Going silicone

[standardthread]

3 hours ago, Hogie said:

Hi Steve,

you are correct  about Hygroscopic.   

However people do not read the punctuation just the words.

It is  not mineral in  any form.

 

Roger

You are correct Roger, too much use of text and mobiles, not for me. And as you say. it's glycol based, nowhere near mineral, or bangers!

Returning to the original question/post.

On 29/05/2022 at 11:57, sparky_spit said:

I'm about to change the mineral based brake fluid in my Spitfire and I'm leaning towards using silicone fluid for the 1st time in the car's life.

 

In the vagaries time and of my memory I either read, or I was told, that the reason the US Military adopted /use silicon hydraulic fluid was to both reduce maintenance, and failures in the field. In doing so they would have had to meet very strict NATO specs., followed by ALL NATO countries, and, which are used for everything from brake fluid to specific types of metal and everything else in between. As I spent my working life in the defence industry I could have come across the information at work.

I have a scrap bin full of brake cylinders that I set out to recondition, they are all ‘rusty’ or pitted because the aluminium has attempted to revert back to bauxite, because of the hygroscopic nature of DOT 3 or 4?

As I said in a previous post I have used silicon fluid for over 30 years, with no issues. My brake and clutch lines can’t rust, they are cupro-nickel.

Fortunately, we live in a free thinking society and we have choices, each to his own.

 

Edited November 5, 2022 by standardthread

[glang]

Id be interested to know if the insurers are as free thinking😁

[Dale]

In my experience if changing from DOT4 type to silicon type without a complete strip, clean, seal change some of the old fluid remains in the system and leaches back out over time which means that repeated fluid renewal is required over many months/years to get rid of all of it and even if it is OK to do that it doesn't seem a good idea.

Silicon is great if you have a leaky cylinder as it doesn't dissolve the paint on your bulkhead and it probably lasts longer than DOT4 but be warned, it does still need changing every few years. When new it usually has a strong deep purple (smoke on the water?) colour but this fades over time and ends up a pale coffee colour if left in the system for too long, so renew when it becomes noticeably paler.

I would also advise those 'press on' drivers not to use it as, if it overheats (I've seen this several times on track days and Alpine passes) it turns to jelly and, unlike DOT4 type fluids, doesn't return to a useable liquid state, albeit not as good as before boiling, which requires the whole system to be purged and refilled with fresh fluid which isn't easy by the side of the road halfway up an Alp.

In short, if yours is predominantly a show/light use car then you may be better off with silicon fluid but if not and if you are likely to get the brakes pretty hot, use Super DOT4, DOT4 Plus or even RBF (race stuff) with a higher b.p. and change it at least every 2 years.

[standardthread]

41 minutes ago, glang said:

Id be interested to know if the insurers are as free thinking😁

In addition to the post above I would add that I would think, given the historical use and length of time silicon brake fluid has been in use, and the precedents associated with it’s use, as well as NATO specs (should someone wish to investigate) that insurers would stay well clear of even attempting to reject any brake failure claim where it had been used. They would also have to contend with the vehicle manufacturers and suppliers who produce and sell silicon fluid.

I would think insurers would be more concerned if crap modern OEM (ish) seals had been used and they had failed.

 

[glang]

I suppose if you get a seal supplier to specify their products are suitable for silicone and then install them, flush the system as indicated and replace with silicone the insurers might be happy. However I think just to change your brake fluid to a completely different liquid with no other measures will not be acceptable...

[Ed H]

11 minutes ago, glang said:

I suppose if you get a seal supplier to specify their products are suitable for silicone and then install them, flush the system as indicated and replace with silicone the insurers might be happy. However I think just to change your brake fluid to a completely different liquid with no other measures will not be acceptable...

It's actually simpler than that.

The DOT specs list the rubber compounds that all DOT compliant fluids must be compatible with.  The list is the same for DOT 3, 4, 5, and 5.1.

Any reputable maker of seals for braking systems would be crazy to use any rubber compound not on that list.

Suggestion of DOT5 incompatibility with modern rubber seal materials is a red herring.

Ed

 

[glang]

ok so its just a case of sourcing suitable seals, installing and flushing before refilling with silicone and informing your insurer👍

[ferny]

1 hour ago, Dale said:

In my experience if changing from DOT4 type to silicon type without a complete strip, clean, seal change some of the old fluid remains in the system and leaches back out over time which means that repeated fluid renewal is required over many months/years to get rid of all of it and even if it is OK to do that it doesn't seem a good idea.

