brakes 101 (spongy feeling - yes, they've been bled!)

[martin_14]

Ok, I admit: I'm useless when it comes to anything electric, electronic or hydraulic (the complete list looks like the phone book of Tokyo, but you get the point). So I need help.

My front brakes have been acting up lately. When I pull the lever, it has way too much dead stroke until some braking starts happening. Bike brakes great and the lever effort has not increased, just the stroke. If I pull the lever, let it go and pull again, all within 1-2 seconds, then the second time I pull it it behaves what I would call correctly: almost no dead stroke and immediate response of the brakes. If I wait more than, say, 5 seconds between the first and second actuation of the lever, it gets spongy again.

So I got the thing bled by my dealer (they are very competent and I trust them, only good experiences with them; he really looks after me as a customer) last Thursday during a rear tire change, and on the way home they sure felt different. Not necessarily better, though.

On Friday morning they were just as before. It's bugging me. I'm planning to spend some long time (several weeks) in ungodly lands and I want the bike to be in as good a condition as possible. Brakes have a tendency to influence very much the chances of getting home or not.

So please tell me what can I look for. A friend explained that there could be a too thin brake disk or pads, but I thought the system would compensate for that, at least to a certain degree. Maybe I exceeded that degree? Disks have 32 000 miles of slightly heavy use, with a few tours to the Alps in all-out banzai mode. Pads have less than 6000 miles, but this is the first non-Kawasaki set of  pads (EBC) I use.

Ideas?

[VirginiaJim]

The dealer who looked at your bike should have looked at the whole system; pad thickness, rotor thickness, obvious leaks, brake lines, etc..  However what you're describing sounds like it has air in the system.  Could also be a faulty master cylinder (seals) or one of the seals in the calipers..  Either take it back to them or find another dealer if they can't rectify it. 

[jwh20]

There are really only two things that cause this:

1) Air in the system
2) A compromised brake line.

The second one is pretty easy to spot as there will be a bulge like a small balloon protruding from the covering.  The air in the system is most likely and it takes only a small bubble.  A vacuum bleeder is the best thing to get rid of this and be sure to start with the one on the brake lever.  Note that sometimes you need to tap the lines so encourage bubbles to head toward the exit.

[Deziner]

If it just started doing it out of the blue, I would be inclined to believe the master cylinder is at fault. Since it's a closed system, air can't enter the system without help..   

[VirginiaJim]

or Aliens.  I'm betting seals (not the barking ones) in the master cylinder as well.

[gggGary]

Year, miles on the bike and is it ABS?


I agree sudden onset means further investigation.
In general the free (non ABS) brake fix is the park the bike on the sidestand, bars turned full left. the more lean the better.  The idea is all uphill from calipers to MC so any air can escape up through  the reservoir. No matter how good the bleed this as a final step usually improves feel.   My 72K 08 non ABS has the lever too far from the bar, the adjustment knob doesn't really let the handle get close enough for a "best comfort" distance.

[VirginiaJim]

I think that's fine to assist in getting the air out but the root cause has to be found.  Air doesn't magically appear in a brake system and these bikes aren't noted for spongy brakes unless something is amiss.  I would recommend that the bike not be ridden far until it's fixed.  If it is the master cylinder you can replace seals but it depends on how bad the walls are scored (hopefully not) as to whether that will fix it permanently.  It could be a seal in the calipers but if it were mine, I'd be replacing all of them.  They don't last forever.

I actually have a truck (don't drive it that much) that is doing that and it's the master cylinder (worn out) that's introducing air into the brake system.  I just have to find time to get it replaced.

[C14_Rider]

In my experience (mostly with cars, but same thing), air in the brake system causes the lever/pedal to feel spongy all the time.  It would be unlikely to account for the full release and second quick lever pull to then feel completely normal, as the op stated.

And a bad master cylinder generally results in the lever/pedal slowly moving to the end of stroke due to the internal leakage.

