E-bikes are sensibly heavier than organic bikes, and enable riders to climb higher or ride longer, thus wearing their brakes faster.
1) Replacing brake pads
To replace the pads we need:
- Pair of gloves: the linings are really very sensitive to the action of oily fluids and our skin could release surface grease on the pads
- Pliers: to extract the safety pin
- Allen key: to remove the locking screw
- New pads
- Cotton rag
- Isopropyl alcohol or disc cleaner
- Any flat plastic tool or tire punch: to reset the stroke of the pistons
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- Wheel screw on the brake lever
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- Unscrewing the pin
Simple steps to replace the brake pads
- On the handlebar, and sometimes on the lower end of brake cable, there are cable registers. Turn them clockwise all the way, to better unscrew them for tightening the cables once pads will be worn but still fit. This will avoid you to pull the levers almost onto the handles when braking.
- Take off the wheel; for the rear wheel, particularly if there is a hub motor with a cable that you can’t take off, just losen the two bolts on the axle to move the brake disc away from the calipers.
- If you have mechanical brakes, losen the pumping lever bolt on the calipers, with a Allen key (hydraulic brakes have no pumping lever on calipers).
- Take off the pin on top of the pads which fixes them to the calipers. If there’s a clip on the pin, take it off with the pliers. Take off the pads and their fork spring.
2) Piston stroke reset
- Reset the stroke of the pistons using a plastic tire punch. Never do this with screwdrivers, pliers, chisels, levers, anything metallic and unsuitable. The pistons are very delicate and some models are ceramic. This means that if they are scratched with a metal object, they will crack and it will be necessary to replace the entire brake body. Push the brake pistons to the inside, make room for the new pads which are thicker than the old ones.
- Put their fork spring on the interior side of the pads and fit the pads into the calipers, aligning the hole of the pads with those of the caliper and fork spring.
- Insert the pin into the aligned holes, and don’t forget to put the clip back if there is one.
- Push the pumping lever upside, then tighten its bolt. Ready!
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- Pistons must be pushed aside
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- Pushing pistons aside with a tire punch
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- New pads mounted
3) Pumping lever modulation adjustment
If the brake levers are too soft, and you must pull them more than a couple of centimeters towards the handle before braking starts, or too tight, just modulate them through the registers as mentioned before, or tighten the cable.
4) Rotor-brake body centering
Rotate the wheel. If you hear a light noise, the pads are touching the brake disc, you must center it. To do it:
- Losen the two bolts that fix the calipers to the frame or the fork, losening alternatively one and then the other, in order to avoid undue pressure on the system
- Push strongly on the brake lever
- Slightly and alternatively tighten the two bolts
- Now release the brake lever and then slightly push it to center the rotor, and alternatively tighten the two bolts
You are done, if the problem persists it should be probably because its piston is stuck, it should go back into its place once you brake.
5) Cleaning brake body, pads and disc
Never use a general degreaser, which can stick on discs, pads and pistons, badly affecting their performance. Always use isopropyl alcohol or a disc cleaner: the first is a particular white alcohol, which has a high cleaning effect but does not contaminate the pads. The second is a special product, designed to be used on bicycle brakes. You can find it in any bicycle shop. Just spray the discs, calipers and pads with either of these two products, then use a cotton rag to remove the dirt. It’s better doing due maintenance than having to repair brake discs on the road.
6) Replacing brake fluid or oil
If your hydraulic brakes have mineral oil, its replacing frequency depends on the heat that they have to endure. In case of an e-mountain bike often mastering steep descents, high brake temperature can alter their oil to the point that it should be replaced every year. In case of a city eBike, brake oil replacement can wait several years, depending on the bike usage, frequency of steep descents, loads carried, and so on. You can easily find online an inexpensive kit with all the necessary tools.
Brake fluid
Especially some e-mountain bikes can use brake fluid instead of mineral oil. This fluid, called DOT (Department of Transportation) can withstand heat much better than mineral oil. Unfortunately, it is hygroscopic (excepted the DOT five, made of silicone and not of glycol) which means that it absorbs water. Should your bike be stored in a moisty place, or should you ride in the rain, a small but considerable percentage of water would be absorbed by the brake fluid. When the latter becomes hot because intensive braking, water would turn into steam, which behaves like air bubbles, therefore diminishing your e-bike braking power. Moreover, water lowers the temperature of the fluid boiling point. Hence the need to replace this fluid once a year.
Here are the different boiling points of the different classifications of DOT fluid:
| DOT Fluid | Dry Boiling Point | Wet Boiling Point | Primary Constituent |
| DOT 3 | 205 ℃ (401 ℉) | 140 ℃ (284 ℉) | Glycol ether |
| DOT 4 | 230 ℃ (446 ℉) | 155 ℃ (311 ℉) | Glycol ether/borate ester |
| DOT 5 | 260 ℃ (500 ℉) | 205 ℃ (356 ℉) | Silicone |
| DOT 5.1 | 260 ℃ (500 ℉) | 205 ℃ (356 ℉) | Glycol ether/borate ester |
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