5.1 Brake fluid

[Andrew S]

I know that 5 is silcone but am I correct in thinking its compatable with DOT 4 and therefore I could bleed brakes flushing the 5.1 through the 4?

Cheers
Andrew

[singapore stag]

Not sure but I used LDparts fluid and it reads.....

Brakes - Brake Fluid 5.1 GBF5102

DOT 5.1 has a wet boiling point of 375 degrees. Better yet, DOT 5.1 is half as viscous as DOT 4. DOT 5.1 provides quicker lever response, better modulation and faster pad retraction. It can be mixed with DOT 3.0 and DOT 4.0 Here are dry Boil(zero water) and wet (3%water) Boil points Fluid Spec..... Dry Boil point......... Wet boil Point DOT 3.0..................401ºF.....................284 º F DOT 4.0..................446º F....................311º F DOT 5.0..................500º F....................356º F....This is SILICONE FLUID DOT 5.1..................518º F....................375º F So for safer braking especially when your car is used in mountainous areas and in Europe use 5.1 the most up to date and safest Fluid. Better pedal feel than Silicone where already present compressibility increases with heat. Sukh.

[Andrew S]

Thanks, this is really interesting

Looks like I can and I have 1.5litres of the 5.1 to play with so will almost flush the 4 out

Andrew

[Stagdad]

I recall that someone on here used it and soon after the brakes started binding .turned out it had swolen the rubber seals in the pistons.think they reverted back,may be it was the mixing of the two types that caused the problem.
Cheers Steve

[Andrew S]

Thanks Steve mmmmmmmmmmmmmmm..................Ill rethinks I think

[Stagdad]

Not saying it's not compatable ,just one story I heard .certainly not conclusive,others will no doubt have more firm facts

[Daz]

I always used 5.1 in my TVRs after boiling the fluid and experiencing very scary brake fade while out playing hard one day. Never had brake fade again and no problems with seals.

[wilf]

IIRC, it was DOT 5 (i.e. the silicon fluid) that could cause some seals to swell?

[Stagdad]

I think you are right Wilf

[Andrew S]

I just know that this may be a stupid question, but on the bottles it says "synthetic", so to me that says non mineral, or is that the same thing? Silicone to me sounds more like a sythetic.

Am I losing the plot?

[wilf]

I think the word "synthetic" is as overused as "turbo" was in the '80s. From a chemists' point of view, surely all brake fluids are "synthetic", since none of them can be found naturally.

Dot 5.1 just has a different chemical base as I understand it.

[new to this]

i dont think you can mix dot 5 with dot 5.1 ,dot 5 is silicon as you know

[andrewc]

Dot 5.1 is not Silicone.
See

http://en.wikipedia.org/wiki/DOT_5.1

[wilf]

So the previous poster was, in fact, correct