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#2312692 - 05/28/17 10:19 PM Talk me out of DOT 5 brake fluid?
GoodysGotaCuda Offline
5.7L Hemi, 6spd

Registered: 11/23/04
Posts: 23914
Loc: Texas
I am working on hydraulics these days and am looking to pick a brake fluid to go with. As my car is freshly painted, I am naturally not too thrilled about conventional DOT 3/4 brake fluids being near my car, if I can help it.

For now, my car will be a primarily street car, some spirited driving and the occasional autocross event. I do not have plans for heavy, high-speed/repeated , braking at this time [road course].

I would like to use DOT5 in my hydraulic clutch and brake system and am curious to hear your experiences.

Wilwoods DOT5 has a 500°F boiling point. Their best DOT4 is about 600°F.
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2016 BMW X1
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#2312717 - 05/28/17 10:46 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
Jeremiah Offline
master

Registered: 03/03/03
Posts: 7956
Loc: Rogue River, OR
I like Cartel brand Dot5. It doesnt seem to foam up like many others I have tried. That said I have not tried Wilwood Dot 5

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#2312735 - 05/28/17 11:19 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
RylisPro Offline


Registered: 06/18/07
Posts: 2146
Loc: NorCal

http://www.castrol.com/en_au/australia/products/cars/brake-fluids/react-srf-racing.html

Only brake fluid I ever use, even in my S2000 street car which is a rare blue color.
Brake fluid takes time to strip paint and unless you spill it all over it should not be a problem

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#2312792 - 05/29/17 06:30 AM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
dickdale Offline
enthusiast

Registered: 03/18/10
Posts: 258
Loc: The Netherlands, OV

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#2312802 - 05/29/17 07:13 AM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
HUSTLESTUFF Offline
pro stock

Registered: 01/21/03
Posts: 1325
Loc: NORTHERN CA
I wouldn't talk you out of it. On a new build with all new lines and fresh paint, pour it in. If you have a leak no peeling paint while you tighten up the fittings. If you later decide to go balls out on a road course, once you know there are no leaks, swap it out for some race stuff.
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#2313030 - 05/29/17 01:39 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
68rrunner Offline
member

Registered: 02/06/10
Posts: 130
Loc: Mountain View, CA
Whenever I bleed a fresh system I keep a squirt bottle of Simple Green handy. Any spills or leaks are vigorously sprayed.

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#2313047 - 05/29/17 02:02 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
69hemibeep Offline
super stock

Registered: 08/04/05
Posts: 1056
Loc: Az
I have put DOT 5 in 2 new builds and I will use it in the next one. Of course they had all new parts.
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#2313654 - 05/30/17 02:56 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
72Swinger Offline
master

Registered: 02/23/11
Posts: 4284
Loc: Nebraska
Motul, just be careful and rinse it off quick if you spill.
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#2313720 - 05/30/17 04:43 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
Not_A_Duster Offline
master

Registered: 06/03/03
Posts: 7373
Loc: SK. Canada
Demon got all new cylinders, lines, prop valve and master cylinder when I had it apart. Been using Kleen Flo DOT 5 since then (2007) with not a single issue.

Car of course brakes much better after changing out the tiny drums it came with, so I can't speak to any potential performance differences between the fluids.
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#2315800 - 06/04/17 12:18 AM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
Hemi_Joel Offline
master

Registered: 01/19/03
Posts: 5252
Loc: Minnesota
I first used dot 5 in 1981, and it is so awesome, I always use it in any thing that matters ever since.
I put it in my 442 in 81, drove it untill the end of 1987, stored it for 23 years, then drove it on power tour
Without changing fluid or touching the brake system. Try that with dot 3!
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#2315835 - 06/04/17 05:57 AM Re: Talk me out of DOT 5 brake fluid? [Re: Hemi_Joel]
Supercuda Offline
I Live Here

Registered: 09/04/07
Posts: 12427
Loc: West Texas
Originally Posted By Hemi_Joel
I first used dot 5 in 1981, and it is so awesome, I always use it in any thing that matters ever since.
I put it in my 442 in 81, drove it untill the end of 1987, stored it for 23 years, then drove it on power tour
Without changing fluid or touching the brake system. Try that with dot 3!


Pretty sure I wouldn't try that with anything.
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#2315840 - 06/04/17 07:03 AM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
70Cuda383 Offline


Registered: 10/07/03
Posts: 21330
Loc: Marysville, O-H-I-O
I had heard that moisture in the system will turn dot 5 to hard solid silicone. No truth to that? All brake systems pick up moisture over time, which is why they rust from the inside too, and fluid turns dark brown or black without regular maintenance.
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#2315911 - 06/04/17 10:56 AM Re: Talk me out of DOT 5 brake fluid? [Re: 70Cuda383]
Mattax Online   content
super stock

Registered: 02/28/10
Posts: 938
Loc: Phila. Pa.
See if you can find anything in print (including internet) that supports that claim.

If you want my guess, it sounds like something posted in sarcasm that was then repeated as fact.
First of all, the DOT designations are part of the FMVSS - Federal Motor Vehicle Safety Standards. They're there to protect us (and the manufacturers) on critical items. So a fluid that turned solid making the brake system completely useless would never have made it into the standard except as a major F-up.
Second, silicone based (primarily dimethyl polysiloxane fluid) was created in large part because it is not hygroscopic.
For that reason FMVSS 116 (Brake Fluid standards) test procedures for DOT 5 relating to water absorbtion are different than for DOT 3 and DOT 4.

