Front brakes spongy


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jayb
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Front brakes spongy

Postby jayb » Wed Oct 16, 2013 8:13 am



I have removed both calipers cleaned and reassembled and put mastercylinder kit in, still soft brakes. thanks JayB



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80-GL100-INT
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Re: Front brakes spongy

Postby 80-GL100-INT » Wed Oct 16, 2013 9:10 am

It's probably the brake lines, the brake fluid breaks down the inside of the rubber hose and allows it to swell, thus not allowing full pressure to get to the calipers.
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newday777
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Re: Front brakes spongy

Postby newday777 » Wed Oct 16, 2013 11:00 am

80-GL100-INT wrote:It's probably the brake lines, the brake fluid breaks down the inside of the rubber hose and allows it to swell, thus not allowing full pressure to get to the calipers.


Agree. Change them out to stainless steel lines.
Is this on your profile gl1000?
How did you bleed the brakes?

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Placerville
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Re: Front brakes spongy

Postby Placerville » Wed Oct 16, 2013 7:40 pm

No. Swapping out brake lines because your newly rebuilt M/C and calipers have resulted in a 'spongy' brake lever isn't logical. Was your lever 'soft' prior to the rebuild? If not, then how is a brake line swap justified now? A soft or spongy feel at your brake lever is, most likely, due to air bubbles somewhere in your system. This is common with a complete rebuild and they are difficult too remove. You must continue to bleed your brakes until you're 100% sure that you've removed any trapped air from your system.

Bleed your brakes again and again until they're free of air. It's trapped somewhere and you've got to get it out. Do one side at a time. Pump the lever slowly and evenly. Don't do a rapid, repetitive pull as this can cause bubbles. Also, do not pull the lever all the way back to the grip (as described in your shop manual). If you can pull the lever back and feel pressure then, do this: Pull the lever back until pressure builds up. Hold the lever in place and tighten it down with a bungee cord overnight. This often works to move the trapped air. Another tip is to bleed the brakes with the bike on the side stand so that air will move out of the "T".

After your brakes are working correctly, stainless steel lines may provide a slight improvement to your braking action as they tend to swell a little less than OEM rubber lines. The comment above regarding the inside of the lines breaking down due to exposure to brake fluid is incorrect. Very old brake lines can become hard and may crack on the outside but, they don't dissolve on the inside.
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Re: Front brakes spongy

Postby WingAdmin » Wed Oct 16, 2013 10:04 pm

Placerville wrote:No. Swapping out brake lines because your newly rebuilt M/C and calipers have resulted in a 'spongy' brake lever isn't logical. Was your lever 'soft' prior to the rebuild? If not, then how is a brake line swap justified now? A soft or spongy feel at your brake lever is, most likely, due to air bubbles somewhere in your system. This is common with a complete rebuild and they are difficult too remove. You must continue to bleed your brakes until you're 100% sure that you've removed any trapped air from your system.

Bleed your brakes again and again until they're free of air. It's trapped somewhere and you've got to get it out. Do one side at a time. Pump the lever slowly and evenly. Don't do a rapid, repetitive pull as this can cause bubbles. Also, do not pull the lever all the way back to the grip (as described in your shop manual). If you can pull the lever back and feel pressure then, do this: Pull the lever back until pressure builds up. Hold the lever in place and tighten it down with a bungee cord overnight. This often works to move the trapped air. Another tip is to bleed the brakes with the bike on the side stand so that air will move out of the "T".

After your brakes are working correctly, stainless steel lines may provide a slight improvement to your braking action as they tend to swell a little less than OEM rubber lines. The comment above regarding the inside of the lines breaking down due to exposure to brake fluid is incorrect. Very old brake lines can become hard and may crack on the outside but, they don't dissolve on the inside.


I have to disagree. On these old bikes, stainless lines make a TREMENDOUS improvement to braking action and feel. I've said quite a few times; putting stainless braided brake lines on was the single best, most beneficial modification I made to my GL1100. The brakes went from weak, spongy and vague to razor sharp, powerful, and precise - it was like a whole new bike.

