These days the majority of bicycles are equipped with disc brakes, which have almost entirely supplanted traditional rim brakes. The former guarantee an improved performance, but are more complicated to deal with by yourself because they function through a really delicate hydraulic system. Rim brakes, on the other hand, still provide a good level of performance and have the advantage that they can allow even an amateur to carry out maintenance operations. Here, with the help of Stefano Casiraghi, the mechanic from the Colpack Ballan team, is some advice on how to tackle the brakes on your own bicycle, starting with the rim brakes, and then moving on to the disc brake system.
Checking the housings and the cables
To check whether the housings and brake cables are worn, all you have to do is to try out the brakes and see how they respond. If the lever provides a soft and uniform result, especially when you first start squeezing it, then basically everything is fine. If on the other hand it is jerky or stiff, then you need to replace the cable and the housing in question. “It is an operation which is not too complicated, but – Stefano advises – it is always better to get it done by a professional mechanic, because the housings and cables are the only two things which allow you to stop before you hit an obstacle”. Another way of saying that it is better not to risk it.
After the cables and the housings, you need to check the degree of wear of the shoes, the rubber part (sometimes cork) which makes contact with the braking surface of the wheel rim. Usually you find a little notch inscribed on the shoe, on which the limit beyond which it should not be used is indicated. “When four millimetres are left, I would say you should change them in any event” advises Stefano. Once you decide to change a shoe, you need to remove the grub screw or the clip which keeps it in place, pull it out (always in the direction of the rear of the bike) and insert the new one. There are some specific shoes, but most of them are universal. Finally, you need to check that they are perfectly perpendicular to the braking surfaces and well-centred in their seats.
Adjusting the cable
In order to adjust the cable, and thus the lever which generates a more or less immediate braking effect, you need to intervene on the control system present in the body of the brake mechanism. “The basic working principle is the same as for adjusting the gearing: if you unscrew the barrel adjuster, you tighten the cable, and you therefore obtain a more immediate braking effect. If on the other hand you tighten the adjuster, the cable is loosened, and braking will take longer” Casiraghi points out.
Air in the system
First of all, you need to check that there is no air inside the system: the symptoms of the presence of air are a very long travel time on the lever, a continually changing braking bite point, lack of braking entirely, or movement of only one of the pistons located in the calliper. “In the event that air is present, you need to bleed the whole system, but it is better to get a mechanic to do it”, suggests the expert from the Colpack Ballan team, as in the case of the housings and brake cables for rim brakes. The reason? “Because every system has its dedicated bleed kit and also the brake fluid inside is specific to each manufacturer”. However, you can still try what Stefano calls “a half bleed”, that is to say getting rid of the air and replacing it with brake fluid, by acting on the lever with a small glass, but being particularly careful not to let any brake fluid fall on the pads: “they are like sponges; they soak it up and are ruined”.
Replacing the pads
These are another component where above all you need to check their state of wear. This is a “relatively meticulous” operation, according to Casiraghi, because you need to remove the wheel, and thus the disc, and to check visually that on the metal base of the pad there is still enough brake lining in contact with the disc. Generally speaking, once the brake lining is down to 1-1.5 millimetres it is a good idea to replace the pad. In order to do so (always with the wheel removed) you need to undo the retention pin or clip which locks the pads in place and remove the old pads. “At this point I advise that you clean the interior of the calliper with soap and water using a small brush and dry it carefully with a piece of clean paper”. Once you have done this, you need to push the pistons apart and insert the new pads, which can also be manufactured by competitors, but which must be compatible with that type of calliper. “You must always have clean hands, in order to avoid corroding the brake linings”.
Centring the calliper
A final operation for this type of brake is to check that the calliper is centred in relation to the disc, in order to avoid tiresome rubbing. To do so, you need to loosen slightly the screws which fix the calliper to the frame, apply the brake a few times remaining stationary and, while keeping the wheel braked, tighten up the calliper fixing screws which you had previously loosened.