Change brake discs yourself – tips and tricks

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Change brake discs yourself - tips and tricks
Markus Jahn

Change brake discs yourself - tips and tricks

Change brake discs yourself - tips and tricks

Change brake discs yourself - tips and tricks

Change brake discs yourself - tips and tricks

9 pictures

Change brake discs yourself - tips and tricks
Ralf Schneider

1/9
There is a need for action here! The heat spots on the panes shown on the left can certainly no longer be “slowed down”.

Change brake discs yourself - tips and tricks
Hertler

2/9
Floaters (round sleeves between the carrier and the disc) prevent the brake disc from warping due to the build-up of heat. It often looks different with racing discs.

Change brake discs yourself - tips and tricks
Cathcart.

3/9
A micrometer can be used to determine whether the disc still has enough remaining thickness (from approx. 20 euros).

Change brake discs yourself - tips and tricks
Ralf Schneider

4/9
Wildly corrugated windows originate from motocross and found their way into the street area mainly for optical reasons.

Change brake discs yourself - tips and tricks
photography mitterbauer

5/9
Sometimes it looks spectacular, but the decisive factor for real sports performers must always be braking performance.

Change brake discs yourself - tips and tricks
Falk Dirla

6/9
Never use “noodled” Torx or Allen bits! However, if the correct tool still has play in connection with the screw, the balloon or glove trick helps.

Change brake discs yourself - tips and tricks
Falk Dirla

7/9
This often also works with slotted screws. If you can’t find a suitable rubber, you can also try hand washing paste.

Change brake discs yourself - tips and tricks
Markus Jahn

8/9
Tighten the clamp on the axle base (two screws pointing forward) only after several times of deflection.

Change brake discs yourself - tips and tricks
Uwe Seitz

9/9
Micro-encapsulated screws are the non-plus-ultra for the brake discs, otherwise use a medium-strength screw locking agent.

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workshop

Change brake discs yourself – tips and tricks

Change the brake discs yourself
Tips and Tricks

Content of

There are three main components to brake problems: the pads, the brake pressure and the discs. We have the first two under control, so let’s take care of the latter.

May 16, 2019

We have been dealing with the subject of brakes for some time. A very important area, because well and reliably functioning stoppers can be our life insurance in an emergency. This time, the focus is on the brake discs, because of course they are also victims of wear and tear, become thinner over time or show clear signs of running, so-called grooves.

When is the brake disc scrapped??

Sometimes you can also see strange spots, brown or blue. These are heat spots caused by very high temperatures. If these cannot be “braked away” after a while, the front brake can rub, causing significant vibrations. The reason for this are so-called changes in the coefficient of friction between the friction partners disk and lining due to structural changes in the heat spots.


Change brake discs yourself - tips and tricks


Cathcart.

A micrometer can be used to determine whether the disc still has enough remaining thickness.

This high-frequency rubbing should not be confused with the classic brake rubbing that occurs with warped brake discs. The lateral runout of the brake disc is responsible for uneven braking, typically associated with a pulsating brake lever. In such a case, the brake disc is scrap. With the heat spots mentioned at the beginning, it is sometimes helpful to insert new brake pads. However, this should be followed by a few kilometers, carefully and cautiously braked.

Measure the thickness of the pane and compare the information

In any case, the brake disc gradually becomes thinner and thinner as a result of braking. It is easy to tell whether it is still thick enough. The minimum thickness prescribed by the manufacturer can usually be found somewhere on the brake disc. Usually this is between 4 and 4.5 millimeters. The actual brake disc thickness can be determined with a micrometer. Of course, there are also special brake disc measuring devices – but such a copy will probably not be found in very few hobby screwdriver garages. If the actual state determined with whatever is the same as the note on the disc, you should of course get new discs.


Change brake discs yourself - tips and tricks


Falk Dirla

If the correct tool has play in connection with the screw, the balloon or glove trick helps.

Does the brake disc even look like an old record and has deep grooves? First there is the question, how deep is deep? If you can see more than feel the grooves or ring-shaped grinding marks, that’s fine. But if you really get caught when running your fingernail over it, you need to act. First of all, you can replace the brake pads – we discussed how to do this in the previous issue. Or you try, if the old ones are still very good, to grind them flat, in the hope that the now scratch-free brake pads will level out the crater landscape on the brake discs. To do this, you remove the brake pads, staple a sheet of 80 grit sandpaper onto a flat board and use it to not grind the pad surface down, but rather flat.

One pane is warped – here’s a service trick

But what do you do if the brake lever pulsates? If the panes are already older and tend to come to an end, the easiest way to dispose of them – together with the deposits! Unless the latter are really quite new and have hardly had to tackle so far. On the other hand, if the panes are still in very good condition and can still be used for many thousands of kilometers, we should find out which pane is really warped. In order to be able to determine this, you actually need a measuring probe and a tripod to measure the lateral runout. This purchase alone is certainly beyond the scope for most of the people. But with a simple trick you can find out from which side the scratching is coming even without an expensive measuring device. All you have to do is dismantle a brake caliper, clamp a piece of wood or the like between the brake pads, secure the whole thing with one or two rubbers, then wrap the brake caliper in a rag and then attach it to the motorcycle using an expander.


