Bloody Brakes!!

[egcSV650s]

Hi everyone, im getting really annoyed with my brakes. Ive had both front calipers rebuilt by a brake specialist, ive got braided lines, plenty of meat on brake pads and discs are fine and also fitted a brembo master cylinder but the brakes still feel soft and the lever is going back to the handlebar if i push hard, ive spent alot of money on the brakes and nothing seems to be working but cant figure out what else it could be, just wondering if anyone has any suggestions as i feel like giving up. Thanks in advance

[DougieG]

A proper bleed see if there are any bubbles?!

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[egcSV650s]

A proper bleed see if there are any bubbles?!

Sent from my SM-G935F using Tapatalk

Do i need one of those pump bleeders or is a normal one way bleed hose ok

[DougieG]

A normal hose is fine I used one for ages before getting a pump for ease

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[egcSV650s]

A normal hose is fine I used one for ages before getting a pump for ease

Sent from my SM-G935F using Tapatalk

Ill try it again, ive used up 2 litres of brake fluid trying to get it right :mad:

[Blapper]

My sure-fire definitive way is to use a huge syringe to push fluid up from the bottom. Vacuum pumps drag air in past the valve and you never know if they are moving that big bubble that is stuck somewhere. If the bubble stops in the line while you top-up the master cylinder , it floats back upwards so why not fill from the bottom to stop that?

[egcSV650s]

My sure-fire definitive way is to use a huge syringe to push fluid up from the bottom. Vacuum pumps drag air in past the valve and you never know if they are moving that big bubble that is stuck somewhere. If the bubble stops in the line while you top-up the master cylinder , it floats back upwards so why not fill from the bottom to stop that?

Will give that a go, thanks

[Talking Heads]

Pull the brake lever fully on, strap the lever to the handlebar then leave it overnight ensuring the master cylinder is at the highest point and above all the run of hose.
In the morning slowly release the brake lever but do not pull the brake lever again until you have manually pushed the pistons back into the calipers.
Once the pistons are back in the calipers bleed the brakes as normal.
Et voila, brand new brakes.

[egcSV650s]

Pull the brake lever fully on, strap the lever to the handlebar then leave it overnight ensuring the master cylinder is at the highest point and above all the run of hose.
In the morning slowly release the brake lever but do not pull the brake lever again until you have manually pushed the pistons back into the calipers.
Once the pistons are back in the calipers bleed the brakes as normal.
Et voila, brand new brakes.

Havent tried that yet so will give that a go, thanks. Just checked the thickness of my brake discs with a tape measure but will check properly tomorrow with a digital caliper but the tape measure was saying 4mm is that the minimum thickness of what the discs are meant to be

[Bibio]

tying the brake lever back overnight does nothing. think hard about it, the system is under pressure so nowhere for the trapped air to go. yes this can work on callipers that are needing stripped and serviced as it pushes the pistons out and puts the pads hard up against the discs but does absolutely fek all to a properly serviced braking system.

air in the system will have a lever feel of 'spongyness'

a feked master cylinder will just let the lever pull straight back to the bar, sometimes with a little resistance

unbedded pads will feel same as air to an extent but not as bad

difficulty in stopping bike (wooden brakes) can be glazed/old pads or more common is the callipers are needing serviced.

difficulty in getting a good bleed on brakes can be weeping bleed nipple threads which require ptfe tape on the threads.

bleeding brakes:
get a jar or clean bottle, a length of clear tubing that fits snugly on the bleed nipple and fresh brake fluid.

put tubing on nipple and place a small amount of brake fluid in the bottom of the jar/bottle, put the other end of the tubing in the jar/bottle so its submerged in the brake fluid. open bleed nipple and pump brake lever keeping an eye on the rez and top the rez up as necessary (do not let the rez run dry under any circumstances). keep pumping the brake lever till fluid starts to come out the tube and into the bottle. watch tube till there are no bubbles coming out the nipple end. close bleed nipple. its that simple. you can do the pull-open-close action if you like but its no necessary.

