Anyone know anything about disc brakes?

Get #2, it's got a cup and a road lever adapter, half your bleed issues can be solved by just putting the cup with some fluid on the lever and pumping the lever repeatedly to burp bubbles out, tap the hoses a bit at the same time. If you actually need to bleed it then I usually syringe the fluid into the caliper, through the system and then into the cup, then lever a bit back through and push that again, close caliper bleed port and do a bit of burping, usually works first time and takes 10 mins max. If it doesn't work then sometimes there are bubbles behind the pistons so allow the pistons out a bit with a thinner temporary bleed block, try above again, spread pistons and should all be good.

Get #2

Ordered. I don't know what fluid is currently within the system, thus is it better to drain it completely and refill? Or are the fluids compatible and I just need to top up what's already there and get rid of the air?

I'd imagine it's full of Shimano oil if you've had them from new and never done anything to them, I don't know if any reasons you shouldn't be able to mix them, different coloured oils might end up looking horrible but the epic stuff looks pretty much identical to shimano. If you're worried you could pull a drop out of the lever and mix it with a drop the new stuff and see if it explodes or summons daemons.

I'd imagine it's full of Shimano oil if you've had them from new and never done anything to them

I took a drop out and the fluid in there is clear/slightly yellow. Wasn't sure if all Shimano systems use the same type of fluid, so if there's no issues mixing I'll just top up. I was more concerned with different fluid contaminating the joints and causing corrosion or something like that, but if it's not an issue, that's fine.

All Shimano use mineral oil, which is all broadly the same with maybe some different additives. One thing you can't mix it with is DOT fluid which is used in SRAM and hope etc. You can't use DOT in shimano systems, DOT is usually clear/slightly yellow but I'm sure some mineral oils are too.

Why does my rear brake squeal when slowing down but immediately stops making noise when I pedal? I assume it squeals because it's dirty and vibrates but the pedaling while braking making it quiet doesn't make much sense - the disc is still rotating, why does it suddenly stop the noise? Is it actually the cassette contributing to the vibration or some weird shit or what?

Confuzzled.

Any luck finding a spare rotor adapter @snottyotter ? Ta

Just checked and no luck, various old IS and post but nowt flat. I'm pretty sure there's a new one at my other workshop but you may as well just buy one online.

Thanks, no worries!

Suspect that it's because you're applying a more even load across the hub, so there's not as much twisting force being applied to only one side. I'm not an engineer though, so it could of course just be witchcraft.

I'd always assumed it was the rotor making the noise and I doubt the hub is twisting or, if it is, that it's twisting enough to contribute to a squeal. I cleaned the rotor and it shut up briefly but I've now taken to pedaling slowly around corners to make it shut up which is doing my head in (and makes some corners interesting!). I'll try again with kitchen scourer but I just kinda want to understand why there's a magic difference in sound even though in both cases the rotor is still moving over the pads.

I also wonder, if I stuck a 140mm rotor on the back, would it make any difference to the noise, given the same contamination amount...

Summoning @gbj_tester for some engineering input...

Or, it's that's because you're pedalling, there's less relative torque being applied to the rotor.

Easy solution, don't brake.

I actually don't know. Sticking with my initial witchcraft idea.

If I don't brake I'll definitely not hear anything again, for a long time.

I'm assuming it's something like that - the pedaling slips the rotor through quicker so the magic howling resonant frequency isn't attained. (aka witchcraft)

Summoning tester

I wonder whether having the chain taught might be coupling the hub to the large mass attached to the pedals, which could act as a damper.

I can't be certain but I think he's calling you fat

I got that impression. It does sound plausible though. Now to find my kitchen scourer...

It's an interesting idea, but I'm not convinced - there is already an excellent connection to a decent damper (the tire).

My money is on the change simply being the pads being pushed more forcefully against the rotor - that can, and sometimes does in my experience, eliminate the rotor vibration (squeal).

a good american video

https://www.youtube.com/watch?v=oF2vAOmplUI&ab_channel=SRAM

So, I bled the brakes. It was the first time I'd done anything like that and to be honest, it was relatively straight forward. (Thanks @snottyotter for recommending the kit) I think there's still a tiny bit of air is the system, as the brakes aren't quite as stiff as I'd prefer, but they're more than adequate! It took about an hour to bleed the rear, as I it took ages to find out how to open the nipple (there's an allen key port above) and all the instructions I could find mentioned I needed to use a 7mm spanner. But once this was figured out it was all fine. The front brake took about 15mins to do.

If you're worried about any leftover air, leave the bike with the levers above the caliper, like just standing there is fine, with the levers pulled hard over night, with a toestrap or similar.

a good american video

It can perhaps be classified as "American". It's not good; it's a muddle, with a lot of fluff.

There's virtually no science there and some important bits of the narration are incorrect, such as the descriptions of friction and rotor size. There is information (useful facts) there, but in no way at all does it help anyone decide what brakes they need, because that's obscured by the rubbish; it's badly done marketing spiel.

Total disc neophyte here, pardon my noobness and possibly my inability to utfs. I was planning on running a 180mm front 160mm rear combo on some Shimano Rx010 centre lock wheels. Having just looked at the Rx010 spec sheet though, Shimano describes them as 140mm rotor compatible. Can I put a 160 or 180 rotor on there or will I need a new set of wheels?

Just bolt that sucker on, it will be fine

just bolt that sucker on

Ha, excellent. Words to live by.