Silicone brake fluid vs normal?

[Eddie]

Does anyone on here use silicone fluid rather than the normal fluid that paintstrips everything and corrodes, what are the pros and cons of it?
I know it is very expensive but surely if it does the same job and lasts as long it's worth it isn't it?

I'm after advice as a bike i had in my shed under a cover in the corner, had unbeknown to me a leaky master cylinder... Fluid has dribbled down the handlebars over the top yoke and down the frame, paint stripping it, which obviously I'm not happy about, thank f*ck i had taken the tank off or that would have been wrecked too.

So as my Zephyr brakes and clutch have been totally rebuilt but no fluids added yet I'm wandering what to use as silicone doesn't seem to be recommended that highly, but for what reason??

Many thanks for any advice

Eddie

[David Richard]

hi yes i have used it for all of my bikes for 20 years for exactly that reason and it will never get any moisture brilliant stuff .david

[Eddie]

Cheers David, that's good to know you've been using it for that long with no probs. Is price the only reason people don't use it? Seems crazy when it can save you a respray!

[bunyip]

Conventional mineral brake fluid is hygroscopic, a fancy word for absorbs water and keeps it in suspension. Silicon fluid does not attract moisture but if any gets in it tends to accumulate and provides an ideal situation for corrosion.
Both needs to be replaced regularly. Silicon withstands higher temperature, say for racing, before losing feel or boiling the moisture.

[Eddie]

After studying the Internet it seems almost a 50:50 split opinion on it, with the main advantage being it won't damage paint. Seems its used more in race machinery for it's higher boiling point and as its changed regularly no water gets trapped at low points causing corrosion. I might give it a try as the bike will be stood most of the time indoors (shed), we'll see

Anymore advice welcome
Cheers eddie

[Stu]

https://www.hemmings.com/blog/2013/12/0 ... -you-care/

I've heard anecdotal evidence that some rubber seals are incompatible with silicon based fluids. I suspect from webpage above that most new seals are fine, but a seal that's been used with DOT4 may not be happy in DOT5.

Have thought about this many times, but always ended up using DOT4 and being careful with it. I have had the odd fluid fountain from the master cylinder reservoir spraying over paintwork, but it doesn't seem to damage anything in the couple of seconds it takes to wipe it off.

I HATE brake fluid... one thing I always wear gloves for. Is DOT5 any nicer to work with?

[Eddie]

Thanks Stu for the link, very helpful info, i was leaning towards trying silicone but am slightly put off now by stories of it not being compatible with older rubber seals, although I have used new genuine seals we're still talking old tech rubber. It does seem only modern bikes are using silicone fluids these days, also I noticed my ktm can't use dot 5 silicone in it's clutch, it must have mineral oil!.
Seems dot 5 is not recommended for hydraulic clutches and ABS systems because it can aerate when pumped causing a spongy pedal/lever...

I'm probably over thinking about it now, doing my head in!, think i might just stick with original dot 4 and change/check it more often

[Freddy]

Just use DOT 5.1

It's conventional, has the highest boiling point, and low viscosity.

As I always overhaul the calipers every brake pad change (only takes an additional 30 minutes at most) the fluid is routinely changed, so little water buildup. The reason I always overhaul the calipers is because I reckon you get way better brakes and far less pedal/lever travel with nice clean properly lubricated caliper pistons. They don't take that long to gunk up, or corrode if dry, and stick to the seals.

[Eddie]

Cheers Freddy, thanks for the advice i do intend to keep the brakes in tip top condition now the bike will not be being used all the time.... Although i know leaving a bike standing is not good for it either, you can't win really!

[hugojose]

Eddie, am not saying you should use one or the other....in general you will be fine using what the manufacturer recommends

But just to add to the discussion and hopefully more understanting

...I personally doubt that any rubber would not like silicone. The reason for the DOT thing is boiling temperature. Ignoring that water would be corrosive to some metal, it could be used on brakes hydraulics if the boiling temperature was not 100 celcius or 212 farenheit. The brakes can reach temperature of 1000 celcius or 1830 farenheit. That's the main reason for the DOT rating, the higher it is, the higher the boiling temperature...... when it comes to DOT 5 silicone based, the main thing is don't mix it with the other DOTs because they are glycol based, thus they are not compatible, however on a entire new system, you could use DOT 5 being the main difference it is not nasty. DOT 5 is mainly not recommended for ABS because it could 'airate', but that's not the case here.

.....all that said, DOT 5.1 has even higher boiling point that DOT 5, but is still glycol based, therefore nasty, and it could be mixed with the lower DOTs other than 5.