Quantcast

My brakes suck!

teedubb

Chimp
Jan 16, 2018
18
7
Brand new bike with Deore m6000 front and rear hydro. Attempted to bed in as normal (clean rotors with alcohol, series of long slow & rapid stops). The rear has been squealing like a stuck pig straight out of the box. The rear struggles to lock up and the front as well.

Took the pads off and cleaned them. No luck. Since it’s a new bike I’ll probably just bring it back to LBS and hope they messed something up on install. Any ideas before I do that?

Pads are Shimano G02S
 
Last edited:

teedubb

Chimp
Jan 16, 2018
18
7
How did you clean the pads? If they are contaminated, you just may have to get a new pair unless metallic and you can bake them at a high temperature. Bring it back to LBS and while waiting, entertain yourself with the excellent brakes threads in the DH forum. :monkeydance:
Some sand paper and wiped them down with a little alcohol. I’m not sure if the bike shipped with pads (I’d assume so) or if LBS put them on.
 

Westy

the teste
Nov 22, 2002
37,644
4,490
Sleazattle
I've had luck breaking-in and decontaminating brakes by just getting the rotors good and muddy before exercising a few good stops. Fine silty mud or clay work the best.
 

Jm_

Turbo Monkey
Jan 14, 2002
10,050
2,312
AK
The only consistent way I've been able to clean pads is bake the F-ers for about 15-20 min at 400 degrees.

But, I don't recall having to "bed in" brakes like that since 1998 or so. The brake material will fill the gaps if you ride it and use the brakes. The more DH, the better.

Turkey-warble vibration is due to resonant frequency and usually a function of the caliper-weight, frame-tubing and rotor, all allowing that vibration to get larger, the pads basically vibrate back and forth real fast and you get very little braking and the bike goes out of control. That usually isn't because of bedding.

Normal squeal/screech usually goes away with hard braking IMO and getting some pad material on the rotor. If not, check for torsional aliment.
 

canadmos

Cake Tease
May 29, 2011
10,536
6,578
Canaderp
I have those same brakes on my fat bike and if they are even slightest hint at being moist, they howl like crazy. However they have no problems locking up the wheels, especially the back. I'm guess they got contaminated somewhere along the way.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,502
1,278
01776
best way to bed in is to get to the top of a large hill, go as fast as you can, brake to about 5mph, accelerate and brake 5 more times. That gets a lot of heat into them, and should make them work. Most times I eff up my brakes, I could fix them by going really fast and cooking them with hard braking.

Resin pads should be less warbly, but I guess you never know. You could buy new metal pads, use one pad of each (metal pads will also help power), or request new pads from the LBS. My guess is they won't give you any because LBSes are kind of dicks when it comes to "opinions".
 

StiHacka

Compensating for something
Turkey-warble vibration is due to resonant frequency and usually a function of the caliper-weight, frame-tubing and rotor, all allowing that vibration to get larger, the pads basically vibrate back and forth real fast and you get very little braking and the bike goes out of control. That usually isn't because of bedding.
I have one rotor that when installed on a rear wheel on my crabon HT, it triggers real bad oscillations of the caliper/stay with an amplitude about 1/4". I could literally feel those vibration in my fingers on the handlebar and worried that the frame was going to crack under the stress.
 

slimshady

¡Mira, una ardilla!
I'm guess they got contaminated somewhere along the way.
@Udi has detailed in several threads how Shimano calipers tend to slowly leak fluid when the bike is sitting idle for a long time. I had a hard time getting a friend who was tired of changing contaminated pads to accept this very fact. But he finally settled for it and changed to Formulas.
 
@Udi has detailed in several threads how Shimano calipers tend to slowly leak fluid when the bike is sitting idle for a long time. I had a hard time getting a friend who was tired of changing contaminated pads to accept this very fact. But he finally settled for it and changed to Formulas.
Could you or @Udi please point me at the most informative of these threads? The XTs on the Intense are getting to be about three years old...
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,818
997
If you haven't spilt anything on your deore brakes, then the "cause" may be what's described below.

The best commonly-available solvent to clean pads/rotors that have been oil-contaminated is acetone (100% pure) - it's chemically superior at dissolving oil than other common solvents (such as methylated spirits and isopropyl alcohol). Isopropyl is the 2nd best of those. It's important to ensure the solvent is pure, many store-bought solvents have other additives.

