Magura brakes don't make noise on their own. Something needs to be wrong for that to happen. I think I have 8 or maybe 9 sets of MT5's... I've lost count. The MT30 is just this year's flavor of the standard-issue MT5/MT7 caliper. They've changed the color discs to black and you get the basic carbotecture levers, and they give you the Type 9 2-piece pads instead of the Type 8 4pc pads that come with the MT7's (and fit just fine on an MT5/MT30 caliper).
@Chargeride what you are showing in that video comes from a set of brakes that have gotten wet enough to wash away the brake bedding that should be on the rotors. You can get rid of that by bedding the brakes, but as soon as you ride in a rainstorm, the day after you'll hear it again until you re-bed. I live at the top of a hill so I can just brake alternately on each wheel down the 200 or so meters of my steep hill and by the time I get to the bottom problem is solved. A more traditional full bed process is here:
Brake bedding is something almost nobody does and everybody should. Its a requirement on performance cars taken to the race track. Its the same procedure for any type of vehicle.
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When riding at certain speeds or cornering they make a metallic fling-fling-fling noise, i think its rubbing against the disc.
It is. You are getting just a touch of flex on your fork (or frame) versus your brake mount, and this is causing just a bit of rubbing. Its not the brakes that are doing this, technically. I say this assuming you hear the noise ONLY when cornering and it goes away when you are going straight. It could also be a slightly warped rotor whose warpage becomes audible only when cornering and that flex puts the rotor into contact with one side or the other of the caliper.
Also they squeal a lot, to the point where people are turning heads so loud.
That only happens on Magura brakes if you have washed off the brake bedding. I'm assuming you bed your brakes as a matter of routine? It doesn't take a lot of water to do this to any brake rotor. One ride in a rainstorm will do it and it will sound exactly like what
@Chargeride showed in his video. You'll also get a nasty vibration. But bedding the brakes makes the problem go away.
My local bikeshop told me its normal with these big 4 piston brakes and changing them for a different set wont make a difference.
Well, ALL brakes have to be bedded. and ALL of them squeal when you wash down the rotors before you get them bedded again. But I think when they told you the issue is with big 4 piston brakes they were kind of brushing you off and telling you to just get used to it... its a simpler answer than explaining to you what brake bedding is, and why you have to do it on occasion.
This is important: What rotors are you using with your Maguras? Magura calipers are wider than normal brakes. Typical brake rotors are 1.8mm thick when new. Magura rotors are 2.0mm thick when new, and when rotors reach 1.8mm they are worn out. IF you are using non-Magura rotors, thats a problem all by itself. Worth noting you can buy Tektro Type 17 rotors which are 2.3mm thick and they fit in Magura calipers (they fit best with pads that are worn down a little but they also fit with brand new pads). Tektro's 2.3mm rotors are REALLY warp-resistant and last forever. Plus they absorb more heat since they have contain more material, which is the rotor's primary job.
Next, your MT Thirtys came with Magura Type 9 pads. Look into buying Type 8 pads which are 4-pc. They can be pulled out of the caliper without removing the caliper from the bike unlike Type 9's, and they give a torque boost since its now 1 pad per piston and they all operate independently.
Finally, if you are getting squealing, are you using the copper-colored race pads? Those are noisy because they require high heat to get up to their preferred operating temp, and they are going to squeal until they warm up. The Type 8.P pads (black backing plates. "P" = Performance) are probably the solution if you're using the race pads.
