Misc: Everything Else Problem Reverse Bleeding Disc Brakes

[Speedtwin]

DOT 5 Wiki Information from American Department of Transport.
Widely Known DOT5 and ABS never.

DOT 5[edit]​

DOT 5 is a silicone-based fluid and is separate from the series of DOT 2, 3, 4, 5.1. It is immiscible with water, and with other brake fluids, and must not be mixed with them. Systems can change fluid only after a complete system changeover, such as a total restoration.

It contains at least 70% by weight of a diorgano polysiloxane.[7] Unlike polyethylene glycol based fluids, DOT 5 is hydrophobic.[8] An advantage over other forms of brake fluid is that silicone has a more stable viscosity index over a wider temperature range. Another property is that it does not damage paint.[citation needed]

DOT 5 brake fluid is not compatible with anti-lock braking systems. DOT 5 fluid can aerate when the anti-lock brake system is activated. DOT 5 brake fluid absorbs a small amount of air requiring care when bleeding the system of air.[9]

 

[oexing]

One fact explaning some effects of silicon is the slightly higher viscosity compared to glycol fluid. That can be the problem with very fast ABS operations that prevent silicon in these systems. Same property is the root of air bubbles from fluid changes that need ample time to climb to the bottle. So sometimes you´d look into the brake fluid container and do another bleeding if you notice some sponginess . But you do that once in decades and no need for component changes due to rust .
As silicon does NOT mix with water or glycol it does not matter if there is some minimal remains in the system - as it does not mix per se. So no ill effects from this too, no magic reactions , just same rust problem in places that could not be flushed unless completely disassembled. But then, how can you know the glycol gets completely flushed in period changes in all corners of the system ??

Vic

 

[andrew peters]

Sometimes on this forum there will be a (heated) discussion between two guys whom I'm sure know a lot about what they are talking about, or at least they believe that. Much of what I learn is experience or to save time, I use other peoples experience. However, after reading or listening I have to determine who may be correct or whos experience is most relevant to me. This 'theory' I apply to my bike(s)...
In my shop I specialize in Harleys, old and new. For over 40 years my favourite bike has been my BMW R90S that has evolved as it is regularly used. Since acquiring my Vincent I have extensively modified it to make it a better (IMHO) riding motorcycle. most of my modifications, especially with the Vincent, have been researched on this forum and from books and articles, I refer to people that I hope know better and have tried and tested. Like we should all do, judge the information given and apply reasonably, if it sounds right, if it looks right, if it makes sense... believe me, look at a BMW Airhead forum for complete nonsense from young bucks building Cafe Racers and Street Scramblers, they may be good with computers, not so good with spanners! Anyway, my point here is that on 99.9% of occasions the manufacturer has thought it out and is correct, if the factory specifies, "use Dot 4 only" that's what you should use. If the guy with the BMW went back to the Factory (dealership) saying his idea (using Dot 5) is better than theirs then they will shrug their shoulders and sell him a complete new system at Very great expense! usually more than the bikes worth! I've seen it a couple times over the last few years, a vehicle literally written off by a simple avoidable misjudged mistake... or worse, you could crash and die! Sometimes.. the designer/manufacturer knows best, unless his initials are PEI or PCV then we happily modify..lol

 

[mercurycrest]

We got not a single vehicle at home with glykol brake fluid. Instead all silicon brake fluids DOT 5 , even in the Jag E-type since 30 years, never changed. Silicon does not attract water so no rust anywhere and no blocked hoses. Best you disassemble the lot and get new seals in all places - the last job you´d have to do for decades.

Vic

Put Dot 5 in my 78 Laverda about 1980 and it was still good when I sold it 2018. Put in everything since including the 62 Morris Minor now in our Garage. Never had any brake problems with anything that used it. Hmmm, where's the Master cylinder on our new I pace Jag???

