What happened to the hydraulic disc brakes on my new bike?

Question

I bought a new Ortler electric bicycle a couple of months ago. My wife used it for a couple of weeks to ride to work each day.

The brakes squealed from almost the first day.

After a couple of weeks, the rear brake started getting weak and then pretty much quit braking at all. It acted much like car brakes when there's air in the brake lines - if you pumped the lever a few times the rear brake would "grab" but it also squealed horribly.

The bike has a speedometer and odometer on it. It shows that we've ridden the bike all of 176 kilometers (about 110 miles.)

Since the bike was new, I contacted the company I bought it from (large, well known internet company here in Germany) for a repair under warranty. They referred me to a (somewhat) local repair shop that has a contract to do warranty repairs. They also sent me a complete brake set for the rear brake (lever, brake line, caliper, pads, disc) for the repair shop to use.

So far, OK. Something is wrong, it'll be fixed at the seller's cost.

I picked the bike up from the repair shop this afternoon, and the guy at the shop told me I might end up having to pay for the repair after all - simple wear and tear isn't covered by the warranty.

It turns out the the rear brake pads were worn completely down to bare metal. He assumed we had simply ridden it a lot and worn the brakes out. I showed him the odometer and he was very surprised - he couldn't see how the brakes could wear that much over that short distance.

He also mentioned that the front brakes are also close to being gone - the disc had deep scratches and the pads are close to worn out. He sanded the scratches out of the disc so they don't make as much noise, but I don't expect them to last long.

Worn brake disc and pad:

Original front brakes:

Replacement rear brakes:

The original front brakes are just like the original back brakes. The new back brakes appear to be from a different manufacturer. I've heard of Shimano, but I don't know if the company itself is good or if the brakes are a good model. The original brakes don't seem to have a manufacturer's name on them.

The route my wife has to ride to work has a long, very steep hill that she has to go up and down. That's why she rides an electric bike.

The route is entirely on city streets - no off-road or dirt or gravel paths.

The old electric bike couldn't quite make it up the hill - she had to push it part of the way. She never had trouble with the brakes on the old bike. It had plain old brakes with a center pull cable and the rubber brake blocks that squeeze the wheel rim.

The new bike goes up the hill with ease, but it seems the hill is too much for the brakes.

1. Do disc brakes normally wear out fast on long hills?
2. Are you supposed to use disc brakes differently from the rim brakes?
3. Do we need special pads or discs to handle the hill?
4. Should I request that the front brakes be replaced as well?
5. Will the new Shimano brakes do better than the original brakes?

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Update 2023-10-06:

The bike shop installed the new brakes on the back. They work fine, and have not squealed at all.

The front brakes are worn down. The company I bought the bike from sent another set of brakes (for free) for the front. They declined to pay for the installation since the front brakes are still working. I'll take the bike to the shop next week to have the new front brakes installed.

Answer 1

Unbranded hydros on DTC ebikes are often total garbage, so rapid wear isn't necessarily surprising.

The balance of usage between the front and rear brake may also be a factor. You want to be using the front as much as possible within the bounds of safety and heat management. The front brake is much more effective at stopping the bike for a given amount of wear expenditure, up until it gets too hot. You could say that the ideal braking habits are a balanced amount of pressure on the levers with a bias towards the front. Conversely, if one was relying heavily on the back brake, wear like in the picture can happen very quickly on an ebike, especially on an organic/resin pad and even more especially on a low-quality one. Excess heat can create the kind of exponential wear that would explain the situation.

Any rotor that's had extensive contact with the backing plate from pad wear is liable to never work great again. There can be a grey area there but the wear into the backing plate shown is fairly extreme. When the rotor surface gets chewed up to match, you may not be able to get back to good, smooth brake feel. Losing a lot of rotor thickness also impacts heat management. A good generic replacement point thickness is 1.5mm, unless the manufacturer says otherwise.

The brake you were sent appears to be a BR-MT520, which is a good part. It likely comes with resin pads, but you can get semi-metallic or metallic ones for it. If you do have resin in it now, they may go fast. Keep an eye on them and if they do seem to wear fast, go to the metallic and a good new rotor and it should be much better.

Answer 2

Something is terribly wrong if you get less than 200 km from a set of brakes and pads. I have ridden my new road bike about 10,000 km this year and the brakes and pads are still working just fine. (It has hydraulic disc brakes made by SRAM, which is a different major manufacturer.)

My gravel bike has Shimano 105 hydraulic disc brakes. I've had it for about 4 years, and have probably ridden it close to 10,000 kilometers. It still has its original brake discs and pads.

It seems likely that the brake pads were defective or improperly installed and began scraping the backing plate against the discs almost immediately.

"Riding the brakes" on downhill segments would cause slightly increased wear, but only slightly.

If the brakes were rubbing constantly that could wear them out prematurely, but would likely cause the squealing noise you describe all the time, not just when braking.

Shimano is a major Japanese component brand. They are well regarded and have a wide range of different components for sale at different price points.

Something was wrong with your bike all along, and the manufacturer should repair it under warranty. That is not normal wear and tear. It is more than a hundred times normal wear rate.

Answer 3

Your brakes were almost certainly not adjusted properly, and probably engaged the entire time, causing significant wear.

Even on normal bikes, slightly rubbing brakes can be hard to notice. On an ebike which generates it's own power, it may be impossible to tell without looking.

Now that you've gotten a repair, you can check. While off the bike, lift each wheel and give it a spin. If the wheel spins freely, you should be good to go!

Answer 4

1. Pads wear faster if you break a lot in steep hilly terrain. At 80kg + 15kg bike I get around 5500km with 45km elevation climb on two pairs of organic(soft) pads riding on roads in all weather conditions. Getting less than 200 km sounds a bit strange even if you have a heavy rider on a heavy bike going down very steep hills, riding aggressively and using organic pads.

2. No, you brake as you feel needed.

3. E-bikes are heavier than regular bikes and if you live in a hilly area and/or are a heavy rider then more durable (metallic or semi-metallic) pads might be needed for longevity. Just make sure the rotors and pads are compatible.

4. I would have the front pads replaced if they are nearly worn out.

5. Shimano is a reputable brand.

Since you have had such a bad experience I would keep an eye on the wear of the pads.