Heat and mud riding (as per Jm and Westy) also help in my experience. It can be good to clean well (with whatever method) and retry so you can see if they come good and then recontaminate themselves later, which confirms the slow leak issue.

Could you or @Udi please point me at the most informative of these threads? The XTs on the Intense are getting to be about three years old...
In the frakenbrake thread there was an aftermarket solution posted if your Shimanos have been leaking (mysterious contamination that users blame themselves for is the usual symptom) in the form of an aftermarket piston and seal kit.

It should fit most Shimano 2-piston brakes, need to purchase two to do one caliper. I have no personal experience but I'd rather try these than persevere with the known-bad genuine Shimano situation.

https://www.ebay.com/itm/282489847007

Some leak from brand new, some can go years without leaking, some develop leaks when left unridden.
In any case, hopefully it's useful to someone.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,818
997
Goes without saying, if it's a brand new bike, just get them warrantied - someone should look after you.

But for anyone with the same issue outside of warranty, I think it's wise to clean everything as much as possible and see if they get "good for a while then go bad again" to confirm the leaking caliper piston issue, and then address it how you see fit - rather than blaming yourself for contamination and buying new pads only to get re-contaminated endlessly.
 

teedubb

Chimp
Jan 16, 2018
18
7
Shop is replacing the pads. We’ll see.

I had the Shimano m315’s (model below these) and they were great straight out of the box.
 

Flo33

Turbo Monkey
Mar 3, 2015
1,277
544
Styria
Some leak from brand new, some can go years without leaking, some develop leaks when left unridden.
In any case, hopefully it's useful to someone.
This! I've been running BR-M785s for some years now, without any issues. LAst November they started to become spongy and I had to pump the rear lever some time - air inside. So I did my first bleed in like 3 years. All was good afterwards. At least for 3 rides, now the rear is spongy again and lacking power...

Formula Curas ordered.
 

FLIPTROP

Chimp
Mar 12, 2018
6
0
Hello, I recommend you clean the pistons with isopropyl alcohol and cotton swabs, with a modified bleed block, to allow one piston at a time to be cleaned and lubricated.
First, push the pistons back, clean the caliper with isopropyl alcohol and reset the pistons with a reset tool or a plastic tire.
Insert the modified bleed block, pull the lever until a piston comes in contact with the modified bleed block, then remove the BB-
Clean the piston with isopropyl alcohol and cotton swabs and push back into the piston
Reinsert the bleed block and pull the lever until the piston comes into contact with BB, and if it is still dirty repeat the cleaning process -
once clean, apply a few drops of shimano mineral oil and push it back in.
Clean again with isopropyl alcohol and repeat the procedure for the second piston.
After cleaning the system, bleed the brake, with gravity system and vertical caliper, changing all the mineral oil.
Your brake will be perfect

PS:
Cura is a very good brake
 
Last edited:

Flo33

Turbo Monkey
Mar 3, 2015
1,277
544
Styria
R0 Racings are installed already.

My XT 785 developed another strange behavior right before the swap. When I pulled the rear lever in a normal speed it felt realtively normal, spongy because of air, but otherwise normal. When I pulled it at a slow speed I was able to pull it all the way to the bar. It was worse when I released the tension a bit an then continued to pull slowly. Whenever pulled at normal speed - no problem. Brake pads are ok, caliper is clean, did a bleed with thorough cleaning 3 rides ago. The bleed was good I think, because the last ride was a long 3 hr nonstop up and down again on some hard and steep trails, no problems. Biting point was relatively consistent.

Any ideas or thoughts? I'm guessing MC seal failure. But I don't care enough to swap levers.
 

FLIPTROP

Chimp
Mar 12, 2018
6
0
R0 Racings are installed already.

My XT 785 developed another strange behavior right before the swap. When I pulled the rear lever in a normal speed it felt realtively normal, spongy because of air, but otherwise normal. When I pulled it at a slow speed I was able to pull it all the way to the bar. It was worse when I released the tension a bit an then continued to pull slowly. Whenever pulled at normal speed - no problem. Brake pads are ok, caliper is clean, did a bleed with thorough cleaning 3 rides ago. The bleed was good I think, because the last ride was a long 3 hr nonstop up and down again on some hard and steep trails, no problems. Biting point was relatively consistent.

