Discussion
camelotr said:
Hi,
May I ask Your opinion on the DOT5 silicon based brake fluids?
I would like to use them in my oldtimers.
Silicone fluid (DOT 5) is OK in non performance applications if it's used in a brand new system. Once filled you don't need to change it as it doesn't absorb moisture unlike Glycol fluids (DOT 3/4/5.1). Silicone fluid is more compressible than Glycol fluids so you will get a more spongy pedal feel than Glycol so not ideal for performance applications. The US military have been using it in all their vehicles since the 90's as there's no real maintenance required with it.May I ask Your opinion on the DOT5 silicon based brake fluids?
I would like to use them in my oldtimers.
Edited by camelotr on Monday 30th August 08:33
Sounds not too bad then for non performance old motors?
The trouble comes when swapping over from Glycol based fluids to Silicone fluid.
Even if you flush the system through there may still be some old Glycol fluid trapped in there somewhere.
The old fluid will contain moisture as Glycol fluids are hygroscopic (absorb water). Water in the fluid leads to corrosion. The Glycol fluids contain corrosion inhibitors to help out with this problem BUT Silicone fluids don't as they don't absorb water so don't need it.
As the Silicone fluid doesn't absorb water any water that's trapped in there sits in separate pockets. Not only do you have pockets of water corroding the system these pockets will also boil when heated or freeze when cold leading to an even more spongy pedal with use.
Your oldtimer cars were designed to use Glycol based fluids, it's a pain to keep changing the fluid but it's best to stick to what they were designed to use.
For a long lasting fluid then try ATE Super Racing Blue and change every 2 years as a maximum.
jagracer said:
mk2 24v said:
or even super dot4, as that is the same as dot5.1 
Is it?If the manufacturer specifies DOT 5.1 fluid then use it. The main reason it's specified is because it has a thinner viscosity specification than DOT 4 which is required for tiny valves used in certain ABS and TC systems. If you use a thicker spec DOT 4 fluid you risk wrecking the brake system.
If they specify DOT 4 and you want to improve the performance then use a decent performance DOT 4 fluid (e.g. Castrol SRF, Motul RBF600/660 etc.). They will outperform any DOT 5.1 fluid in the important Wet/Dry boiling point performance aspects.
I build my cars with all-new brake parts if only possible. Thats a rule for me. Soo its not a problem. I also prefer to use teflon braided brake pipes which does not allow water to diffuse into the system. Soo it realy sounds a good solution. I think I will give it a try on my next project.
Edited by camelotr on Wednesday 1st September 06:12
jellison said:
jagracer said:
jellison said:
SRF is what you want. Bloody Expensive...
I use DOT5.1 at £4.99 a litre, bloody cheap.jagracer said:
jellison said:
jagracer said:
jellison said:
SRF is what you want. Bloody Expensive...
I use DOT5.1 at £4.99 a litre, bloody cheap.FYI - think I might not race again this year (just had my engine bill!).
jellison said:
jagracer said:
jellison said:
jagracer said:
jellison said:
SRF is what you want. Bloody Expensive...
I use DOT5.1 at £4.99 a litre, bloody cheap.FYI - think I might not race again this year (just had my engine bill!).
Gassing Station | Suspension, Brakes & Tyres | Top of Page | What's New | My Stuff