Topic: Anyone here ever tried Silicone Brake Fluid???

[Gaither]

Sorry this is long.

I do not have a brake problem at present. However, I can't recall seeing a Post involving Silicone Brake Fluid. So, I'm curious. Has anyone tried it on these ol' bikes?

FWIW

I have used it in various antique cars very sussessfully, including: '48 Ford, '34 Ford (with '48 Lincoln brakes), '66 Mustang GT with 4-piston disc (which I drove hard for 7 years and never touched the brakes again) and others cars. 'Never heard a complaint from other antique car nuts who used if.

*I always used new hoses and new kits.

Example: I sold the '34 Ford - the guy put disc's on it, stored the Lincoln brakes OUTSIDE over a year. I bought 'em back to use on another car. When I disassembled them, the wheel cylinders were perfect. I wiped out the perfect bores and installed new cups "just because" (they, too were perfect) and put 'em on another old Ford. ***If this had been DOT fluid I couldn't have driven the pistons out with a hammer and the bores would have been badly pitted and useless.

It costs more than the "DOT" fluid but it, is a "permanent fix" if properly done (at least in  my experience). Unless something very unusual occurs, you will never rebuild the system again.

Silicone Fluid: ***Will not hurt paint! Has a minimun boiling point over 500 degrees F.
***And, the best part - does NOT absorb moisture or cause corrosion. (DOT fluid absorbes moisture which screws up everything, as we all know too well.)

The DOT fluid must be completely removed from the entire system. I flooded the system with denatured alcohol (paint store) and flushed (bleed) the system until it was very clean - then blew it all out with air pressure to remove the alcohol. Only then did I add the Siclicone Fluid (using new cups and and M Cyl kit.

***While bleeding the system the big no-no is do NOT "flog" the pedal - in this case the brake lever, as you normally would while bleeding the system (I learned this the hard way). This fluid must be bled very slowly with very slow, deliberate movement of the pedal (cars) or brake lever. Otherwise, you will entrain air bubbles into the fluid - which are VERY difficult to remove. Other than slow, careful movement of the pedal or lever (in both directions) he bleeding process is typical.

Racing applicaions (cars or bikes ) will not likely enjoy Silicone Fluid. At extreme temps encountered in racing, it tends to expand a bit and can cause brakes to bind. For street use, this is not a problem. (I drove that mustang really hard with no problems.)

When the 550 needs a brake rebuild, Silicone Fluid is what I'll use.

As I said FWIW.

[dave500]

i thought silicon fluids have to be changed more often,they dont darken as they age and also have a less lubricating nature,it does attract moisture but not as bad.

[TwoTired]

We've had long discussions about Dot5 (silicone) break fluid.  I'm not a fan.

Here's one of them:
http://forums.sohc4.net/index.php?topic=10692.msg100427#msg100427

I got shouted down by DOT5 zealots in a previous thread.  The DOT5 conversion is a one way switch, as it is nearly impossible to completely remove silicone from the hydraulic system and is incompatible with DOT3 or glycol based fluids.  The American military would like to get rid of Dot 5, too as their entire fleet was converted many years ago.  There are studies in progress on how to flush systems.  But, so far no findings on an effective solution have been published (that I know of).  I think they're stuck with it as is anyone who who uses DOT5 now.

Silicone has a few drawbacks besides the one way decision to use it.
Silicon is more compressible than the Glycol based Fluids.  This leads to a "spongier" brake feel, like you can never quite get all the air out of the system totally.

While it doesn't absorb moisture.  It doesn't prevent moisture from entering the system.  You still have to flush the system about every two years, or the water simply collects in the low points, where corrosion still occurs.  At least with the glycol fluid types, as it does absorb moisture, when you flush the system all the water comes out easily during the flush.

Don't even think about using the old seals that were used with the glycol based fluids.  The rubber membranes do have some porosity and absorbs some of the fluid.  As the silicone and Glycol based fluids are incompatible, any mixture fouls the brakes. 

Silicone is probably advantageous to museum pieces and garage queens that don't see a lot of water or high humidity, which can ingress the system via osmosis through rubber seals/membranes.

The military found out that the flush interval is the same as glycol, to keep the water inside from corroding the brake systems at the low collection points.

If you need the Hi temp capability that DOT 5 affords, DOT5.1 will work even better.

Well, that's my viewpoint after some analysis.