FWIW, SAE J1704 is where the composition of the different brake fluids is described. That's an industry standard rather than a Federal standard. The Feds only care if it works, not how it works.

As a result, DOT 4 usually has esters as well as glycol. It mixes with DOT 3 and has similar viscosity. Both absorb moisture over time. Both should be changed as needed; If racing, the moisture lowers boiling point and increases compressiblity. If just regular or weekend driving; the corrosion inhibitors get used up and rust can become a problem.

DOT 5 silicone based has several characteristics that make it unsuitable for certain uses. The viscosity doesn't work well with some ABS. In some environments, moisture that does get in the system could (theoreticly?) collect in low points. (I suspect if this was a real issue, we'ld hear and read anecdotal stories about it). Finally it is more compressible than the glycol and ester fluids. This compressibility goes up with temperature.

Road racing requires every bit of pedal feel and braking performance possible. Road courses also require repeated braking that can elevate brake fluid temperatures far higher than seen on most public roads or other competition venues. A pedal that gets spongier and travels further during a race is at best disconcerting!

One public road situation where brake fluid can get pretty hot is long and repeated downhills with heavy braking loads. So yea if you're driving your classic in places where the brakes get hot enough you can smell 'em, DOT 5 may not be the best choice there either.

So to the original question by the OP, for many situations DOT 5 is fine. Yours seems like it would good for what you want and plan to do.


Edited by Mattax (06/04/17 11:12 AM)

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#2316061 - 06/04/17 03:28 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
72Swinger Offline
master

Registered: 02/23/11
Posts: 4284
Loc: Nebraska
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#2316086 - 06/04/17 04:05 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
Supercuda Offline
I Live Here

Registered: 09/04/07
Posts: 12427
Loc: West Texas
I dunno what's with the Aussie brake fluids being linked, how about y'all kink a North American source?
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#2316171 - 06/04/17 06:29 PM Re: Talk me out of DOT 5 brake fluid? [Re: Supercuda]
RylisPro Offline


Registered: 06/18/07
Posts: 2146
Loc: NorCal
Aussies seem to do motorsports better than us Yanks, burnouts too!
One can easily get Castrol SRF or Motul from Summit, Amazon, major race tracks, etc.

The good stuff doesn't come cheap though!
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#2316249 - 06/04/17 08:06 PM Re: Talk me out of DOT 5 brake fluid? [Re: Mattax]
jcc Offline
I Live Here

Registered: 12/21/03
Posts: 16735
Loc: Trumussia
Originally Posted By Mattax
Finally it is more compressible than the glycol and ester fluids. This compressibility goes up with temperature.


I concur with most of your other points, but I have "read" the compressibility issue with DOT5 is, it traps/entrains air when pouring, and first impressions just after installing, leads to the compressibility observations, unfairly, if confirmable. The rising temp issue leading to increased compressibility, is the first I have heard of that condition.

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#2316331 - 06/04/17 09:57 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
Hemi_Joel Offline
master

Registered: 01/19/03
Posts: 5252
Loc: Minnesota
Any car with DOT 3 that I have left sit for more than a couple years has no pedal when I get it out of storage. The fluid has absorbed moisture and rusted up the cylinders. Minnesota is damp. My experience related in the post above positively demonstrates that DOT does not attract moisture and ruin the brake system. For those of us who store our cars over the winter or longer, this is vitally important. We don't want to rebuild the hydraulic system of the brakes every other year. All of the internet hype about the drawbacks of DOT 5 is irrelevant to 95% of users, including me and the OP.
In 2002 I bought a set of Wilwood front disc brakes for my race car. They had a tag warning not to use DOT 5. I called them and asked why. They said DOT 5 is not hygroscopic, so moisture will collect in the brake system and it will fail. I called bs on that and put in DOT 5. 14 years later I still have those brakes and they have not yet failed or had any issues. Wilwood has since changed their tune, and now they sell DOT 5 with their own name on it, they still say don't put it in a race car. I suppose in another 14 years they will sell race car DOT 5.
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#2316350 - 06/04/17 10:31 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
GoodysGotaCuda Offline
5.7L Hemi, 6spd

Registered: 11/23/04
Posts: 23914
Loc: Texas
Thanks for the feedback all. I went ahead and bought DOT5 and have gotten the clutch out of the way thus far. Even if I were to swap it out every year for moisture, the peace of mind is worth it.
_________________________
1972 Barracuda - 5.7L Hemi, T56 Magnum 6spd - Build Thread
1976 Dodge Warlock - "Her Truck" - 360/727 2wd
2016 BMW X1
2016 Subaru WRX

Build page -> https://www.facebook.com/GoodysGotaHemi<-

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#2316402 - 06/04/17 11:55 PM Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda]
RUNCHARGER Offline
I Live Here

Registered: 01/20/03
Posts: 15250
Loc: Chilliwack B.C. Canada
I use DOT5 in my stuff too with no problems. It's nice not worrying about it when it gets on the backing plates and painted calipers when bleeding too.
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