What I’ve had happen that accounts for all symptoms is uneven brake pad wear, by itself, or combined with brake rotor runout, which may not be “warped” but may be toward the high side of normal.  What happens is if any pad (it doesn’t have to be all of them) is even slightly wedge-shaped in any direction due to wear, the caliper pistons will run normally retracted until 1) there is little pressure on the highest point of the pad, and 2) the pistons are aligned straight in their bores.  This takes a little time as the rotor runout (all rotors have some even if it’s not bad enough to call them “warped”) repeatedly pushes on the pad with wheel rotation.

Then when the brakes are applied, the caliper pistons will move beyond the first point of pad contact and actually become cocked and unevenly extended to the degree of the pad thickness variation before they will firm up and give full braking.  This takes more fluid, thus the first pull is greater than normal.  If you release and pull again quickly, however, they will not have had time to retract, so the second pull will feel normal.

Of course this will not happen suddenly, but the op said he had noticed this “lately”, so perhaps it did develop over recent time and, like many wear situations, it became noticeable after it got to a certain point.

I would remove and carefully measure the flatness of the pads, and check the rotor runout.

[VirginiaJim]

The whole system needs to be checked out.

[B.D.F.]

What you describe is the classic case of air in the system. The fix is to bleed the system, as you have had done. The brakes may need a further re- work if they turn spongy again anytime soon; that would indicate that the source of the air is significant.

As I have said in the past, these bikes are a cast- iron bit$h to bleed the hydraulics. I have found over and over again that they do not bleed or do not bleed completely unless power bled and a LOT of fluid is used. I have had the exact same situation you describe on the front brake and repeatedly on the clutch; the fix has always been to power bleed them and they stiffen right up (Easy Boys!).

I know conventional bleeding techniques <should> work on a C-14, and sometimes they appear to work but I have yet to power bleed a single one where the hydraulics do not feel significantly crisper in operation after power bleeding them. Not sure what the root problem is but I suspect the reservoir port into the master cylinder is too small; at any rate, the hydraulics on this bike do not pass much fluid even when wide open and so I believe that is the cause of the poor bleeding results using manual bleeding.

My suggestion would be to find a dealer with a power bleeder and have them pass most of a pint of brake fluid (1/2 liter or so) through the front brakes. Power bleeders are actually very reasonable in price these days in the US but I have no idea about Germany, and you will need an air compressor to use the power bleeder.

Brian

Ok, I admit: I'm useless when it comes to anything electric, electronic or hydraulic (the complete list looks like the phone book of Tokyo, but you get the point). So I need help.

My front brakes have been acting up lately. When I pull the lever, it has way too much dead stroke until some braking starts happening. Bike brakes great and the lever effort has not increased, just the stroke. If I pull the lever, let it go and pull again, all within 1-2 seconds, then the second time I pull it it behaves what I would call correctly: almost no dead stroke and immediate response of the brakes. If I wait more than, say, 5 seconds between the first and second actuation of the lever, it gets spongy again.

So I got the thing bled by my dealer (they are very competent and I trust them, only good experiences with them; he really looks after me as a customer) last Thursday during a rear tire change, and on the way home they sure felt different. Not necessarily better, though.

On Friday morning they were just as before. It's bugging me. I'm planning to spend some long time (several weeks) in ungodly lands and I want the bike to be in as good a condition as possible. Brakes have a tendency to influence very much the chances of getting home or not.

So please tell me what can I look for. A friend explained that there could be a too thin brake disk or pads, but I thought the system would compensate for that, at least to a certain degree. Maybe I exceeded that degree? Disks have 32 000 miles of slightly heavy use, with a few tours to the Alps in all-out banzai mode. Pads have less than 6000 miles, but this is the first non-Kawasaki set of  pads (EBC) I use.

Ideas?

[martin_14]

thanks guys for the replies.

First I'll address gggGary: bike is '08, ABS, 61 000 miles.

I agree with some of you, particularly C14_Rider, as the spongy feeling symptom should be always there to point at air in the system. I had the lines checked 2 months ago while on valve job, and they are in very good condition.

Yesterday I had a talk with the chief mechanic and he told me that he will personally bleed the system once more, but he made a suggestion: he had cases on other Kawasakis where the piston seals on the calliper make the piston retract too much when releasing the brake lever, hence the need to put them again against the disc (first pull of the lever) before any braking happens (second pull). He'll look at that and clean or change the seals as needed, and proceed to look at more stuff if that doesn't fix the problem.

