Silicone brake fluid

Hi Dave.

Be prepared for a lot of different opinions. Take each for what it's worth, and look for first-hand experience.

A lot of people will tell you to NOT use DOT 5 in your brake system. By and large, this will be by hearsay.

The only DOT 5 I've used was in a Harley that saw very little use and my daily BMW 540i. It works great. As you say, it doesn't absorb water, and it also has great heat characteristics. Also, it doesn't eat paint.

I haven't used it in my Ferrari only out of trepidation. I probably should flush the system of my old fluid and use the new silicon stuff. Contrary to fairly popular opinion, it won't eat seals or hoses, but may leak past already weak ones. You don't absolutely need to replace connections and hoses when changing to DOT 5, but it's a pretty good idea while the lines and master cylinders are empty already.

I'd say go for it. It's a better technology, and should work great with a Ferrari.

--Matt

P.S. Are any new Ferraris sold with DOT 5 fluid?

 

No. If you drive the car, don't use silicon. Silicone fluids are best for true museum pieces, or for uber dollar pebble beach cars where the risk of damaging the finish with brake fluid is a pallatable concern.

 

Like Matt says, there are lots of opinions.

http://home.att.net/~ferrari/brakes7.htm
http://www.cartalk.com/content/columns/Archive/1992/October/10.html
http://www.digest.net/bmw/archive/v10/msg00091.html
http://www.356registry.org/tech/brake_fluid.html
http://www.velocetoday.com/lifestyle/lifestyle_25.php
http://realbig.com/pipermail/detomaso/2003-May/027738.html
http://www.0800brakes.co.nz/pg8.htm (a bit hard to read with the floating text)
http://sl113.org/forums/topic.asp?TOPIC_ID=903 (discusses conventional vs silicone vs synthetic)

 

Some years ago I used Dot5 in a 72 Aston I restored. no problem. the Aston went to the states and returned to the UK some years later. The fluid was replaced again with DOT 5. The system has given no problems.
I have used it in a variety of cars, modern and old without any problem.
The only car I do not use it in is a Lotus that we use for track events, I was told that the boiling point was lower that "standard" fluid.
Systems that I have stripped down after useinf D5 has always been cleaner and shows less signs of corrosion.
I have just replaced the fluid in my 84 Mondial with D5.

 

All you said is very true Matt, I have used silicon brake fluid in my FIAT2300S for the last 25 years and the one thing I needed to do when I swapped from regular to silicon was to replace the seals and rubber throughout the braking system as the original brake fluid had already perished the rubber seals even at that early stage of the cars long life.

What I have noticed is that the brakes use to stick and drag if left for some time when running normal brake fluid but since putting the silicon stuff in over 20 years ago the brake pedal feel and stopping ability has never changed since the conversion.

I seem to remember flushing the old fluid out with methylated spirits, changing all the rubber components of the system, using about a litre of the stuff (maybe slightly more) and the brakes have been as near new performance since that day over 20 years later and the pedal never sticks or drags the pads on the rotor like it use to always do if the car was left for more than a day.

If you intend to leave your car for any extended period I would whole heartedly endorse silicon from personal experience.

John

 

I've been in the silicone business for 25+ years and have owned my own silicone conpany for the past 14 years. Some commments:

--Silicone brake fluid (DOT 5) was developed primarily for the military which wanted to have its deep-storage vehicles ready-to-go on a moment's notice. Entrapped moisture is the primary cause of corrosion in a brake system and since silicone doesn't absorb moisture it is an excellent choice for vehicles stored for long periods of time. Entrapped moisture can also lower the boiling point of the brake fluid and thus cause serious brake fade in racing situations.

--Silicone is more compressable than glycol (DOT 3 & 4) and will thus give a softer pedal feel unless you increase master cylinder size by 1 or 2X. A system designed FOR silicone brake is the way to go.

--Silicone does entrap air quite readily. As a result, it takes long and careful bleeding to get most of it out.

--Silicone has a higher boiling point than DOT 3 or 4 fluids.

--Silicone will not rot or swell seals used in normal brake systems. If your seals are made from silicone rubber (usually colored red) , they will swell and leak in the presence of silicone brake fluid.

I have raced for many years and have tried silicone brake fluid in my race cars and street cars. The negatives outweigh the positives . I would only use silicone brake fluid in a car that is driven very infrequently. In a race car, changing fluid every two races with FRESH DOT 5 FLUID FROM NEW, SEALED CONTAINERS will ensure that it is moisture free.

I use NAPA DOT 4 . I've never had a problem on or off the track.


I hope this helps.


Tom

 

Hi Tom and thanks for the insight into dot5 +s and -s.

It is interesting what you say about having a braking system designed for silicon as I'm sure my FIAT wasn't back in '63 and yet by some lucky coincidence it performed better and more consistent with silicon than it ever did with glycol based fluids. It definitely operated better on the track under heavy use.

I remember swapping over due to the US army article which stated all the reasons you did but was unaware of the silicon seals swelling, thanks

John

 

You're welcome John. Aren't you on Ferraritech ? If you ever have any other silicone questions, just ask.

Tom

 

I would also note that DOT 5.1 is a glycol fluid like DOT 3 and DOT 4

 

Tom B, one comment has confused me, You say
"I have raced for many years and have tried silicone brake fluid in my race cars and street cars. The negatives outweigh the positives . I would only use silicone brake fluid in a car that is driven very infrequently. In a race car, changing fluid every two races with FRESH DOT 5 FLUID FROM NEW, SEALED CONTAINERS will ensure that it is moisture free.

I use NAPA DOT 4 . I've never had a problem on or off the track."

and yet earlier in ypur post your endorsed the fact that silicone fluid does not absorb water ! I used it on the basis that the cars would not get that much use and that it would remain moisture free, and so preserve the system, as commented by moretti.
As someone in the business i am interested in your comments.

 

I have just visited the http://www.0800brakes.co.nz/pg8.htm website.
I have to rethink the whole thing, go there it is good reading.

having said that if the car has infrequent use and is not caned all the time I will still keep the silicone but I may just revert back in the Ferrari to the castrol fluid mentioned by the 0800brake guy's.(I have a contact at Castrol).

 

I would use it if it weren't for the amount of time and money I would have to put in to the swap.

 

Don't use it in an old 308!

 

Sorry for the confusion. I'll take a crack at explaining it better:

The negative aspects of using Silicone brake fluid are its tendency to entrap air and thus make bleeding the brakes diffficult and its high compressability thus resulting in a softer pedal than I like. The biggest positive of silicone brake fluid is its resistance to moisture absorbtion. Moisture in the brake fluid lowers its boiling point (the water vaporizes at a lower temperature and this equates to NO BRAKES) and increases the likelihood of corrossion to system components.

That said, I used glycol brake fluid in my race cars so as not to deal with the negatives. The main positive of silicone was rendered a mute point since I changed my brake fluid so frequently that moisture did not have time to collect in the system.

Hope this helps.


Tom