Hydraulic Brakes, Brake Rotors, Brake Pads

[Stefan Mikes]

It is not a post in which I would be preaching or asking for an advice re hydraulic brakes and their components Let me tell you about my experiences with different disk brakes and their components. I expect you to be talking about your own experience!

When I owned a Giant Trance E+ e-MTB or demo rode a Specialized Levo SL, I was terrified about the aggresive behaviour of powerful brakes with 203 mm rotors. Actually, the easiest way to do was crashing or even doing the Over-The-Bars on emergency braking, especially at a very low speed! Powerful e-MTB brakes have an immediate initial bite, and these are expected to stop your e-bike instantly! I will not elaborate on e-MTB brakes: they just serve their purpose of stopping an MTB-er whenever needed on a technical singletrack. These are not made for city cycling, heheheh

Currently, my Vado 6.0 has a TRP Zurich front brake, and the TRP Slate on the rear. These brakes are of the Post-Mount type, and I equipped them with two different 180 mm rotors front/rear. It is a Shimano SM-RT86 (Ice Tech based) for the front and a little less advanced SM-RT66 for the rear. Both are the 6-bolt type. The reason for installing the less advanced rotor for the rear was to ensure the speed-sensor-magnet-bracket would fit. I consistently use high-end TRP Q20.11 semi-metallic brake pads.

The SM-RT66 with the magnet bracket.

A TRP Zurich e-bike brake (discontinued) as dismantled for service and cleaning. The brake lever includes a sensor for the STOP indicator light.

A TRP Slate HD-M807 brake. Both Zurich and Slate are Post-Mount, 4-piston hydraulic disk brakes.

My Vado 6.0 is a heavy speed e-bike, and the total mass (rider, e-bike and cargo) often exceeds 130 kg (less than 300 lb). I sometimes ride the Vado in high mountains, so the high stopping power is necessary here. What makes my Vado brakes different from MTB ones is the stopping action is very smooth. I could be riding 58.5 km/h (36 mph) on a steep gravel decline, and I could stop the e-bike smoothly and safely over a relatively short distance. Yes, these brakes can be modulated successfully. Emergency stopping at high speed on asphalt is fast and safe, too. With my style of riding, brake pads are good for 6,700 km (around 4,100 mi) or more than a year when I'm riding on the flats.

These brakes with their rotors and brake pads can be noisy, especially during wet weather.
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My Vado SL is equipped with Tektro HD-R290 2-piston, 160 mm, Flat-Mount, Centerlock brakes. I'm not taking this e-bike into montane areas, so the brake pads and rotors are long living. I'm only on the third set of pads since June 2021 or for 14,000+ km (8,700+ mi). I rode the original semi-metallic Tektro F10BS brake pads for almost two years or some 8,000 km (5,000 mi). I replaced the next set in a year, probably because my use of Vado SL had greatly intensified. Necessary to mention the braking action of Vado SL brakes felt very similar to the ones on my Vado 6.0, only these brakes/rotors/pads were far more quiet.

My recent maintenance action was replacing the front rotor to Shimano SM-RT64 (160 mm, Centerlock) as I felt it would be safe to do it. I also swapped the brake pads for SwissStop Disc 34 E, which are advanced organic pads. And here a surprise comes!

The organic brake pads feel totally different to the semi-metallic ones! The initial bite is very slow (it is safe to brake violently) but I feel I need to apply more force on the brake levers to get an equal stopping power I had with the previously used pads! And yes, the organics pads are deadly silent!

What would you like to tell me about your brakes?

 

[spokewrench]

It is not a post in which I would be preaching or asking for an advice re hydraulic brakes and their components Let me tell you about my experiences with different disk brakes and their components. I expect you to be talking about your own experience!

What would you like to tell me about your brakes?

Heat can soften pads and cause fade. I've found that dampness can do it, too. The other day I rode a bike that had been sitting in an open garage for weeks. The brakes were virtually useless. Braking several times from 20 mph improved performance greatly but caused incredible wear. I guess the organic pads had absorbed enough humidity from the air to soften. I wonder if warming them with a heat gun would have restored them by drying them.

I had the same problem with another bike that hadn't been ridden much in several weeks. I guess the pads had absorbed moisture. I think metallic pads are less affected.

I wonder how hot the surface of a pad gets under various braking. One tech with a youtube channel made a device to record IR readings from his front disc as he descended at 6% for several miles, braking for turns. He showed peaks of 180 F (82 C), rapidly returning to ambient. I see cause for doubt. Polished stainless steel has a low emissivity, and a little error in estimating emissivity could cause a big error in temperature. Also, when you scan a whirling disc, much of what you're seeing is holes. I don't know if his microprocessor took that into account.

Another youtuber took IR readings on calipers right after descending a mountain trail. The flat black paint on a caliper would probably give pretty good readings. Generally, they were about 180F/82C, but on one bike on one run the caliper read 185C/ 365F. Wow! Heat produced at the surface of the little pad is dissipated by the big disk and big caliper, so the surface of the pad must get a lot hotter.

I wonder if engineers can measure how hot the surface of the pad gets where it rubs the rotor.

 

[BEC111]

Heat can soften pads and cause fade. I've found that dampness can do it, too. The other day I rode a bike that had been sitting in an open garage for weeks. The brakes were virtually useless. Braking several times from 20 mph improved performance greatly but caused incredible wear. I guess the organic pads had absorbed enough humidity from the air to soften. I wonder if warming them with a heat gun would have restored them by drying them.

I had the same problem with another bike that hadn't been ridden much in several weeks. I guess the pads had absorbed moisture. I think metallic pads are less affected.

I wonder how hot the surface of a pad gets under various braking. One tech with a youtube channel made a device to record IR readings from his front disc as he descended at 6% for several miles, braking for turns. He showed peaks of 180 F (82 C), rapidly returning to ambient. I see cause for doubt. Polished stainless steel has a low emissivity, and a little error in estimating emissivity could cause a big error in temperature. Also, when you scan a whirling disc, much of what you're seeing is holes. I don't know if his microprocessor took that into account.

Another youtuber took IR readings on calipers right after descending a mountain trail. The flat black paint on a caliper would probably give pretty good readings. Generally, they were about 180F/82C, but on one bike on one run the caliper read 185C/ 365F. Wow! Heat produced at the surface of the little pad is dissipated by the big disk and big caliper, so the surface of the pad must get a lot hotter.

I wonder if engineers can measure how hot the surface of the pad gets where it rubs the rotor.

The important lesson isn’t how hot the brakes get. What’s important is not touching them with your fingers to find out!

 

[Stefan Mikes]

The important lesson isn’t how hot the brakes get. What’s important is not touching them with your fingers to find out!

Word!

 

[spokewrench]

The important lesson isn’t how hot the brakes get. What’s important is not touching them with your fingers to find out!

I think you're onto something. The emissivity of polished chrome is only .058, so grabbing is the simplest way to tell if a motorcycle header pipe is hot, as I vividly recall. Then I'd need only compare the mark with this chart to tell the temperature!

What language is that?

 

[BEC111]

Lorem ipsum is fake Latin text used as a placeholder. Most recently used in page maker and other Adob

 

[BEC111]

Lorem ipsum is fake Latin text used as a placeholder during design phases. Most recently used in PagemMaker and other Adobe software.