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Original thread located here- http://www.lotustalk.com/forums/f91/silicone-brake-fluid-29530/



I think one of the magazines wrote that one of the new Elise/Exige versions (track only?) comes with silicone brake fluid. I used silicone (Dow Corning) when racing a G/P Spitfire in the 70's/80's and used it in my '70 muscle car. The advantage is supposed corrosion resistance, especially for the long term. Does anyone know of a current silicone fluid, especially what is used in the new Lotus (assuming it really is)?
 

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Lotus does not use silicone (DOT5) fluid. They only use DOT4 or DOT5.1

5.1 is NOT silicone-based, but like DOT4 it's a mineral fluid.

Do NOT use Silicone/DOT5 in the Elise's brake system. It is not designed for it.

Silicone based DOT5 has some serious drawbacks when used in systems that were not designed for it:

- can attack the rubber seals on master cylinder, ABS unit and in brake caliphers because of incompatibilities in material
- Silicone fluid is more compressible than DOT4/5.1, so results in a much more 'spongy' brake pedal
- Silicone fluid is not hygroscopic, but water will still find a way into the system. This water will not be absorbed into the brake fluid and 'pool' inside brake lines and caliphers, causing rust and oxidation.
- Silicone fluid expands more under heat than regular DOT4/5.1 and can cause hot brakes to 'stick on' or result in non-linear brake response

A system speficically designed for silicone fluid has measures to reduce or eliminate these effects, but the Elise is not one of them.

Bye, Arno.
 

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Less Moore said:
I think one of the magazines wrote that one of the new Elise/Exige versions (track only?) comes with silicone brake fluid. I used silicone (Dow Corning) when racing a G/P Spitfire in the 70's/80's and used it in my '70 muscle car. The advantage is supposed corrosion resistance, especially for the long term. Does anyone know of a current silicone fluid, especially what is used in the new Lotus (assuming it really is)?
Yes, the Lotus Sport Exige 240R uses Silicone brake fluid (link). It's generally not something you want to use in a street car as it doesn't absorb moisture like conventional fluid will.
 

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DOT 5 silicone fluid is great for collector cars that sit for long periods since the fluid is not hydroscopic and thus does not need to be changed very often. It can be compressed a tiny bit giving a spongier brake pedal feel. Use the new synthetic DOT 5.1 fluid instead. It has a high boiling point but does not absorb as much water as traditional racing brake fluid. Motul is my favorite.
 

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Arno said:
Lotus doet not use silicone (DOT5) fluid. They only use DOT4 or DOT5.1

5.1 is NOT silicone-based, but like DOT4 it's a mineral fluid.

Do NOT use Silicone/DOT5 in the Elise's brake system. It is not designed for it.

Silicone based DOT5 has some serious drawbacks when used in systems that were not designed for it:

- can attack the rubber seals on master cylinder, ABS unit and in brake caliphers because of incompatibilities in material
- Silicone fluid is more compressible than DOT4/5.1, so results in a much more 'spongy' brake pedal
- Silicone fluid is not hygroscopic, but water will still find a way into the system. This water will not be absorbed into the brake fluid and 'pool' inside brake lines and caliphers, causing rust and oxidation.
- Silicone fluid expands more under heat than regular DOT4/5.1 and can cause hot brakes to 'stick on' or result in non-linear brake response

A system speficically designed for silicone fluid has measures to reduce or eliminate these effects, but the Elise is not one of them.

Bye, Arno.
You da man, Arno. :bow: I had the exact same question in mind since I used DOt5 on my 66 Vette that I ran production modified class back in the 80's. We used it to prevent rusting calipers. It's got a very high boiling point as I recall, so I have been thinking about putting it in the Elise. It's good to know the downsides. I'll stick with Dot4 in the Elise. Thanks.

One question I would beg is why is Motul's Dot4 better than Lotus OEM fluid which is also Dot4 and I would assume very good quality. I have heard that Lotus brakes run cool anyhow, but haven't yet tracked my newly purchased Elise to verify this myself. And if Motul Dot5.1 is compatible and superior, why does everyone recommend Motul Dot4? Even Sector 111 sells Motul Dot4, not Dot5.1.
 

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DOT 5.1 is not really any 'better' than DOT4. A high quality DOT4 can have better temperature properties than an average DOT5.1 type.

The biggest difference between 5.1 and 4 is that the standards for 5.1 require it to be less viscous than DOT4, which was a requirement for early ABS systems to function properly.

5.1 has a slightly higher boiling point too, but good DOT4 fluids also reach that easily.

Personally I just use Castrol Super-Response DOT4 (or as they call it DOT4+) and flush it every 6 months or so. Works fine and doesn't cost an arm and a leg like Castrol SRF..

Bye, Arno.
 
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