DOT 5 - Is this new to anyone else?

[Donald H.]

Re: DOT 5 - Is this new to anyone else?

Thanks Joe, I just ordered front and rear Raybestos caliper rebuild kits.

Don

[Ed D.]

Re: DOT 5 - Is this new to anyone else?

Thanks Joe for the assurance. I went to the garage to check my old container of DOT 5 for the certification, as I dont remember seeing mil std certification on the can. I must have finished the can, as it is not around. I will have to replenish my supply one of these days and will look for the mil std.
Ed

[Ronald L.]

Re: DOT 5 - Is this new to anyone else?

need to merge these two threads

[Richard M.]

Re: DOT 5 - Is this new to anyone else?

Call Ken McCormick at Lonestar Caliper Co. 903-829-8400, he told me not to use Dot 5 fluid something about the formulation had been changed, I
don't remember all the details of our conversation its been a few years ago but they should know from all the rebuilds they've done.

[Jim L.]

Re: DOT 5 - Is this new to anyone else?

Call Ken McCormick at Lonestar Caliper Co. 903-829-8400, he told me not to use Dot 5 fluid something about the formulation had been changed, I
don't remember all the details of our conversation its been a few years ago but they should know from all the rebuilds they've done.

That's the persistent folklore but so far no one has come up with any specifics.

I'm skeptical.

[Richard M.]

Re: DOT 5 - Is this new to anyone else?

Just try calling Ken and he will give you specifics.

[Jim L.]

Re: DOT 5 - Is this new to anyone else?

Just try calling Ken and he will give you specifics.

I'm not that motivated. DOT5 works fine for me, even in my road racing Corvette.

[Joe L.]

Re: DOT 5 - Is this new to anyone else?

Just try calling Ken and he will give you specifics.

Rich------


Well, I hope someone calls Ken and reports the specifics here. And, I mean REAL SPECIFICS, REAL HARD EVIDENCE, not this conjectural, anecdotal stuff.

[Duke W.]

Re: DOT 5 - Is this new to anyone else?

In order to achieve DOT certification, brake system hydraulic components, including fluid, must pass a battery of performance and compatibility tests, and claiming DOT certification without having successfully passed all the tests could result in serious civil or even criminal charges by the federal government against the vendor.

So, like others in this thread, I am highly skeptical that current DOT 5 fluid is not compatible with current brakes system elastomers.

But, as I have stated before, I highly recommend that DOT 5 fluid only be used for complete brake system overhauls, were everything is clean, dry, and clear of any traces of DOT 3 or 4 fluid, and that would include flushing all the brake pipes and hoses, new or used, with denatured alcohol and thoroughly drying. Also, all hydraulic components should be assembled with DOT 5. That means if you buy assembled master/wheel cylinders or calipers, you need to disassemble them, clean as above, and reassemble with DOT 5, because they are likely assembled with DOT 3.

Duke

[Donald H.]

Re: DOT 5 - Is this new to anyone else?

I'm not an engineer or chemist, but I've been reading available documents or referenced to documents like SAE J1703 and SAE J1705 and per these documents DOT 5 (SAE J1705) is compatible with the same elastomers as DOT 3, 4, 5.1 (SAE J1703) as Duke stated.

I found an interesting document (PDF attached) from a racing brake fluid manufacturer and it tends to support this. They do not discount using DOT 5 due to issues with seals and such, but do warn of potential issues with compressibility due to dissolved air, i.e. DOT 5 apparently can have significantly more dissolved air in the fluid than DOT 3, 4, or 5.1. This has the to potential of softer pedal and more pedal travel, especially at higher altitudes and higher brake temperatures. Thus this paper recommends that DOT 5 not be use in racing conditions.

But what I found very interesting in this paper is the following comment "It is best in very cold (think arctic) climates or in brake systems in weekend, antique, and collector cars that sit for long periods and are never driven far, although it is not suitable for ABS systems."

[Duke W.]

Re: DOT 5 - Is this new to anyone else?

Yes, it's my understanding that DOT 5 can dissolve more air, which can come out of solution and form bubbles at high altitude or by rapid, repeated pressure cycles, which is why it is not recommended for ABS systems. This is also why silicone fluid should be added to the master cylinder reservoir slowly so as to minimize turbulence that might cause air to be dissolved.

Also, we tend to think of liquids as "incompressible", but all are slightly compressible as expressed by the "bulk modulus" and silicone fluid has a lower bulk modulus than most liquids, which may cause increased pedal travel in severe service.

