Fail story. Did I mess up my brake?
 

I was trying to troubleshoot a resonance/squeal from a Magura MT4 back disc break. So I did what everyone with time to spare does: I watched a Youtube video of a guy straightening his break by loosening two screws on the disc break, and then pressing the break in order to 'align' it, before tightening it. So I did that. Unfortunately in my utter noobidity, I loosened the screw which apparently holds the break fluid. So when I pressed the break to 'align it', it ended up squeezing a couple drops of fluid out. In my horror I tightened the bolt again, cleaned up the break and forbid myself from messing with it further... However now I can feel that the break is a bit 'gritty' at the bottom out. Can you tell me:

1) did I mess up the break or is it kind of fine? Do I need to bleed it now?
2) is this 'grittyness' an imagination? Are the two breaks, left and right, supposed to feel identical?

It is time to "Take a Break" before "Working on your bicycle Brakes"... otherwise you will "Break your Brakes".

If the brake lever stops the wheel or can skid the wheel before the lever bottoms out, then I doubt you need to bleed the brakes. What about lever movement before the brake starts applying?

Oil on the rotors is bad.

Are your rotors bolt-on, or some time of spline attachment? If bolt on, are the bolts on the rotors tight? Without breaking them, of course....

Also slowly spin the wheel to observe whether the rotors are true, or wobble. They may be able to be trued if they have a wobble.

Dirty rotors?

Well, you're alive, so its not a fail story. It's a learning story. Good luck.

If it is just a couple drops of oil it may or may not need a bleed. The grittyness likely has nothing to do with the bleed and was most likely there the entire time. You can tell if it needs to be bled again by how much braking power you have why applying the brake and how far the lever throws. If the brake is lacking stopping power bleed it, if the lever pulls all the way to the grip to get power bleed it, if it has the same power and throw as before (grityness aside) its fine you can leave it be.

I recently accidentally spilled DOT 5.1 fluid over my pads because of lazyness (didn't want to remove them to do a bleed). They were new, so I decided to try to save them.

I first tried to clean them with water, but they were still oily, so I tried to use a chain degreaser on them (it's the thing I had at hand) which seemed to work ok. I then mounted the pads back with an old rotor, just in case, and went out to try it. It braked like crap (impossible to go OTB with that brake, but I still didn't want to throw the pads. I went on a downhill street, accelerated to 30kph and braked as hard as I could twice. Brakes squealed like mad, but braking improved a little, so I went to the steepest street I have close to home (a 15% descent), and descended most of it dragging the brake around 30kph with a sharp brake at the end. That seemed to do the trick and burned whatever crap was left on the pads. I replaced the original rotor and it's been working fine since.

Not that I'm advising to do that. Especially considering the pads were less than 10€. Just wanted to say that it can be done.

In the case of the OP, I think it's better to bring the bike to a shop and let them do a bleed and replace pads as needed. It's not that expensive, and it's better not to mess with brakes if you don't know what you're doing.

Thanks guys. I don't think any of the oil dripped on the break pads or the rotors, the bike was inverted at the time. It just guzzled out a bit from under the loose bolt. I can see that the impacted break squeezes perhaps 10-20% more than the break I didn't mess with. Still breaks fine, just goes a bit further in.

I am thinking of getting a Magura Royal Blood bleed kit and bleeding the thing myself (never done this before), as I feel that taking it to the shop might end up with a different oil being mixed up with the original. I guess I could ask them to show me they have this 'Royal Blood' one, if that's important...