Sudeen Brake failure with crash - Triumph675.Net Forums
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post #1 of 9 Old 03-28-12, 07:48 Thread Starter
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Sudeen Brake failure with crash

I've just done a track day a Donington Park and had sudden brake failure (Standard OE system) which lead to me dropping it in the gravel trap. I'm still not sure why it happened so any thoughs from anyone would be appreciate.

Ever since changing pads from OE to EBC and then bleeding the brakes, I've never been happy with the front brake. It still stopped but never had the same feel. I finally changed to twin lines in the hope of ensuring the air was bled.

I then ran these at Donington for five track sessions without any problems then in the final senssion I came out of the pits used the brakes as normal, got to the Melbourne hairpin (less than a lap), grabbed the brake and got absolutly nothing. Scrubbed off as much speed with the rear brake and dropped it in the gravel.

When I picked the bike up the lever still came back to the bar even after pumping the brakes. Inspection of the system has shown a very very slight weeping from the bleed nipple of the master cyclinder (not enough to give zero resistance to the lever), however the system is still full of fluid and otherwise tight, there are no other signs of leakage and no explaination of why from one corner to the next it went from all to nothing.

I've considered the possibility of the pads being pushed back due to tank slapper type movement, but this did not occur and the subsequent pumping of the lever did not return the brakes to normal or normalish.

My present thoughs are with the master cylinder piston, however I would expect problems here would be gradual rather than sudden. I'll strip it tonight but I suspect I wont see anything obvious.

Does anybody have any thought on my problem.

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post #2 of 9 Old 03-28-12, 08:54
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Sorry to hear about your mishap, and glad you're OK! Having no brakes suddenly is not the kind of thing anyone wants to experience!

When you changed the pads and bled the brakes, did you change from DOT4 fluid to DOT5 fluid? I seem to recall that they are not compatible, and the rubber master cylinder seal may have become affected in some way, leading to a sudden failure (although I may be wrong on this).

Please let us know what you find, in order to try and avoid a similar surprise at the worst possible moment!
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post #3 of 9 Old 03-28-12, 10:42
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Wow!! That is some scary shit! Gla you're ok!

At first I was going to say maybe your pads weren't bedded in yet since you replaced stock with EBC, but then you said you ran it 5 times with no problem, so I really don't know. All I can think of is air in the master. Try bleeding or back bleeding from the calipers up an change your fluid again?

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post #4 of 9 Old 03-28-12, 15:04
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What type of ebc brakes were you using? I know i was running ebc pads last year and there were plenty of times i experienced fade and my brakes didn't work but i still had a lever.

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post #5 of 9 Old 03-31-12, 12:24
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I warped one of the front rotors on my 08 model at a track day a few years ago. The result was no brake pressure and the lever went all the way to the bar.
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post #6 of 9 Old 03-31-12, 13:48
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How's the level on the fluid tank ?

The slower you move, the more dangerous your bike is... I'll let you work out the conclusion from there

If you find wearing proper gear's too hot, you're just not fast enough !

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post #7 of 9 Old 04-01-12, 12:57
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Originally Posted by 2BRacing View Post
When you changed the pads and bled the brakes, did you change from DOT4 fluid to DOT5 fluid? I seem to recall that they are not compatible, and the rubber master cylinder seal may have become affected in some way, leading to a sudden failure (although I may be wrong on this).
I have heard this also. I was also told that they react with each other and form a sort of gel!

If the system is still tight and your fluid levels are still OK as you said, then it's a really difficult one and I'm struggling to come up with an answer, mainly due to limited knowledge.

I've also noticed a slight weeping of fluid from the bleed nipples on the calipers. I had the same problem on my GSXR1000 which also used Nissin calipers. I cured that on the GSXR by wrapping the bleed nipple thread with PTFE tape before putting them back in. That sorted that problem, however I doubt that was the cause of this problem.

All I can come up with is a problem I had on on my 1996 ZX-7R when I used it on track. After a few sessions the lever would be coming back to the bar. I tried everything: different pads, different brake fluid, braided hoses, bleed brakes with fresh fluid before a track day. Nothing worked. They were Tockico calipers and I came to the conclusion they just got too hot and boiled the fluid.

What I would suggest, possibly backed up by you saying the brakes never felt as good after fitting the different pads is that possibly you haven't got all the air out the system and the fluid is boiling up and compounded by the air in the system you eventually reach a point where they are too hot.

Before working on them, what are they like now you haven't used the bike for a while?

Other than that if no fluid is leaking out, maybe there is an issue with the MC as you suggest.

Like the others, I really hope you solve this one. Keep us posted.

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post #8 of 9 Old 04-04-12, 07:55 Thread Starter
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I have not got very far with this so far due to other commitments. As I said there was a very slight weep from the MC bleed nipple. I now know why. The bleed nipples are made of cheese. Granted I know I over torqued it, but what happened is the small bleed hole in the nipple has squashed and the top of the cone is know slightly slanted over, causing it not to completely seal.

Unfortunately this still does not explain the sudden failure from all to nothing. Still need to check the MC, but have bought new after market bleed nipples and will check system sealing first.
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post #9 of 9 Old 04-07-12, 10:43
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If an air bubble got into the M/C, it certainly could explain why it went from all to nothing.

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