Cheers,

[Jerry Rxman Griffin aka MuthaF'er]

I have  but I won't initiate conversation other than to say I have no problems yet.

ps just don't ask about oils please

[wrenchmuch]

I've had DOT 5 in my two 750's for about 6 years now with no problems . I did notice a slightly spongier feel to the brakes after switching but nothing that truly bothered me . The switch was done after a complete brake rebuild including lines so the system was clean . I changed the fluid once in that time (due again now) and didn't find any water in the system . My primary reason for the switch was to reduce the number of toxic subsances I'm exposed to . Given the pros and cons I'm happy I switched .

[bwaller]

I changed to DOT 5 as soon as it was available and I found the pistons didn't retract as well as 3. There was more heat/squeal and eventually read how this fluid may offer less lubrication which I figured may have been my issue.

I have read here where others never experienced this so I can't comment on why it had the affect it did on my calipers.

Further, I completely disassembled all parts for cleaning and switched back to DOT 4 without issues being aware of the compatability problem.

[Bodi]

I tried silicon and had the brake start "sticking" enough to heat up to smoking hot on the highway, if it was at night probably the disk would have glowed red. I only noticed because the bike was feeling sluggish and I thought there was an engine problem... problem was the front brake was soaking up a lot of horsepower. The caliper piston was really jammed in (new piston after 3 weeks or so) and needed strong MC lever pressure to push out. The caliper seal looked OK visually but popped out in a bump/bubble (?) from the groove with the pistonout.
I had changed to new braided lines and rebuilt the MC and caliper with all new seals - no other brake fluid ever touched the brake system after thorough cleaning of the non-replaced parts. I lubed the seals and piston with the new fluid for reassembly. The switch tee was deleted and a new switch banjo installed.
Did this whole process again with DOT4 and have had no problems.
Others have succeeded. I think the seals are not specified to be resistant to silicon fluid. There are different suppliers for such items and I guess some are OK and others are not but Honda has no need to keep track of them, they specify DOT3/4 fluid for these brakes. SO use DOT5 if you want for it's supposed (illusory IMO) advantages and maybe you will have no problems - but maybe you will.
The only advantage is that spilled DOT5 doesn't eat paint (it just makes it impossible to paint over). I have damaged paint with brake fluid but learning to be careful is easier and cheaper than changing fluid type.

[hoodellyhoo]

I switched to 5 after a complete disassembly/cleaning of the system. My brake light switch went out a little while after and I read of a similar problem a guy was having when he switched to 5 as well. I might go back to 3 if I ever get braided lines.

[Kong]

Both of our Harley's have DoT-5 fluid, standard from the factory.  They have been using it exclusively for about a decade.  We've never had any problems with either bike's brakes and between them we've put about 45,000 miles in the last 5 years.

The reason your brake pistons rust and your seals turn to garbage is because standard brake fluids are hydroscopic, they will absorb water out of the air (through the fluid cap vent) and over the years so much water is absorbed that the rust begins.  That does not happen with Dot-5 fluids.

[Skunk Stripe]

Never had an issue with silicon fluids. It may not be the same but I currently use dot4 synthetic and it has worked great. So much so that I see no reason at all to go back to dot 3.

[Bodi]

Dot4 synthetic is not silicon. No Dot4 fluid can be silicon based.

Dot5 is not a problem with race bikes.
Silicon brake fluid is absolutely 100% banned from every paved race track in North America and probably worldwide. You have to certify that there is no silicon brake fluid in the bike to pass tech inspection. The rule is that no racing vehicle with silicon brake fluid or glycol engine coolant is allowed on any paved track. These fluids are very difficult to remove from pavement and leave a dangerous slippery residue without time consuming and expensive cleaning. The standard post crash cleanup with absorbent powder works fine with normal brake fluid. Yes this is a glycol ester fluid but there's not much similarity to the slippery ethylene glycol used in engine coolant.

The reason your internal brake systems corrode is that you don't replace the fluid as per the maintenance schedule. This happens with either "normal" or silicon fluid, the corrosion happens different places but will occur regardless of your fluid type. Replace the fluid every year or two.

[754]

What does Honda use on bikes today??

 How is Dot 4 with Paint?

 And can we use this "mineral oil" Fishead spoke of in regards to  Magura slave cylinders..?

[Kong]

Bodi,

Just to reinforce your very nice post; I first became aware of the problem of water in brake fluid years and years ago when I got into rebuilding BMW 2002's.  At that time, probably around 1990, BMW was including annual brake fluid change as a routine matter of maintenance.  Not only can water be absorbed via the vent in the master cylinder but also through the flexible brake lines material used at each wheel. 

Also, because I was towing it through the mountains of West Virginia and eastern Maryland I converted the brakes on my boat trailer from 2-wheel drum to 4-wheel disks, utilizing stainless lines throughout.  I towed this thing about 2,000 miles per year, mountains to coast, where it stayed for the summers, and back again.  So it saw use and it also saw lots of salt air.  I had to change the fluid in it every fall, and it was always much discolored even with that minimal use.

You are right - change that fluid at least annually.

[MRieck]

 I tried it years ago and was not impressed especially with lever feel. Use 4 and just change it at the right interval

[Bodi]

Most DOT3 and DOT4 makes good paint remover. I don't know about the synthetic DOT4.

[TwoTired]

Just to clear up a misconception.  The brake fluid system is NOT vented.  It is sealed by membranes throughout.  The master cylinder has a rubber accordion to provide for changes in system volume via temperature and barometric changes.

None of the membranes are 100% with regards to sealing materials of all molecular sizes.  H2O is a smaller molecule than the brake fluid molecules, which allows some H2O to pass into the brake system via osmosis and collect/accumulate within.  Dry climates and avoidance of water contact minimize the ingress with whatever fluid is used inside the brake system.

The problem of converting back after Silicone is used, is that nothing mixes with silicone fluid.  You cannot dilute it with any solvents.  Removal is only via mechanical means.  You can push it off a surface.  But, any material porosity that can hold a silicone fluid molecule is NOT easily flushed and is free to migrate into any fresh fluid introduced to the system.

Cheers,

[Gaither]

Well, I blew it! I had not noticed any Posts on this subject and simply FAILED TO DO A SEARCH! I apologize to each and all! I should have known better. 'Just wasn't thinking.
'Almost like starting an oil thread! Sorry, guys!

In any event, I appreciate each of you for jumping in. Obviously, some like it and some don't, each for his own logical reasons. All points are well taken.

I wasn't attempting to get anyone to convert to DOT5 - just asking a stupid question and sharing my experience/s (which does not include bikes) which have all been very successful. Since were are here, I will offer a couple of other thoughts from what happened to me and DOT5.

***If you have a spongy feel, you may well have done the same as I the first time I used DOT5. Starting with a dry, clean, rebuilt system, I filled the M Cyl and began pumping the brake pedal to fill the system just as I would with DOT3 - a BIG MISTAKE! Of course, you can do the same thing with a lever. This rapid pumping entrains tiny air bubbles into the fluid - almost too small to notice while bleeding the system. 

When I thought I was done, I had a spongy pedal. Then, it took me forever to finally get those blasted tiny bubbles bled out. ***Move the pedal or lever VERY SLOWLY- boringly slowly and this will not become a problem. After learning on the first one, I never allowed this to happen again.

If you are now using DOT5 and have a spongy lever, you might consider attempting to bleed them again - very slowly, particularly if you didn't bleed 'em very slowly the first time. Watch for tiny air bubbles and keep on til you get 'em all out.

As far as changing back, I never even considered it until I read Two-Tired's Posts. I can see how it would present a problem. Silicone if tenacious.

As an example, Two-Tired also mentioned silicone paint and the problems it presented. A few of you will recall Packard painted their cars with silicone paint around the mid '50's.
They drove the body shops crazy attempting to repaint 'em!

A friend, one of the best auto painters in this area, just laughed about it and had no trouble repainting a Packard. When he had one ready to paint, he pulled it outside, washed it thoroughlly with gasoline, pulled it back inside and cleaned it again as with any other car and laid the paint on 'em. He never had a come-back on any Packard he painted. They gave others fits.

***Now, I AM NOT even suggesting anyone clean anything with gasoline - I say do not do it -a dangerous undertaking to say the least. I'm just tellling you what Bob did to paint Packards painted with silicone paint.

Thanks to all for sharing. And, I apologize again!

May we all ride safely, with a big grin!

 

 

[Toxic]

No need to apologize as it was a useful thread for myself ... so thanks.

And your tip on how to bleed DOT5 slowly is well considered.

I will use a vacuum system and pull the fluid through the lines instead of pumping like mad.

[MRieck]

Just to clear up a misconception.  The brake fluid system is NOT vented.  It is sealed by membranes throughout.  The master cylinder has a rubber accordion to provide for changes in system volume via temperature and barometric changes.

None of the membranes are 100% with regards to sealing materials of all molecular sizes.  H2O is a smaller molecule than the brake fluid molecules, which allows some H2O to pass into the brake system via osmosis and collect/accumulate within.  Dry climates and avoidance of water contact minimize the ingress with whatever fluid is used inside the brake system.

The problem of converting back after Silicone is used, is that nothing mixes with silicone fluid.  You cannot dilute it with any solvents.  Removal is only via mechanical means.  You can push it off a surface.  But, any material porosity that can hold a silicone fluid molecule is NOT easily flushed and is free to migrate into any fresh fluid introduced to the system.