Tip: tap the brake lines with a spanner or something while bleeding, this will dislodge any air in the lines.

[Talking Heads]

It works by allowing the trapped air to move to the top from where it is easier to got rid of.

[Mickle]

Pull the brake lever fully on, strap the lever to the handlebar then leave it overnight ensuring the master cylinder is at the highest point and above all the run of hose.
In the morning slowly release the brake lever but do not pull the brake lever again until you have manually pushed the pistons back into the calipers.
Once the pistons are back in the calipers bleed the brakes as normal.
Et voila, brand new brakes.

Plus one on that also I unbolted the splitter block under the lower yoke ( leave the hoses on ) twisted it so the master cylinder hose is upper most and gave it a good shake so any trapped air rose to the master cylinder

[SV650rules]

I certainly don't understand how tying the lever back will get air out of the system, as Bibio says all it does is compress the air, but unless the compressed air somehow manages to sneak passed the seals during the night it will still be there in the morning. There is a equalization port on the master cylinder that is only uncovered when piston is fully retracted, the purpose is to let air out and fluid back in, in other words brakes are designed to bleed themselves every time you use them. If the piston on your master cylinder never gets fully retracted or this port is obstructed then brakes will not self bleed.

[21QUEST]

Tying the lever back (not too tight) does work....don't ask me about the science but it does work.

Back to issues with bleeding bleeding brakes.
Provided the calipers have been rebuilt properly , *insert own words* etc and other company of the braking system are in order, 9/10, any difficulty is to do with the upper part of the braking system.
That is to say, the master cylinder needs to be bench bled....fancy way of saying, 'air trapped in master cylinder.

What usually one needs to do is, pump the lever a few times, hold it back and crack open the banjo bolt to let ut the air trapped. Make sure you tighten (not fully yet) the banjo bolt before lever comes back to bar..

Do that 3-4 times and then bleed as normal....caliper furthest from master cylinder first.
I'd usually bleed each side twice and job done.

Oh as someone(Bilbo) mentioned, if the pads eg new pads needs to bed to discs, the brakes will feel bit even after having been bled properly.
That said, even if that were the case, the lever should come back to the bar.

[650]

Nobody has mentioned the obvious thing here...the master cylinder size. You can't just whack a MC on and think it'll do the job. If it's too small then it'll result in long lever travel, too big and it'll result in virtually no travel with a wooden on/off feel.

What size is the standard MC?

What size is the Brembo, is it radial or axial? What bike is it off?

The brakes on a 650 aren't magical by any means but you should be able to lock the front up with a good squeeze of the lever.

[egcSV650s]

Nobody has mentioned the obvious thing here...the master cylinder size. You can't just whack a MC on and think it'll do the job. If it's too small then it'll result in long lever travel, too big and it'll result in virtually no travel with a wooden on/off feel.

What size is the standard MC?

What size is the Brembo, is it radial or axial? What bike is it off?

The brakes on a 650 aren't magical by any means but you should be able to lock the front up with a good squeeze of the lever.

The brembo mc i have is made for the sv650 it was brand new but there is different bore sizes, 18,19 and 20. Its on 19 at the moment which is what it came like but not sure about what one to put it on as you can change it

[650]

You need to work out the ratio, on a radial (as it sounds like it's an MCS...which isn't made for the SV, it's just a general one size fits all unit) the ratio needs to be around 130:1 to 135:1 to have decent lever travel and feel. There's a calculator available that a chap made a while back.

It was originally an XLR file but I've edited it to be a standard Excel file. It can be downloaded here: https://www.dropbox.com/s/pvouln3vre66gmy/MC%20calculator.xlsx?dl=0

You'll need to know caliper piston cylinder sizes, lever to pivot distance...so on and so forth. Leave the 'mid piston' section as 0 and fill in the 'small piston' for the smaller SV piston size.

