Dot 4

[Paul Marx]

Maybe a silly question but I'm about to renew the brake fluid on my SF2 still running the original Brembo gear. I bought a bottle of Dot 4 fluid but it turns out that the stuff is synthetic. Is it OK to use that with my old seals? I thought Dot 4 was mineral.
Ciao
Paul

 

[Reggie3cl]

I use DOT5.1 which is synthetic based and is fine.  I think the DOT5 silicon stuff is not compatible with Brembo seals.

    DOT 2 is essentially castor oil;
    DOT 3, DOT 4, and DOT 5.1 are composed of various glycol esters and ethers; and
    DOT 5 is silicone-based.


http://moodle.student.cnwl.ac.uk/moodledata_shared/cdx%20etextbook/dswmedia/brakes/brake/comp/brakefluid.html

Only reason I use 5.1 is that it doesn't seem to strip paint.

 

[scuderia]

   DOT 3, DOT 4, and DOT 5.1 are composed of various glycol esters and ethers..
   

and are all compatible

 

[Paul Marx]

Ok, thanks. I just need to get down to it then!
Paul

 

[GregT]

If any of you do use Dot 5 silicone, for gawds sake put a sticker or something on the bike saying so....I just had a Ducati through that had Dot 3 added on top of Dot 5....Orange jelly sums it up.
A full system strip and clean out - brakes and clutch too.

 

[1200ts]

I spoke to Brembo about 10 years ago in regards to DOT 5 silicone brake fluid. The answer was the rubber we use in not compatible with silicone fluids. So don't use it.

 

[jotajoe]

I have read that Dot 4 and Dot 5.1 brake fluid are Polyethylene glycol based. They are compatible so if you drain Dot 4 you can fill with Dot 5.1 without flushing.
It is very important to be aware that Dot 5 is a completely different product to Dot 5.1 in that it is synthetic and not compatible with Dot 4 and is detrimental to the compound the Dot 4 type seals are made of.

I understand Dot 5.1 has a higher boiling point than Dot 4 which makes it more suitable for race applications. It is however more hygroscopic ie it soaks up water more readily and this means that it needs to be changed more frequently.

This is my understanding but please as this is brakes do your own research !!!!

joe

 

[Simonr501]

I believe you are spot on Joe.
Been there, done that, got the 'T' Shirt regarding Dot 5 and the standard Brembo seals.
Dot 5 is NOT compatible, it swells the seals over time until the master cylinder pistons stick!

 

[Rusty Spokes]

I've been using a synthetic DOT4 for years.

Synthetic no problem with the original Brembo parts.

I've heard of bad experiences with DOT5.

 

[Paul Marx]

Thanks again all.
Brakes done with Dot 4 synth.
Now change fork oil and fix instrument holder again, then change primary chain and put in one of Andy's Merc. duplex, then change swingarm bearings, and if I find the time mount the horns.

Then on to another machine. Track day on May 27th, don't know if the track bike will be ready in which case I'll take the SFC but need to change primary and secondary chains on that.

Ciao
Paul