Article [13] ST1300 - Brake Maintenance - Getting all the air out of the brake system

[Igofar]

Wow, Mr. Heath, what an incredible reply. Yes, new front and rear tires installed. I am very glad to read that when first changed the rear pads are likely to drag a little. I did my very best to follow your procedures in installing the tires and new brake pads, as well as reading everything I could from Igofar regarding the same. I did not observe any damage to the rear brake stopper bolt when it was out, and I did not torque it until after tourquing the rear axle. I hope that was correct. If all goes well this issue will self correct very soon. Thanks so much for the time it took to respond. Cheers from NC!

She damage will not be on the stopper plug, but inside the aluminum rear caliper mounting bracket.
If there are flutes, or spirals, it’s damaged and should be replaced.
AND, if you tightened the plug AFTER you tightened the axle nut, you will have that damage pretty soon.
The stopper plug MUST be torqued to 51 ft lbs BEFORE you tighten the axle nut to 80 ft lbs, or things will drag and start damaging stuff.
If your response is correct, you did it backwards, and in the incorrect sequence.

 

[jfheath]

I did not observe any damage to the rear brake stopper bolt when it was out, and I did not torque it until after tourquing the rear axle. I hope that was correct.

Did you read that in one of my posts ? If so it is wrong - I need to correct it. Can you remember where ?

Think of it this way. When you are putting a screw or bolt into its mating thread, there is some wiggle room. It is only when it is tight that you cannot move it sideways, or tilts it in its threads.

When you tighten the Axle bolt, the caliper bracket is on the axle so the bracket is going to try its best to rotate around the axle as you tighten- and in doing so it will tilt the stopper bolt. Unless, of course, the stopper bolt is locked solid against the 'boss' on the swinging arm.

 

[Magicman]

Did you read that in one of my posts ? If so it is wrong - I need to correct it. Can you remember where ?

Think of it this way. When you are putting a screw or bolt into its mating thread, there is some wiggle room. It is only when it is tight that you cannot move it sideways, or tilts it in its threads.

When you tighten the Axle bolt, the caliper bracket is on the axle so the bracket is going to try its best to rotate around the axle as you tighten- and in doing so it will tilt the stopper bolt. Unless, of course, the stopper bolt is locked solid against the 'boss' on the swinging arm.

Okay, I did read that somewhere, and I'll try to find it, after I go and correct my mistake. Thank you both.

 

[Magicman]

Feel free to call me on the white courtesy phone, and I can run you through a few checks/inspections, and maybe request a couple pictures from you to help you sort things out.

Trying to figure out how to get your number.

 

[Magicman]

Corrected the earlier mistakes.

 

[Magicman]

Okay, I did read that somewhere, and I'll try to find it, after I go and correct my mistake. Thank you both.

Mr Heath, my apologies. I believe I just confused myself on the bottom of pg. 5 in your rear tire removal and refit article. You clearly state on pg. 4 to tighten the stopper bolt first, then the axle bolt. Again, apologies!

 

[Willsmotorcycle]

Trying to figure out how to get your number.

https://www.st-owners.com/forums/pages/RAN_US/

 

[jfheath]

Mr Heath, my apologies. I believe I just confused myself on the bottom of pg. 5 in your rear tire removal and refit article. You clearly state on pg. 4 to tighten the stopper bolt first, then the axle bolt. Again, apologies!

There's no need, but thanks anyway. I was more concerned that I had let an error slip through. It has happened.

I used to teach. I am still more concerned about passing on understanding than I am about giving facts, but no one can understand if the 'facts' are wrong or they don't make sense. You do right to question or point something out. Even if the information is correct, it points out that it isn't clear enough.

I remember the article to which you refer. I tried a different approach. Describing how to remove the wheel and on the same page adding notes about what to do to reassemble it. I didn't do that again. The sequence for reassembly is broken in the wrong places.

