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Discussion Starter · #1 ·
I recently had my brakes bled and new pads put on. Initially they felt great but it seems like it has quickly faded where I really need to grab the rear brake lever for it to bite / grip.

Any recommendations on how to fix? Should I try sand paper both the pads and rotor? Grad the brake down a really long hill and hope the heat burns off any corrosion?
 

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Do you mean your lever goes to the bars or do you mean they do not have power within the normal range of the lever?

Have you bed in the pads yet?

You say "initially" they felt great. Did that mean after repair or before repair?
 

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Discussion Starter · #3 ·
Do you mean your lever goes to the bars or do you mean they do not have power within the normal range of the lever?

Have you bed in the pads yet?

You say "initially" they felt great. Did that mean after repair or before repair?
No power with normal range.

I have not bed in the pads

They felt great after the repair
 

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Bed them and and see if the performance improves.
You an do that in the street in front of your house. Or the parking lot in your apartments, etc.

Ride the bike and slowly bring the bike to a near-stop (do not stop).
Repeat this, increasing the speed and stopping forces.


If you've already ridden the bike a few times on trails, they are probably bed in, in which case disregard bedding them in. And I do not have other suggestions.

I suppose if you had the work performed at a shop you could take it back and let them know the brakes aren't working so they can fix them up.
 

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I recently had my brakes bled and new pads put on. Initially they felt great but it seems like it has quickly faded where I really need to grab the rear brake lever for it to bite / grip.

Any recommendations on how to fix? Should I try sand paper both the pads and rotor? Grad the brake down a really long hill and hope the heat burns off any corrosion?
If the level travel & firmness hasn't changed from when the brake felt good, then it sounds like the pads have been contaminated.

To test this, you could:
1. ensure that each piston is moving freely (this shouldn't matter, but...), if they aren't, then google, "balancing brake pistons" and as part of this make sure that they're clean
2. check that the rear brakes aren't leaking fluid onto the pads. If they are then this is the answer...and you probably need new brakes

then,
3. clean both front and rear rotors with isopropyl alcohol
4. swap the pads front to rear to see if the front brakes are now sub par.

If the front brakes are now weak then the pads are contaminated, in which case you'll want to clean the front rotor, then buy some new pads.

If the rears are still an issue, then I'd be surprised...because it wouldn't make sense unless the feel at the lever and/or the lever travel changed...
However:
a. there must be an issue with the bleed (maybe some bubbles moved?) or
b. the brakes have somehow sucked in air since you started riding post bleed Have you checked the bleed screws are tight?

Here's a great article about cleaning pads and rotors.
Enduro Mag - Enduro Workshop: Fixing noisy disc brakes

Let us know how you go. Good luck :) :thumbsup:
 

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Discussion Starter · #8 ·
If the level travel & firmness hasn't changed from when the brake felt good, then it sounds like the pads have been contaminated.

To test this, you could:
1. ensure that each piston is moving freely (this shouldn't matter, but...), if they aren't, then google, "balancing brake pistons" and as part of this make sure that they're clean
2. check that the rear brakes aren't leaking fluid onto the pads. If they are then this is the answer...and you probably need new brakes

then,
3. clean both front and rear rotors with isopropyl alcohol
4. swap the pads front to rear to see if the front brakes are now sub par.

If the front brakes are now weak then the pads are contaminated, in which case you'll want to clean the front rotor, then buy some new pads.

If the rears are still an issue, then I'd be surprised...because it wouldn't make sense unless the feel at the lever and/or the lever travel changed...
However:
a. there must be an issue with the bleed (maybe some bubbles moved?) or
b. the brakes have somehow sucked in air since you started riding post bleed Have you checked the bleed screws are tight?

Here's a great article about cleaning pads and rotors.
Enduro Mag - Enduro Workshop: Fixing noisy disc brakes

Let us know how you go. Good luck :) :thumbsup:
That's a great way to troubleshoot. I wound up cleaning the rotors and switching the pads and sure enough, the front lost a ton of stopping power while the back felt significantly better.

I didn't notice any obvious leaks, but I wonder if there's a small leak as there is a bit of greasy gunk on the caliper. I'm going to clean the calipers (any recommendations how/with what?) and then run as is for a bit. Hoping the problem doesn't come back. If it does, it seems like a leak and may be time for new brakes :(
 

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That's a great way to troubleshoot. I wound up cleaning the rotors and switching the pads and sure enough, the front lost a ton of stopping power while the back felt significantly better.

I didn't notice any obvious leaks, but I wonder if there's a small leak as there is a bit of greasy gunk on the caliper. I'm going to clean the calipers (any recommendations how/with what?) and then run as is for a bit. Hoping the problem doesn't come back. If it does, it seems like a leak and may be time for new brakes :(
Great that you've had some progress! :cool:

To clean brakes I use isopropyl alcohol in two forms:
  1. 1. in a spray bottle - spray alcohol on the caliper, then wipe/rub it off. I also use cotton buds to clean (you can even dip them in the alcohol first)
  2. 2. the little medical fold-able wipes (I think that they're used to clean skin before giving an injection?) and wipe the gunk off

You might be able to clean & restore the contaminated pads by cleaning them with alcohol (or heating them...but that seems a little random for me)
 

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I think just the regular Shimano pads. The brake doesn't feel soft.
There are quite a few different types of pad from Shimano but the key two variables are resin and metallic. Resin ones have noticeably better initial bite and overall better feel. The metallic ones are more resistant to fading at extreme temperature and last longer but in practice I've not found either of these to be a problem.

Your situation does sound like contamination. Anything oily on that rotor and the brake will just slip.
 

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Discussion Starter · #11 ·
I just took them off and cleaned them pretty well which helped. Still getting some slipping from the contaminated pads but definitely working better and much more confidence inspiring. Assuming the rear pads stay in good shape (no caliper leak), I may sand down the front ones more or just buy new ones.

There are quite a few different types of pad from Shimano but the key two variables are resin and metallic. Resin ones have noticeably better initial bite and overall better feel. The metallic ones are more resistant to fading at extreme temperature and last longer but in practice I've not found either of these to be a problem.

Your situation does sound like contamination. Anything oily on that rotor and the brake will just slip.
I have the metallic ones.
 

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Any chance you contaminated them while doing something like lubing your chain? Sounds like contaminated pads. Still, running them through a bed in process is always worth a shot.
 

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Had same issue on my road bike----followed forum suggestions and this worked
Clean disk
Bake pads in oven at 350 for 30-----
Sand a bit

The baking seemed to be key-as I had done all the above before to no avail
 

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I'm not sure but I sanded the pads a good amount today and they feel much better.
What has worked for me for the past 10 years every time is to:
1) take the rotor off the wheel along with the pads
2) put the rotor in a clean set of players or vise grips with leather gloves,
3) burn them on the stove or with a torch until red hot (go all the way around the rotor)
4) Burn the pads for about 15 sec.
5) lightly sand rotor and pads with clean gloves
6) Reinstall and bed the brakes.

Guaranteed to have very strong bite after this. This gets rid of all the oil contamination. I've never had tipo replace a rotor.
 
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