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View Full Version : Complete Brake Failure....!



nige harford
07-28-2008, 11:47 AM
I do a fair amount of track days , but this is the first time I have used the Tuono. Completed about 4 or 5 laps getting progressively quicker and then it happened........absolutely no front brake at all. On the entry to the previous corner, they were fine, 400 yards later it took 3 good fullstrokes to get the pads to the discs.I pulled off the track and bled the system through, although the fluid that came out seemed fine.
I thought maybe there was something wrong with the discs , so I swapped the wheels for my other set with road tyres on and joined the next session. Same thing happened again after I began to up the pace.
I was getting pretty cheesed off but didn't want to write off the day, so I rechecked everything. No leaks, no bubbles of air in the system, no bad wheelshake or anything like that to force the pads back and no loss or drop of fluid level.
I went out again and by this time I was pre braking before the braking point to check if they were still there...............took about 6 laps and then it happened again.
Anyone else suffer from anything similar or have I just got a special mod to help me carry more corner speed ? Completely ruined day.....well pissed off.

whiner
07-28-2008, 12:39 PM
If it took a couple of laps,perhaps it maybe heat related, or the seal on the master cylinder isn't playing as good as it should.


A seal went in my KTM 525 EXC master cylinder, it to gave strange braking for a while and then just gave up.
Someone had put the wrong brake fluid in at service. Which melted the seals.

The Dr.Jon
07-28-2008, 12:45 PM
Sounds like sticking pistons....never heard of this on a Tuono, but can happen for a number of reasons. Sounds like a strip down and re-build is called for.

:burnout:

nige harford
07-28-2008, 01:52 PM
I've just been speaking to a friend of mine who raced the Isle of Man on a Mille 5 years ago and he had the same problem. He replaced master cylinder and both calipers in progressive sequence and still couldn't get rid of the problem. He did say that he was fairly sure that it wouldn't happen on the road. I took the bike out this afternoon and rode as hard as I dared on roads I knew and it was absolutely fine for a 30 mile ride. Bizarre.

nige harford
07-28-2008, 01:55 PM
Sounds like sticking pistons....never heard of this on a Tuono, but can happen for a number of reasons. Sounds like a strip down and re-build is called for.

:burnout:
Done, about 3 months ago. I had a piston that was sticking on and a full strip and re seal was in order, so I did it. ( well, it had just turned 45,000 miles)

GrahameA
07-28-2008, 03:26 PM
What brake fluid do you use and how old is it?

Hope not teaching my grandma to suck eggs but brake fluid is hygroscopic so absorbs water. Under extreme conditions the water can boil, get air bubbles in the system and cause the symptoms you describe. By the time you got back to the pits everything will have cooled down enough so bubbles will not be evident.

Tell me you used fresh DOT 5.1 and I'll get me coat:).

The Dr.Jon
07-28-2008, 03:47 PM
hygroscopic

Well you learn something everyday, just looked that up....cheers!
http://www.tis-gdv.de/tis_e/misc/hygro.htm

:cheers:

Rlhay2
07-28-2008, 03:58 PM
Same thing happened to a racer bud of mine.

He had mistakenly purchased DOT 5 fluid!!:eek: It worked fine until the fluid temperature increased.

Kid Thunder
07-28-2008, 04:11 PM
Sounds like a high speed wobble But you say no. You said that there were "no bad wheel shakes". Were there any at all? Doesn't need much.
Was it a good DOT4 fluid. DOT5 is a no no as you know 5.1 will mix but it is REALLY hygroscopic, made for bikes where the fluid is changed often from what I have read.

nige harford
07-28-2008, 04:49 PM
I am reasonably sure I used 5.1 but can't find the container . I possibly left it at the track as I was pretty angry and threw most of the stuff in the van.I will re- bleed tomorrow with 5.1 but won't know if anything has changed til the next time at the track by the looks of things.

GrahameA
07-28-2008, 05:05 PM
I am reasonably sure I used 5.1 but can't find the container . I possibly left it at the track as I was pretty angry and threw most of the stuff in the van.I will re- bleed tomorrow with 5.1 but won't know if anything has changed til the next time at the track by the looks of things.

The age is important. If it's been it there a long time will have deteriorated and much more likely to boil up.

I know some guys who change the fluid on their racebikes every couple of races. Think that's a bit over the top but at least once a year for a road bike and more frequently if you do trackdays.

Anyway secret of going fast is not how hard you brake but how soon you get on the throttle so the bike was only trying to help:cheers:

OldTLSDoug
07-28-2008, 08:55 PM
DOT 5.1 is more likely to boil at a lower temp than DOT 4. I would recommend using DOT 4 and get some with a higher boiling point like Motul or Brembo. That should fix it up, unless the heat is coming from a dragging pad related to a sticking piston. The fact that it doesn't do it on the road implies it is not sticking, but rather is fluid boiling point related. Just a guess on my part, but using DOT 4 vice DOT 5.1 should help you out sir.

QuickHX
07-28-2008, 10:11 PM
RBF = Racing Brake Fluid. DOT4.
As in RBF600 (is that as in their 600th try to get it right?)
Brake fluid: Racing Brake Fluid 600 Factory Line

Scroll down a bit. It's the good stuff... good for clutch bleeding (AND that nasty rear brake issue) as well:
http://www.motul.fr/uk/conseils/index_moto.html

Quote:
"This new 100% synthetic brake fluid posseses an extremely elevated boiling point which also guarantees high performance levels in competition, especially for racing brake systems, with their carbon discs. RBF 600 is a product that exceeds existing standards of performance and the following exacting norms: FMVSS 116 DOT4 / SAE J 1703 / ISO 4925"

Get Yours Today! And if you act before midnight, ask for the Ginsu knives!

-Quick

GrahameA
07-29-2008, 02:12 AM
DOT 5.1 is more likely to boil at a lower temp than DOT 4. I would recommend using DOT 4 and get some with a higher boiling point like Motul or Brembo. That should fix it up, unless the heat is coming from a dragging pad related to a sticking piston. The fact that it doesn't do it on the road implies it is not sticking, but rather is fluid boiling point related. Just a guess on my part, but using DOT 4 vice DOT 5.1 should help you out sir.

Following table is from the HEL (brake lines) website

Minimum Specification Good Brand Min Spec
DRY WET DRY WET
DOT 3 205 Deg C 140 Deg C 220 Deg C 150 Deg C
DOT 4 230 Deg C 155 Deg C 260 Deg C 170 Deg C
DOT 5 260 Deg C 180 Deg C 270 Deg C 190 Deg C
DOT 5.1 260 Deg C 180 Deg C 270 Deg C 190 Deg C

All I can say is that I have raced (a bit) and trackdayed (a lot) and never had a problem using DOT 5.1 fluid.:cheers: