benrep

I can't find it on here but I remember reading of problems lately with dot 5 silicone brake fluid. I have used it in many old vehicles over the years with great results. Has it changed? I am finishing up a 1954 GMC truck brake overhaul; new steel lines, hoses, master, wheel cylinders, and would love to ship it with dot 5. I also want to convert my 1960 C1 to silicone when I do all the brakes on it. So if it isn't working any more I need to know. Nothing bad shows up when googled, pretty sure I heard it here. Let me know if you have facts on this issue, thanks.

Scott

Rdelvalle

My 1959 Vette has DOT 5 Dow Corning Silicone brake fluid, The person I bought the car from had all the brake system restored including pads. pistons everything. He fill the system with the Dow Corning Dot 5 brake fluid. According to him and my Google searches this fluid has an infinite life because it does not absorb moisture (is not hygroscopic).

I can not comment on how good or bad is it because I have driven the car very few miles. We have been doing a full frame on restoration for over a year. The previous owner had the car for 40 years but did not drive it much and I do not know when he did the brakes. Good or bad I am stuck with the DOT 5 for now.

Robert61

I've had it in my GTO for 6 years and I'm extremely glad it is. I cut a front brake line do to a bad mechanic, me. The fluid went everywhere slinging off of the wheel. If not for dot5 there could have been a lot of costly ruined paint.

Bill Pilon

I put dot 5 in my 60 Vette about 15 years and several thousand miles ago, have trued the the drums and arc ground new shoes since then but no problems with the hydraulics, I have dot 5 in all my cars that don't have abs, no problems with any of them.

Bill

Factoid

There is a a lot of negative urban legend out there around DOT 5 ( silicone based) brake fluid. Little is true. I believe some of it comes from the general lack of approval for racing and other “official” opinions. One that is true is that while it doesn’t absorb water, it does absorb air and can sometimes present challenges in bleeding your brakes. However, for this very reason it is superior for classic cars that are not driven as often or see extended periods of storage. It is also true that it cannot be mixed with mineral based traditional (DOT 3, 4 or 5.1 fluid). Simply draining your system is insufficient, it must be flushed. Therefore often the decision to go with silicone fluid is made when a completely new braking system is installed.

Bottom line, make the choice that works best for you and be happy with that choice. Either will work.

jim lockwood

Can you explain this a little more?

jerry gollnick

I live in the mountains and have heard of issues when going from 4000 or 5000 foot elevation to 8000 plus. Air bubbles form in the system at the lower atmospheric pressure and cause mushy brake pedal.

C.T.

Some people claim that repeated full-on braking results in a soft pedal with silicone, but I'm skeptical about that. I think its more likely due to air in the system.

There is a lot of discussion, both pro and con, over on the NCRS Technical Board. Personally, silicone has been great for me. I had it in my 72 for years, and my 57 is now over 20 years with silicone. It doesn't get a lot of miles, but I haven't had to touch a thing.

MOXIE62

I think performance wise it holds up as well as the others. I just had a problem with leaks at the brake line fittings. I have the correct open end wrenches for flare tubing so I'm getting good torque, but some would leak. Now it could be the stainless steel brake lines that the restorer installed. If I was doing it, I would of used steel lines which for me seals better.

MikeM

It would seem to me that if air bubbles form in the system at lower altitudes, it would be a reflection of a fault in the brake system. Not the fluid. I don't drive at 5000 feet, let alone 8000 so that doesn't affect me anyway.

Man up suppliers. What's the real problem?

But, I have Dot 5 in 4 different old cars and one motorcycle. Been in there for years. I never had problems with getting air in the system. Either driving , pouring it out of the can or bleeding. No service require on any of it in years.

The lasted Dot 5 bashing has come from the suppliers of brake calipers, warning that warranty is void if Dot 5 is used. That's fine but I've yet to see ANY of these dooms dayers step forward and tell the peanut gallery specifically why the warranty needed to be voided. Have you?

MOXIE62

I was told dot 5 causes the rubber cups to become soft and leak. Who knows, maybe they have stock in dot 3 and 4.

Tom Austin

I've had Dot 5 in my'66 for 40 years! . . . no issues at all!

C.T.

The caliper suppliers and rebuilders claim problems result from the newer Dot 5 which supposedly is different. I haven't seen anything that substantiates that, but my fluid and components are definitely not 'newer'.

MikeM

Federal FMVSS standards have been in place for years, requiring extensive testing to circumvent any incompatibility between fluid and rubber components.

All brake fluids sold OTC today casue the seals to swell a slight amount. On purpose.

So, are the rebuilders/supplier using component parts that are cheap Chinese KO's that don't have to follow the rules or why is it that their rubber parts are no longer compatible with Dot after being accepted for years and being used by government military forces all over the world?

jim lockwood

Toro poo.

See my vintage racer in my avatar? Thousands of road racing miles with "full on braking" several times per lap and never, ever a problem with the DOT5 fluid.

Avispa

Debate the merits of silicone v every other kind of brake fluid all ya want. Silicone brake fluid is harmless to paint. Spill a little of the other stuff on your freshly restored suspension parts or a nice shiny fender and then call me back.

427/42566 coup

rebuilt master and replaced front and rear calipers many years ago on my "66" No problems with silicone dot 5

Factoid

Jim, I cannot explain why they say DOT 5 is not recommended for racing or performance driving, but I know that is exactly what Wilwood and other aftermarket brake suppliers put in their instructions. Perhaps the lawyers told them it would limit liability in event of a brake system failure? What I do know is that I used it in the brand new brake system in my ‘41 *****’s with no issue at all, it doesn’t eat paint like glycol based fluid does, and I’ve never had a bad experience or had friends with bad experiences, yet the rumors persist.

jim lockwood

Rumors. I think you nailed it.

We've run DOT5 in both my vintage racer (see avatar) and my bride's track car (also a Grand Sport reproduction). Neither vehicle has ever had a brake issue of any kind. In fact, the brakes on my vintage racer are so good that I count on them to let me make passes under braking.

Too, being basically a lazy individual, having DOT5 in the brake lines has meant I haven't had to bleed the brakes before every track event. I hate bleeding brakes.

Jim

GUSTO14

I too have been using Dot-5, Silicone brake fluid for decades with excellent success, in a wide variety of vehicles. I will very likely continue using it as I have in the past, until I personally experience a problem I believe is related to the use of Dot-5 brake fluid. And of course with due regard to any component warranty impacted by its' use.

In the mid 80's I discovered the we were converting all of our rolling stock (with hydraulic brake systems) in the Marine Corps (as was the U.S. Army), to silicone (Dot-5) brake fluid. We were purchasing it in 55 gallon drums by the pallet from Dow-Corning. At the time the stated purpose was to reduce maintenance costs. Much of our rolling stock sits for extended periods of time. Particularly equipment intended for use in an expeditionary environment (re: time of War). Very often when a piece of equipment was needed for use or training purposes, it would be sidelined for maintenance to repair the brakes. It was a never ending battle to keep the equipment in a state of readiness. By switching the brake systems to Silicone brake fluid our maintenance time and costs were reduced significantly. If it was good enough to go to War, it was good enough for me to use.

Here is some excellent technical information related to the use of Dot 5, Silicone Brake Fluid, I found at the Type34 Registry, Technical Library. While I can not verify the veracity of all of the information, I can say it is consistent with what I have learned and personally experienced regarding Dot 5 Silicone brake fluid over the past 35+ years.

Good luck... GUSTO