Brake fluid choices

[gstallons]

What is your opinion on different types of brake fluids ? DOT3 or 4 v DOT 5 (silicone) fluid ......... I am thinking of changing to DOT 5 in the brake hydraulic sysytem(s). 

[-Martin.Glaeser-]

DOT 4

or

DOT 5.1

only

 

-M-

 

...TAPAtalk via Samsung Galaxy Nexus...

 

 

[GuzziMoto]

You can not switch from DOT 3 or 4 to Dot 5 (silicone) without changing out every seal in the system and completely flushing everything else. It is not practical.

There is DOT 5.1 which is not silicone and you can switch from Dot or 4 to DOT 5.1 without even flushing.

DOT 5 is pretty crappy fluid for performance riding. My Buell had it (it is a HD thing) and it sucked. The only advantage I can think of it it does not harm paint.

[dxhall]

 

You can not switch from DOT 3 or 4 to Dot 5 (silicone) without changing out every seal in the system and completely flushing everything else. It is not practical.

 

here is DOT 5.1 which is not silicone and you can switch from Dot or 4 to DOT 5.1 without even flushing.

 

DOT 5 is pretty crappy fluid for performance riding. My Buell had it (it is a HD thing) and it sucked. The only advantage I can think of it it does not harm paint.

[dxhall]

DOT 5 (silicone based fluid) is suitable for collector vehicles which don't get much use. It will not handle the temperatures generated by hard braking. When I tried it in my vintage race car years ago, I overheated it, got a spongy pedal and couldn't stop. Don't repeat my mistake.

[dale-j]

I have silicone based DOT5 in a vintage VW and for the intended purpose (slowing a 1900 lb car powered by all of 34 bhp) it is fine.  The car is driven infrequently and it is more important to not seize up wheel cylinders from sitting and moisture.  I was told at the time that silicone DOT5 fluids were NOT suitable for ABS, stability control systems (due to cavitation and foaming under high frequency applications) or any car that needed a high boiling point (high performance braking) so I have steered clear of this in anything remotely modern.

 

For my other vehicles and for the Guzzi, I tend to alternate ATE Typ. 200 and Super Blue with each bleeding, and use the ATE SL6 in my newer car that has a stability and traction control system (Acura).  IIRC the only way that the SL6 differs from the Typ.200 is that it is lower viscosity and therefore more responsive to the system interventions by the stability system... I've used both in the car and to be honest I'm not sure I can tell any difference at all.

 

I'm sure there are other high performing but not excessively hydroscopic fluids that will work similarly and will be available locally wherever you are, like the StopTech offerings or Motul RBF600, etc.....    IMO you get more benefit from changing it each year than worrying excessively about whether you have the "better" or "best" dry boiling point in the fluid you select.

 

Regards,

 

Steve

[68C]

I remember chatting to the Rotary Norton team at the Isle of Man TT races who mentioned not using silicon fluid on their race bike.

 

Their theory was the silicon is too slippery and caused the pads to drag on the disc - a bad thing on a race bike. 

 

Disc brakes automatically adjust as the piston slides through the square section seal until the pad makes contact with the disc.  The seal distorts as it attempts to grip the piston, when the brake is released it is this distortion that pulls the piston back slightly to allow the pads to clear the disc. It was the adoption of the square seal that finally cured the dragging problem early disc brake designers faced.

 

No doubt this 'slipperiness' problem can be overcome by the careful choice of seal dimensions, perhaps having it grip the piston tighter, but may cause problems with brakes not designed for silicon fluid.

[GuzziMoto]

I used DOT 5 on a race track, once. It was a Buell X1 (I also rode it on the street at the time), and it came from the factory with DOT 5. On the track, under hard use, the brake lever completely went away. The brakes faded so badly I was getting more deceleration from downshifting. The lever would come right back to the bar. It was hairy. I will never make the mistake of using DOT 5 again.

DOT 5 is not suitable for any kind of performance use as when heated it out-gasses which results in what is basically air in the system. The result is horrible fade, more then I have ever experienced with any other kind of fluid.

 

You do need to use different seals with DOT 5 then you would use with normal brake fluid. And once a system has been exposed to one type of brake fluid it is very hard to switch to the other as the two fluids are not compatible. It is easier to replace the system, master cylinder, caliper, and line.

[-Martin.Glaeser-]

Here are some of my private&proprietary principles on brake fluid:

 

(i) *DOT5.1* is compatible to both *DOT4* ( the mineral oil-based) and *DOT5* ( the silicon-based).

(ii) You may mix *4* + *5.1* .... Or *5* + *5.1*  

(iii) Never mix *4* and *5*.

(iv) A brake system which was initially filled with *4* cannot be turned into *5* (and vice versa) except you do total cleaning, and replacement of e.g. seals and hoses

(v) don't play around with your brake system!

 

-M-

[GuzziMoto]

I have always heard that DOT 5, being silicone based, is not compatible and should not be mixed with poly-glycol ether based fluids like DOT 3, 4, and 5.1 .

The seals for the two fluids are usually different and word has it that using the wrong fluid can cause your seals to swell resulting in brake issues.

If you can mix 5 and 5.1 it is news to me, and most of what I can find on the inner neck.

[-Martin.Glaeser-]

Hi,

for details on the various brake fluids you might want to study U.S. Dept. of Transportation DOT Standard No. 116; Motor vehicle brake fluids. http://www.fmcsa.dot.gov/rules-regulations/administration/fmcsr/fmcsrruletext.aspx?reg=571.116  (sorry, the details will come in heaps when u click there)

 

More simple reading is WIKI : 

DOT3: http://en.wikipedia.org/wiki/DOT_3

DOT4 : http://en.wikipedia.org/wiki/DOT_4

DOT5: http://en.wikipedia.org/wiki/DOT_5

DOT5.1: http://en.wikipedia.org/wiki/DOT_5.1

 

-M-

[-Martin.Glaeser-]

... mix 5 and 5.1 it is news to me...

I didn't  find my source of information anymore. Thus, I better corrected my statement above. Thanks GM!

 

-M-