All,
Installing a whole new braking system on my Demon.
Wilwood m/c, ‘73& up front disc, and right stuff rear disc setup (‘85 Caddy) caliper.
I’ve heard DOT 5 won’t harm paint but isn’t recommended for daily street use?
Anyone have experience with this?
Thanks all!

Wally.

It's working fine in my '72 Dart. Good firm pedal (nonpower front disc conversion) for years now. Tried it in the hydraulic clutch too but the Howe pull slave cylinder leaked it, so had to go back to conventional fluid there. Any recently manufactured brake components should have compatible seals.

DOT 5 silicone fluid does not absorb water like DOT 3/4/5.1 glycol does, so any water in the system will collect at a low point, usually wheel cylinder or caliper.
This can cause localized corrosion (as opposed to the wet glycol which rusts everywhere just a little bit).
On the other hand, silicone won't attract water out of the air in the first place.

And it will not turn into a goo or explode if inadvertently mixed with glycol. It just won't combine, and the purple dye will eventually migrate from the silicone to the glycol.
There is a large amount of misinformation and phobias on the Internet, but you have to do your own research to find out what's real and what's not.

The only disadvantage I know of is that it has to be bled slowly and carefully, because air bubbles entrained in the fluid take FOREVER to settle out. Same caution with shaking the container or pouring it into the master too fast.

I have been using DOT 5 in my cars since 1981. It is the very best thing out there. I put it in my '67 442 in 81, drove it till 87, parked it till 2010, dug it out of storage, and the brakes still worked perfectly with zero issues, so I drove it on Power Tour 2011, Drag Week 2014, and Cars 'n Cones Road Trip 2016 with no issues. And I live in damp, humid MInnesota. How can you beat that? I rebuilt the brakes in my 65 F100 in 1990. Let a friend drive it for 6 months, then parked it till 2019. Drug it out of storage from my neighbors barn. The brakes are still working.
I put in my 67 GTX in 2002 when I put the wilwood discs on the front. Wilwood said do't use DOT 5 but I did it anyway. Never had an issue. Race cars, street cars, cars that get stored, DOT 5 always works.
Just do it!

Edit: I agree on the bleeding. I usually allow a week or so for that. Pour it slow and careful to avoid bubbles. I bleed the master, install it, do an initial bleed using a slow downward pump of the pedal with the screw open, and a slow release with the screw closed. I do all 4 and don't have to get it perfect. Then let it sit for a few days for the air to collect. Then I jiggle the pedal just a tiny bit while watching the master for little bubble to rise. I pause for a few minutes, then jiggle till the bubbles stop. Then repeat daily till no more bubbles. Usually the pedal is rock solid by then. If not, repeat the bleed thru the screws.

I have read that due to the air entraining characteristic with Dot 5, the reason newer cars cannot use it is because they have anti-lock brakes. And the anti-lock solenoid pulses which would aggravate that issue. That is what i’ve always believed. I use it in my 68 b body with manual disc brakes and it works great for 10+ years.

There is no reason on earth why the OEM's would use DOT 5. Dot 3 is cheaper, faster to bleed, and will outlast the warranty, yet foil the brake system when the car is old, prompting new car sales. DOT 5 is for cars like ours.

You should be OK using it IF the system is all new or is completely rebuilt before installing it. I don't think I would use it on a system that previously had regular fluid in it. Strange recommends against it in their stuff for reasons stated - absorbs water, slightly compressible possibly causing a soft pedal, etc.

I agree I've used DOT 5 since the 80's. Never had a corrosion problem, leak, or any other issue. Use it in the drag car as well.
Doug

dot 5 in both my street cars for decades. never an issue.

Use it in my street car

Me, too.

I don't, Dot 4 only now due to the brake makers like Wilwood saying to not use Dot 5 in their parts

I asked Wilwood if I could use Dot 5 in their clutch slave cylinder and they said I could, but still recommend Dot 3 or 4.

After many years of telling us not to use DOT 5 in their stuff, Wilwood has now flip-flopped and says it's OK, and now they even sell it.

