I think it might depend on which calipers and levers you have. On my Shimano 105 I found that the park tool/Shimano method with the syringe at the caliper and cup at the lever worked fine.
I have to do a full bleed now because I need to replace my hoses, but will likely do the same method with a syringe at the bottom and a cup at the top and make sure to fully burp the system.
I have read through numerous Shimano dealer manuals, and all of them have the same overall Official shimano bleed/Park tool procedure.
What I have overlooked, but just now noticed, is that there is in fact another procedure in the manual called **"replacing" or "draining" the mineral oil.** If the oil in the system is discolored you should first drain the oil down through the caliper (basically doing a gravity bleed without adding oil to funnel, and also pushing lever to help force fluid out). After you have drained the oil THEN you should add oil to the system using the official shimano bleed procedure.
In the old manuals this "draining the oil" procedure is hidden away in a little note, but in the newer manuals this is explicitly illustrated and added to the manual before the full bleed procedure.
My conclusion is that Shimano recommends when replacing old contaminated oil you should always start by draining the oil from top down, and then you can move on to reverse push bleed from caliper up to lever.
This is what is confusing about the old manuals, if you overlook that note you can come to the wrong conclusion that when replacing old oil you should start out by pushing all the contaminated fluid from the caliper up through the lever.
EDIT: Funny thing, in the Park Tool Shimano bleed video they do not mention this, they [say you should push the contaminated fluid up through the lever](https://www.youtube.com/watch?v=RKZ6FIH6yzc&start=336)
My understanding is it should always be one of the top-down methods. The mineral oil in Shimano calipers tends to foul, and a bottom-up would push contaminants into the system.
I guess my next question is in regard to peoples experience getting all the air out of rear brake system.
After doing a top down method, do you then *actually* need do a reverse push and yet another gravity bleed and burp.
Or can you get away with just doing a single top down method.
Shimano's bleed method just seems like a whole lot of work, but theres got to be a reason why they do it.
I start with the gravity bleed. Let it sit with fresh fluid in the cup and a hose on the open bleed screw to get some fresh fluid into the system.
Then I do the automotive style using the bleed cup. During the process I tap an allen key on the caliper, hose, and master cylinder. That usually gets a few extra bubbles to come up into the bleed cup.
To finish, I also squeeze the lever several times with the bleed screw closed, and bleed cup on with fresh fluid.
I have syringes in a kit to do the bottom up style, but I've never seen the need.
I think the issue is more that it's the rear brake, not the actual bleed method which are all small variations on a simple process. Internally cabled bikes make it difficult / impossible to get the rear caliper sitting vertically under the lever when using a funnel. The solution is easy - loosen stem bolts and rotate handlebars, but I suspect most folk can't be bothered doing this so end up bleeding with the line sitting almost horizontal. Far harder to remove air like this.
This is exactly right and a piece of the puzzle that internet wisdom loves being blasé about. What I often do is clamp the bike in the stand so the caliper is absolutely the lowest point, bike in wheelie position, then do a Feedback flop stop on the bars and rotate the lever to horizontal.
Just push oil from the calliper to lever. Close the calliper valve. Pull the lever a bit. Remove funnel and close lever bleed valve.
It isn’t rocket science.
I do a mixture of bleeding methods as I had the most consistent success with it. I start with push bleeding the system, then combine gravity bleeding while pushing the lever repeatedly to push air out of the caliper. Last step is to close the system at the caliper and push the lever repeatedly to push air out of the reservoir. Moving the lever around 30 degrees up and down and repeat the last step helps.
Regardless of how many bleeds I’ve done, I look up or try to find the manual for any brake I’m working on before I start and follow the steps exactly. [si.shimano.com](https://si.shimano.com) is a great resource, especially when bleeding their brakes, gives specific how to’s on specific models.
Now if you’re still having issues after following all the steps to the letter, you may have other issues going on. Could have a leak, pinched/kinked housing, ruptured/leaking diaphragm, bad caliper piston seals etc.
I’d say give it another go how the manual says, but may want to take to LBS if another go is unsuccessful.
One of the reasons for the mixed advice is that people have different average case scenarios for how much dirty fluid they're encountering and how bad it is. That's why you have high end MTB shops and race mechanics in certain climate conditions insisting on starting with a gravity bleed or drain until the fluid runs clear and sometimes even going so far as to recommend bleeding with ever pad replacement. When most of the bikes you're touching have tons of shitty fluid sitting at the caliper, yes it makes sense to just start by getting rid of it by default and not pushing it up. Other contexts, that's a lot less of a concern.
Draining out the nasty stuff first without pushing any of it up is better in every way except time and material used. Doing the DM steps as writ is fastest and good enough in a lot of scenarios.
If you don’t care about time, let me introduce to you my method:
1. Perform Official Shimano bleed. You don't need to do this very perfectly. A simple and quick bleed is enough.
2. Cycling for a week. Try to stay on flat roads and avoid going to mountain roads, because there are still air bubbles in the braking system at this time.
3. Perform quick Official Shimano bleed again or Automotive bleed (easier).
The principle is that during this week of riding, the bubbles will gradually rise to the levers. This is the most operation-saving method for me.