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80-GL100-INT
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1986 Kawasaki 440 LTD
1974 Suzuki 550
1986 Kawasaki Ninja 600 (First Street Bike-way back in '88)
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Re: Front brakes spongy

Postby 80-GL100-INT » Wed Oct 16, 2013 11:53 pm

Placerville wrote:The comment above regarding the inside of the lines breaking down due to exposure to brake fluid is incorrect. Very old brake lines can become hard and may crack on the outside but, they don't dissolve on the inside.


Yes, I would agree on the need to completely remove the air in the system, especially if you did not notice a "spongy" feel prior to rebuild. However, the primary reason for a rebuild, more times than not, is the lack of braking (spongy feeling).

That being said, brake fluid is one of the most caustic fluids used in any motorized vehicles. It most certainly will break down the inside of a rubber brake line. It does not happen overnight, like it will your paint job, because the lines are made specifically to endure this.
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Placerville
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Re: Front brakes spongy

Postby Placerville » Thu Oct 17, 2013 2:13 am

WingAdmin wrote:
Placerville wrote:No. Swapping out brake lines because your newly rebuilt M/C and calipers have resulted in a 'spongy' brake lever isn't logical. Was your lever 'soft' prior to the rebuild? If not, then how is a brake line swap justified now? A soft or spongy feel at your brake lever is, most likely, due to air bubbles somewhere in your system. This is common with a complete rebuild and they are difficult too remove. You must continue to bleed your brakes until you're 100% sure that you've removed any trapped air from your system.

Bleed your brakes again and again until they're free of air. It's trapped somewhere and you've got to get it out. Do one side at a time. Pump the lever slowly and evenly. Don't do a rapid, repetitive pull as this can cause bubbles. Also, do not pull the lever all the way back to the grip (as described in your shop manual). If you can pull the lever back and feel pressure then, do this: Pull the lever back until pressure builds up. Hold the lever in place and tighten it down with a bungee cord overnight. This often works to move the trapped air. Another tip is to bleed the brakes with the bike on the side stand so that air will move out of the "T".

After your brakes are working correctly, stainless steel lines may provide a slight improvement to your braking action as they tend to swell a little less than OEM rubber lines. The comment above regarding the inside of the lines breaking down due to exposure to brake fluid is incorrect. Very old brake lines can become hard and may crack on the outside but, they don't dissolve on the inside.


I have to disagree. On these old bikes, stainless lines make a TREMENDOUS improvement to braking action and feel. I've said quite a few times; putting stainless braided brake lines on was the single best, most beneficial modification I made to my GL1100. The brakes went from weak, spongy and vague to razor sharp, powerful, and precise - it was like a whole new bike.


That's OK, we'll agree to disagree. I've had both on various bikes I've restored and, while I do notice a difference, I certainly wouldn't classify it as 'TREMENDOUS'.
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newday777
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1983 GL1100A Wineberry to sell 36,000 miles

1999A Restored and sold at 19,000 miles

1999SE Totaled by cager at 105,000 miles

Re: Front brakes spongy

Postby newday777 » Thu Oct 17, 2013 7:50 am

There are a lot of factors in proper brake performance, condition of all the parts from old hoses and seals, pistons without pits (rust) caused by lack of flushing brake fluid yearly, hardened gunk in seal grooves, hardened old fluid in return ports of master cylinders.
Most rubber hoses are dead after 6 years and will flex and constrict causing loss of pressure to the pistons.
http://www.hoseandfittingsetc.com/techn ... ake-lines/

Yes it's your choice if you want to use stainless steel or not. But at least tell the OP to change out to new rubber hoses. Yes he may still have air in the lines.

