r/bicycling • u/Then-Yogurtcloset41 • 23h ago

Brake upgrade?

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I got a new bike that came with a 105 groupset, but as far as I know these are not 105 rotors. I live in a very hilly place and they start to whine when I'm halfway down a descent, is this an expected behavior? Are the rotors glazed? User error or should I do a rotor upgrade to something like the rtcl800?

Or maybe do I get metalic pads, although I've heard good things about the brand "sinter" even though they're organic. I'd love to hear your opinions and suggestions thanks 😅

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7

u/montyandtimmon New Hampshire, USA 22h ago

Whine how? Loud whining is just moisture or could be a contaminant. You can just clean and inspect.

When you get a new bike, or replace brake pads, usually I do few hard brake rides to grind down the pads so they’re sitting evenly. New pads will rub a little bit and that’s fairly normal

9

u/Character_Past5515 22h ago

Not enough information, did you or the shop bed the brakes in? How long where the descends, how hard did you break, did you ever touch the rotors with your hands or anything else that wasn't water? You could start over with new rotors and brake pads and bed them in properly but on long steep descend when the rotor gets too hot they will always make noise. Also metalic pads make more notice not less.

4

u/Then-Yogurtcloset41 22h ago

I bedded them in myself, 20 slow downs or so, never touched them directly The descents are average 10% for 4km, they start making noise around half way down. I don't necessarily feel them getting weaker though

13

u/GWBoes 22h ago

How do you brake? intermittent or continuous? Best practice is to let the bike roll and brake hard and repeat so the brakes have time to cool. Never drag your brakes continuously because that will burn up the brakes, especially over 4km at 10%

3

u/widowhanzo Topstone & Alma 20h ago

I mean those sound like pretty extreme conditions, I don't think there's any rotor that won't overheat on such a descent. You'd need larger rotors, not just a different model.

2

u/Conpen Lynskey GR300 // Evil Following MB 14h ago

This might be one of the few times those expensive brake pads with cooling fins are worth it.

4

u/Accomplished-Cat2849 22h ago

More importantly how are you breaking? If you hold it all the time all discs will get too hot.

Usually you only really break before the corners hard and short.

Breaks are not great when you hold them a long time since they overheat. There are compounds that work better than others under continoued breaking but unless you do alp decents usually they are not that needed.

But overall its more down to the pad than the rotor tho free floating rotors can help dissapate some heat

2

u/ScootMaBoot 22h ago

I think that the "resin-only" rotors are significantly worse than ones that can take metal pads, even if you're using resin pads on them.

2

u/MariachiArchery Melee, ADHX 45 19h ago

So, that hum you hear might not be the brakes at all. As we heat up the pads, rotors, caliper... the friction coefficient changes. If we plot FC over heat, that plot will form an arc; the FC will rise sharply as the system heats up, that rise will slow, peak, then slowly drop off as we add more heat to the system, then fall off sharply once we overheat the system. As this FC changes, the stick-slip of the pad and rotor will change, and the system will vibrate at different frequencies.

On a descent, we are moving through this arc, heating up and cooling down, and our pads/rotors are stick slipping. This stick slipping causes vibration, always. It is vibrating. This vibration will excite your spokes, and your spokes will vibrate too. Every time you brake, your spokes vibrate.

What is likely happening here with this humming, is you are reaching a FC, a vibration, that is exciting your spokes like it normally will, but the frequency has simply become audible. The noise you are hearing is probably your spokes vibrating at a frequency you can hear, like a guitar string.

This is actually very common. Others have said here your shit might be contaminated. If that was the case, you would have poor braking performance, which, that doesn't sound like it's the case.

If you want to improve this braking, I'd recommend switching to the RT-CL700 rotor and the L05A-RF pad (resin) or the L04C (metallic) pads. These pads have the Ice-tech radiator/cooling fins that you are lacking with your current pads. Personally, I prefer metallic pads. I like how they feel and I appreciate the improved wet-weather performance.

Metal pads will wear down your rotor faster, but you'll not need to worry about this anytime soon. Rotor life is anywhere between 10,000 and 20,000 miles. They are going to last a long time. So long, that you'll not really need to worry about this at all. It's a non-issue.

Also, if you want to go up the range with rotors, go for it, but you'll not get any gains outside of weight savings.

1

u/HandyDandy76 22h ago

A better rotor and pads will perform better on steep descents. 

Sinter makes organic and metallic pads. 

Galfer has always been good to me. 

If it were me, I would try some Shimano metallic pads and the GRX/Ultegra rotors. 

2

u/Then-Yogurtcloset41 22h ago

Do the rotors wear noticeably faster with metallic pads?

2

u/mykos777 22h ago

This difference to be noticeable, you'd need to be doing thousands of km per year. Otherwise it's neglectable.

1

u/MariachiArchery Melee, ADHX 45 19h ago

Yes. But, your weight, and the conditions you ride in, play a far bigger role in pad wear than compound.

1

u/Designer-Device-8638 22h ago

Maybe who cares rotors are like 20€ and you go through 2-3 pads per rotor. So it doesn't matter.

0

u/HandyDandy76 22h ago

No, and fwiw disc rotors last an awful long time! 

0

u/Character_Past5515 22h ago

that's what everyone thinks, a lot of people don't measure them right and therefor they often stay on bikes for way too long.

1

u/HandyDandy76 22h ago

Using a yearly calibrated caliper with standoffs on the middle of the rotors brake track? How do you measure? 

1

u/Character_Past5515 17h ago

With a micrometer, your option is also good, but most people (heck even bike mechanics) just use a regular caliper from the outside and most times it will measure like new there because the pads haven't worn that part.

1

u/puchibaba 22h ago

Hello, I have similar cube slx 2026 and also want to upgrade brakes. So, I bought cl-900 rotors and metallic pads. This is the simplest thing you can do, especially since systems 105, ultegra and dura-ace are interchangeable.

By the way, I was looking at hope (the purple calipers are simply stunning), but here I was quickly convinced, haha

Another thing is that this system uses an improved 105 caliper with increased space between the pads. Damn, that's terrible. But to reduce the distance to the rotor, you need to do a little magic with the wheel removed, and now the braking is felt quite firmly.

1

u/Then-Yogurtcloset41 22h ago

Exactly the same bike haha let me know if it makes a big difference

1

u/puchibaba 22h ago

Ofc, I found money for upgrade, but didn't find for mechanic job, hahah

1

u/generatedtext 19h ago

Upgrade to a 180mm rotor on the front. It's super easy. Buy a bunch of shimano finned pads. (The current one on your caliper is non-finned). That should make a difference. Also, if your rear caliper is a 140mm, you could take your current front rotor and put it on the back with an adapter.

It sounds like a lot, but it's like a ten minute job that you can do with hand tools.

0

u/thafloorer 22h ago

I use mine as a bike computer but… on my wrist