 

[leondante]

Hello there. I want to give you my contribution. Along a lot of brakes dissasembling and fixing, I noticed frequent common issues that usually people pass over them without noticing how important they are. I'm listing them, but BEFORE I'm commenting the thing about that rear caliper clip.

That clip job is to slide the brake pads sideways when they move to push the disk. The caliper's body wouldn't do that without eating itself until destruction. So, the glue have two purposes, one to avoid losing that clip when you take out the brake pads, the other to avoid even more the possible worn out that the clip could do to the caliper's body along time. So, any glue that do that would be good enough. I used a double sided glued tape of very good quality that is like a rubber slice with pretty good glue in both sides. Expensive but pretty good. Still have to test it. The important thing here about that clip is that it's straight and well seated on the brake caliper. But that will NOT matter if the next things are out of shape.

The list of things I personaly think that are very important to have in good condition regarding brakes:

- Do NOT have old brake fluid in your brakes. It corrodes the things inside, specifically aluminium things. You should change it every two years. Also water goes down, under brake fluid, so it gets stuck at the lowest part of brake calipers. Do a good cleaning inside the calipers, as you'll have a small puddle of water at the lowest piston, corroding that part, specially if you don't change brake fluid for more than 5 years. And don't trust just changing brake fluid (it helps but it's not enough), check your condensation puddle inside the calipers from time to time. It happens to the clutch cylinder too.

- Calipers should move freely along the pins. I've seen blocked calipers to the extreme that were using only one brake pad, or only a side of them, as they got twisted with the brake force because being stuck only in one side. Again, cleaning it will solve this issue. Brake calipers are there to transfer the brake force comfortably from the disc to the bike's body, so they need do move easily and freely for that purpose even under pressure.

- Goo gets around the pistons and inside the cylinders in the calipers and twist and stuck the cylinders, sometimes deforming calipers and brake pads, getting half the brake power and stability. Brake drag can be caused because of this. Also can cause the symptoms I said in the previous item. Cleaning the pistons and rubbers and cylinders is mandatory in order to get good quality braking.

In one word, every five years take out your pistons and clean them, and the inner part of the cylinders too. If you want the best, take out the seals and clean them. With that you'll be forced to change the brake fluid, clean the pins and caliper seatings and to check all the important stuff to work properly and freely regarding a good brake pad seating comfortably on your brake disk, making a good force spreading along each brake pad and between calipers.

Hope it helps.

 

[Andrew Shadow]

I just put on new tires and oem brake pads all the way around. I did not do a flush and fill of the brake fluid after doing this.

Because you haven't touched the brake fluid, just for kicks check the fluid level in the master cylinders. If they are overfilled complete brake pressure release is not possible.

This can easily happen if fluid was added at some point when the pads were partially worn. Pushing the pistons back in to the calipers pushes more fluid in to the master cylinder than it is capable of holding due to the extra fluid that was added part way through the brake pad wear cycle.

 

[Magicman]

Because you haven't touched the brake fluid, just for kicks check the fluid level in the master cylinders. If they are overfilled complete brake pressure release is not possible.

This can easily happen if fluid was added at some point when the pads were partially worn. Pushing the pistons back in to the calipers pushes more fluid in to the master cylinder than it is capable of holding due to the extra fluid that was added part way through the brake pad wear cycle.

Thanks, Andrew. Prior to pushing the cylinders in I removed some brake fluid from each of the master cylinders.

 

[jfheath]

Thanks @leondante . All good points. Most are covered in the "Avoiding the pitfalls" article.

I'm surprised about the pool of water, as generally any water ingress is absorbed by the brake fluid. After two years is considered to be 'too wet'. Its moisture content reduces the boiling point of the combined fluid and water and it becomes less effective and potentially dangerous as the fluid can boil. When brakes are released, the expanding gas (steam) ejects more fluid into the reservoir than normal, which leaves a mixture of fluid and gas in the lines. With less fluid in the lines, the cooling gas is now compressible. No brakes.
Some time after the two year period, the wet mixture starts to form a crystallised sludge which can clog up behind the pistons and seals and block the linkage ports (between cylinders)

To avoid this I suggested sluicing the fluid in the pistons. ie pumping the pistons out as far as is safe, and then pushing it out by opening a bleed valve and pushing the piston back in.u When two cylinders are connected, push one in, and then close the valve and push the other in allowing the first to be pushed out. Finish with the one furthest away from the bleed valve being in, and eject the fluid from the one closest to the bleed valve. Repeat.