Regarding the lever to pivot, the info is available from Brembo, but I've copy/pasted it here for you to see:

The RCS system consists of an adjuster that sets the brake lever pivot distance to either 18 or 20 mm, for the perfect feedback between rider and machine: setting the pivot distance to 20 mm makes the braking system more reactive and immediate, while a pivot distance of 18 mm makes it more precisely controllable.

Changing between the two settings is extremely quick: simply adjust the master cylinder pivot distance by turning the adjuster on the front of the guide lever with cam mechanism by 180° using a screwdriver (red indicates 18 mm, black indicates 20 mm). This changes braking power distribution without modifying the pure power of the system itself.

The piston, gaskets and push rod of RCS master cylinders are exactly the same components as those in the master cylinders used by practically all MotoGP and SBK riders, and are manufactured to extremely fine tolerances and ensure very low friction.

The lever consists of two main components: the racing lever guide and the folding, forged lever itself.

With this you should be able to work out a suitable ratio to give good lever travel and feel.

On the topic of bleeding, if it is in fact an RCS19 that you've got, then you have a bleed valve on top of the lever body as well, air can easily get trapped here so it's worth investing in a one way bleed valve so you can happily pump away without having to repeatedly open and close the valve.

Hope this helps!

[egcSV650s]

You need to work out the ratio, on a radial (as it sounds like it's an MCS...which isn't made for the SV, it's just a general one size fits all unit) the ratio needs to be around 130:1 to 135:1 to have decent lever travel and feel. There's a calculator available that a chap made a while back.

It was originally an XLR file but I've edited it to be a standard Excel file. It can be downloaded here: https://www.dropbox.com/s/pvouln3vre66gmy/MC%20calculator.xlsx?dl=0

You'll need to know caliper piston cylinder sizes, lever to pivot distance...so on and so forth. Leave the 'mid piston' section as 0 and fill in the 'small piston' for the smaller SV piston size.

Regarding the lever to pivot, the info is available from Brembo, but I've copy/pasted it here for you to see:



With this you should be able to work out a suitable ratio to give good lever travel and feel.

On the topic of bleeding, if it is in fact an RCS19 that you've got, then you have a bleed valve on top of the lever body as well, air can easily get trapped here so it's worth investing in a one way bleed valve so you can happily pump away without having to repeatedly open and close the valve.

Hope this helps!

Wow thats alot of info lol, ill have to get all the measurements and try it out, i might change the pivot distance to 20 and see how that feels but i do have a one way bleed valve so will give that another go. Thank you for all the info appreciate it :thumbsup:

[650]

It looks like a lot, but it's not really. You just need the diameter of the pistons on the SV sliding calipers. The Brembo information is easy to input as it's in that quoted box. Then you can play with the Brembo to get that magic ratio. If the magic ratio doesn't work, then it's an issue elsewhere - air in the lines still (the lever being closed on a radial with a top bleeder won't work as it would with an axial MC) or the Brembo just isn't a good match for the sliding calipers (in which case, I might buy it off you if you want rid, as I've been eyeing them up). I think the standard MC size is 5/8? It'll be stamped on the cylinder body if you still have it.

[egcSV650s]

It looks like a lot, but it's not really. You just need the diameter of the pistons on the SV sliding calipers. The Brembo information is easy to input as it's in that quoted box. Then you can play with the Brembo to get that magic ratio. If the magic ratio doesn't work, then it's an issue elsewhere - air in the lines still (the lever being closed on a radial with a top bleeder won't work as it would with an axial MC) or the Brembo just isn't a good match for the sliding calipers (in which case, I might buy it off you if you want rid, as I've been eyeing them up). I think the standard MC size is 5/8? It'll be stamped on the cylinder body if you still have it.

Ill have a look tomorrow at all that info and see what i can do, if i want to get rid of the brembo mc if it doesnt do anything then ill bare you in mind that you might want it, ive still got my original sv mc and also got a gsxr750 mc that i put on to see if it made it better but didnt really

[Bibio]

did you buy the brembo mc off ebay by chance?

[egcSV650s]

did you buy the brembo mc off ebay by chance?

