Trying to bleed SRAM brakes...badly

Does this help?

SRAM.COM "https://www.sram.com/globalassets/document-hierarchy/bleed-manuals/sram/dot-fluid-mtb-disc-brake-hose-shortening-and-bleed-manual.pdf"

Here’s my notes. I did ok with the push fluid from top method.

SRAM Code bleed, bleeding edge
SRAM MTB: Bleeding Edge Brake Bleed video:

Troy Bosnan mechanic Canyon video:

SRAM use DOT 5.1 fluid
Never DOT 5.0. That’s silicone. (WHY!!!)
Apparently you can also use DOT 4, which has a lower boiling point

Gloves on
Load syringes with fluid,
just 1/4 in the calliper syringe
3/4 full in lever syringe
“Bleed the syringes” close clamps
Pull to degas

Pads out 2.5mm Allen - careful with that clip
Bleed Block in

Rotate reach knob til lever tip is 75-80mm from bar centreline
T10 remove lever bleed screw, wipe
Install lever syringe

Caliper, remove rubber plug,
4mm hex loosen bleed plug then tighten lightly
Push bleeding edge tool in - make sure it clicks
Counterclockwise 1 turn

Open lever syringe clamp then caliper clamp
Push fluid from the top

IF fluid discoloured expel it, refill syringes and start again

Pull fluid back from the top
Go back and forth til virtually no bubbles

Close bleeding edge tool

Squeeze and release lever blade
Pull syringe to suck out bubbles
Press plunger to pressurise system
Repeat til virtually no bubbles

Compress and release to equalise

Close syringe clamp and remove it,
T10 replace screw 1.5-1.7Nm / 13-15 in lb

Check lever pull is nice. Can adjust with lower syringe

Remove bleeding edge tool at calliper end (don’t rotate)
4mm hex, Tighten to 1.5-1.7Nm / 13-15 in lb
Replace bleed plug
Remove block
Clean off
Gloves off to avoid pad contamination
Pads in
Bolt in 1-1.2Nm / 9-10 in lb
Clip on

Wheel in
Squeeze lever and repeat to set pistons

I push new oil in through the caliper side and pull at the same time with syringe on lever, I push enough through so that obviously all bubbles are gone but ensuring there is a good bit of fresh dot 5.1 appearing in the bottom of the lever syringe.

I nip the syringe closed at both ends, remove the caliper one and replace the nut, then back at the handlebars unclip the syringe and push quite hard some extra fluid into the lever whilst squeezing the lever back and forth too, when I can't fit anymore 5.1 in I nip the syringe closed then unscrew it, at this point a good few drops of dot 5.1 will spill out and then I just replace the nut and close the system, refit everything else as normal

I've found that's what works best, if I don't force extra fluid in the brakes still feel crap after.

Where are you forcing the extra fluid into??

Google is your friend....

https://m.youtube.com/watch?v=DRt-CP2l474

I find pulling the fluid from either end to create a vacuum in turn gets a bit more air out. Check all syringe connections are tight and bleed kit o rings are in good nick.

@bikerevivesheffield It's not really forcing extra fluid in, its closing one end of the system off and putting pressure on the syringe at the other end which as a result pushes a bit of fluid in, as soon as the syringe is removed this excess fluid leaks out from the bleed port. If you mean where it actually goes when you put pressure on, I don't know!

It's a tip I learned from my LBS a good few years back after they felt sorry for me having to bring my bike in for a brake bleed every 2-3 months then trying it myself and still ending up having to bring it in.

I struggled to get a good bleed on some Guide RE brakes recently. A couple of hours with the brakes cable tied on hard and calipers oriented to let the air rise made them solid. I think the new caliper must have trapped an air bubble.

@mudfish , why are you not closing off the bleeding edge port before removing the tool?
I always do, thinking this prevents any fluid loss when removing the tool.

I did my Guide RSCs following the SRAM ebay vid - I did them twice, cos in the bike stand the lever pull before the pads connected seemed crap.

So after the second time, I left a zip-tie holding the lever to the bars for a while, then just took the bike for a ride. After a couple of pulls they were fine.

I find pulling the fluid from either end to create a vacuum in turn gets a bit more air out. Check all syringe connections are tight and bleed kit o rings are in good nick.

I do this as well.  I believe the reason it gives a better bleed is the vacuum increases the size of the bubbles and makes them easier to shift.

I'm not sure why most bleed guides recommend pushing the fluid through rather than pulling it.

a technique I picked up years ago when trying to bleed Formula Oros was to do a full system bleed, then a separate calliper and lever bleed

as above, you’d push half a syringe full of fluid from calliper to lever (whilst tapping the hose with something in case there are any bubbles lodged there), then zip tie the lever to the bar to close off the lever and spend a bit of time pulling (gently!) and pushing the calliper syringe whilst tapping the calliper to loosen and remove any stuck bubbles in the calliper .

