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Considering Silicone?


Bordfunker
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Now before anyone gets the wrong idea I am not considering implants, but whether it is worth switching over from DOT 4 glycol based fluid to DOT 5 silicone based.

My main reason for thinking of swapping is because I'm looking to repaint the bulkhead at some point in time, and having seen the mess that DOT 4 spills can have on paintwork, I want to try and avoid that in future.

I know there are some fairly strong views on the pros and cons of silicone, but what I am interested in understanding is whether the swap can only be made to a freshly rebuilt system, or a system that has already used DOT4?

Further to that, how do you flush all of the old DOT4 out of the system?

My brake system has been sitting pretty much drained for the last 6 months, and roughly 50% of the pipes are new.

Karl

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This is a real can of worms.

 

People have just filled with silicone, but personally I think new rubber seals throughout would be a very good idea.

Leaving the system empty won't do it much good either, that alone would make me think of new seals.....

 

Besides, not expensive to do, must be under £50 for 2 sets of master, one clutch slave, calliper  plus either re-seal or replace rear cylinders... And while you are at it a set of brake flexi's.....

 

As to pro's and con's, you could read about it for ages. I tried silicone, no issues apart from somebody sold me (a "specialist" at the old international) some silicone that must have been contaminated and dissolved my master cylinder seals. Obviously the stuff doesn't mix so didn't affect the rest of the seals, but rather disturbing. After that I changed back to DOT4. Mainly because my car does get a hard time on trackdays, and AFAIK nobody uses silicone on performance cars. Could just be horror stories, but I want to be safe. Especially as I am off doing mountain passes including a little one called Stelvio next week....

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Hi Karl,

As Clive says, this is a "can of worms" topic!

There are some very good articles on the subject, and it's probably worth doing a search on this forum. There is a very good link to (I think) a TR owner who has done a great deal of research on the subject.

My own experience is that I've been using silicone in my Vitesse for about 30-years.  My main reason for using it that it is not hygroscopic, unlike convention DOT4.  So ideal for a car that sits in the garage, unused for long-ish periods. It is the moisture that gets into conventional fluid that causes corrosion in the system, most noticeably in the caliper-pistons, that can lead to seizure.  This can of course be overcome by regularly changing the fluid (every two year, I think).

A lot is down to personal choice.

Clive, let us know how you get on at Stelvio?

Regards,

Tom

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Talking to Ashley yesterday and he had used silicon in his cars for many many years , he decided to strip one down and found wheel cylinders   and master  cly to look good as new , clean shiny ,  after 30, years  no corrosion and no black gunge from dgraded rubber 

If that helps

Mentioned before but theres some sound advice on many things on , but look up fluid choice

http://www.buckeyetriumphs.org/technical/technical.htm

 

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24 minutes ago, TomL said:

 

Clive, let us know how you get on at Stelvio?

Regards,

Tom

Not just me, but 85 cars off on the 10CR.

Not just Stelvio, We are also doing:

Offen Pass, Passo Di Lavaze, Timmelsjoch, Bernina, Splugen and many many others!

Best place to see updates will be the CT forum I expect. And we will be posting on our FB pages for both our friends.....

 

Anyway, that is why I am tetchy about brakes. Vented discs, DS2500 pads and fresh fluid should mean no fade. I am carrying spare fluid in case anything does get too hot, and an emergency fluid change is needed. Maybe I ought to stop driving the car so hard. (maybe in another 25 years)

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It is really personal choice. I use the original DOT4 but that's because I'm happy to flush it every year just before the start of the show season, after the cars have been laid up all winter. For a daily driver that might be a different matter but as these days, I'm quite a sedate driver, so little danger of overheating from hard usage. 

That reminds me too.. I must change my stainless hoses, they'v been on for a few years and I've no idea what's going on inside.

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Thanks all.

Having read through the Buckeye article I'm inclined to blow through all the old lines with compressed air, strip and clean the calliper pistons and rear brake cylinders, as well as the master cylinder.

I have yet to check the flexible hoses, so these may yet require replacement, but I know the seals on all the other components are either already new, or in good condition.

So it looks like I've made the decision to go silicone.

