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Shimano M820 Front Brake Not Grabbing


Sam Song

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I cannot for the life of me to get the M820 Saint Brake to grab properly upfront. 

I have it set with a 8 inch Icetech rotor on a Rockman Spade 26 disc fork. Yes, pads have been worn in since I dragged the brake down a hill multiple times. I am using stock pads. 

Things I have tried:

- taking the rotor and pads off for cleaning with Brake cleaner spray and medical alcohol. 

- bedding in the pads 

The thing is: it can work pretty well when the disc is sprayed with water but as soon as the disc dries, it is back to not grabbing. 

I am using stock pads but I have seen people saying great things about Saint Brake even with stock pads. 

The brake is bought new, only few months old. 

Any ideas for setting up?

20220629_171737.jpg

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I always avoid using disc brake cleaning products on my brakes…any time I’ve ever used them it’s ruined the bite.

 

 If this was me I’d get a blowtorch and burn off whatever is on the pads and then give the rotor a little blast too (not too much though, just to evaporate whatever might be on it).

 I’ve done this with some pretty contaminated pads and had them completely transformed.

If that doesn’t work then get new pads and don’t use anything other than clean water 

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how about metallic / sintered pads? 

I also have that experience before with organic pads (shimano deore/ magura mt2, mt4)

being contaminated by i don't know. always have to bring water or alcohol.....

But when I changed the pads to metallic, only oil can ruin my ride....

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I use only organic pads. Either stock pads or Trickstuff power. This is how I proceed when I have trouble with pads:

I first spray a good brake cleaner on the pads before I burn them. When they are contaminated, a black/gray smoke is produced. As long as they are hot, I spray some brake cleaner further. After they cool down, I send them to remove what the brake cleaner dissolved.

My next step is to spray some brake cleaner on the rotor and to whip it with a tissue. If there was some oil, the tissue gets some black marks. I repeat this step with a clean tissue until there is no mark visible on the tissue.

To finish I sand the rotor slightly.

Mostly the first brakings are not so powerful (maybe because I sand the rotor and pads), but after a few brakings, I have a good result.

 

Something a friend and I noticed with Shimano organic brake pads: somehow, after a long period not being used, they do no brake correctly as if they were contaminated. Sometimes they are even loud. After a 10 minutes ride in mud, they brake again as they used to. I read also some similar feedbacks on different forums. Our assumption was, that it has to do with winter and wet roads contaminated with oil. But somehow I had this on my DH bike and I don't ride with it on the road ... 

So the next hypothesis was that the pads somehow oxidized. 

Executing the procedure I described above solved this issue.

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I'm with Ali on this one, never had any good results from brake cleaners. I'll use alcohol (99% industrial stuff, not the drug store stuff w additives) if I have to clean the caliper or rotor and even that can be questionable. Flame usually does the trick - plenty of vids on youtube for that. Gas stove or a butane lighter works. From the photo you posted, it does look like something's on your rotor. When it's all working top notch the rotor should look mirror polished on the braking surface.

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you are alright, the rotor seems contaminated on the picture. Sharp eyes!

 

Did you wipe out the surface after spraying so brake cleaner?

 

I found this article. These might explain why brake cleaner give a first wrong impression:

James Alberts, SRAM's brakes Product Manager, has this to say: "Disc brakes work best when there is a consistent braking surface created by material transfer from the pad to the rotors.  We have found that cleaning with isopropyl alcohol does a good job of maintaining this relationship while removing grime." 

 

Recently I observed that after cleaning my rims on my comp trial with these brake cleaner - I had dirty fingers and touch them, the HS33 wasn't loud and did not bite as it did. The rim is ground correctly though. I rode a little and then it went back to normal. I think this is because the pads material was no longer present.

 

I used the brake cleaner a friend used in his car repair shop.

There are different brake cleaners too :

Hope told us "We recommend either methylated spirits or isopropyl alcohol as these both leave no residue on the rotors. Keep away from white spirit as this will leave an oily film.

"If using brake cleaners make sure you use bicycle specific ones as car brake cleaners sometimes include oil to stop cast iron discs from rusting."

 

They recommend to use soap. I am not sure it is a good idea though (Soap is created by mixing fats and oils with a base)

 

 

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4 hours ago, La Bourde said:

Something a friend and I noticed with Shimano organic brake pads: somehow, after a long period not being used, they do no brake correctly as if they were contaminated. Sometimes they are even loud. After a 10 minutes ride in mud, they brake again as they used to. I read also some similar feedbacks on different forums. Our assumption was, that it has to do with winter and wet roads contaminated with oil. But somehow I had this on my DH bike and I don't ride with it on the road ... 

So the next hypothesis was that the pads somehow oxidized. 

This happened to me with the Zees (stock pads), to the level that both of the brand new brakes were almost every time just completely useless and I decided to get rid of them to buy Maguras. Not locking up at all, added with some really intense howling. This was after the bed in of course, and the weather was nice and dry all the time. 20mins of hard braking made them work like they should, but everything was gone again when the bike rested a couple of days inside my apartment.

I checked the pistons few times and they didn't seem dirty or anything that could indicate leaking. Something weird was going on with the pads, or there was a minor leak that was invisible.
That added to the inconsistent bite point issue (also well documented on other forums) and horrible pad knock made me to forget Shimanos forever. Still can't understand how so many people like them so much with all the annoying flaws, bit of a mystery.

I'm not completely happy with Maguras either, but at least they have worked consistently for 5 years with correct bleeding.

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That is really funny. I know the problem with the moving bite point too, it is really an issue. To solve it, I just remove the wheel and pull the lever 3-4 times. That is enough for a couple of rides for a few months. But it get worse with time and I eventually bleed the brakes, which is something really easy compare to most other brakes. That is why I still ride some Shimanos.

I hate Maguras. The levers are so bad, I don't want to ride with. On my HS33, it is still OK, I can accommodate with. But I don't like how weak they feel and if I could find better levers, I will go for them (A friend has some Jitise and he does not like them that much, he has to adjust them regularly cause the adjustment screw is always getting loose). And I am always pushing back the axle of the lever...

A friend of mine has MT7 on his Inspired, he is constantly adjusting the lever, breaking some parts of it ... To me, they have to move away from this carbotecture.

But the HS33 and MTx brakes are really powerful, easy to dose and with better levers, I would buy some disc brakes of them for sure.

 

Sometimes  I have the impression there is no good hydraulic disc brakes on the market... That is why I use some mechanical ones on my street/trial.

 

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Those Shimano brakes are notorious for micro leaks past the caliper pistons. I've had it with Zee, XT, and Ultegra on the road bike of a friend of mine. If you use the blowtorch/acetone/alcohol method, and you find it works for one or few rides, and then it happens again, it's time to contact the warranty department. And don't buy Shimano brakes again.

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i used to try brake spray only once and no more than that. I hate it and usual method works until today. Dishwashing liquid-brush-sand paper-fire - Done

I just felt metallic pads works well for me since every time humidity reaches 92% here, organic pads started to mess up...

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