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Discussion Starter · #1 ·
I've been having this strange problem lately. If I'm off the bike for 5 or 6 days, the front brake acts like it needs re-bedding. As in it has almost no power. But if I do the 20+ hard brakes it comes back up to full power (I could put myself over there bars of I wanted to). Next day it will be fine. And if I ride every day it's fine, but if I'm off the bike for close to a week it goes back to needing to be re-bedded.

Anyone had this happen? Is it just crap pads?

Magura MT7
Sixpack semi-metalic pads
Shimano 203mm rotor.

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Is it a bleed issue or a power issue?

As in, is the lever stiff and brakes don't perform well or is it more of a lever travel is too far and brakes don't perform well?

I've never needed to rebed brakes.

My SRAM brakes work less well when I haven't ridden, but most of the times is because I forget the feeling of SRAM when switching between the SRAM and Shimano bikes.
 

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Discussion Starter · #3 ·
Is it a bleed issue or a power issue?

As in, is the lever stiff and brakes don't perform well or is it more of a lever travel is too far and brakes don't perform well?

I've never needed to rebed brakes.

My SRAM brakes work less well when I haven't ridden, but most of the times is because I forget the feeling of SRAM when switching between the SRAM and Shimano bikes.
It's a power issue. The bleed seems good. The levers are firm and consistent. Just very low power until I do about 20 hard stops, then they are back to full power.

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I have had that problem in the past with brake pads that have been sitting unused over the winter. I think the metal pieces within the brake pad material corrode or oxidize or something like that. The only time ive had to re-bed in pads over the course of a few days is when they have been contaminated with oil or something similar
 

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Elitest thrill junkie
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Shimano brakes will weep some oil past the piston seals when they sit for long, as in a few weeks or more.
 

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Discussion Starter · #7 ·
Shimano brakes will weep some oil past the piston seals when they sit for long, as in a few weeks or more.
I was wondering about leaking pistons, as it is the only source of contamination that would seem to be possible (bike is stored in a storage room in a garage and travels to and from the trail uptight in the back of a cargo van). But they haven't needed bleeding and everything feels consistent. Plus, when I've contaminated pads before, the power just went down and wouldn't come back.

Regardless, its coming to in a year, so I'll do a flush and bleed and throw in new pads.

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Elitest thrill junkie
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I was wondering about leaking pistons, as it is the only source of contamination that would seem to be possible (bike is stored in a storage room in a garage and travels to and from the trail uptight in the back of a cargo van). But they haven't needed bleeding and everything feels consistent. Plus, when I've contaminated pads before, the power just went down and wouldn't come back.

Regardless, its coming to in a year, so I'll do a flush and bleed and throw in new pads.

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If the air bubble works it's way to the top of the lever and reservoir, it will appear to be working fine, kind of a "self-bleed". IF it is doing this, passing a little bit of fluid, it's probably going to be hard to detect, because it's so little that you can "burn it off" with a bit of riding. That is usually not possible for any significant amount of contamination, it usually takes baking the pads at 400 degrees for 15 minutes. But the symptom sounds very similar. I go take my shimano XT or XTR brakes out that have been sitting for a few weeks or longer and I sometimes have almost no braking power. I haven't resorted to trying to "build it back up" anymore, I just put the pads in at 400 degrees for 15 minutes and clean the rotors off with rubbing alcohol and that does it. It's part of shimano's crappy brake design feature though and they won't sell you replacement piston seals (or any other parts for that matter), so I'd advise to stay away from them. I was talking with a friend the other night about this and he's a Magura ambassador and has gotten brake seal parts with no problems from Magura.
 

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Where do you store your bike? If you're storing it some place that might get contaminates could get on the pads, say a garage and you're spraying lubes for other stuff you're doing, or there's a outlet for a clothes dryer etc, that could be your problem. If you want to accelerate the "bed in", quirt some water on the pads, help's it a lot.
 

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Discussion Starter · #10 ·
Where do you store your bike? If you're storing it some place that might get contaminates could get on the pads, say a garage and you're spraying lubes for other stuff you're doing, or there's a outlet for a clothes dryer etc, that could be your problem. If you want to accelerate the "bed in", quirt some water on the pads, help's it a lot.
I store them in a storage room in the garage. There is a closed door between them and the rest of the space. The other bike I store in there is fine (magura mt5 brakes on that one). So I don't think it is a storage issue. I've reached out to Magura for seals. I'll do a caliper service and bleed and replace (or bake) the pads/clean the rotor. See where that gets me.

Just seems like a weird problem, so wanted to reach out and see if anyone else has run into it.

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I'd try a new set of pads first, not that expensive and much easier to do. You may have just picked up some contaminate on those pads at some point and riding them and putting heat into them lets them work or burns away the stuff enough to work, but then it rises to the surface again once it stays un-ridden. I've had Shimano pads do that to me, makes no sense and new pads solved the problem, no further issues, just somehow contaminated. Could also try baking the pads a few times, letting them cool between cycles and see if that does the trick.
 
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