Author Topic: DOT 5 Silicone Brake Fluid (Read 5641 times)

MRieck · « **on:** March 24, 2018, 05:54:29 PM »

Can we all come together and say that stuff is absolute crap. Made with good intentions it is not installed in any car or bike in almost 30 years. If you have any throw it away or sell it on ebay for curiosity value. I have several bottles of Belray.....maybe it is worth a fortune.

slikwilli420 · « **Reply #1 on:** March 24, 2018, 06:49:25 PM »

Benefits don't outweigh any issues that could come up. I run DOT4 Motul rbf660 and it ranks right at the top of many tests. I'm sticking with it.

MRieck · « **Reply #2 on:** March 24, 2018, 07:04:26 PM »

Billy......get rid of that stuff. I have to say I am busting Bill's balls as he has used the stuff for years. I won't be disingenuous.
I am just thinking about the automatic which will have the new....great engine soon. It deserves the good parts.

Don R · « **Reply #3 on:** March 24, 2018, 10:54:39 PM »

That's the best shi7 there is. I rubbed it on the sidewalls on my old hot rod tires and they looked good for a week! Not so good for internal use though.
I had it in my 40 chevy and I had to warm it up for 5 minutes before the pedal would come up. After I got pedal it was good all day. But that sucks. Or as they say in England, suckes.

bwaller · « **Reply #4 on:** March 25, 2018, 06:48:14 AM »

No argument here. I too have tried it and there is no need for explanation. There are really good DOT3/4's

Bearings arrived in good shape, thanks. Mike's right though Bill, change that fluid and be done with it.

Jerry Rxman Griffin aka MuthaF'er · « **Reply #5 on:** March 25, 2018, 11:03:01 AM »

Yeah but it doesn't eat paint on old leaky masters, calipers, tanks etc

kmb69 · « **Reply #6 on:** March 25, 2018, 11:13:10 AM »

Quote from: Jerry Rxman Griffin aka MuthaF'er on March 25, 2018, 11:03:01 AM

Yeah but it doesn't eat paint on old leaky masters, calipers, tanks etc

Lesson to be learned there: DON'T SPILL IT ON PAINTED ITEMS!

Jerry Rxman Griffin aka MuthaF'er · « **Reply #7 on:** March 25, 2018, 12:56:47 PM »

And repair the leaks

dragracer · « **Reply #8 on:** March 25, 2018, 02:08:42 PM »

Mike doesn't post often, but when he does, he knocks it out of the ballpark. Lol

gschuld · « **Reply #9 on:** March 25, 2018, 03:14:20 PM »

Quote from: dragracer on March 25, 2018, 02:08:42 PM

Mike doesn't post often, but when he does, he knocks it out of the ballpark. Lol

George

Bill/BentON Racing · « **Reply #10 on:** March 26, 2018, 04:41:26 AM »

LMAO, I quit using it cause of all the things Mike said etc. I use Dot 4 in everthing now. Carry on. 2018 could be the year!
The Motul is good stuff. Looking forward to hearing some IC noises today that you had a hand in, Stage III holey head. Thanks for the input, see y'all in the lanes soon! Yippee Kai Yeah. And Billet block engine hopefully this week also!

Captain · « **Reply #11 on:** March 26, 2018, 02:36:53 PM »

Sorry but I disagree......
I won’t use anything but dot 5 in anything I have.
Installed into totally and absolutely clean system I have had nothing but success. Operation and pedal “feel” are unaffected.
The only thing that I can say against it is the price.

Captain

slikwilli420 · « **Reply #12 on:** March 26, 2018, 03:32:21 PM »

Seal compatibility is the major concern. When I bought my Brembo master cylinder the guy at bevel heaven said never to use DOT5 as the seals are not made for that formula. That was enough for me to find the best DOT4 I could and just change annually.

MRieck · « **Reply #13 on:** March 26, 2018, 03:41:54 PM »

Quote from: slikwilli420 on March 26, 2018, 03:32:21 PM

Seal compatibility is the major concern. When I bought my Brembo master cylinder the guy at bevel heaven said never to use DOT5 as the seals are not made for that formula. That was enough for me to find the best DOT4 I could and just change annually.

Not for use in AP Lockheed systems either.