Change brake discs yourself - tips and tricks


Ralf Schneider

Wildly corrugated discs come from motocross.

The rag because we only want to repair the brakes and not paint the fairing as well. Carefully check the pressure point and then – of course only on a closed route and very carefully – drive and brake lightly. Has the scratch gone? Then we have the right disc. If it still rubs, repeat the same play with the other brake disc. There is another reason a brake disc needs to be replaced: excessive play in the floaters. Most of the brake discs are floating. However, this does not mean the play in the axial direction as with the brake calipers, but rather some “air” in the radial direction between the brake disc and its carrier. The aim of this design is to anticipate the distortion of the brake disc as a result of extreme heating, since the brake disc ring expands due to the action of heat. But if the window rattles and rattles, then it belongs to the old iron. Some brake disks from motorsport are an exception, in which the preload disks to eliminate axial play are dispensed with.

Which discs are worth buying?

Are the panes definitely gone? Then a replacement is needed. Here we are faced with the difficult decision as to which pane from which manufacturer we should install. The original ones always work, they are just correspondingly expensive. Which cheaper part is also recommended? First of all: Wave discs come from the motocross and enduro area. There, the sawtooth-like outer contour should rasp the dirt out of the brake calliper. Should there ever be something to rasp out of the brake calipers on our street sweeper, we will have completely different problems. Therefore, wave discs are a visual gimmick. In any case, the outer contour has no influence on the braking behavior.


Change brake discs yourself - tips and tricks


Hertler

Floaters prevent the brake disc from warping due to the build-up of heat.

Rather the thickness, because thicker discs heat up more slowly and more evenly, so that they brake perfectly and stably even under the most extreme conditions. In addition, they are less prone to default. As a rule of thumb: Experience has shown that everything is possible except for this cheap no-name junk from the World Wide Web. It is important that the brake pads match, so it’s best to order new ones right away. And new screws, because nothing is more annoying than having to break off work because you can’t get any further with the noodled things! We could use liquid threadlocker as well, unless the new screws are microencapsulated. Then they usually have a blue or greenish rubber layer on the thread.

Changing discs made easy

Is everything there? Then it goes to the conversion. It is best to loosen all screws before jacking up the motorcycle. Often the screws are brutally blasted and so you avoid the risk of throwing the bike off the trestles. Then the machine is jacked up, the front wheel comes out and on the workbench. When unscrewing the brake disc screws, it is advisable to only use perfect Allen or Torx sockets. If the corners are already rounded, especially with Allen nuts, the screws are also rounded for reasons of solidarity. In the box at the top left there are tips on active screwdriving. When the new discs are finally there, the wheel is reinstalled. To do this, use the following trick: do not tighten the floating side of the fork clamp (see picture gallery) at the beginning after the brake calipers have been tightened with the correct torque value and the brake pads have been applied (pump the brake lever through a couple of times).


Change brake discs yourself - tips and tricks


Ralf Schneider

The heat spots on the panes shown on the left can certainly no longer be “slowed down”.

Jack off the motorcycle completely, apply the front brake and compress as much as possible a few times! What for? To align the fork. In this way, tension-free assembly of the front wheel axle is guaranteed, and there is no tension in the fork, which is important for a fine response. Then of course tighten the axle clamp. Finally, check the brake fluid level in the expansion tank again (see PS 08/18) and make sure that we have not tapped our grease fingers on the brake disc. We can already go on a test drive, but at first we have to approach the matter a little gently, because new brake discs and pads need several kilometers before they really bite hard. In the next issue we will close the chapter on brakes with new steel braided cables, and there are also other useful tips and tricks from the toolbox. Until then, with two fingers on the brake!

Assembly tips

To make it easier to loosen the screws, you put the nut into the screw and hit it briefly with the plastic hammer. If the first screw loosens only with difficulty or not at all, break it off and snap the hot air dryer. Often the screws were then unnecessarily glued in with Loctite Ultrafest. Such a screw locking device also becomes soft again through heat. Do you think that even the new nut in the screw head has too much air? Then maybe one of the following tricks will help. The air number: Put the Allen or Torx nut with the hexagonal part in a small balloon. This has two advantages: Firstly, the play between the tool and the screw head is reduced and the rubber also has a lot more grip than steel on steel! Incidentally, this also works with slotted screws. If there are no more balloons left from the last children’s birthday, the cut-off tip of a latex glove can also be used.

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Sand in the gears: smears some fine-grain hand washing paste into the screw head, the abrasive particles in it get caught between the tool and the screw head. You can transmit a lot more torque this way. Please do not start with an impact wrench here, because the brake disc screws tear easily due to the high loosening torque in connection with the high speed of rotation. The thread is often only six millimeters. Important: Thoroughly clean the contact surface between the rim and the brake disc. Then unpack the new discs and wash them thoroughly with brake cleaner. Then mount a new disc, paying attention to the direction of rotation, if there is one – it is indicated with an arrow like on the tire. Screw in the new screws. If these are microencapsulated, do not apply any additional screw locking agent. If not, only use the “medium strength” type, but only a small drop at the very beginning of the thread. Some screws have a shaft under the head for centering, so finally tighten the screws evenly crosswise up to the prescribed torque. Then mount the second pane. Make sure that the hole pattern of the disc or the brake disc carrier is aligned on both discs.

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