Dot 5 Silicone fluid opinions

-
goldduster318 said:
... There are exactly zero silicone DOT3 and DOT4 fluids.
Click to expand...
Quite a mis-understanding. DOT 5 is a performance rating, not "silicone" (originally). Only recently has any glycol fluid been able to meet that standard. It was decided to term it "5.1" to not confuse with silicone fluid, but I am sure many do get confused. If looking for military surplus, they termed it "BFS" = Brake Fluid Silicone. There was talk of the military moving to glycol fluids to save money. Perhaps not wise because it costs much to haul equipment to remote areas, so you want the very best quality there, similar to how Everest climbers don't skimp on boots.
 
KnuckleDuster said:
... prove DOT 3 stops 3ft shorter my ears are open.
Click to expand...
Probably not possible, because brakes don't stop a car, tires do, and even drum brakes can skid the tires. The performance question is how evenly braking is applied, and the driver's ability to brake right to the edge of skidding, where you get the maximum braking. Drum brakes can be worse in the "evenly" area, and take much longer to cool down after braking ("fade" = melting friction linings).

The only place the fluid enters into this is that brand new glycol has a higher boiling point, but as it absorbs moisture that can lower below silicone, usually much sooner than most people flush in new fluid. Racers flush new fluid before each race, which is one reason they use glycol. Silicone's main advantage is in keeping the system corrosion-free and working long term.
 
Anyone remember why the early db systems used to have problems with pistons sticking,back in the day? Yeah they would rust up.And there was no silicon on the shelves in those years.
My KBs have been running silicon since assembled in 1998. I cannot recall ever opening the system since, and they are still performing just like new. I cannot see how water would get into the brake system.I mean as far as I can recall, the brake fluid molecules are smaller than the water molecules; so if the brake fluid cannot leak out, then how would water get in? And even if it did, how much and how fast?
Ima thinking somebody would have had to let it get in there. Accidently I'm sure. If I was in the least concerned about water getting into my silicon brake system, I would install a water-trap.
I put silicon in everything I own, and since I did my own miscibility tests, I am not afraid to add it to anything I own either.And I love it that it doesn't attack paint. Almost nothing will break your heart as much as wasting sombody's hi-dollar paint job.
This conversation has raged on for decades. I think it will go on for decades more.
 
Not used in racing.


"Because of the dissolved air, silicone fluids are up to three times more compressible than glycol based fluids. This can contribute to a slightly spongy feeling brake pedal, particularly near the higher end of their temperature range but well below the dry boiling point. While this is of absolutely no consequence for normal street use, this is why silicone fluids are not used in race cars. A spongy pedal makes it difficult to modulate the brake pressure under racing conditions."

Bleeding Air From Systems with Silic
 
GMachineDartGT said:
Not used in racing.
"Because of the dissolved air, silicone fluids are up to three times more compressible than glycol based fluids. This can contribute to a slightly spongy feeling brake pedal, particularly near the higher end of their temperature range but well below the dry boiling point. While this is of absolutely no consequence for normal street use, this is why silicone fluids are not used in race cars. A spongy pedal makes it difficult to modulate the brake pressure under racing conditions."
Bleeding Air From Systems with Silic
Click to expand...
After 16 years, my pedal feels exactly the same. Well exactly might be a bit overstated, cuz I can't actually go back in time and compare.lol. Suffice it to say that the pedal is hard like it is supposed to be.
Perhaps it would also be fair to remark that shortly after day-one, I installed Teflon lines on the front.
 
hmmm...did someone say this argument could go on forever?
Dot 3, Dot4, and Dot 5 w / or wo silicon will all stop your car equally well.
 
AJ/FormS said:
After 16 years, my pedal feels exactly the same. Well exactly might be a bit overstated, cuz I can't actually go back in time and compare.lol. Suffice it to say that the pedal is hard like it is supposed to be.
Perhaps it would also be fair to remark that shortly after day-one, I installed Teflon lines on the front.
Click to expand...
I doubt anyone here is using their brakes hard and hot enough to be able to feel/detect any sponginess due to fluid compressibility.

Now, NASCAR at Martinsville would be a severe test of anything in the brake system; it might show up very readily there.
 
Sponginess can come from several things. The largest is from air bubbles, second is flexible brake hoses and seals (why Teflon is better). Fluid compressibility is the final factor, and something you can't do anything about other than by selection of fluid. While silicone fluid is more compressible than glycol, most people wouldn't notice. You can find a web article where an anal engineer (U.S. owner of old British car, of course) did his own tests of silicone vs glycol. I recall he did measure a difference in pedal travel, but just ~10% of stroke. But, silicone is much more susceptible to entraining small air bubbles. Never shake the jug (not for James Bond) and if you drop the jug, give it a day for bubbles to settle out. Always pour it slowly down the side of the funnel, and good to wait a day after filling the reservoir before bleeding. Entraining air is the likely reason why silicone has gotten a reputation as "spongy".
 
any truth to leaving it in a hot or warm environment to get rid of bubbles?
i do know 2 guys who used silicon and have a soft pedal ,maybe they
weren't careful during the install.
...but that stuff can be pricey.
 
Silicon is a crystal extracted from rocks/minerals.
Silicone is a fluid or resin, usually.
Had to say something, so many people get confused by this.
 
IMHO, all subtleties aside..DOT 5 is going to be my choice of fluid w/upcoming brake upgrade, after seeing the nefarious stains of DOT 3 on my firewall after I meticulously strived to sparkle the Engine compartment, the performance parameters at high temps of Dot 5 will more than surpass my needs..just sayin'..
 
I appreciate everyone's thoughts and responses. I decided to go with the silicone dot 5. I had a brand new system with the exception of the proportioning valve. I bled the system starting with a bench bleed of the master cylinder, install MC on car and go to the right rear, left rear, right front and finished with the left front. Pedal is very solid and the little bit of driving thru the lane feels great and needs just normal foot pressure. My biggest reason for using the dot 3 is for the added protection of not having paint peel if I develop any leaks over the years. Again thanks for everyone's thoughts on this subject.
Rod
 
I think you made a good decision based on a new system. I would probably do the same.
 
One new data point. Silicone jugs typically state, "not for use in ABS systems". Car site lurkers have speculated why. Probably just a lawyer disclaimer since most/all ABS systems are qualified using glycol fluid. Somebody had to test this, so why not me? I had sucked the reservoir out during a pad change in my 96 Voyager w/ ABS, and had a gallon of silicone fluid on the shelf so went for it. It was easy to tell when the silicone (dyed blue) replaced the glycol bleed at each wheel, and didn't take much to change (~1/2 qt). The pedal is as firm as before, after the new pads wore to match the rotors. I did skid tests on a wet road and the ABS system activated and pulsed as it should. Couldn't tell if the pulsing frequency was different. The engineer in me thinks the only system difference would come from the different compressibility of silicone, but glycol can be the same or even more compressible with a few air bubbles in the system (easy to do). Seal compatibility shouldn't be an issue since silicone is more benign. Indeed, some 1950's cars required silicone fluid since glycol degraded the rubber seals.
 
You must log in or register to reply here.
-

Back
Top