Back in the eighties and nineties when I ran my Cosworth Vega in track events with DOT 4 I always noticed an increase in pedal travel during the first session, and it remained so despite the hour or two between sessions when the brakes had likely cooled down to ambient. My first thought was rear drum expansion, but if that was the case, pedal travel should have returned to normal at the beginning of the next session an hour or two later, but it didn't.

I also tried braking in reverse just before the next session to activate the rear self-adjusters if shoe wear was the cause, but that never seemed to make any difference.

During the 75/100 mile drive home from Riverside/Willow Springs or the next couple of drives pedal travel would decrease back to normal. I never did figure out a logical explanation.

BTW, with the upgraded "Monza" front brakes (without installing the stamped steel dust shields to improve cooling) that had ventilated rotors and larger piston calipers along with the OE proportioning valve (that caused severe premature rear lockup with the OE solid rotor/small piston calipers) and the OE rear 9.5" drums (same as the F and X-body) nothing on street legal tires could outbrake me, and I just used the OE semi-metallic front pads and OE organic rear shoes. A couple of times a front brake locked up momentarily when I was passing a Porsche or Ferrari in the braking zones, which was easily stopped by a little less pedal force. The rears never locked, which is a good thing because that usually causes a spin.

I went through about six sets of front pads in the 5000 miles or so of track events over a 15 year period with only about .015" front rotor wear. I recall replacing the rear shoes when I installed the Monza front brakes in '81, but never had to replace them after that. I also disassembled the rear wheel cylinders at that time and found some corrosion with the car only being five years old. That's when I got religious about fluid changes. l usually ran four events per year, about 100-200 miles per event and changed the brake fluid at least once a year.

Duke

[Jim L.]

Re: DOT 5 - Is this new to anyone else?

I found an interesting document (PDF attached) from a racing brake fluid manufacturer.....

This has the to potential of softer pedal and more pedal travel, especially at higher altitudes and higher brake temperatures. Thus this paper recommends that DOT 5 not be use in racing conditions.

Just a hunch..... that manufacturer didn't produce or sell DOT5 fluid so they stood to lose a little coin every time someone bought DOT5 instead of their product.

Both of our road race cars have used DOT5 exclusively for thousands of track miles. While I can't speak to high altitude performance, I can address the matter of high brake temperatures and its effect on DOT5: There isn't any. Our cars' brakes would get so hot the rotors would turn blue and crack. The brake fluid never even noticed.

Thanks for your research, Don.

Jim

[Justin A.]

Re: DOT 5 - Is this new to anyone else?

actually Ken from Lonestar and Luke from CSSB are correct. Dot 5 is not regulated in the U.S. and the formula of it has changed since it came out. Whatever the new stuff is, it does not work. It will swell the seal up and dissolve them. From what I have come to understand is that the European countries I believe TUV does regulate it and theirs has not changed. I am not sure where to find European Dot 5 but that is suppose to work.

[Larry M.]

Re: DOT 5 - Is this new to anyone else?

Here is a link to one company/manufacturer that specifically states that that their DOT 5 fluid is for brake system use. The only problem is minimum sale is 5 gallon.........with 55 gallon being another option. Not many folks can afford this.

http://www.clearcoproducts.com/dot5-brake-fluid.html

I do not know this company and cannot recommend it at this time, although if you were to call and talk to them they might check out okay for use....as well as provide good info on what is currently happening with DOT 5 fluid.

I just checked the Brembo website and they too do not recommend DOT 5 for their products...............BUT THEY SAY IT IS BECAUSE THEY USE A DIFFERENT SEAL ELASTOMETER in their brakes that is no longer compatible with this fluid.

The only path forward I see at this point is for the DOT to investigate the DOT 5 manufacturers for compliance to their specs, or for a group of companies or individuals to legally challenge the DOT 5 brake fluid sellers to prove they are still in compliance. Neither will likely happen due to $$$$$$$$$$$ costs.

I guess the only other alternative is to do your own testing using Lone Star or CSSB or ??? (your favorite manufacturer brake components) and soak them in your favorite DOT 5 fluid and check the results. This is way to much for most folks (I agree) and so the change back to DOT 3/4 will eventually occur for most of us.

For racers like Jim L this becomes a big issue on who to trust for continued use of DOT 5. But if he has a source for both fluid and elastomer that still works, then he must always be sure to use that brand. But an occasional hot soak test with elastometer and fluid that he uses is still a good idea for safety sake.

FWIW.

Larry

[Duke W.]

Re: DOT 5 - Is this new to anyone else?

If some people contact DOT with the problem, they will likely investigate because it's a major safety issue. I'm sure the DOT web site has a link to send in a complaint.

Duke