Brake system screwdriver tips

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Brake system screwdriver tips
Ralf Petersen

counselor

workshop

Brake system screwdriver tips

Brake system screwdriver tips
Everything on stop

If you want to move forward quickly, you should always come to a safe stop. Indispensable: a well-maintained braking system. In this workshop sequence, we give tips and advice on how to skillfully inspect brake calipers and discs and what to look out for when changing brake pads.

Ralf Petersen

06/30/2017

Modern ABS brake systems in brand new motorcycles with their hydraulic or electronic control are often complex systems, but in terms of the brake calipers and brake pads they hardly differ from the classic disc brake systems installed since the late 1970s. Since both the discs and the pads are wearing parts, they should be checked regularly and replaced if necessary. However, the brake caliper must also be checked from time to time for correct function and contamination and cleaned if necessary.

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Everything on stop

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function

If you operate the brake lever, a brake pump piston pushes the brake fluid through the lines into the brake caliper. The brake pistons in the caliper are pushed out and press the brake pads against the disc, the desired deceleration occurs. The friction creates heat and the covering is easily “sanded off”. The resulting very fine abrasion adheres to the caliper and brake piston, among other things. The brake pistons are sealed from the brake fluid by special rubber rings in the caliper, the shear stress of which also means that the pistons return to their original position after the end of the braking process.

Floating caliper brakes only have brake pistons on one side that press the pads on. The other pad is pressed on by the brake calliper, which can be moved and slides on bolts. If you look from the inside at a floating caliper brake, you don’t see any pistons and you can look directly at the back of the pad. But if the floating caliper brake is movable, then you have to be able to feel it. If you grab the brake caliper with your whole hand, you should be able to push and move it very easily. The whole thing feels like the brake caliper is a little bit loose. But this is normal and not because the retaining screws are loose! If the caliper of a floating caliper brake cannot be moved at all or only with great difficulty, the bolts may be dirty or corroded, the caliper no longer slides properly and the pads are only pressed on on one side. The result is poor braking performance and pads worn on one side. This can be remedied by dismantling the brake calliper and cleaning and lubricating the bolts (with silicone / copper paste, depending on the specifications). The advantages of floating caliper brakes are their lower weight and their compact overall width.

A fixed calliper brake always has opposing pairs of pistons that press the pads evenly against the brake disc from both sides. The pliers are rigidly attached to the fork and must therefore not move. Otherwise the retaining screws would actually be loose here. The latest state of the art are actually from racing, so-called radially screwed fixed caliper brakes. This means that the pliers are screwed to the fork at an upper and a lower point, which results in greater rigidity during braking maneuvers. It is entirely possible that a motorcycle has a combination of the two types (e.g. fixed caliper brakes at the front, floating caliper brakes at the rear).

Base control

Regardless of which system it is, a regular check of the coverings is essential. A first indication of worn brake pads is a change in the level of the brake fluid. Wear during braking causes the pads to become thinner, and the brake pistons have to be pushed further out of the pliers in order to press the pads on. This means that more brake fluid flows into the brake calliper and the level in the reservoir drops. Most pads have wear marks. These are mostly elongated notches in the toppings, which are also visible from the narrow side, both from above and below. Similar to the tire tread, the state of wear can be seen, and when you check it, you can also see whether the surface is being pressed at an angle, because then the notches are different depths. With floating caliper brakes, the inner lining is often very difficult to see. Mirrors and flashlights only help to a limited extent. In case of doubt, remove the brake calipers to check. In the case of fixed caliper brakes, the upper plastic cover or sheet metal holder can in many cases be easily removed, thus allowing a clear view of the condition of the pads.

Pad change

To change, of course, the old surfaces have to be removed. There are also different designs here. With some brakes, the pads can be changed relatively easily from above. With other brakes, the caliper must be removed for this. I would recommend this anyway, because I always thoroughly clean the brakes when I change the pads. It is also easier to push back the brake pistons when the caliper is removed. The coverings are of course secured against falling out or slipping. One or more retaining bolts are either screwed or fixed with a split pin, etc. In addition, there may be retaining clips / brake pad springs. It is therefore advisable to look up the repair instructions beforehand and use a sectional drawing to obtain clarity about the structure of the brake. Many specialists (e.g. TRW) offer inexpensive, high-quality alternatives to the original coverings. A look at the machine’s Internet forum provides information on this.

cleaning

The brake pistons come out of the caliper more and more during operation and are therefore inevitably exposed to corrosion and contamination. When installing the new pads (which are back to their original thickness) they have to be pushed back into the pliers. Before doing this, you should clean them thoroughly with brake cleaner, otherwise the soiled pistons can jam and the brake is stiff. Caution: Since cheap brake cleaner can attack both paint and rubber, the sealing rings of the brake pistons can be damaged. That’s why I use the (more expensive) brake cleaner from Caramba to clean the pistons, which is guaranteed not to attack rubber. I still cover tires and painted parts well. The spray head is aimed directly at the area to be cleaned, and the brake pistons are then thoroughly polished with a soft cloth or strip of fabric – do not use anything that is scratchy! I use a special reset device to push back the pistons (at Louis for about 40 euros). Thanks to the even pressure and the large contact surface of the reset device, the pistons do not tilt. Alternatively, you can also work with pieces of wood and a screw clamp. If there is too much brake fluid in the expansion tank, it will be sucked out beforehand. Before the new coverings are installed, copper / ceramic paste, also known as anti-squeak paste, is used. It prevents the unpleasant squeaking of the brakes when it is wet. The paste is applied thinly to the back of the pads and where the brake pads come into contact with the caliper. With a floating caliper brake, the sliding bolts are also lubricated with silicone or copper paste, because the pliers should slide as well as possible. If you find that the rubber sleeves are porous or damaged, they are replaced. When installing the pads, don’t forget the brake pad / retaining springs and mount the bolts or retaining screws according to the specifications. When the pliers are placed on the brake disc, it often happens that the pads tip inwards and the pliers cannot be placed on the disc. I always use a piece of wood that is a little thicker than the brake disc, as a kind of spacer. So you can easily put the pliers on halfway and then pull out the piece of wood. Secure the fastening screws of the pliers with Loctite, tighten the screws with the prescribed torque and check the brake fluid level. Warning: The brake is not yet under pressure. Operate the lever several times and pump until the brake pressure is built up. New pads must first adapt to the brake disc. Only after a few hundred kilometers does the brake regain its full efficiency.

Brake discs

The brake disks, which are usually made of steel or gray cast alloys, also belong to the wearing parts of a brake system. Since the brake systems are becoming more and more efficient, so-called floating brake discs are increasingly being used in addition to the classic rigid ones. The brake disc then consists of an inner and an outer ring. Movably mounted floaters ensure that the outer ring of the disc can expand and contract more easily under high thermal loads. This way, the panes stay flat even when heated. A brake disc is worn if there are severe scoring or a clear burr can be seen or felt. If the brake lever pulsates when braking, the disc is warped and a replacement is also due. On the Honda Sevenfifty used here as an example, the rear brake disc had both scoring and a clearly palpable burr. For the replacement, based on good experience with the manufacturer, I chose a lens from the specialist Lucas / TRW, which is not only significantly cheaper, but also considerably lighter. At the same time, the coverings were also renewed. The TRW washer was a perfect fit and assembly was basically easy. The problem when changing are the retaining screws of the disc, which are often very tight. Attention: Depending on the manufacturer’s information, they also have to be replaced! Exactly fitting, high-quality tools (e.g. impact wrench) are essential for dismantling.

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