AP RACING NEITHER MARKETS SUCH FLUIDS NOR RECOMMENDS THEIR USE WITH OUR OWN OR ANY OTHER BRAKING SYSTEM

Virtually all of the problems with Silicone Brake Fluids relate to : -

Long/spongy pedal
Sudden loss of brakes
Hanging on of brakes

They reflect certain properties of silicone fluids identified by us over may years and recently ratified in SAE publications, namely : -

High ambient viscosity
High air absorption
High compressibility
Low lubricity
Immiscibility with water

Research has shown that the relationships between problems reported and properties identified may be expressed as follows:-

Long /Spongy Pedal

a) Compressibility, up to three times that of glycol based fluids
b) High viscosity, twice that of glycol based fluids, leading to slow rates of fill and retention of free air entrapped during filling, and hence bleeding difficulties.

Sudden loss of brakes

a) Air absorption. Gasification of absorbed air at relatively low temperature produces vapour lock effect.
b) Immiscibility (failure to mix) with water. Whilst the presence of dissolved water will reduce the boiling point of glycol based fluids any free water entrapped in silicone-filled systems will boil and produce vapour lock at much lower temperatures (100°C or thereabouts)

Hanging on of brakes

a) Low lubricity. In disc brake systems the sole mechanism for normalisation of system pressure upon release of pedal pressure is a designed-in tendency of seals to recover to their ‘at rest’ attitude. Low lubricity works against this tendency.
b) High viscosity exacerbates the effect of (a) above.

It should not be assumed, therefore, that the high price of silicone fluids implies higher performance in hard driving or even normal road use.

AP Racing glycol based fluids do not contain the adverse properties described above. The recently introduced Formula DOT 5.1 which exceeds the performance criteria of DOT 5 (Silicone), is suitable for all conditions likely to be encountered in modern driving conditions.

Captain · « **Reply #14 on:** March 26, 2018, 04:22:59 PM »

Again, sorry but I disagree with these issues. The aP posting is an biased statement in favour of their own product.
Although the subject and basics has “some” truth it is presented in such a way that one is lead to believe that it’s all negative......It’s not and some are just to small to even be a consideration.
For example, compressibility. This is so small as to be completely invisible to all. The compressibility of the seals and other components is greater and no one ever mentions that. As for water absobsion, this is a positive and the archills heel of glycol based fluid.......and so it goes on.
There are arguments for and against most engineered products and Dot 5 is but one.
I personally are very satisfied with the tech, it’s actual performance and my experiences using it.

Captain

MRieck · « **Reply #15 on:** March 26, 2018, 07:09:03 PM »

Quote from: Captain on March 26, 2018, 04:22:59 PM

Again, sorry but I disagree with these issues. The aP posting is an biased statement in favour of their own product.
Although the subject and basics has “some” truth it is presented in such a way that one is lead to believe that it’s all negative......It’s not and some are just to small to even be a consideration.
For example, compressibility. This is so small as to be completely invisible to all. The compressibility of the seals and other components is greater and no one ever mentions that. As for water absobsion, this is a positive and the archills heel of glycol based fluid.......and so it goes on.
There are arguments for and against most engineered products and Dot 5 is but one.
I personally are very satisfied with the tech, it’s actual performance and my experiences using it.

Captain

I have never seen seen a factory race team over the past 30 years (in the USA) ever use a silicone based brake fluid. My personal experience with 600cc superstock racers in New England in the 90's was change Motul fluid along with bead blasting the rotors to get rid of the embedded crap every other weekend

scottly · « **Reply #16 on:** March 26, 2018, 07:54:57 PM »

I've never used anything but DOT 3/4, so I can't comment about DOT 5, but IIRC, there is an issue when switching from DOT 5 back to DOT 3/4? I know brake cleaner doesn't work very well removing silicone shock absorber fluid. There is a product from NAPA's painting products specifically made to remove waxes from finishes before painting, and I think it may also work for silicone products?

PeWe · « **Reply #17 on:** March 27, 2018, 12:52:53 AM »

A brake fluid that react badly with the paint can be seen as something good, it encourage the rider/owner to fix the leak ASAP and risk of no working brake is sorted

Tintop · « **Reply #18 on:** March 27, 2018, 04:37:14 AM »

Quote from: scottly on March 26, 2018, 07:54:57 PM

I've never used anything but DOT 3/4, so I can't comment about DOT 5, but IIRC, there is an issue when switching from DOT 5 back to DOT 3/4? I know brake cleaner doesn't work very well removing silicone shock absorber fluid. There is a product from NAPA's painting products specifically made to remove waxes from finishes before painting, and I think it may also work for silicone products?