One problem is that on some models, you have to separate the two caliper halves to remove the pistons and those three bolts need to be replaced with new. The newer front calipers from 2008 are a different single casting design

I've never taken out my pistons (except by accident !) as part of regular service, but I do change fluid and sluice old fluid out in the manner I described, every 18 months or max 2 years. I use the half used fluid from the bottle I filled up with 18 months earlier to flush out all of the old fluid and sluice the bores. The fluid from the bottle will have absorbed moisture over that time, but its the same stuff that went in 18 months ago is sludge free and probably not as wet as the fluid in the lines. Then I use the brand new stuff to flush out the 'cleaning agent'.

A couple of years ago, I noticed one of my pistons was pitted, so I took the opportunity to investigate. The bike was about 10 years old and had about 60,000 mile on the clock. Ridden in all weathers (there isn't any other sort in the UK). I Removed the caliper from the hydraulics and bought brand new seals and two pistons. (It turned out that another piston was also pitted). The seals that I winkled out of their grooves looked pristine and there was no sludge or grunge behind where the seals had been. I was both surprised and pleased - it seems that my procedures for replacing fluid work pretty well at keeping the system sludge free.

Maybe just fresh fluid every two years is enough, but in my head there are 'brackish' spots- fluid that doesn't move when it is being renewed - eg behind the piston furthest from bleed valve - particularly the forward piston on rear caliper and the bracket end if the SMC. So it is importnat to do something to flush that out and replace with with new. So see-sawing the double pistons, tilting and pumping the SMC, flexing the brake lines, and the clutch - pump the lever a few times - agitate the clutch and hold the lever in so that the slave piston is pressed in, then without relaease the lever, open the bleed valve so that the slave piston pushes the fluid out. Repeat.

 

[ST1100Y]

...if you don't change brake fluid for more than 5 years...

cringe...
Such isn't neglect, its plain reckless...

 

[Alex4747]

Special thanks to Mr John Heath for his pdf, describing the brake system. It is so much easier to bleed the brake system when you know how it works and understand what you are doing.
I have one question about changing brake fluid in the future. If there is no air trapped in the system, can you change the fluid without the need to bleed the PCV-valve? ( this safes a lot of work for dismantling the fairing). What is your opinion about omitting PCV bleeding for 2-yearly fluid change.

Alex, (the Netherlands)

 

[Fawlty]

Special thanks to Mr John Heath for his pdf, describing the brake system. It is so much easier to bleed the brake system when you know how it works and understand what you are doing.
I have one question about changing brake fluid in the future. If there is no air trapped in the system, can you change the fluid without the need to bleed the PCV-valve? ( this safes a lot of work for dismantling the fairing). What is your opinion about omitting PCV bleeding for 2-yearly fluid change.

Alex, (the Netherlands)

Hi Alex. Pleased you met with success. You won't find much support for omitting the PCV bleed on the forum.

 

[jfheath]

I have one question about changing brake fluid in the future. If there is no air trapped in the system, can you change the fluid without the need to bleed the PCV-valve?

Not really.

If you change your fluid and your brakes are feeling good then you could look at it one way and say - well there's no air in the system, so why bother ?

But bleeding is not just about getting rid of air. Its about getting rid of the old fluid. One of the places where the fluid gets 'old' very quickly is at the SMC. It is in the worst possible location for being exposed to the elements; it is facing uphill and in normal operation it doesn't get the full travel of the piston in the bore - and it has a one way valve inside it.