Karl

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Hi Bordfunker - I had the same situation as yourself and after upgrading all cylinders decided on DOT4 . My logic was that in a significant brake issue DOT 4 would be easier to get hold of . I did purchase a Master Cylinder alloy tray which helps with Dot 4 overspill . Comes from Australia, available on Ebay - approx £30 deld - Very easy to fit 

Paul 

Master Cylinder Tray.jpg

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2 minutes ago, Pete Lewis said:

Paul  your support brackets are incorrectly fitted the brake has the reinforced spreader , as more pedal loads the clutch has the simple bracket

yours are swapped about 

 

Pete

Thanks Pete - well spotted and Ive learnt something 

Paul 

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12 hours ago, Bordfunker said:

Now before anyone gets the wrong idea I am not considering implants, but whether it is worth switching over from DOT 4 glycol based fluid to DOT 5 silicone based.

My main reason for thinking of swapping is because I'm looking to repaint the bulkhead at some point in time, and having seen the mess that DOT 4 spills can have on paintwork, I want to try and avoid that in future.

I know there are some fairly strong views on the pros and cons of silicone, but what I am interested in understanding is whether the swap can only be made to a freshly rebuilt system, or a system that has already used DOT4?

Further to that, how do you flush all of the old DOT4 out of the system?

My brake system has been sitting pretty much drained for the last 6 months, and roughly 50% of the pipes are new.

Karl

Hello Karl

                 When I bought my Spitfire(2010) it had silicon fluid in it(brakes)

I replaced the caliper pistons(a bit rusted) with stainless steel ones and seals

I have also done the clutch as well

We have covered about 30,000 miles since and been to Classic Spa,Classic Le Mans,Italy,Ireland and Spain twice with no  braking problems(a few others!)

I may be different for a race car that is doing lots of heavy braking and lots of heat but in my experience it is ok for every day driving (with NOS brake pads that work) I know that is politically incorrect but compared to all the other pollution in world its small beer!

Roger

 

 

 

DSC04835-001.JPG

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Roger, good to know that you have had a good experience with silicone.

I've just had the passenger front calliper and pistons off and they look to be brand new, much like the seals on the rear cylinders, and the master cylinder is new as well, so I'm fairly confident that the system should be able to cope with silicone fluid when the new brake lines turn up next week.

Just need to order some silicone fluid now.

Karl

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4 hours ago, Pete Lewis said:

Paul  your support brackets are incorrectly fitted the brake has the reinforced spreader , as more pedal loads the clutch has the simple bracket

yours are swapped about 

 

Pete

Hi Pete , support brackets switched - Will I get a better braking performance <_< NB can you spot the extended bleed nipple for the Clutch ?

Paul 

Master Cylinder Tray 1.jpg

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I have changed over to Silicone DOT 5 when I refurbished the brake rubbers, pistons etc etc. I blew the old fluid out into a can at each wheel using a foot pump with a football adapter before refitting new flexi lines, pistons, rubbers and all the other stuff. Filled up with DOT5 and bled.  There were still traces of the old DOT3 coming through as globules as I was bleeding it soon stopped and on MOT there was no trouble with the brakes and any softness in pedal travel I just put down to the difference between driving a modern with servo assist and a classic without.  I now have no worries about stripping paint having just repainted my bulkhead due to the damage done by DOT3..... but the can of worms will wiggle on forever. By the way Paul, how did you get the master cylinder boots to seat. Mine won't go into the bulkhead all the way round.

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  • 1 month later...

BW, saw your comment about getting the boots in. Did you manage it? Both mine are still not fully engaged. I've been advised to boil them to soften them up, but I guess you've got to be quick and wear some gloves.

There is stuff on ebay called anti silicone for removing silicone from paint work before repainting, worth a try?

I would thoroughly recommend fitting a servo to avoid that shock when you swap between your modern and ancient. A Lockheed type is the best £80+.

 

 

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Doug. No, boots are still only half fitted. Love to know how they fitted them in the factory. I did read somewhere about fitting them like a windscreen, by running a string around the rebate and pulling from the inside. After hanging upside down doing the brake light switch, no thanks. As for the brakes, no problem, I just make sure all loose items are fastened down whe I brake in the modern!!!

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