is position the wheel cleverly to allow oil to creep down along the cable into the cable housing, see image p. 71. With hydraulic brakes, the drop of oil should be behind the pad, pull the brake, carefully dribble a little oil between the base and the pad and distribute it by braking several times.

Cleaning

You can use a grease-dissolving cleaner to clean the rims; cleaners from specialist shops that are actually intended for the chain have proved effective. Riding in the rain can wash sand onto the rim; although this does not necessarily interfere with braking, it does increase wear, so simply rinse with water from time to time. If aluminium shavings or stones have actually landed in the brake pad and scratched the rim, the wheel must be removed or the pad, which is quicker. You can work on rubber pads with sharp objects - simply remove all foreign objects and carefully refit everything.

Repairing hydraulic disc brakes

Many owners have the greatest respect for servicing modern discs. This may be due to the relative unfamiliarity of the technology, perhaps also because of the rather encapsulated design: You can see much less of what is happening. We also advise non-experts not to open up the hydraulic system completely and, for example, to lay new lines, but checking and changing the pads is twice as easy as with the mechanical system and is also limited to just three major tasks: checking and, if necessary, changing the pads, aligning the brake disc and bleeding the system.

• As the pads in the sockets of all disc brakes, including mechanical brakes, cannot be positioned incorrectly, there are only two potential problems with them. They can be worn or damaged, which can be caused by foreign objects or heat during extremely long, hard downhill braking. However, both of these occur rarely and are more likely to happen in high mountains and during technical off-road use. Wear can be felt in the significantly longer lever travel of the brake, but in contrast to mechanical brakes, only when the brake pad is at the end of its life. Before that, a huge advantage of hydraulics, the fluid compensates for the deteriorating pad. However, you can also see the wear on the pad itself, albeit not as clearly - so in addition to regular visual inspections, always keep an eye on the lever travel.

• Disc brakes can grind or make a rhythmic "sling sling" sound either after servicing or after small bumps, falls or "tumbles". You don't have to put up with this. If there is a noise or the wheel does not turn freely as usual, you should realign the brake calliper as quickly as possible and, if necessary, carefully adjust the disc. Such imbalances in the running of the brake disc grind in, which means that once one part of the disc has been ground differently than the rest, this leads to an uneven braking effect, which in turn leads to an even stronger imbalance.
• Unusually spongy braking behaviour is usually due to air in the hydraulic system. You then have the feeling that there is a cushion or pad between the lever and the brake, and the brake reacts with a time delay. Only by pumping the lever several times does a similarly direct braking sensation develop. The brake should then be bled, as the reaction time increases significantly and at some point the lever travel to the handlebars is no longer sufficient to build up any usable brake pressure.

Disc brake maintenance: DIY or service man?

The main work is to observe and assess the condition of the brake. We editors don't want to decide whether you should visit the workshop or do it yourself if you notice any of the symptoms. Changing the brake pads is so simple that in 99 per cent of cases no technician is needed. Complete novice mechanics should outsource disc alignment and system bleeding.

Coating change

Brake pads are really just inserted into the base (see illustration above). To remove them, the wheel must be removed. On the side facing away from the disc, the pads are held in place with a thin screw (very rarely just a metal pin), which is often secured with a split pin. New pads are supplied with these two parts. Once the split pin and retaining screw have been removed, the pads can simply be pushed out towards the disc. Depending on the manufacturer, they are either firmly pressed into a retaining clip or lie loose in it. When removing them, please note how these three parts are combined and take a photo if necessary. Using the pad as a pattern, provide a replacement and insert it back into the shaft in the same way, secure with a screw and split pin, done! If the pistons that push out the pads do not slide back into their original position in the brake calliper on their own, it is worth buying a resetting tool (round picture below right). The brake plungers can be easily pushed back with such a "trowel" - do not experiment with screwdrivers or similar, as this could damage the system!

Align base and disc

If the disc and the pads are rubbing against each other, you can at least try to get to grips with this by repositioning the brake pedestal. This is extremely simple. The base is only ever attached to the frame or fork with two bolts. Loosen these two screws one turn each and check whether the component can now be moved against the wheel. If so, tighten the corresponding brake to align the base. Tighten both retaining screws one turn again. Important, as it is difficult to find the correct tightening torque without a torque spanner. If you have one, you should definitely use it here.

At least the continuous grinding should now be gone. With the rhythmic "sling sling", the problem is more likely to be that the disc is slightly bent at the side. There are alignment tools for this, such as the one in the picture below. Ideally, the disc should be aligned in a special centring stand, but small imbalances can also be corrected on the wheel. To do this, turn the wheel and look for the points where the noise is audible. A look inside the brake calliper shows whether the disc is hitting on the right or left. Mark the point in front of and behind the base on the outer edge of the disc with a thin felt-tip pen. Now place the alignment tool between the markings and bend very carefully in the direction that does not rub. Turn the spot between the brake shoes again. If there is still contact, repeat the process. Patience or experience is required here, the "bending" should always be done very sensitively and slowly intensified.

Venting

To get air bubbles between the master and slave cylinders in the brake lever and brake itself out of the closed system, you need a so-called bleeding kit such as the one from Park Tool, probably the most functional for SRAM and Shimano, for all other brands we recommend www.bleedkit.com. The principle: Suitable adapters with syringes are connected to both the lever and the brake caliper, which are filled with the same brake fluid that was filled in during assembly. Bubble-free fluid is fed into the system from below, a mixture of air and brake fluid is pressed into the syringe plunger at the top and the bubbles settle at the top. By moving the fluid from the upper syringe to the lower syringe several times, the system is free of air at the end and can be closed again. The brake pressure should now be immediately available again when pulling. The procedure is not difficult, but such a set costs around 150 euros and must be compatible with the brake manufacturer.

Important!

New brake pads should be braked to extend their service life and to prevent uneven wear of the disc. The reasons for this necessity are of a physical and chemical nature, but have been proven hundreds of times. To do this, drive off with the brake rubbing minimally on the first journey after changing. This rubs off the uppermost, never 100 per cent smooth particle layers of the pads in such a way that perfect, conclusive contact with the disc is achieved afterwards. This should take several minutes or up to two kilometres. Hot braking is not quite as essential, but if possible, take a long, steep descent at speed as soon as possible after the change, but keep the brakes slightly applied. The discs and pads get hot and sometimes even turn blue. This causes chemicals to evaporate, without which the pad material will last longer.