Yes it came from Italy cost £250

[Bibio]

i'm beginning to think that you have a dud MC, might not be a knockoff but it could be faulty. even if the MC has the wrong ratio it would still give a firm lever.

stick the SV one back on and see if you have joy with that.

top tip. you dont need to bleed the whole system when fitting the SV MC back on. disconnect the banjo, remove old MC, put new MC on then connect banjo. DO NOT PULL THE LEVER. top the rez up and then quickly 'flick' the end of the lever using around 5-10mm of the lever travel with a finger rapidly for about 5min. this will dispel any air in the MC back up to the rez. do not use full lever travel till the 5 min are up.

[650]

Next thing to check is that the bleed valves on the calipers are in good condition. They more or less rot over time and the threads don't hold it tight any longer. A good give away is a firm press on the top of it and see if any fluid leaks out.

Mind posting a couple of pics of your Brembo MC? I'd be surprised if it's a fake tbh

[egcSV650s]

i'm beginning to think that you have a dud MC, might not be a knockoff but it could be faulty. even if the MC has the wrong ratio it would still give a firm lever.

stick the SV one back on and see if you have joy with that.

top tip. you dont need to bleed the whole system when fitting the SV MC back on. disconnect the banjo, remove old MC, put new MC on then connect banjo. DO NOT PULL THE LEVER. top the rez up and then quickly 'flick' the end of the lever using around 5-10mm of the lever travel with a finger rapidly for about 5min. this will dispel any air in the MC back up to the rez. do not use full lever travel till the 5 min are up.

Might give that a go with my old sv mc on see what it feels like

[egcSV650s]

Next thing to check is that the bleed valves on the calipers are in good condition. They more or less rot over time and the threads don't hold it tight any longer. A good give away is a firm press on the top of it and see if any fluid leaks out.

Mind posting a couple of pics of your Brembo MC? I'd be surprised if it's a fake tbh

Had the calipers rebuild with new everything egen bleed valves but will check that tomorrow, im not with my bike at the moment but this is the one i got its a ebay item number 361899616678

[650]

Looks legit enough. The packaging should have a serial number you could check with Brembo

I'm assuming you bought the right angle banjo eyelets to go under the MC?

[egcSV650s]

Yes its got a serial number and a brembo card which i might check and if the banjo eyelet is whats on the brake hoses then im guessing yes as when i brought the bike it came with braided hoses

[650]

oh OK cool, seems like a VERY good price for an MCS19 and lines!

[egcSV650s]

Sorry i meant the lines were already on the bike with my original sv mc i just used them with the brembo mc

[650]

You must have has to twist the crap out of them to get them to fit. If I'm not mistaken, the lines attach to the bottom of the Brembo MC. Unless you've got an adaptor?

[egcSV650s]

It was a bit tricky to get them on as there braided aswell, yes they attach to the bottom of the brembo mc

[650]

That might be your issue, you might halve kinked the line. We'd need to see a photo to judge it properly really. The lines nd to be as straight as possible.

[Bibio]

if there was a kinked line it would firm the lever up due to restricted flow.

[650]

Aye, suppose. My money's still on the Brembo either being set up incorrectly or just being the wrong ratio with the SV calipers

[egcSV650s]

Havent had a chance to look at the ratios yet but taken a picture of the lines and also of where the brake fluid reservoir goes into the mc looks like a leak, ive attached the photos, whats your thoughts

[650]

Hard to say, clean it up and see if it's back to that state after a few days. Lines look fine and not overly kinked to fit them.

Where abouts are you based?

[egcSV650s]

Cleaned it up this morning and will see what its like in a few days, im based in Hertfordshire

[650]

Are the brakes safe enough to use on the road? Can always ride over to me for us to look them over if you like. I'm just outside Greenwich, so about 45 minutes from you (roughly)

[egcSV650s]

Yes there safe enough, just adjusted my lever out a bit and they seem alot better really strong feel now finally. Thanks for the offer will keep you in mind if i need any help, thanks