Topic: Spongy brake lever even after bleeding

[mgilvary]

After weeks of stop/start work, I finally finished my dual brake conversion on my 550. I filled the system today and bled both sides (using the spectacular speedbleeders I installed). I took her for a quick ride and the brakes working, but I'm a little disappointed in the feel. I upgraded to Russel steel braided lines and am using a new Nissan M/C. Calipers were completely cleaned out and new seals installed. I was hoping for a rock-hard brake lever, but it's about as spongy as it was with the stock M/C and the 31-year-old rubber hoses.

I ran a lot of fluid through the system while bleeding, and made sure to keep the reservoir full, but the tiny air bubbles never stopped coming. Is that my problem. Do I simply need to keep on bleeding until it's perfectly clear?

I never had so much trouble bleeding my brakes before. Is the problem that I'm dealing with a new, dry system?

[Bob Wessner]

Short of some sort of leak somewhere, hate to say it, but it does sound like more bleeding is in order. I would think with all the time and expense you've put into the upgrade, the lever feel should be better than you are describing.

[TwoTired]

Tiny air bubbles are still compressible.  And, don't move very quickly through fluid.  They will eventually collect at high points of the system.  Hopefully the physical arrangement on your bike makes the master cylinder the highest point in your brake system.  If so, they will self bleed in time.  If you were flailing on the brake handle to pump up the pressure, you can be sure that the fluid became foamy and high internal pressures can make large bubbles into very slow moving tiny ones.

I find it is helpful to mentally visualize the inside of the liquid vessel.  Peering inside, start at the very bottom and imagine where a tiny bubble would rise in the vessel.  If you can make it move toward your speed bleeder so much the better.  If there is a line loop or shelf that can prevent a bubble from rising to the master cylinder, that's your problem.  Sometimes you can reposition bars or bike to eliminate the capture pockets, and that allows the bubbles to rise with time to the master. Then a slow pump on the handle squeezes out the air, and the brakes get a hard lever.

The other factor could be new pads that have not worn to the point of full contact with the rotors.  Inspect those and note how much of the puck surface is showing wear factors.  If the surface contact is full, flat, and complete, spongy levers are probably bleed issues.

Cheers,

[mgilvary]

Thanks for the responses, Bob and Two Tired. I see a couple of problems already.

1) I was flailing on the brake lever. Quite a bit actually. There was some sort of blockage in one of the bleeders and I sat there pumping like a maniac before I figured out the problem, removed the bleeder and cleaned it out. Afterwards, the fluid flowed very easily through, but was filled with tiny bubbles (i.e. foamy).

2) The brake pads are right out of the package, so they probably need to break in a bit.

I'll let her sit a day or two and see what happens. The good news is, if I have to bleed again, those speedbleeders are a real treat.

Thanks again, guys.

[Magpie]

An easy way to get the tiny bubbles out of the lines that has worked for me is to use a large elastic band or tape the brake lever in the full on position and leave it over night. The bubbles work their way up and out.
Cliff.

[TwoTired]

The bubbles tend to not join in larger bubbles under pressure, and larger bubbles rise faster.  In fact, holding the lever closed blocks the exit hole in the master for the bubbles.  They do care about taking their time to rise to the surface, so waiting overnight is a good advice.

Cheers,

[mgilvary]

Just thought I'd add an update:

After simply letting the bike sit -- without the lever retracted -- the lever is considerably stiffer. So, lesson learned. Don't flail on the lever while bleeding, or you'll foam up the fluid.

[Chris Liston]

Which speed bleeders did you wind up buying. I need some of those bad boys.  Had them on a previous Jeep I owned and it made life so simple.

[mgilvary]

They're Russell speedbleeders. I got them -- and all my lines and fittings -- from Flanders (which is not to far from me).

I did have an odd thing happen, though. When I first filled the system, I bled the right side no problem, but nothing would come out the left side. I thought the speedbleeder was faulty, so I pulled it and cleaned it out. It worked fine after that. I have no idea what the problem was.

[kine8282]

You live in pasadena, ca? I'm curious becouse so do I and aside from Flanders do you use any other shops in pasadena that I can also check out?

[RSV12K]

Speed Bleeders work great, but if you're getting bubbles and dribbles, you ain't done bleeding, as others pointed out. The only way you know for sure that the job is thoroughly done is to make sure the oil literally spurts--squirts--ejaculates, even--out of the bleeder!  Attach a piece of tubing to the bleeder; if you don't have one, wrap a rag around the caliper if yours is painted.i

[merc2dogs]

 Typical leeding for me constitutes filling the resevoir, letting it sit for a few minutes, (adjust rear breake etc) tapping the caliper with a small rubber handled screwdriver then bleeding, after I'm through getting air out I take it for a short spin, then bleed one more time always get a couple more bubbles out the second time around. tapping the lines and riding loosen up the bubbles and let them float to the top, or get pushed out easier

  if there is no air in the lines, check to make sure everything is bolted tight. One customer brought a bike in with badly spongy brakes, after taking a good look at them aand bleeding them, I noticed that he had used 'soft' replacement bolts, (cheap home depot grade) when the brake was applied, there was enough flex inb the bolts to make them feel spongy, swapped him over to some grade 8's and no more spongy feel. 

Ken.