DOT5 Fluid in Brembo Systems
 

Hi all

In the depths of my memory, I seem to recall someone posting something a long time ago about DOT5 fluid being incompatible with Brembo systems.

Can anyone confirm/refute? The system in question would be the Brembo 4-pad system as fitted to the 998S.

Any (prompt) feedback would be very welcome - you there, Shazaam?

I can confirm this, there is a article on there website about it.

. All brembo braking products use natural-rubber base seals, and therefore are INCOMPATIBLE with DOT-5 SILICONE-based brake fluids. DOT- 5 SILICONE-based fluids react with natural-rubber seals to swell them WHICH CAN CAUSE SEVERE PISTON RETRACTION PROBLEMS. There is no cure for problems caused by DOT- 5 use other than complete seals replacement - USE ONLY DOT-3/4 NON-SILICONE TYPE FLUIDS such as CASTROLTM 'LMA' in your brembo components.(Yes, we know the cap on the rectangular master cylinders says "DOT 3 - 5 Fluids"-BUT PLEASE NOTE: Silicone DOT- 5 fluids are NOT generally in use in Europe, but Glycol-based “DOT-5.1” fluids ARE. Hence, the “DOT-5” cap designation). For best braking performance, we recommend changing brake fluid twice a year. If the machine is to be stored in a damp environment (over the winter, say), we recommend installing fresh fluid before and after the storage period. At minimum service levels, glycol brake fluids MUST be completely changed at intervals not to exceed a period of 18 months.

Did this come from the Brembo Website?
 

Skidlids

Can you confirm whether this text came from the Brembo website, and if so, the URL?

I spoke to JH Performance today (John Hackett) himself. Whilst I was on the line, he called Brembo and they confirmed that DOT5 fluid is incompatible with Brembo fluid (I didn't get a chance to ask JHP what "Brembo" fluid is, as JH was taking three calls at once), but that it is fine, both alone and with the fluid Ducati put in the bikes when new.

HELP!

[Edited on 15-8-2003 by 998Addict]

That quote was from a Yoyodyne Brembo FAQ page that has been deleted. I think that it was Yoyodyne's assessment of the issue, not Brembo's.

Most everyone will tell you not to use DOT 5 in brake systems that already have had DOT 3 or 4 in them. It's true. When you mix a glycol-based fluid with a silicone-based fluid the mixture coagulates and piston-retraction problems occur.

What they don't tell you is that you CAN do it if you completely disassemble the brake system and clean it thoroughly with denatured alcohol. Also you really should replace all the seals. You can however soak good old used Brembo seals in alcohol for several days (renew the alcohol daily) and then re-used them in a DOT 5 system. The optimum situation is to only put DOT 5 in a new system that hasn't seen glycol.

One owner of a '90 851 and '93 888, both having Brembo brake systems (master cylinder and caliper), reports that he has had DOT 5 in them for 10 & 7 years respectfully (after flushing and refilling) without a problem.

So, if it really is a seal/fluid materials issue as Yoyodyne has previously suggested then how does flushing help? Direct experience indicates that it is not a seal compatibility issue but one of what happens when these two brake fluids mix.