The forks on my RB have been showing slight signs of leaking over the winter and as I will be making the trip to Switzerland for the International Meeting in June, I thought today it was time to replace the seals. When I put it all back together it would be a good idea to replace the brake fluid as it has not been changed recently. I’m thinking of using Silicone Dot5 fluid and wondered if anyone else has any experience of silicone fluid.
There was some discussion about this somewhere, and the fact that 1980’s brake systems should stick with what they are designed for, which I think is Dot3 isn’t it? Dot 4 absorbes moisture less quickly than Dot 3 but is the same Poly-glycol based fluid, so in that sense
it might not make much difference.
The Silicone based DOT5 is quite different and could damage seals or hoses it’s not designed for.
Also… Silicone based stuff (DOT5) doesn’t change colour as it absorbs moisture, so you don’t get a tell tale sign that your brake fluid needs changing, and it’s recommended you change it annually… but that’s a minor consideration if it’s going to stuff the lines up.
There is a DOT 5.1 which is also a Glycol based fluid, although I’ve never seen it anywhere.