Cheers,

I had to junk some stainless lines for that very reason.

[Hondell]

Our fleet of police bikes runs DOT5 and ALL of the riders say "the brakes need bleeding,they feel spongy". Also like TT says, the water pools in the low points of the system. Real life observations, not heresay.

[Toxic]

Just to clear up a misconception.  The brake fluid system is NOT vented.  It is sealed by membranes throughout.  The master cylinder has a rubber accordion to provide for changes in system volume via temperature and barometric changes.

None of the membranes are 100% with regards to sealing materials of all molecular sizes.  H2O is a smaller molecule than the brake fluid molecules, which allows some H2O to pass into the brake system via osmosis and collect/accumulate within.  Dry climates and avoidance of water contact minimize the ingress with whatever fluid is used inside the brake system.

The problem of converting back after Silicone is used, is that nothing mixes with silicone fluid.  You cannot dilute it with any solvents.  Removal is only via mechanical means.  You can push it off a surface.  But, any material porosity that can hold a silicone fluid molecule is NOT easily flushed and is free to migrate into any fresh fluid introduced to the system.

Cheers,

I had to junk some stainless lines for that very reason.

Would not also have to junk the M/C as well as the caliper and start over with a complete new system, not just new lines?

Specifically, I have a new one piece line I am going to instal but my M/C and caliper have had DOT5 in them.  So based on the "real world" experiences here, not encouraging as I don't like a mushy brake feel, would I even be able to switch to DOT3 or 4?

None of these concerns turned up when I did my initial search BTW.  I just knew DOT5 wouldn't damage my paint and that is not compatible with DOT3 or 4.

[BobbyR]

I tried it years ago and was not impressed especially with lever feel. Use 4 and just change it at the right interval

I use DOT 4 and I just change it every year.  You turn the bars away form the tank when you are have the MC open and you don't have to worry about your paint.

[Gaither]

I think I recall several Posts involving difficulty in bleeding CB brakes using DOT3. Evidently some folks tie the lever back and give it time to allow air to work its way into the M Cyl with some success - DOT3 fluid. I don't know if this would work with DOT5 [?].

In my experience, if you have those tiny bubbles in your DOT5, it is very difficult to get 'em out. And, they will be mixed into all of the fluid - not just next to the bleeder. IMHO this is the cause of a spongy feel in any event. As I said, I ran into this the first time I used DOT5. I had to slowly bleed ALL of the air-contaminated fluid completely out of the system to get rid of the bubbles. Every other time, I bled 'em very slowly to start with and had no problem.

Hondell

Wouldn't you think the "spongy" problem would be air in the brake system/s? DOT3, 4 or 5 will not compress. As we know, air will readily compress. So, they do need bleeding.

They likely have been bled while squeezing the lever rapidly. You just can't do that with DOT5 without aquiring those tiny bubbles. Thus, the spongy feel. And, once they are in the system, it takes patience, determination and a lot of SLOW bleeding to get 'em out. I agree it makes no sense - but that is what happens. Been there, done that (but only one time). There should be a warning about this on the DOT5 labels.

Incidently, FWIW As an experiment, I have a partially used bottle (plastic bottle) of DOT5, (with the cap on it) that has been in my garage for almost 15 years. There is absolutely no moisture or any other type of contamination in the fluid.

Thanks, Toxic. I've learned a lot.

To each his own - -

[gnarlycharlie4u]

I see a lot of people mentioning that they switched from 3 to 5 or vice versa.

You all hopefully already that you CANNOT mix the two types of fluid at all. Therefore I hope you did a through cleaning and flush of your brake lines, master cyl, and calipers before changing the fluid.

[Gaither]

Charley

You are exactly right on changing over. Clean system with new seals, etc. The fluids will not mix without bad results. (I've never tried to go from 5 to 3 or 4.)

Once, I topped off an M Cyl on a '67 Comet with DOT5 when it had DOT3 in it to start with (I was out of 3). In a couple of weeks, the pedal moved closer and closer to the floor - reducing braking significantly.

I removed the M Cyl lid and found a gelled slug of stuff floating on top of the DOT3 fluid - fortunately it hadn't mixed at all. The net effect was as if the M Cyl was low on fluid and couldn't supply the wh cyl's when the pedal was applied. I was able to lift the mass of stuff out of the M Cyl in one piece. Topped of off with 3 and it was OK.

***Ironically, the label on some DOT5 bottles say, "Compatible with all DOT3, 4 and 5 fluids". (That is why I thought it OK to add 5 to the 3 in the Comet). IT IS NOT TRUE!!!

As you indicate, these fluids WILL NOT successfully (safely) mix.