Any ideas or thoughts? I'm guessing MC seal failure. But I don't care enough to swap levers.
Hi
For rear brake , bleed must be done with caliper in vertical position, because if the caliper is in this position
upload_2018-3-13_23-14-46.jpeg



air bubble can get trapped at the top of caliper
 

FLIPTROP

Chimp
Mar 12, 2018
6
0
The whole brake was taken off the bike and caliper was dangling freely down vertical.
Are you sure?
You have change all mineral oil ?
You have change with gravity system?
Because if you push oil to caliper vs pump, when oil is exaust and dirt, is not correct, correct is viceversa, dark dirt flush must out trougth the caliper.
Dirt oil makes system spongy
 

valve bouncer

Master Dildoist
Feb 11, 2002
7,791
36
Japan
In the frakenbrake thread there was an aftermarket solution posted if your Shimanos have been leaking (mysterious contamination that users blame themselves for is the usual symptom) in the form of an aftermarket piston and seal kit.

It should fit most Shimano 2-piston brakes, need to purchase two to do one caliper. I have no personal experience but I'd rather try these than persevere with the known-bad genuine Shimano situation.

https://www.ebay.com/itm/282489847007
This is great stuff Udi thanks so much. Got my eye on some first gen SLX with a leaking rear caliper in the auctions, seems this might be a way to sort them. At the very least a cheap and easy fettle, if I do it I'll update this thread with the relevant info.
 

Kurt_80

Monkey
Jan 25, 2016
282
229
Perth, WA.
Anyone have a substitution for iso propyl alcohol? Looking to redo my Formulas that use DOT4, and I'm getting low on reserves.

I was thinking Shellite, as that seems to dry with no residue, but I don't want to stuff things up, especially right now where shipping of spare parts is getting difficult.

Cheers
 

Jm_

Turbo Monkey
Jan 14, 2002
10,050
2,312
AK
Anyone have a substitution for iso propyl alcohol? Looking to redo my Formulas that use DOT4, and I'm getting low on reserves.

I was thinking Shellite, as that seems to dry with no residue, but I don't want to stuff things up, especially right now where shipping of spare parts is getting difficult.

Cheers
Good ole soap and water, put the pads in the oven at 400 degrees for 15 minutes.
 

Kurt_80

Monkey
Jan 25, 2016
282
229
Perth, WA.
Yes. High test vodka would probably work as well.
Good ole soap and water, put the pads in the oven at 400 degrees for 15 minutes.
They have this shit at the autoparts stores called brake cleaner
New pads. Saves hours of faff time.

The super cheap sintered ones I got from amazon kick ass.
Sorry guys, I wasn't clear.

I'm replacing my pistons and seals in a DOT 4 braking system. There's going to be fluid everywhere, so I need something I can clean up with that won't eat seals and ruin paint. Contact cleaner seems to be the best option at this point; you can't get plain IsoPropyl alcohol anywhere.

Anyone tried this stuff?

WD40 CC.jpg


It contains:
IsoPropyl alcohol (good)
Heptane (solvent, not sure)
Difluoroethane (propellant, sounds legit).

Cheers for any further assistance.
 

6thElement

Schrodinger's Immigrant
Jul 29, 2008
5,328
2,783
Use your bleed syringes to remove the fluid from the system first.

Then you can use water initially to clean up the fluid on your work top if you don't have enough alcohol or other.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,818
997
For future reference, DOT (3/4/5.1) fluid is heavily hygroscopic, plain water is the best thing to clean it up.
Keep a bucket of water nearby and splash it on anything you get it on - especially paint and your skin.
It's best to wash and dilute completely ASAP before wiping.

Acetone is best for (attempting to) clean contaminated pads.
Isopropyl is good for cleaning of brake surfaces but ensure purity is 100%, otherwise it can contaminate.
 

Sandwich

Pig my fish!
Staff member
May 23, 2002
16,502
1,278
01776
I've found that contaminated pads will be cleaned by several heat cycles or nothing at all. If I can't make my brakes work again after a serious downhill, then they're better off being replaced.

I've been unfortunately covered in dot fluid and a little hot water cleaned if off just fine, cept for the cancer.