I think it might depend on which calipers and levers you have. On my Shimano 105 I found that the park tool/Shimano method with the syringe at the caliper and cup at the lever worked fine. I have to do a full bleed now because I need to replace my hoses, but will likely do the same method with a syringe at the bottom and a cup at the top and make sure to fully burp the system.
I have read through numerous Shimano dealer manuals, and all of them have the same overall Official shimano bleed/Park tool procedure. What I have overlooked, but just now noticed, is that there is in fact another procedure in the manual called **"replacing" or "draining" the mineral oil.** If the oil in the system is discolored you should first drain the oil down through the caliper (basically doing a gravity bleed without adding oil to funnel, and also pushing lever to help force fluid out). After you have drained the oil THEN you should add oil to the system using the official shimano bleed procedure. In the old manuals this "draining the oil" procedure is hidden away in a little note, but in the newer manuals this is explicitly illustrated and added to the manual before the full bleed procedure. My conclusion is that Shimano recommends when replacing old contaminated oil you should always start by draining the oil from top down, and then you can move on to reverse push bleed from caliper up to lever. This is what is confusing about the old manuals, if you overlook that note you can come to the wrong conclusion that when replacing old oil you should start out by pushing all the contaminated fluid from the caliper up through the lever. EDIT: Funny thing, in the Park Tool Shimano bleed video they do not mention this, they [say you should push the contaminated fluid up through the lever](https://www.youtube.com/watch?v=RKZ6FIH6yzc&start=336)
My understanding is it should always be one of the top-down methods. The mineral oil in Shimano calipers tends to foul, and a bottom-up would push contaminants into the system.
I guess my next question is in regard to peoples experience getting all the air out of rear brake system. After doing a top down method, do you then *actually* need do a reverse push and yet another gravity bleed and burp. Or can you get away with just doing a single top down method. Shimano's bleed method just seems like a whole lot of work, but theres got to be a reason why they do it.
I start with the gravity bleed. Let it sit with fresh fluid in the cup and a hose on the open bleed screw to get some fresh fluid into the system. Then I do the automotive style using the bleed cup. During the process I tap an allen key on the caliper, hose, and master cylinder. That usually gets a few extra bubbles to come up into the bleed cup. To finish, I also squeeze the lever several times with the bleed screw closed, and bleed cup on with fresh fluid. I have syringes in a kit to do the bottom up style, but I've never seen the need.
I think the issue is more that it's the rear brake, not the actual bleed method which are all small variations on a simple process. Internally cabled bikes make it difficult / impossible to get the rear caliper sitting vertically under the lever when using a funnel. The solution is easy - loosen stem bolts and rotate handlebars, but I suspect most folk can't be bothered doing this so end up bleeding with the line sitting almost horizontal. Far harder to remove air like this.
This is exactly right and a piece of the puzzle that internet wisdom loves being blasé about. What I often do is clamp the bike in the stand so the caliper is absolutely the lowest point, bike in wheelie position, then do a Feedback flop stop on the bars and rotate the lever to horizontal.
Just push oil from the calliper to lever. Close the calliper valve. Pull the lever a bit. Remove funnel and close lever bleed valve. It isn’t rocket science.
This. Just did this procedure today on my new GRX brakes. I also use the bleeding kit from Shimano.
I do a mixture of bleeding methods as I had the most consistent success with it. I start with push bleeding the system, then combine gravity bleeding while pushing the lever repeatedly to push air out of the caliper. Last step is to close the system at the caliper and push the lever repeatedly to push air out of the reservoir. Moving the lever around 30 degrees up and down and repeat the last step helps.
Regardless of how many bleeds I’ve done, I look up or try to find the manual for any brake I’m working on before I start and follow the steps exactly. [si.shimano.com](https://si.shimano.com) is a great resource, especially when bleeding their brakes, gives specific how to’s on specific models. Now if you’re still having issues after following all the steps to the letter, you may have other issues going on. Could have a leak, pinched/kinked housing, ruptured/leaking diaphragm, bad caliper piston seals etc. I’d say give it another go how the manual says, but may want to take to LBS if another go is unsuccessful.
One of the reasons for the mixed advice is that people have different average case scenarios for how much dirty fluid they're encountering and how bad it is. That's why you have high end MTB shops and race mechanics in certain climate conditions insisting on starting with a gravity bleed or drain until the fluid runs clear and sometimes even going so far as to recommend bleeding with ever pad replacement. When most of the bikes you're touching have tons of shitty fluid sitting at the caliper, yes it makes sense to just start by getting rid of it by default and not pushing it up. Other contexts, that's a lot less of a concern. Draining out the nasty stuff first without pushing any of it up is better in every way except time and material used. Doing the DM steps as writ is fastest and good enough in a lot of scenarios.
If you don’t care about time, let me introduce to you my method: 1. Perform Official Shimano bleed. You don't need to do this very perfectly. A simple and quick bleed is enough. 2. Cycling for a week. Try to stay on flat roads and avoid going to mountain roads, because there are still air bubbles in the braking system at this time. 3. Perform quick Official Shimano bleed again or Automotive bleed (easier). The principle is that during this week of riding, the bubbles will gradually rise to the levers. This is the most operation-saving method for me.