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Placerville
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Re: Front brakes spongy

Postby Placerville » Thu Oct 17, 2013 3:31 pm

Good Web site. Not many places around that will make both OEM style rubber hoses and stainless to order.
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jayb
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Re: Front brakes spongy

Postby jayb » Fri Oct 25, 2013 7:12 pm

Thanks for all the input on my brake probem you were correct about air in the system, I used vaccume bleader, pressure from the bottom up and the old pump the lever and release the pressure at the bleader valve with no luck. I finally got the air out of the calipers by removing the bottom attach bolt rotating the caliper untill bleader valve points up, and out the air came, now I have good solid brakes. JayB

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Placerville
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Re: Front brakes spongy

Postby Placerville » Sat Oct 26, 2013 10:25 pm

That's good to hear! If you would, could you please clarify something you wrote.

You said you, "rotated the caliper until the bleeder pointed up", and that allowed trapped air to escape. The bleeder valves already point 'up' on stock calipers. No at an exact 180 degrees but, very near so. So, are you saying that by tilting the caliper a few degrees until the valve pointed 'straight' up that the trapped air found it's way out?
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jayb
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Re: Front brakes spongy

Postby jayb » Sun Oct 27, 2013 7:54 am

yes that is correct, I isolated the problem to the calipers by pinching off the hoses to find out if it was in the master cyl. after that it only be air in the calipers. JayB

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Placerville
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Re: Front brakes spongy

Postby Placerville » Sun Oct 27, 2013 12:04 pm

Very interesting, and it just shows how much opportunity you can create for air bubbles when you do a full brake cylinder and caliper rebuild. Thanks for that explanation.
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Fred Camper
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Re: Front brakes spongy

Postby Fred Camper » Sun Oct 27, 2013 6:06 pm

Just remember if you want to improve the time it takes to bleed front brakes, then removing the splitter and using two hoses directly from the master cylinder to each caliper is a great improvement. After removing the splitter, air leaves much easier. But rotating the caliper is not a bad idea for sure as the bleed is not exactly at the top.

motojo
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Re: Front brakes spongy

Postby motojo » Sun Jan 19, 2014 8:10 pm

jayb wrote:yes that is correct, I isolated the problem to the calipers by pinching off the hoses to find out if it was in the master cyl. after that it only be air in the calipers. JayB


This is a fantastic tip!/\/I had rebuilt my front master cyl and both calipers with all new seals and pistons. I could not get the brakes bled despite using conventional beeding as well as a reverse bleeder and using a mighty vac. I was convinced it was a crappy bore on the m/c that I cleaned up and rebuilt so I bought a ebay Chinese m/c. Actually wasn't as poor quality as I expected. I installed today and worked all afternoon and could not get the air out of system. I just came in all frustrated and found this thread. I was still wondering where all the air was (suspecting m/c) so in 2 minutes I went to the bike, placed c-clamp on brake hose below the m/c. Wahlah! Instant pressure at the lever! Now I know the air is trapped below that point either in the tee or in the calipers (most likely). Next chance I get I will pull the lower caliper bolts, rotate calipers up as suggested, bleed brakes and hopefully END THIS ORDEAL!
Thanks for all the help people!

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Re: Front brakes spongy

Postby ntintruder » Sun Feb 09, 2014 4:41 pm

I have had good luck bleeding brakes with the vacuum bleeder from HF. Before that I would pump the brake lever for twenty minutes at a time and still not get the right feel to the brakes. I also make it common practice to install stainless lines on all my old bikes. Don't like the idea of relying on forty-year old rubber lines.

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Fred Camper
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Re: Front brakes spongy

Postby Fred Camper » Sun Feb 09, 2014 6:36 pm

And a 5/8th boar or 14mm master cylinder helps brake feel also. My formula is 5/8ths master, no splitter and two Stainless lines.

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twofest5
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Re: Front brakes spongy

Postby twofest5 » Sun Feb 23, 2014 9:40 am

question having redone my whole front brake system yesterday as well. on the top of the splitter with the brake light switch there is a 8mm(?) bolt. could a person possibly crack that open to get trapped air out of it? want to ask before trying. :?:

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Fred Camper
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Re: Front brakes spongy

Postby Fred Camper » Sun Feb 23, 2014 1:10 pm

Never tried. But seems to me you would need a syringe to put pressure in the caliper to push the air up and out. Using pressure only at the master would try to push the air down and may be less effective.




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