Silicon is great if you have a leaky cylinder as it doesn't dissolve the paint on your bulkhead and it probably lasts longer than DOT4 but be warned, it does still need changing every few years. When new it usually has a strong deep purple (smoke on the water?) colour but this fades over time and ends up a pale coffee colour if left in the system for too long, so renew when it becomes noticeably paler.

I would also advise those 'press on' drivers not to use it as, if it overheats (I've seen this several times on track days and Alpine passes) it turns to jelly and, unlike DOT4 type fluids, doesn't return to a useable liquid state, albeit not as good as before boiling, which requires the whole system to be purged and refilled with fresh fluid which isn't easy by the side of the road halfway up an Alp.

In short, if yours is predominantly a show/light use car then you may be better off with silicon fluid but if not and if you are likely to get the brakes pretty hot, use Super DOT4, DOT4 Plus or even RBF (race stuff) with a higher b.p. and change it at least every 2 years.

Interesting info.

 

I had to switch to DOT 5.1, drilled discs, brake ducting and Mintex 1155 pads to overcome fade. Mine doesn't get used on track days.

[edh]

6 hours ago, glang said:

ok so its just a case of sourcing suitable seals, installing and flushing before refilling with silicone and informing your insurer👍

I'm not sure most insurers would know what to do with that information.

Ed

 

 

[glang]

Doesnt matter as long as you have proof of them having been informed👍

They want to know just if I change the exhaust on my motorbike or put go faster stickers on my car but brakes are much more safety critical!

[Adrian Girling]

On 05/11/2022 at 13:16, ferny said:

Oh, so it's a vegetable? We're meant to use vegetable oil for braking systems? 

I'm not sure what brake fluid has in it these days but in the 1970s when many Triumph cars were on the road the main ingedient was sunflower oil.  During my appenticeship with Lockheed brakes I recall being told that the biggest difference between brake fluid and margarine was the water content.

[Guppy916]

What a can of worms we've opened !

when i did the GT6 ALL cylinders were new, and the questions were asked are your seals compatable with silicone fluid, along with the brake lines, servo unit, the calipers were sent to https://www.bcs-automotive.co.uk/#/

"BCS" did come back to me and point out that the rear drums would fade with use, but to date, they were done in July 2015 the drums and calipers are still red,  

[foshi]

all i can add  not seen a lot of spitfire gt6 heralds in hedges lately so can only assume most brake fluids seem ok paul

[edh]

2 hours ago, Adrian Girling said:

I'm not sure what brake fluid has in it these days but in the 1970s when many Triumph cars were on the road the main ingedient was sunflower oil.  During my appenticeship with Lockheed brakes I recall being told that the biggest difference between brake fluid and margarine was the water content.

Glycol based DOT3 brake fluid was standard spec for Triumphs at least back into the 60s.

Previous DOT 2 Fluid was castor oil based.

Ed

[Dave Clasper]

On 05/11/2022 at 19:21, Ed H said:

Any reputable maker of seals for braking systems would be crazy to use any rubber compound not on that list.

Well, there seems evidence out there (and my personal experience), that a lot of remanufactured hydraulic seals for our classics aren't up to spec and fail early, whatever fluid your using.

[Ed H]

21 hours ago, Dave Clasper said:

Well, there seems evidence out there (and my personal experience), that a lot of remanufactured hydraulic seals for our classics aren't up to spec and fail early, whatever fluid your using.

In my book, those wouldn't be from a reputable maker.

Ed

[Dave Clasper]

1 hour ago, Ed H said:

In my book, those wouldn't be from a reputable maker.

Hi. Would love info for any reputable makers, and where these are available for a Vitesse, please

Dave

[Ed H]

4 hours ago, Dave Clasper said:

Hi. Would love info for any reputable makers, and where these are available for a Vitesse, please

Dave

Ive had my LBCs for decades, typically buy from the usual sources, and can't say i've had any real problems with inferior seals.

But ask the group about their experiences.

Ed

Edited November 11, 2022 by Ed H

[glang]

I think its like many components for our cars these days where the big mainstream manufacturers when they run out of stock dont want to produce the small quantities that the limited demand now requires. The supply then gets taken up by companies, often in lower income parts of the world, who can do small production runs profitably but unfortunately not always to the same spec as the originals...