@Brian, thanks for that bit of info about the power bleeder. I'll mention it to the mechanic and see if he raises an eyebrow 

@Jim: I really trust this dealer. They've been very good every time and fixed stuff that others simply couldn't be bother to look at, but most of all, they are not arrogant, something so difficult to find around here. The biggest and best selling dealer in all of Germany is in the north of Munich, very close to my place, and I wouldn't take my bike to them if they serviced it for free 

On a side, unrelated note, yesterday evening I was feeling a bit blue and decided to go out for a spin with the bike. Temps were just perfect, cool enough to comfortably wear all the gear, warm enough to keep the flip helmet open and enjoy the breeze. I kept it mostly at 60 mph but I had a small sprint up to about 140 when taking the Autobahn. Holly cow I like this bike! I came back home like new 

[gPink]

The old standby is to pump the brakes and strap the lever tight to the bar and leave it over night.

[VirginiaJim]

On a side, unrelated note, yesterday evening I was feeling a bit blue and decided to go out for a spin with the bike. Temps were just perfect, cool enough to comfortably wear all the gear, warm enough to keep the flip helmet open and enjoy the breeze. I kept it mostly at 60 mph but I had a small sprint up to about 140 when taking the Autobahn. Holly cow I like this bike! I came back home like new 

Exact feeling I have when I ride mine..

[Steve in Sunny Fla]

Bleed the master cylinder. I've experienced the same issue with pleeding the 14, and the final resolution was bleeding the m/c which gave me rock hard brake feel.

 also i'm interested in what your dealer mechanic said about the dust seals causing the pistons to retract to much. I completely agree, it was a real issue on older models too, like the concours 1000. absolutely no air in the system but the brakes are squishy til the pads are against the rotors.  Steve

[tonedeaf]

If it just started doing it out of the blue, I would be inclined to believe the master cylinder is at fault. Since it's a closed system, air can't enter the system without help..

I am going with the brake lines. People usually do not consider them when thinking about spongy brake feel. And brake hoses are generally good for a very long time. But they can deteriorate and the brakes will feel spongy even if the system is completely free of air.

[martin_14]

if somebody has a minute, could you explain me the difference between bleeding the thing, power bleeding the thing, and bleeding the master cylinder thing? 

[Deziner]

1. Bleeding is the most common and generally used way to bleed brakes. That's when you "pump" the brake lever or pedal, then open the bleeder to force fluid and air from the system.

2. Power bleeding is generally done with a vacuum source connected to the bleeder, the bleeder is then opened, suckung the fluid and air out of the system.

3. The master cylinder itself has a bleeder on it to remove air at an upstream point. It can be bled by either of the previous methods.

4. Feel free to insert "easy, boys" where necessary.

[maxtog]

4. Feel free to insert "easy, boys" where necessary.

Or not!!

[martin_14]

thanks deziner.
Just one more bit of info: I went and measured the thickness, and it's at 4.6 mm, and Kawa specifies 4.5 as the limit before replacing. So although they are theoretically within range, I think I'll change the discs. They have some 35 000 miles anyway  You can easily feel the groove on the unused part of the disc, the last 0.5 mm on the edge of it, both outer and inner side of the contact surface.
A colleague of mine here at work knows "a bit" (a gross understatement) about brakes and pointed that I changed the pads not long ago, and although they look good, they are being retracted too far out, hence the need to first bring them in contact with the disc before the braking starts happening.

[Stephen.G.Fiddes]

The following is according to my shop, and it makes perfect sense with what I have experienced.

Since your bike is ABS, the brake pads should all be replaced at the same time. If theyre not, it will not brake as correctly.

First pad change: Fronts only. Brake lever felt a bit spongy after that. But it was consistant and I attributed it to non-OEM EBC HH pads. Bite didnt feel as good as it should, but better than stock.


Second pad change: Front And Rear.  Still EBC HH, and I've still never bled the lines or replaced the fluid (24k miles). But the lever and pedal feel is SOOOOO much better than it ever has been. Way better bite, and way better feel. Aside from the annoying linked brake fiasko that kawi ignored until '15, im actually happy with the brakes now!

Change front and rear at the same time.