 

[Speedtwin]

Love you Vic we all have differing thoughts and opinions what unites us is the love of riding and our Vincents.
First round is on me.
Al

 

[oexing]

Well, I don´t care about who made the round, a case about how one sees it. My arguments did not deal with ABS and silicon, not my business, no experience with this and I will never have any with ABS. So apart from silicon not suitable for ABS systems due to higher viscosity there is NO good argument not to have silicon in brake systems. My guess, there was never any trouble with Harleys before ABS times, nor with military vehicles in US which were filled with silicon exactly on request and because of long time troublefree qualities and no maintenance required. Lots of reports , even in this forum about silicon brake systems and no troubles from this - unlike all that mess with glycol which everybody has accepted for decades to be "normal" .
As to experience, I had silicon in the Jag 3.8 l E-type from 1964 since 1990 and had it in other cars as well for decades. So that will do for me about long time tests , don´t care about other views as typically there are lots of OWTs from people without knowing from own tests. Certainly arguments will be different depending on who you ask and what economic background is involved - as is so often in lots of discussions and you don´t always get the full information for various motives . . . .

Vic

 

[CarlHungness]

DOT4 and DOT 5.1 are glycol based.

DOT 5 is silicon based and was used by some manufacturers then dropped some years back, including Harley Davidson.
Was designed for wet applications such as motorcycles.

DOT5 can not be put into any system that has had any DOT 3,4,5.1 based fluid in it.
It most diffinity produces very serious ill effects which result in brake failure.

I do love to change all my fluids regularly why would you not?
They are the largest moving part in any machine.
Sealed auto transmissions yes chage fluid and filter every 20k miles.
Even Volkswagen/Audi recommend this now for there auto and semi systems.

We see synthetic oil or long life oils that have allowed premature engine failure every day in cars and bikes.
Change every 20k or every year they say on the label, when ever comes first, folks dont understand oh my oil is good for 20k ah yes but it has been in the engine for four years that's why it blew up it has lost its performance protection.
All things have a shelf life.

If one flushes the Dot 3 out of the system by removing calipers, rebuilding the master cylinder, why can't one replace it with Dot 5. It doesn't seem reasonable that there would be enough residue from the Dot 3 to interfere with the new Dot 3. I surely understand never mixing them, but total replacement seems reasonable. I have taken my calipers off, drained them, rebuilt the MC and ready to install new fluid, and thought DOT 5 was to be the replacement. Am I incorrect?

 

[oexing]

I guess you don´t have ABS on the bike. So your preparation for new fill is perfectly allright with silicon fluid. In case you want to be 300 percent safe about silicon you could soak seals for a few weeks in silicon and see if they swell . But I cannot see any modern seals do do this with silicon - but funnily silicon hoses get a bit softer with silicon fluid and I could see "sweat drops" on the outside of the hose. So I changed the hose for PVC plastic for connecting the tanks to the master cylinder.
What do you think I did with Jag E-Type , Ford Capris or Honda Clubman for preparations ? Some were rebuilt systems, some I flushed with alcohol (white spirit?) for washing the glycol out the system, had an airgun for drying the alcohol within and then got the DOT 5 - done for decades.
Yeah, ask the manufacturer - the answer would be obvious: Keep the old stuff and keep changing rusted and stuck components and buy new - as we used to do in the trade.
Maybe you know somebody in maintenance in the army as they specified silicon fluid for their gear - for good reasons . My gess, they don´t even remember if they got silicon in brakes - as they never have to deal with it - it lasts forever , no troubles.

Vic

 

[CarlHungness]

Use the product recommended by the manufacturer…what does it say on the reservoir?

It's a Yamaha master cylinder mated to old Kawasaki discs mated to an even older Black Shadow. A couple of years back I put the system on and Oh Boy, 'twas the best mod I'd ever made. I can ride in traffic without being as afraid as I was with the drums. They worked great, I failed to flush and replace the Dot 3 and the system went duff. Thus I'm rebuilding and most likely installing Dot 5 after a good flush of the (removed) calipers and rebuilt MC. I now find out that Dot 3 swells and hardly ever seeps out, and one can't say that about Dot 5.

 

[oexing]

What part swells with DOT 3 ? Should not happen ! I do know stories about old hoses growing shut by glycol so have to be changed in times. Not so with silicon, provided all components rustfree , no leaks to be expected ever with silicon, a bit higher viscosity too , they say. With poor bores in cylinders and all from dirt or rust no joy with either fluid definitely. But working on silicon systems is a lot nicer, does not strip paint when messing around a bit carelessly.

Vic

fresh restoration Ford Capri 2.3 with silicon in white container right side :