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Re: Talk me out of DOT 5 brake fluid? [Re: jcc] #2317024
06/06/17 05:27 AM
06/06/17 05:27 AM
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Originally Posted By jcc
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.


A reason for the assertion of compressibility is that if dot 5 container is not handled very gently, that very fine air bubbles can be produced in the fluid that will cause this problem as air is compressible. The key is to not shake the container and if it has been do not use until fluid is again clear. I have no idea how long that might take.

Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2317831
06/07/17 09:07 PM
06/07/17 09:07 PM
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I just recommend what handles actual use the best. I dont really care what is best at sitting still. People out there beating the snot out of their cars lap after lap, I can pretty much promise do not use DOT 5.


Mopar to the bone!!!
Re: Talk me out of DOT 5 brake fluid? [Re: Sxrxrnr] #2369449
09/12/17 02:21 PM
09/12/17 02:21 PM
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Originally Posted By Sxrxrnr
Originally Posted By jcc
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.


A reason for the assertion of compressibility is that if dot 5 container is not handled very gently, that very fine air bubbles can be produced in the fluid that will cause this problem as air is compressible. The key is to not shake the container and if it has been do not use until fluid is again clear. I have no idea how long that might take.


I know this is an older post, but I heard of the bubble issue too. I read somewhere to put container of brake fluid in a pan of boiling water just before use. The warmer temperatures will cause the smaller bubbles to expand and float to the top. Handle gently after wards once it cools.


68 Road Runner (383/4speed, post car w/decor pkg)
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70 Challenger R/T SE EF8 w/ V9J, U - A32 - Major Project
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2369457
09/12/17 02:30 PM
09/12/17 02:30 PM
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I tried that trick once to get air bubbles out of Dot 5 and just about killed myself. The Dot 5 gives off some powerful fumes when it is hot and I haven't to get a chest full of the fumes. Not a good deal at all.

These days I stick with a high quality non Dot 5 brake fluid and change it on a regular basis. I find that if I flush the brakes every couple of years then there isn't any rust and pedal stays nice and firm.

Re: Talk me out of DOT 5 brake fluid? [Re: AndyF] #2370757
09/14/17 02:03 PM
09/14/17 02:03 PM
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Originally Posted By AndyF
I tried that trick once to get air bubbles out of Dot 5 and just about killed myself. The Dot 5 gives off some powerful fumes when it is hot and I haven't to get a chest full of the fumes. Not a good deal at all.

These days I stick with a high quality non Dot 5 brake fluid and change it on a regular basis. I find that if I flush the brakes every couple of years then there isn't any rust and pedal stays nice and firm.


I don't recall fumes being getting too strong. Then again, maybe my memory is fuzzy because of the fumes. But I heated up a pan of water and sat container in the water. Never got above boiling point of water, so maybe that wasn't warm enough.


68 Road Runner (383/4speed, post car w/decor pkg)
69 Road Runner w/472 Hemi & 4 speed.
70 Challenger R/T SE EF8 w/ V9J, U - A32 - Major Project
Re: Talk me out of DOT 5 brake fluid? [Re: RoadRunner] #2370771
09/14/17 02:21 PM
09/14/17 02:21 PM
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I would think a fluid designed for high temp (500F+?) use would be rather limited in ANY fume discharge, as fumes indicate an increase in evaporation of a fluid component, ie bubbles? I suspect another unknown factor in the Andy choking experience.


"Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws." Plato
Re: Talk me out of DOT 5 brake fluid? [Re: jcc] #2373558
09/19/17 08:15 PM
09/19/17 08:15 PM
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I'm using Dot 5 with no issues so far.

Last edited by JH23; 09/20/17 06:58 AM.
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2373824
09/20/17 10:18 AM
09/20/17 10:18 AM
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Phila. Pa.
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Air can get in a system when servicing (replacing) components.
With respect to compressibility, introduced air bubbles was not the characteristic I was referring to.

If air is entrapped in the system (bubbles) this will of course be noticible when the brakes are pushed hard because air is far more compressible than hydraulic fluid.

It appears that the reason silicone based fluids are more compressible relates to the density of the fluid. Further, that the dimethyl polysiloxane contains significantly more disolved air than glycol ether based fluids. This is air between the molecules and does not effect volume.

This dissolved air is not something to generally be concerned about. The problems for racers is twofold. First, they tend to be very sensitive to changes in pedal feel and vehicle response. Second, the brake fluid can get hot, very hot. The silicone fluids get noticibly more compressible as the temperature rises. This is disconcerting to say the least.

For making a decision about whether this may be a concern here's something to consider. If the pads and shoes aren't getting that hot, then the brake fluid isnt going be very hot. So the first question is whether the car will be in situations that require linings for higher temperatures and/or use up pads each event.

ref. Air solubility information comes SAE J1705, Appendix A, A.2.2.8 which was quoted in two unrelated sources. One a manufacturer's promotional paper The ABCs of Brake Fluid and the other in appendix A of a 1992 US Army investigation Purdy, Ellen Report 2505 (pdf)

The practical effect of compressibility is covered in the army report but does not cover situations where the fluid temperatures get elevated. A 1981 SAE paper given by G W Holbrook has been referenced for testing that showed that gycol fluids compressed less than .3% from 77 to 250 degrees F. Whereas silicone fluid compressed .85% at 77 F and had almost doubled that to 1.54% at 250 F.
At 400 degrees, the silicone compressed 2.41% while the glycol was around 0.5% A couple of important points here. If the glycol based fluid is old, it will have absorbed moisture and its boiling point could be under 400 F. Second is that depending on the braking system, the compressibility may be noticible not just in feel but in pedal motion. Holbrook reported additional 1/2" of pedal movement at 400 F. The reporter (who clearly prefers DOT5) calculated increased pedal movement for his triumph at different conditions. He came up with very just 1/10" with new pads at 150 F, to 0.4" with worn pads when at 440F.
One thing every source seems to agree on is not to mix the two types of fluid!