Then do the same at the lever end whilst the lever is tight against the bar so that any bubbles are removed from the reservoir. Then slowly(!) release the lever and push a bit more fluid back and forth.

occasionally I removed the calliper syringe but kept the lever one attached and left the brake overnight so that any air bubbles floated to the top of the system and could be removed with a quick lever bleed next-day.

I do this as well.  I believe the reason it gives a better bleed is the vacuum increases the size of the bubbles and makes them easier to shift.

I’m not sure why most bleed guides recommend pushing the fluid through rather than pulling it.

Ideally you do both, but be careful of creating too much of a vacuum as that just sucks air past the seals and you’ll be there all week!

better to push the majority of the fluid but also use the vacuum trick at both ends to remove any stubborn bubbles

I found they were very picky about technique, it was the official SRAM way or the highway.

Once they're bled it's probably less picky as there's (theoretically) no air so you just have to flush the fluid through.

Pulling a vacuum always seems like a bad idea as it's going to find any leaks far more effectively (a bit of fluid weeping out of the syringe isn't a problem, air bubbling in is) than pressure. A bit like central heating systems, they're fine for years at 1.5bar with no leaks, as soon as that pressure drops to ~0.5bar (which means it's likely negative at the top of the system) you end up having to bleed everything because air finds it's way in. When bleeding I always push on the syringe and gently pull on the other just to encourage it to move so that it doesn't need so much pressure that the syringe pops off. There's just a gentle final step where you push/pull to get any air out of the bleed port but that's only breathe the reservoir diaphragm in and out, it's not creating any pressure (and I think the caliper port is meant to be closed by that point).

Well, OK.  But then of my brakes are leaking at all I'd want to know about it.

The pressures you're going to be putting into the system when you're hauling on the levers at the bottom of a hill are going to be way in excess of anything you could put into it while bleeding.

I've been using vacuum as much as possible for years and not at any problems with dragging air into the system, at least.

The guide that Epic have on their website is spot on for the process. Works every time.

I’ve been using vacuum as much as possible for years and not at any problems with dragging air into the system, at least.

It's not the system that generally ends up leaking*, it's the bleed connections, especially anything threaded, any sort of vacuum and air will get drawn down the threads.

*As far as anyone would know anyway. The seals will only seal well in one direction though, hundreds of psi one way stopping fluid getting out, and <1psi the other way letting air in wouldn't be surprising. But you can't see that, whereas you can often get into a situation where the bubbles never stop coming as you're pulling air down the bleed nipple threads and out the nipple. In itself that's fine, but you can't then know if air is coming in the bleed port at the other end too.

This is why I dont use SRAM brakes, no matter what I do, following the SRAM video or other suggestions they never bleed well. I can get them ok but never good. Shimano take 10 minutes using the gravity method an works every time

Sure, but Sram actually tells you to pull vacuum on both the caliper and the lever after bleeding the hose so the bleed ports are designed to take at least some negative pressure.

At least, they did with the Juicy and Elixer.  Not 100% sure about the Guides.

This is why I dont use SRAM brakes, no matter what I do, following the SRAM video or other suggestions they never bleed well. I can get them ok but never good. Shimano take 10 minutes using the gravity method an works every time

I'm the opposite.  Or rather, it's not that I can never get a good bleed with shimano, it's just a bit more hit and miss.

I do sometimes miss the messy simplicity of a Hope bleed but get it right and SRAM can be clean and quick.

My order -

• push some fluid from lever and out of caliper first if they've had a lot of hard use (ie the fluid is dark/black) until it runs clear. Dispose of that and start again.  If theres really dirty fluid in the caliper I don't see the point in dragging that through the rest of the system.
• Then push from a "syringe full" from caliper to lever (to get out any air you may have introduced).
• back and forth for a while until no bubbles
• Pull in lever and push fluid from bottom while releasing lever
• gentle vacuum bleed on both ends (this nearly always brings out some air)

That's been giving me good bleeds for a few years now.

I've always found with SRAM brakes the problem is between the stiction in the bleed kits, and the  bleed process.

At the end, the official process tells you to withdraw the plunger on the lever syringe and then let it settle back to neutral before undoing. With a normal (non-pro) bleed kit I actually find you need to put a tiny bit of positive pressure on it. Too much pressure and you're making the reservoir diaphragm bulge, and so it'll spew DOT4.1 when you unscrew the syringe. Too little and you're pulling the diaphragm in, and so it'll suck air into the system when you unscrew. If you get it just right, the reservoir membrane is neutral and the reservoir is full.

Every time I've had a bad bleed, it's been because of the reservoir not being full enough. Same with having to snap the levers, or brakes going to the bars when the bike isn't stored upright.