+1 scottly DOT 3/4 & DOT 5 are completely incompatible, and mixing (going from one to the other) will destroy seals. The system must be completely purged, which generally means a complete rebuild. The only advantage to DOT 5 is that the silicone base does not absorb water like DOT 3/4 do. Therefore it's good for long term storage.

slikwilli420 · « **Reply #19 on:** March 27, 2018, 06:15:38 AM »

Quote from: Tintop on March 27, 2018, 04:37:14 AM

Quote from: scottly on March 26, 2018, 07:54:57 PM
I've never used anything but DOT 3/4, so I can't comment about DOT 5, but IIRC, there is an issue when switching from DOT 5 back to DOT 3/4? I know brake cleaner doesn't work very well removing silicone shock absorber fluid. There is a product from NAPA's painting products specifically made to remove waxes from finishes before painting, and I think it may also work for silicone products?

+1 scottly DOT 3/4 & DOT 5 are completely incompatible, and mixing (going from one to the other) will destroy seals. The system must be completely purged, which generally means a complete rebuild. The only advantage to DOT 5 is that the silicone base does not absorb water like DOT 3/4 do. Therefore it's good for long term storage.

The hygroscopic nature of DOT 4 is really only present at 2 times, one is if you store it open like an idiot, which no one does. You open the container, pour into the master and then put cap back on. The time that takes is minuscule. The time the cap is off the master as you bleed is also pretty small. Higher humidity will allow more to absorb. The other is when the brakes are used, causing the fluid to heat up. Good practice here is to make sure you brake system is totally cool before opening the cap to check fluid level or make changes.

"Regular" DOT 4 has a pretty wide variance in wet and dry boiling points, and the fluid, once saturated with water, has a pretty unsafe boiling point for track/race use, let alone aggressive street riding. Premium blends like Motul RBF660 (which I use) has a superior boiling point to most DOT 5.1 and DOT 5 variants, as well as a superior wet boiling point. What's that all mean? Even when the fluid is fully saturated (3.7% water by volume) it still has superior stopping power and boiling resistance relative to many other fluids on the market.

The bottom line is that good handling practices of DOT 4 and choosing a premium blend will give the very best performance without the worry of seal/fluid compatibility that is found with the silicone based fluids that were once considered the answer to a question no one asked.

Tintop · « **Reply #20 on:** March 27, 2018, 07:40:55 AM »

Not quite true slikwilli420, the fluid is continually absorbing water through the vent. The issue with absorbed water is the damage it does through rust in the system, and is the primary reason DOT5 was invented to solve. Many auto manufacturers now use DOT5 for this reason alone. Not advocating for DOT5, just pointing out that it has it's place, and when used in the proper application can be a better solution. As for 'boiling' DOT3/4. If the brakes got hot enough to do this, your immediate next step is the completely change the fluid as it is no longer viable.

paul_cb836 · « **Reply #21 on:** April 01, 2018, 03:51:39 AM »

Harley’s use Dot 5

bwaller · « **Reply #22 on:** April 01, 2018, 06:42:02 AM »

Absolutely Brian, I used a premium Dot 4 race fluid last season. High boiling point alright but much more hygroscopic than the same brand "non race" formula. (I bought into the high boiling point and "race" part

)

Point is, for most of us who do say four races a good DOT 4 fluid might last a season depending on conditions. Last year's fluid should have been changed every couple races. Piss on that,

I've moved on to different fluid for this year.

BigJimG · « **Reply #23 on:** April 29, 2018, 02:01:28 PM »

DOT 4. I flush my brake systems every couple years anyway. (Yes even my cars)

Bodi · « **Reply #24 on:** May 01, 2018, 07:06:46 PM »

The tracks around here - for races or track days - seem to have two rigid rules: 1) no (NO!) silicon brake fluid, and 2: only water (water-wetter type stuff is OK but no antifreeze) in cooling systems. Apparently antifreeze is hard to clean off the track after a crash/spill, and silicon brake fluid is impossible to clean off without ruining the pavement (OK, it would be ruined anyway with a crazy slippery spot). I guess the Hogley-Ferguson guys don't do track days?

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Author Topic: DOT 5 Silicone Brake Fluid (Read 5641 times)