Spongy front brakes

[canamant]

On ‎24‎/‎05‎/‎2017 at 1:47 AM, bluedog59 said:

Tying the lever back has a use. You put pressure in the system, you can't compress a fluid but you can compress the air in the system and so the air pressure in any bubbles rises and the bubble are more inclined to rise up in the system.

 A few taps on the hoses and they'll all be waiting for you when you "waggle the lever" and back bleed it up through the m/c.

Been doing it like that for years. 

Thank you for the clarification.  Just tying the lever back on its own doesn't get rid of the bubbles.  The first bit of advice is often trotted out without the second bit to get rid of the accumulated air.

[Scara]

On 24/05/2017 at 5:07 AM, canamant said:

Tying the lever back does naff all.  The reason for spongy brakes is little bubbles trapped in the system.  If it is in the master cylinder, take the assembly off the handlebar and with the lever pointing up give the lever a waggle, the air trapped in the high point of the cylinder will bubble up the cylinder into the reservoir.  Much more effective than putting a rubber band on the lever.

 

 

On 24/05/2017 at 8:47 AM, bluedog59 said:

Tying the lever back has a use. You put pressure in the system, you can't compress a fluid but you can compress the air in the system and so the air pressure in any bubbles rises and the bubble are more inclined to rise up in the system.

 A few taps on the hoses and they'll all be waiting for you when you "waggle the lever" and back bleed it up through the m/c.

Been doing it like that for years. 

Actually What I discovered was the rubber band technique on the lever works in a different way. It compresses the pad itself reducing the spongy feeling on new pads when you r first go to bed them in. Most times we fit new pads then spend the next 100 clicks bedding them in, this technique does in-fact aid that situation.

Being a slabby owner myself, The countless hours one used to spend removing air out of the system, I finally bought a brake bleeder vacuum pump kit for it. What once used to take hours, now takes 30 minutes from caliper to master. Then I use the rubber band technique over night before I go riding the following day.

Was the best $40 AUD I ever spent.

Now, inside the master cylinder itself, their is a plunger which over time and piss poor fluid changes the rubber loses its seal. Hence even though you bleed them one day, they are shit the next. A serious problem too on the K7 K8 L0 thou's as well.Suzuki had a recall on them in the last 2 years because of it.

Alot of the posts here recommending complete caliper rebuilds is also sound advice given A). the particular age of the machine, plus B). usage and C). Location on the planet.

Im not saying its for everyone, but I refresh the fluids in all masters annually with a complete bleed out no matter how many k's the bike has done, its all solar and moisture effected (Example: Colour change in opaque fluid bottles) unless your racing the bike causing fluid overheating.

 

My 2c worth, good luck with it

[martyngsxr]

What I normally do is use a big syringe fill it with brake fluid and then connect to the bleed nipple crack it open and then basically back bleed 

[gixeriain]

Since posting this post, I have moved to Wiltshire. I think new lines are in order. 

[martyngsxr]

If you need a hand I'm in Bristol 

[strima]

Try putting the calipers and pipes above the master cylinder, this should make the air bleed out easier. Once you've got a load of fluid in the system then refit and do the final bleed.

Theory being the fluid pushes the air upwards in the direction it wants to go rather than trying to push against it.

[MeanBean49]

Quick check nobodies mentioned yet thats worth a quick 20 seconds before you waste hours bleeding to no avail.

Put a finger on your disc next to the caliper and pull the brake. Repeat on the other disc. If you feel the disc moving then its quite likely your discs have gone dished. 

You can have perfectly bled brakes but they stay spongy because all the lever travel is taken up straightening the disc up before the pads can bite. When you let the lever go the disc acts like a spring and pushes pistons back in too far.

Ive had this problem loads of times on gsxr's

Edited June 29, 2017 by MeanBean49

[fatblokeonbandit]

14 hours ago, gixeriain said:

Since posting this post, I have moved to Wiltshire. I think new lines are in order. 

Where in Wiltshire??

Im in Trowbridge the cosmic centre of the universe, I have a big box of syringes, they work every time for me, 14 bandits, 4 pots, 6 pots, radials and now brembos, always worked with a syringe.. 

 

 

 

[gixeriain]

On 29/06/2017 at 12:39 PM, fatblokeonbandit said:

Where in Wiltshire??

Im in Trowbridge the cosmic centre of the universe, I have a big box of syringes, they work every time for me, 14 bandits, 4 pots, 6 pots, radials and now brembos, always worked with a syringe.. 

 

 

 

Eyup fatblokeonabandit.

Long time no hear.

Im in westbury.