Boxerworks.com

DOT 4.
Take care of leaks and no paintwork will be spoiled.

I've read that DOT 5 doesn't absorb moisture so it stays as pure water inside the system, being more suspectible to rusting things as well as freezing. It would probably be easier to get any water out if it gets absorbed but if it stays as water and gets trapped, you might not get it out. I suppose one might want to use 5 or 5.1 in a race application and/or where brake fluid is getting changed out on a frequent basis. For the average person, DOT 4 is far better to use.

Kurt in S.A.

Hmm, for the airhead I'm not in doubt. 4.0 it is and will stay so. But for the R850R where I don't know what have been used in the past? And it is a ABS system. Planning on changing the lines to braided and might consider rebuilding calipers as well. Good idea after 15 years of use I guess.. Sorry not all airhead related but.

From CycleBrakes.com, an authorized Brembo retailer:

B. 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).
http://www.cyclebrakes.com/html/brembo_tech_info.html

I have, in the past, posted a link to this same information on the Brembo site itself, but I can no longer find that page. So, while I'm glad that 2Valve has not had a catastrophic brake failure (so far), and I did use DOT-5 in a Japanese bike back in the 80's for exactly the same reason he is using it, I will not be using DOT-5 in a BMW.

its strange that all the info regarding not using DOT 5 with all the associated problems iv'e never had any issues at all for nearly eighteen + years of use . the bm shop that i use to go to ( until he retired ) actually recommended it and was a stock item on the shelf and the new OE master cyllinder which i fitted is still working and not leaking after seventeen years of using DOT5 ( maybe different composite seals by BMW ? ) . me i'll keep using it in my BM .

1985 R80 Mono (Brembo Brakes)

My R80 was using Dot5 by the PO.
Purchased 15/7/10. The PO gave me a list
of the products he had been using. The brake
fluid was listed as Silicone Motorcycle Brake
Fluid.
Replaced the front rubber hose with a SS braided one
and refilled with HD (Sorry) Silicone Base Dot 5 Fluid.
Everything is still working fine.
He was also using Castrol GPS synthetic engine oil
and the joint between the engine and gearbox was
starting to sweat oil.
Changed to Casrol GPX 20w-50 and the sweating
of oil stopped straight away.

hi kutter, shame shame on you using a harley product on a BM it'll never be the same ! was going to try synthetic engine oil but wasnt game enough just in case it did weep ! thinking about trying penrite gas 10 when my rebuilt engine beds in , by memory one of our other members use it also.
5/81 r100rs shed find ? whats the story with that ? ( sorry to hijake te thread )

2valve wrote:hi kutter, shame shame on you using a harley product on a BM it'll never be the same ! was going to try synthetic engine oil but wasnt game enough just in case it did weep ! thinking about trying penrite gas 10 when my rebuilt engine beds in, by memory one of our other members use it also.

I'm using the Penrite GAS 10. $40 for a 5 litre bottle. Is this an oil thread now

SteveD wrote: Is this an oil thread now

Yes.
I use Penrite HPR 30 20W/60

im game if your game ! take a vote !
at the moment im using valvaline XLD classic to run the engine in then onto maybe penrite HPR GAS 10.