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Discussion Starter #1
About a month ago purchased a used Ducati 999s. Previous owner stated he had done all the fluids etc. He also had installed some very aggressive HH brake pads. I noticed some pulsing in the brake lever and after cleaning and lightly sanding the rotors the problem remained. Runout was normal so just decided to put new stuff on.

I installed some new rotors and some less aggressive brake pads ( GOLDfren SR) and all is well.

Just one odd thing. The previous owner used some special DOT 4 brake fluid in both the clutch and brakes. I will have to look it up since I don't have it here right now. But, I have noticed since I got the bike I get some fluid on the rubber hose between the Reservoir and the Master cylinder. I am not losing any fluid but still get this build up that looks like condensation. The previous owner installed cyclecat bar risers that uses a different reservoir for the brakes and clutch because of clearance under the upper fairing.

So, my gut tells me this is just the brake fluid attracting some moisture on the brake line, but have never had this happen before on any bike I have ever had. Cause for concern? Given the pattern it does not look like a leak, but just condensation.
But a little scary that the brake fluid in the line could attract moisture like that. Or is it just heat from the brake fluid causing that? Very Humid down here in the south right now so don't know if that has anything to do with it. Think I may just do a Flush and bleed with some good ole non-exotic DOT 4 fluid.


 

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Discussion Starter #2
SHould have searched first

It would appear the tubing used was not compatible with brake fluid. That is brake fluid seeping out. So ordered the correct stuff. ( at $5.00 a foot) WOW!

Will certainly flush and fill with regular Synthetic DOT 4 now. :blind:
 

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Brake fluid is hygroscopic - that is, it attracts water. Which is why we keep changing it.

I haven't seen it form condensation like that on brake lines though. Have you had unusually high humidity recently?

Edit: Just noticed your reference to high humidity in the first post.
 

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I didn't think any Dot 4 fluid was synthetic. I thought that was only the Dot 5 used by Harley Davidson.

But flushing through some conventional Dot 4 fluid should be your first step.

Dot 5.1 is recommended by some. I believe it is recommended for ALB systems, so as such not necessarily what these bikes require.

But I understand it is a thinner viscosity than Dot 4. And compatible with it.

So if that's what was used a simple flush and bleed should see you right.
 

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One clear tubing material that is compatible with brake fluid is Tygon 2075. The wetness that you will get with other incompatible tubing is actually brake fluid leaking through the tubing wall.
 

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Discussion Starter #6
Yea that is what I found out. I have ordered the correct tubing Tygon tubing. I am going to do a complete flush and fill when it comes in. I have a reverse brake bleeder system so should be good to go. Master, left caliper, right caliper ......... that is the correct order right?

Also going to do the clutch side since I am getting new tubing and clips.

Is it ok to use a high quality synthetic DOT 4 brake fluid in both the clutch and brake system?

Or is it like BMWs that require some kind of high priced mineral oil for the clutch system?

Recommendations please

 

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Keep in mind that the clutch hydraulic fluid doesn’t see the same high temperature conditions as the brake fluid so don’t waste your money on the high performance fluids. Any inexpensive name brand DOT 3 or 4 fluid will work well, but needs to be changed on Ducati’s maintenance schedule.

Some fluids have been noted to not darken over time in the clutch system — Valvoline Synpower, ATE Super Blue, Galfer Super DOT 4 and Motul RBF 600.

From the table below it looks like Castrol SRF is the best, which it is. Unfortunately, it normally sells for $75+ a bottle and is comparatively hard to source. Its worth to you depends on whether you have experienced brake fade. If you have, then it’s perhaps worth the premium cost. BTW, it’s used by virtually every Formula 1 team.

The second best choice would appear to be Motul RBF 600, but I have heard that it is very quick to absorb water from the air. Consequently, it seems most suitable for racing applications where the fluid is changed much more frequently. I have not tried it myself.

This seems to leave the ATE as the most practical choice for brake fluid in a street bike. BMW recommends this brake fluid for their street cars mainly because it, like Castrol LMA, absorbs moisture very slowly. One advantage it has over LMA is that ATE has a much better wet boiling point. You can put this stuff in your bike and forget about it for a longer time. Consequently, it’s an excellent choice for a weekend track bike which also sees regular street duty.

All brake fluids come in sealed containers which means they can be stored unopened for long periods. However once the can is opened, the fluid will degrade quickly. BTW, DOT 5.1 fluid is not usually any better than DOT 4, particularly after absorbing moisture.

Most of us don't change our brake fluid very often so the wet boiling point numbers are more important than the dry numbers. On the track, brake fade is our main concern so we necessarily change the fluid more often, and use a higher dry boiling point fluid. Unfortunately as a practical matter, the higher the dry boiling point, the faster the fluid absorbs moisture from the air, Castrol SRF and the ATE fluids excepted.

Finally, if you don't change your brake fluid once a year or so, the absorbed moisture in the fluid corrodes expensive brake bits. So, do it in the off-season.

Glycol brake fluids MUST be completely changed at intervals not to exceed 18 months.

Do not use DOT 5 silicone-based fluid in a Ducati having Brembo components.
 

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Same

Hi guy's,

I have had my 2005 999s here in Australia now for the past 5 years.

It has the standard resies and lines (steel braided) and I change the brake & clutch fluid each year with noname DOT 4.

I have never had an issue with the DOT 4 nore excessive condensation attraction into the fluid (when I change it it does not appear foamy or thick or excessivley dirty).

So long as the tubing is applicable for the purpose, use the cheapest DOT 4 which meats standards. Because you are changing it every year it wont have time to turn to mush (service schedule recommends every 2 years).

On the order of bleeding, I have always worked by left, right then master (assuming standard set up of one line from master to right and then one from right to left).
 

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Discussion Starter #10
Thank you

Went on and ordered a set of speed bleeders for the clutch and brake calipers, so flushing in the future will be so much easier.

Funny thing the kit does not include bleeders for the clutch and brake Master Cylinders, so once installed it must be good enough to bleed at just those locations.

Will See
 

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Just to round off this discussion - I find that the clutch fluid needs frequent flushing/bleeding on Ducati road bikes. I do mine as soon as it discolours - it only takes a few minutes when you have a system, and are in the habit.
I do mine about as often as I lube my chain - about 500-600 kms (350 - 400 miles).
Brake systems of course need more attention when used at the track, where higher temperatures are generated.
And in case you missed it - Dot 5 fluid is silicone, and recommended for Harleys. It is completely incompatible with Dot 4 fluid, or Brembo components..
But Dot 5.1 is a newer variant, not silicone, and my understanding is that it was developed for anti-lock brake systems (ABS). I think it has a thinner viscosity.
Not necessary on our bikes, but not harmful either.
 
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