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Shimano brakes

Feb. 5, 2020, 9:36 a.m.
Posts: 198
Joined: March 6, 2017

Has it not occured to anyone that calipers made of 2 halves and bolted together with bolts and o-rings probably shift and move under extreme pressure and heat? I only buy 1 piece calipers like Magura, Hope, Hayes etc. 

At the end of a long run I can pour some water on my calipers and theres steam/sizzling. Aluminum expands under heat. Do the math.

Feb. 5, 2020, 12:09 p.m.
Posts: 512
Joined: March 15, 2013

Posted by: ReductiMat

Has anyone tried this way?

That's the only way I've ever done it.

Works great.


 Last edited by: thaaad on Feb. 5, 2020, 12:09 p.m., edited 1 time in total.
Reason: spelling
Feb. 5, 2020, 1 p.m.
Posts: 11165
Joined: June 4, 2008

Posted by: thaaad

Posted by: ReductiMat

Has anyone tried this way?

That's the only way I've ever done it.

Works great.

Yeah, it seems so easy... definitely going to go that way from here on in.

Feb. 5, 2020, 1:29 p.m.
Posts: 204
Joined: April 15, 2017

Well, bugger me. That is a fantastic method for the whole process. Especially not having to piss around with pressurizing the system afterwards. I also hate working with mineral oil.

It’s pretty similar to the Hope method except they use the lever to create pressure to push the fluid through and then opening/closing the bleed valve at the bottom.

Feb. 5, 2020, 3:14 p.m.
Posts: 1172
Joined: Sept. 30, 2006

I do a similar method to this, but usually push fluid up through to the funnel first with a syringe.  After that, I attach a bag with a hose to the caliper and allow it to gravity bleed down and out like he is showing.  Im not a huge fan of letting mineral oil pour all over my caliper, though lubing the pistons is a good side benefit.  Depending on how much air is in your brakes, I would fear that a simple gravity bleed wouldn't get all of the air out of the areas near the lever. Im sure these mechanics are bleeding the racers brakes on a much more regular basis than any of us are, so probably only need a quick gravity bleed to get things right.

Feb. 5, 2020, 5:28 p.m.
Posts: 228
Joined: Feb. 24, 2017

Posted by: ReductiMat

Has anyone tried this way?  

Yes. My local shop does it like this too.

Feb. 6, 2020, 10:04 a.m.
Posts: 192
Joined: June 28, 2011

Posted by: andy-eunson

Posted by: ReductiMat

Has anyone tried this way?  

Yes. My local shop does it like this too.

Yes, found this video a few weeks back and all I can say is OMG it's totally transformed how I bleed my brakes.

So simple & so effective and the best part you can leave a small about of brake fluid and extra funnel in your car and if you have any issues on the trail can return and simply get it fixed. Its literally a 5 min job.

Also, the fact that the mineral oil lubes all the pistons is a great addition to the whole process.

One extra step I do is after the clean down of the calliper with the cloth, I then get kitchen roll and then clean again. Just as a necessary step of precaution.

The watering of the brake pads before installation is also another great tip.

Feb. 6, 2020, 10:12 a.m.
Posts: 192
Joined: June 28, 2011

Posted by: shoreboy

I do a similar method to this, but usually push fluid up through to the funnel first with a syringe.  After that, I attach a bag with a hose to the caliper and allow it to gravity bleed down and out like he is showing.  Im not a huge fan of letting mineral oil pour all over my caliper, though lubing the pistons is a good side benefit.  Depending on how much air is in your brakes, I would fear that a simple gravity bleed wouldn't get all of the air out of the areas near the lever. Im sure these mechanics are bleeding the racers brakes on a much more regular basis than any of us are, so probably only need a quick gravity bleed to get things right.

I didn't read your reply before writing.

Yes, if you have a large amount of air in the system it would be useful to push some fluid through first.

You shouldn't be worried about getting fluid on the pistons though, I was at first, but making sure that you double clean is all you need. Benefit - no more sticky pistons!!!

Now I have this method, I'm bleeding all my brakes every time I install a new set of pads. It really should help with overall consistency.

Feb. 6, 2020, 11:21 a.m.
Posts: 1172
Joined: Sept. 30, 2006

Posted by: Kieran

Posted by: shoreboy

I do a similar method to this, but usually push fluid up through to the funnel first with a syringe.  After that, I attach a bag with a hose to the caliper and allow it to gravity bleed down and out like he is showing.  Im not a huge fan of letting mineral oil pour all over my caliper, though lubing the pistons is a good side benefit.  Depending on how much air is in your brakes, I would fear that a simple gravity bleed wouldn't get all of the air out of the areas near the lever. Im sure these mechanics are bleeding the racers brakes on a much more regular basis than any of us are, so probably only need a quick gravity bleed to get things right.

I didn't read your reply before writing.

Yes, if you have a large amount of air in the system it would be useful to push some fluid through first.

You shouldn't be worried about getting fluid on the pistons though, I was at first, but making sure that you double clean is all you need. Benefit - no more sticky pistons!!!

Now I have this method, I'm bleeding all my brakes every time I install a new set of pads. It really should help with overall consistency.

Im not worried about getting the oil on the pistons, in fact I usually lube up the pistons with some oil and a q-tip or string during the bleed.  Id be more worried about not getting every last drop of oil off the piston when trying to clean it up and contaminating my new pads.  The hose and bag idea is the same, just less of a mess in my opinion.

Feb. 6, 2020, 1:33 p.m.
Posts: 192
Joined: June 28, 2011

That's why I do the double clean with the kitchen tissue. No issues yet.

Feb. 8, 2020, 4:40 a.m.
Posts: 1
Joined: Oct. 16, 2019

My Maguras have never done it and (so far) my Codes have never done it but Guides, and everything Shimano since they went Servowave have done it to me in some degree.

Feb. 9, 2020, 8:10 p.m.
Posts: 90
Joined: March 1, 2017

I can never tell if Marshy is trolling at times in that video. For sure 100% bleed from the lever down for the first stage as the fluid gets so black in Shimano brakes that it can wreck the levers pushing all that crap into them. I'm not convinced that sucking the fluid out of the caliper is going to boil it though! It hasn't on the 100's (Hell maybe 1000's now...) of Shimano bleeds that I have done. It's always room temperature when it goes into the syringe ha ha..... Sucking the fluid through will also force any dirt that he mentioned into the syringe. Push the pistons out as far as possible and clean / lube with a q-tip. Expel as much air out of the lever before even starting the bleed process. No point drawing air through the system. We always do a second bleed from bottom to top as one bleed is never enough to get the fluid clean in a typical brake. 

His way obviously works for him as a race mechanic, but I'd be doing extra processes and doing a cleaner job on a brake that hasn't been bled for a year (which is most....). He didn't even properly clean the caliper. It doesn't matter how much you wipe it with a rag, one blast with a compressor and you'll see how much oil is left in the nooks and crannies of the caliper, especially if you dumped oil all over it....

Feb. 9, 2020, 10:01 p.m.
Posts: 1
Joined: May 26, 2017

I feel like there is a lot of confusion and misinformation about this issue. I have even received different info and explanations from Shimano. I do know it has next to nothing to do with bleeding. Some brakes will have this wandering bite point issue even when bled perfectly. It’s far less common with the saint and zee brake systems but they are very different brakes than the xt, slx and xtr brakes. *marshys way is the correct way to change the fluid in my opinion

Feb. 10, 2020, 6:13 a.m.
Posts: 765
Joined: June 29, 2006

The (imho) most plausible explanation I've read somewhere is a tolerance/variance in bores and holes somewhere between the fluid in the line and the fluid in the reservoir. When viscosity changes (either very hot or very cold temperatures) and you pump the lever quickly for several times, your bite point can vary, because the amount or pressure (not sure how to express that properly in English) of fluid in the line changes and equalization sometimes doesn't result quickly enough. Depending on the fluid (some use Putoline 2,5WT fork oil and claim that it solves the "issue") and probably also the degree to which the bore or hole is smaller than it should be for a quicker equalization the bite point will wander a little or a lot. The problem seems to occur more often and in stronger form at the rear brake, which has more fluid (longer line), smaller rotors and gets dragged more. Which makes a fluid/equalization issue more probable.

Closed system hydraulic brakes like the Hope C2 or the Magura HS33 rim brakes can show a similar, but more dramatic, behavior.

If the brakes are not bled very thoroughly you can probably have the above issue and ALSO bite point wandering because of air somewhere in the system at the same time. Also a misaligned caliper and sticky piston, pad wear and worn rotors.

Combine all that and internet message boards...

However: Shimano DID warranty the odd brake. But they warrantied quite a lot of M8000 XTs back from the first batches. I warrantied a M8000 right hand lever and saw a couple of pairs go through my LBS for warranty.

Now I am riding M8020s (same lever, 4pot caliper) and they are almost not showing this behavior.

I bought some M8120s and am curious how these will feel. Mostly for the fatter lever blade and the stiffer clamp.

My personal voodoo, apart from not bleeding my brakes while drunk, is to lube the lever piston with a q-tip and some mineral oil. I swear it solves the issue!

As the mineral oil doesn't damage my paint and is not THAT poisonous I don't mind bleeding my Shimano brakes. With the little plastic bucket it is so easy...


 Last edited by: Znarf on Feb. 10, 2020, 6:15 a.m., edited 4 times in total.
Feb. 10, 2020, 11:15 a.m.
Posts: 346
Joined: May 11, 2018

Does the gravity bleed work for magura trail brakes as well? Can't see why it wouldn't but I'm no expert.

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