By 'old' I mean it is getting wet. That is what brake fluid does - absorbs moisture. You change it every two years because after 2 years it is considered to be too wet (ie has absorbed too much water) to be safe.
The SMC also has an arear of brackish fluid - fluid that doesn't get to move about a great deal. It is the area up at the top of the sloping cylinder. Behind the secondary seal and above the inlet port.

The SMC needs to be pumped to make sure that this is sluiced out through the outlet port and is prevented from passing through the rest of the system to lodge in all of the joints in that complex bit of pipe work under your seat and down across the swinging arm to the rear outer pistons.

And the best place to get rid of it is at the valve just below the petrol tank on the right hand side. The Valve near to the Proportional Control Valve mechanism. (often called the PCV bleed valve).

I once had a plug of Brake fluid gunge behing the PVC bleed valve. It had obviously migrated from somewhere else - but it couldn't get out, so I removed the nipple and it shot out like a cork at the first press of the pedal. It is also at the heighest point of the brake line circuit to the rear brake and that is where any air will want to escape.


I know it is possible to get at the bleed valve without removing the fairing. I've tried it, but it is fiddly and if the tube pops off, very messy. So I never bother with that. Its good to get the fairing off to see what else is going on.


And if it bothers you trying to get it on again, then you might find this handy.

Article [13] - ST1300 - Maintenance - Fairing Installation | ST1300 Articles

A set of notes about putting the fairing back onto the ST1300. It covers most of the fitting gotchas, which might otherwise catch you out and/or result in broken tags. Also lists all of the fasteners - photos, description,, part numbers, where they fit and why it matters. Very useful for...

www.st-owners.com

 

[Sadlsor]

I know it is possible to get at the bleed valve without removing the fairing. I've tried it, but it is fiddly and if the tube pops off, very messy. So I never bother with that. Its good to get the fairing off to see what else is going on.

@Igofar bleeds the PVC (he tells me) without fully removing the right side upper cowl / side fairing, and I believe him.
But I have big fat hands, and when I tried it his way, I felt it was really pulling on the plastic for me to slip my hand under it, and bending it outwards more than I was comfortable with.
With my luck, it would just crack. And even IF you can get your mitts under there, it's still hard to connect a bleed hose to it, with the very real possibility of just squirting brake fluid all over where you don't want it.
And like John, I like to ogle what the engine and all under there looks like.
Let's face it... we can't all be @Igofar!

 

[Alex4747]

Thanks so much for valuable advices and back-ground, in such a short time. That make sense to me. Btw this is a wonderfull forum. So much knowledge and enthousiasm to share! I am happy I join it.

 

[jfheath]

An additional observation from me - the original author.

I can get quite complacent about my abilitity to 'fix my brakes'. I reckon that I know how to do it and nothing is going to catch me out. I don't even follow the rules. I can tell if I have got air in the system - as anyone can. I know that even a tiny bubble can be the difference between the lever feeling solid and feeling rather spongey. And on the rear circuit in particular, if the pedal feels spongey, I know where the most likely place for the bubble is - just by feeling how firm the SMC feels. So I bleed that section first.

My last bleed was two weeks ago. I'd fitted (or tried to fit) new HEL lines to my ST1300 A9. I'm struggling getting around the bike still having snapped two parts of my calf muscle trying to put the bike on its centre stand. 3 months hobbling around and feeling more like an old man than I have ever felt before - I decided to tackle this job. I could stand up and balance (Ish), my calves were not hurting any more, but all of my strength in all of my muscles had gone walkabout. So progress had to be slow. Picking up a dropped spanner from the floor was a major exercise which had to be accompanied with a considerable amount of huffing and puffing and expletives.

So a bit at a time was the order of the day. In the end, after much discussion with HEL and various attempts to modify what they had supplied so that they would actually fit, they were returned because they didn't match their claim that "Each HEL brake line kit arrives complete with every essential component, resulting in a smooth and straightforward installation." That may be the case for non ABS and for pre 2008 models. But not for mine. I note that they have now changed their description of the website and excluded ABS models and models from 2008 onwards. If you want them for those models, you'd need to provide patterns.