I haven't used DOT 5.
When I put new master cylinders in my racing Daytona with Wilwood system, I used this Jeg's product, DOT 4.
https://www.jegs.com/i/JEGS/555/28073/10002/-1

Cool! 479* Racing brake fluid. Is that made by the same company that made the 200mph Racing tape?

5.1 for me in a drag, or street car

What is the difference between DOT 5 and 5.1?

DOT 5 is silicone
DOT 5.1 is glycol.

Thank you very much!
All advice given here was great and much appreciated!,

DOT 5 it is.

Wally.

DOT 5 has disadvantages. DOT 4 has a higher boiling point than DOT 3 and is what I use.

Moisture will get into the system from the atmosphere. DOT 3 & 4 will absorb it and take it along with it when you do an occasional bleed and flush. DOT 5 will allow it to settle out and rust/corrode parts.

DOT 3 & 4 will hurt the paint. Don't spill it, don't be a slob when bleeding and don't have any leaks. That's my plan.

5.1 has a higher boiling point than silicone too.

i found this info in my documents-----

Brake fluid is engineered to do specific things in specific ways. So it's important to put the right kind in your car or truck.

DOT 3 and DOT 4 brake fluids are glycol-based. They're used in most modern cars and trucks, because they work with ABS brakes. DOT 4 has a higher boiling point than DOT 3. You can use DOT 4 where DOT 3 is called for, but not the reverse. Using DOT 3 in a DOT 4 brake risks boiling the brake fluid. Glycol-based fluid can absorb water over time, which leads to corrosion. It also changes the quality of the fluid in braking. This is one reason to have your brake fluid changed regularly.

DOT 5 is silicone-based. Its advantage is that it doesn't absorb water, so it doesn't corrode brake systems. However, it doesn't work with ABS brakes. So it's mostly for older cars and trucks.

I saw a video of dot 5 swelling seals is that true.? That's the only reason I have been hesitant to use it.

I totally understand the paint issue, but as long as you don't use a squirt pistol to add fluid I would just be careful. Talk to strange, mark williams, or wilwood they all recommend 5.1.

I have been using Dot 5 in my all cars for at least 30 years, have it my '70 Roadrunner that is in that 30 year range, drained some at all the 4 corners a few years ago and it still had a bit of that purple look to it. The reason I went to Dot 5 30 some years ago is that after 2-3 years of Dot 3 fluid I was having brake leakage from the wheel cyls due to rusty bores, I live where we have that good old white crap, in the snow belt for 1/2 a year. Not to mention it doesn't destroy your paint!!!I I also have it in different year Vipers, '02, '03 with ABS and no problems.

If this was true then that means it would/could cause brake failures. Can you imagine the legal liability for someone selling a product, that if misused, could kill you?

What is interesting about this whole question is that when this came up 10 years ago or more, the majority said don't use it. Its good to see "we" have become more informed.

some years back I saw or read something about dot 5 swelling seals/rubber stuff. i'd been using dot 5 on one of my cars for several years and thought i'd better check this out. it was complete bunk. no damage and everything was as good as the day it was installed. I don't understand the anti dot 5 thing. I probably have close to 25yrs on the brake system with dot 5 and the car has never stopped better.

The reason I have wanted to do this was I have a charger and belvedere that sit for long periods and i have had rusty seepage from the master cylinder pushrod area that eventually eats all my firewall paint below the master. If this would stop that it would be great!

go for it. your reasoning is the same as mine. both my cars are fine with dot 5.

So just drain as best I can and refill?

you need to flush the dot 3 out. dot3 and dot 5 are not compatible. when I switched over I took the master cylinder, distribution block and wheel cylinders apart and cleaned all the dot 3 off/out of them. I took a couple cans of brake cleaner and flushed all the lines. it's a little work but not difficult.

DOT 3/4 and DOT 5 are not miscible. But they do not react with each other. The glycol and the silicone oil will form two separate layers if mixed. That's all.

You want to get all the glycol out that you can, only because any that is left will gradually attract water and cause corrosion where it sits.
DOT 3 & 4 also have a lower boiling point than 5, so any glycol left in the system will boil first