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Decide to upgrade my levers. M6100 to put on 4pot MT420 calipers. Shimano SLX rotors that came with the MT420 system.
Bled with levers screwed all the way out. Not too good results. Bled with levers screwed all the way, then opened after. Bit better. Still not perfect. There's a lot of lever pull before the brakes actually start biting.
I did a gravity bleed. Pushed back pistons with a tyre lever. Put plastic block in between pistons. Kept topping up the cup on the lever. Open caliper bolt, squeeze lever closed, close caliper bolt, release lever. Repeat.
Did I miss something?
Not direct help but my usual go-to here is Doddy or similar on Youtube.
Are the levers squishy? If so, air is still there. If not, now the pistons are set, top the system up again from the caliper - this will reset the piston start position to where they are now but should reduce the lever throw. It isn't ideal if you aren't using brand new pads.
I'd suggest lever all the way out and anything other lever settings all the way out for a bleed, then any adjustments shouldn't adjust lever throw for the worse.
Any brake bleeding I do generally involves tapping the caliper, hoses and lever extensively to move any bubbles along to the lever and then pumping the lever.
I did a gravity bleed.
This is probably the cause of the problem. You had a caliper full of fluid and a lever full of air, then you forced fluid into the lever and pushed the air into the hose and caliper. You most likely have air in the caliper now.
I would suggest you drain the system completely and then bleed from the bottom up, attach your syringe to the caliper and pump fluid in from that end. If you have the caliper and hose full of fluid, you can attach a funnel to the reservoir and work the lever to get the final bubbles of air out of the lever end. Clamp the lever hard for a few seconds, then release it suddenly. Keep doing that until you have a solid lever and all the bubbles are out of the reservoir.
This is the reason why whichever system I'm bleeding, I'll try to find a way to vacuum bleed with syringes.
I'll also always try to go caliper - hose - lever when bleeding.
Yeah, bleed from caliper up as air rises easier than falls...if you have syringe connected at both ends then make sure caliper end has more fluid in it. You can also have syringe pointing upwards (so plunger is at top and give it a sharp quick pull as that will suck and air through and have it at the plunger end of the syringe...helps if you seal the lever end i.e. crimp the syringe hose.
One way bleeding is misleading - it just means that there's only one route for fluid to take through the caliper, which cleans air pockets out more easily. In the linked images, the old 975 design means that fluid pushed through the caliper can effectively bypass the piston bores - later designs avoid that.
Shimano recommend bleeding from caliper up, then a gravity bleed, but without pumping the lever while doing so as this breaks up larger bubbles into smaller ones and makes a good bleed more difficult to achieve.
Flicking the lever should be the last part of the process rather than a major feature of it.
https://si.shimano.com/en/dm/MBDBR01/replace_genuine_mineral_oil
Every time I go to put my syringe on the caliper I see air in the tube. Freaks me out. I automatically assume I'm shoving air into the system and messing things up.
That said, I'll give it another shot that way around. Shove it up the bottom end, then trickle back down shaking it all.
Someone above said have the levers out, but I feel better screwed in.
I'm sure I have loads of pads in my parts boxes, but ordered another load just in case. 3rd party metal pairs are like £2 where I am. Resin ones even less. Everything Shimano related is.
i use the Marshy technique on Shimano. Fill the funnel and gravity bleed the system until clean fluid is coming out at the calliper end. Then close off the caliper ado a lever bleed with the funnel until the lever goes nice and stiff
Every time I go to put my syringe on the caliper I see air in the tube. Freaks me out. I automatically assume I’m shoving air into the system and messing things up.
If the system already has fluid in it, draw some fluid out of the caliper until the air in the tube is drawn back into the syringe. Then force fluid with no air into the system.
If the system is empty, it doesn't matter, you'll have to fill the entire system and the air will get forced out the reservoir end.
I get my best results by pushing fluid up from the caliper to the funnel at the lever, so I'd suggest giving that a go.
With the lever all the way out, but then squeeze and tap it a lot to tease any little bubbles out.
TBH I sometimes forget to wind the lever out and still get decent results.
TBH I sometimes forget to wind the lever out and still get decent results.
As long as the transfer port from the reservoir to the master cylinder is open, it shouldn't make any difference.
I've done a syringe bleed upwards, then a gravity bleed, with levers screwed inwards, rattling the hoses from rear to front, and put new pads in.
It's a lot better now. Like twice as good. Not saying it's perfect. But then new pads, haha.
But I find other brakes easier to bleed and get firm, like MT200, some MEROCA brand cheapies (MT200 are only £15 each end as it is!)
It just feels a bit hit and miss (sensitive) with these servo wave M6100s levers.
I'd suggest you may still have some air in there...I find once I have clean fluid and no more air bubbles I need to keep doing a push of syringes another 10 or so times and there are really small bubbles that do come out...then it all feels very good.
But I find other brakes easier to bleed and get firm
I've only bled Hayes HFX and El Camino, Avid Juicies, plus various Shimano brakes. They can all be fiddly, but I agree that Shimano almost never work perfectly without a bit of pushing fluid back and forth to get all the bubbles out.
Yeah, seen so many tiny bubbles come out in the cup it's ridiculous! After pushing up with a syringe, then gravity feeding down with lever pulls, over and over, and over.
In future I'll definitely be doing it this way. No more (sole) gravity bleeds.
With new resin pads in (I've got metal ordered for a riding holiday), after I beded them in I had solid brakes and was able to lift the rear a bit.
Every time I go to put my syringe on the caliper I see air in the tube. Freaks me out. I automatically assume I’m shoving air into the system and messing things up.
Some of the bleed nipples are so loose when they are open, a bit of plumbers tape on the threads really helps.
FWIW, the SRAM Bleed-a-ma-jig thing is way easier.
Another reason to love Hope. They bleed conventionally top down needing nothing more than a bit of tubing and a jam jar (and even that is just to prevent mess). Takes a couple of minutes and never fails.
*runs away*
another vote for pushing fluid up through the caliper
and agree with this
thols2
......If the system already has fluid in it, draw some fluid out of the caliper until the air in the tube is drawn back into the syringe. Then force fluid with no air into the system.
really here to say I have small hands as does everyone in our household and I've never bothered to change the pull setting screw when bleeding ...