Re: Talk me out of DOT 5 brake fluid? [Re: Mattax] #2373840
09/20/17 10:49 AM
09/20/17 10:49 AM
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Very interesting, however it is hard to fathom this whole issue revolves around a 2%? difference of compressiblity at 400F?, if I digested your details correctly, and I have little knowledge on the this subject to dispute them in the first place. Would not be the first time we get lost in the weeds. grin


"Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws." Plato
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2374488
09/21/17 12:32 PM
09/21/17 12:32 PM
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No one has to talk you out of anything.
Dot 5 is not allowed in most high performance driving schools and road racing venues. When it gets hot the brake pedal goes to sponge.
It's a poor choice in the handling forum. Period
I don't care of about analalfie and his whatever car and his braking data. As usual advice is only good if you listen to it.

Last edited by Tom_Q; 09/21/17 12:34 PM.
Re: Talk me out of DOT 5 brake fluid? [Re: jcc] #2376026
09/24/17 06:13 PM
09/24/17 06:13 PM
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Phila. Pa.
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Originally Posted By jcc
... it is hard to fathom ... Would not be the first time we get lost in the weeds. grin

Dude, You're the guy who asked. No one is lost in the weeds but you. You can't fathom the pucker factor when your foot goes another 3/4" at 100 mph? Really? coffee

Re: Talk me out of DOT 5 brake fluid? [Re: Mattax] #2376143
09/24/17 10:21 PM
09/24/17 10:21 PM
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Originally Posted By Mattax
Originally Posted By jcc
... it is hard to fathom ... Would not be the first time we get lost in the weeds. grin

Dude, You're the guy who asked. No one is lost in the weeds but you. You can't fathom the pucker factor when your foot goes another 3/4" at 100 mph? Really? coffee


Yes, really, I only push hard enough to accomplish the task, and if one is so set in driving our non F1 cars that the idea of pushing 2% more fluid volume is a huge problem, you might want to stay in the weeds (every turn, every second, every time, every wind shift, any fuel consumption, etc requires a new/different braking pressure as conditions vary) (I have no idea where your 3/4" number comes from) (and if you are getting 400F fluid temps, you are on the proverbial edge in more ways then just fluid temps) ( a sudden 400F fluid temp rise would be a rather unusual set of circumstances) Dude.


"Good people do not need laws to tell them to act responsibly, while bad people will find a way around the laws." Plato
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2412317
12/02/17 05:00 PM
12/02/17 05:00 PM
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We use DOT 5 in Postal vehicles(the old ones) We have never had a problem with corrosion,air or bubbles. I use it in my cars with no problems.


Nautilus Racing-
We use Superformance gaskets and Turbo Action converters/products.
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2412593
12/03/17 07:24 AM
12/03/17 07:24 AM
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not sure why but fluid for ford's have a higher temp rating so I usually buy these for DOT3
http://www.canadiantire.ca/en/pdp/oem-dot-3-brake-fluid-ford-500-degrees-946ml-0381928p.html#srp

Re: Talk me out of DOT 5 brake fluid? [Re: dangina] #2415356
12/08/17 05:48 PM
12/08/17 05:48 PM
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DOT 5 is the way to go with fresh paint. Problem I ran into is the stuff is hard to bleed out with fresh lines and getting a good seal at the fittings.

Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2415517
12/08/17 10:50 PM
12/08/17 10:50 PM
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You should be using DOT4 in a performance car. You can replace DOT3 in any vehicle directly without worrying about having leftovers.

I use ATE Typ200 which has a 534 F boiling point. It also has good anti-corrosion properties. Spec'd by people who manufacture OEM brake calipers.

I am not aware of any OEM vehicle that comes with DOT5. My job is working on ESC modules and we don't allow DOT5 with our parts whatsoever.


'70 Duster 470hp 340/T56 Magnum/8 3/4 3.23 Sure-Grip
Re: Talk me out of DOT 5 brake fluid? [Re: goldduster318] #2416909
12/11/17 06:03 PM
12/11/17 06:03 PM
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Originally Posted By goldduster318
. I am not aware of any OEM vehicle that comes with DOT5.


Avanti, Harley Davidson, probably some exotics.


I'm supposed to respect my elders, but its getting harder and harder for me to find one now.
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2416981
12/11/17 08:08 PM
12/11/17 08:08 PM
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Dot 5 or Dot 5.1?

Dot 5 isn't compatible with ABS systems so I doubt any OEM is using it.

5.1 is NOT silicone based.


They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2416999
12/11/17 08:44 PM
12/11/17 08:44 PM
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For what it's worth, for street use I haven't had any issues with the DOT5, but it's also only been 1,500 miles.

....the Wilwood pad knockback, however, is a different story.


1972 Barracuda - 5.7L Hemi, T56 Magnum 6spd - https://www.facebook.com/GoodysGotaHemi
1976 Dodge Warlock - "Her Truck" - 360/727 2wd
2016 Subaru WRX - E30 Tune ~320whp
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Re: Talk me out of DOT 5 brake fluid? [Re: GoodysGotaCuda] #2417409
12/12/17 03:02 PM
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Originally Posted By GoodysGotaCuda
For what it's worth, for street use I haven't had any issues with the DOT5, but it's also only been 1,500 miles.



(Have had DOT 5 in a street car for over 20 years...

20,000+ miles...

In all kinds of conditions...

Zero issues...

Wouldn't even consider going back to 3...

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