I now have 5 non return valves and some new clear hose for bleeding. So I can tube-up my bleed points and wander around the bike letting out air and fluid as the whim takes me.

I'd gone through the usual sequence. It takes a while to get all the bubbles out when the lines have been emptied. But I got to the point where the pedal was feeling positive. But it was pressing down too far. Every line was pumping out clear bubble free fluid. So there were bubbles that were stuck. I'd taken the precaution of not torquing up the banjo bolts at the master cylinders properly - so they were not leaking, but they were only secured up to about 20Nm. So I burped those. and went round tapping joints and flexing the bends in the hoses - U bends and n bends.

I got some more bubbles out, and the pedal felt firmer. But still not right. So I had another circuit of the bleed valves without getting any more are out, called it a day and tied the pedal down to the ratchet loops on the bike ramp, added a weight and left it overnight.
Overnight was the intention. The reality was different. I was so stiff and aching from my workout picking spanners up that I gave it a miss for a day.

The following day, I went back, slowly released the pedal and pumped. Still soft. A bit better, I kidded myself. But not good enough. So I started at the rear centre bleed valve - which had never shown signs of bubbles and had bean clear fluid from the early stages, and was clear fluid on my last bleed 36 hours ago. But this morning, massive bubble came out followed by a stream of milky grey fluid with tiny bubbles - invisible to the naked eye, but they were what was causing the milkiness. So I kept topping up and pumping that through until it was clear, then went to the front centre pistons. Same again. The PCV valve got rid of a massive bubble, but no milky fluid. And the rear outers - well a bit more of the same a few big bubbles and milky fluid.

And that was it. Solid brakes. I left it overnight again with the pedal tied down and weighted. The following day it still felt soild. Perfect. So I tightened the master cylinder banjo bolts to full crush 31Nm and felt smug again.

Now for a long time I have tried to explain why tying the brake lever back and the pedal down makes the brakes feel firmer. It does, but why ?
And I have 'explained' to myself and it on here that applying pressure to the system can only do one of three things. Push the pistons out. Make the flexible hoses bulge. Squash the air bubbles.

Squashing the air bubbles is the most obvious thing. It reduces the size of the bubble to miniscule. Being smaller, they have much less surface area so I deduce that there is less ‘surface tension’ so that frees the bubbles from whatever they are attached to - the sides of the tubes or to the joints. They break away and float up. Sometimes to a higher spot where they are still trapped, sometimes to the compensation port, from which they can escape into the reservoir if the master cylinder piston is released slowly.

I always assumed that these smaller bubbles would attach together to form bigger bubbles, which now being rounded up together would be easier to shift. So seeing the large bubbles come out was expected, but seeing them come out in microscopic form was a big surprise. It took half a reservoir before the fluid was clear again.

it’s a working theory and may even be true, but I am only ‘guessing’. But the difference between the bleeding 2 days previously when I could absolutely get no more bubbles out. Tapping and flexing and pumping - nothing would coax any more bubbles to be expelled, So seeing the large bubbles and a whole lot of milky fluid come out after 36 hours of just sitting there and being squeezed - was remarkable. It was as if something had been through the tubes with a pipe cleaner and left the grotty fluid all in convenient heaps ready to be swept up..

I have experienced the benefit of pressurising the system and leaving it. It works. But I have never seen anything so visually dramatic as this before. Unless it had something to do with the delay valve and the proportional control valve - which can only operate if enough pressure is applied. But I could apply the pressure before I left it for 36 hours. It was just that the amount of travel of the pedal was too much.

Watching the last load of fluid emerging into the bleed tube was something like a smoke ring, working its way down the tube. I thought that it might have been a circle of PTFE tape that had detached from the bleed nipples and got into the lines, but when I tried to get hold of it, it just disintegrated into fluid, so I haven't got a clue what that was.