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Model specific boards => Golf mk3 => Topic started by: sharki786 on 29 December 2012, 15:14

Title: brake fluid
Post by: sharki786 on 29 December 2012, 15:14

Which is better for long run (4-5 years) dot 4 or dot 5.1?
Thanks

Title: Re: brake fluid
Post by: trog_nfs on 29 December 2012, 15:16

Dot 4 is less hygroscopic than Dot 5.1, so it will last longer.

Title: Re: brake fluid
Post by: sharki786 on 30 December 2012, 10:45

Quote from: trog_nfs on 29 December 2012, 15:16

Dot 4 is less hygroscopic than Dot 5.1, so it will last longer.

Sorry mate but what does that mean??

Title: Re: brake fluid
Post by: thai-wronghorse on 30 December 2012, 11:22

Basically it'll absorb less water (moisture from the air) therefore not allowing the efficency of the brake fluid to diminish as quickly . 

Title: Re: brake fluid
Post by: Khare on 30 December 2012, 12:48

You're getting it wrong.

Dot 3, dot 4 and dot 5.1 are poly glycol compounds and dot 5 is silicone.

It's dot 5 that does not absorb water, but silicon is more compressible and hasn't got the lubricating properties of poly glycol so it needs to be used in a system that is designed for dot 5. Dot 5.1 is best for our cars for fast road/track, but it's expensive compared to dot 4, which unless you're real heavy on the brakes will be good enough for fast road.

Title: Re: brake fluid
Post by: VW BUSH on 30 December 2012, 16:26

Quote from: Khare on 30 December 2012, 12:48

You're getting it wrong.

Dot 3, dot 4 and dot 5.1 are poly glycol compounds and dot 5 is silicone.

It's dot 5 that does not absorb water, but silicon is more compressible and hasn't got the lubricating properties of poly glycol so it needs to be used in a system that is designed for dot 5. Dot 5.1 is best for our cars for fast road/track, but it's expensive compared to dot 4, which unless you're real heavy on the brakes will be good enough for fast road.

Correct, glycol based fluids are hygroscopic and are used to preserve rubber seals and flexi's in the braking system.
Silicone and and mineral oils are not suitable for use with conventional seals or junctions in the braking system.
Just use standard brake fluid and bleed it through well, I change mine with every pad change as its easy and cheap to do.

Title: Re: brake fluid
Post by: sharki786 on 01 March 2013, 15:05

Thought id bump this up. As some may know im sorting my whole braking system out. Im going to be refurbing the calipers and replacing the rears with mk4 calilers. My braided line kit is on its way and have yellow stuff pads & groovesd discs.
What my question is which dot 5.1 should i use? Any brands?

Thanks peeps

Title: Re: brake fluid
Post by: boneybradley on 01 March 2013, 15:27

dot 4 will be fine, i have even used it on a few track days without fade/boiling it

Title: Re: brake fluid
Post by: sharki786 on 01 March 2013, 16:06

Reason i want to use 5.1 is because i use my breaks hard and now im getting brake fade. So want to try out 5.1.
Motul 5.1 good shizzle?