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DOT4 to DOT 5 Silicon
McCabe-Thiele (Ted):
There can't be pooling as there is no emulsified water if you use 5.0 so where can the water come from? No water to boil off with 5.0. You can use Dot 5.1 as an alternative - I'm guessing it's not humid where you live so if you're worried stick with 5.1.
You can mix 5.1 with anything except 5.0.
Lobo:
I guess Ted, said water comes from the same place as it does with DOT 4 - ie it just sneaks in there one way or another, accepting of course that DOT 4 is ‘actively’ hydroscopic. And we live right on water, so it is indeed humid at times.
Interestingly Johnny, that ‘precaution’ of more frequent changes with Silicon is indeed mentioned in what I’ve been reading.
Trigger:
I have DOT 5 silicon in all my old bikes, some have had it in for the past 7 years and have read somewhere that it never needs changing .
DOT 5 is mainly used for classic cars and classic motorcycles. Since they do not run ABS and it is a really good application for these types of vehicles. In addition to this, this type of fluid prevents corrosion and this makes it perfect for bikes intended for long-term storage. So, if you have a classic car or bike, this is the right fluid for you. Though i did disassemble the whole system and cleaned and renewed everything before reassemble. You should always treat brakes as a whole system and after years any rubber parts are on there way out and passed there best ;)
McCabe-Thiele (Ted):
--- Quote from: Lobo on January 19, 2023, 10:08:34 PM ---I guess Ted, said water comes from the same place as it does with DOT 4 - ie it just sneaks in there one way or another, accepting of course that DOT 4 is ‘actively’ hydroscopic. And we live right on water, so it is indeed humid at times.
Interestingly Johnny, that ‘precaution’ of more frequent changes with Silicon is indeed mentioned in what I’ve been reading.
--- End quote ---
Trying to work out how water might pool with Dot 5.0 fluid.
As you will know with hygroscopic brake fluids the water is absorbed from the atmosphere via the master cylinder venting system - this absorbed water then leads over time to corrosion and under extreme braking can boil in the brake caliper leading to loss of braking performance.
With Dot 5.0 not being hygroscopic the only way I can envisage that water might get into the brake system would be by condensation within the master cylinder top area - a very slow process I would imagine. If water is denser than the Dot 5.0 fluid I guess it could sink over time down the brake lines to the caliper - next time I'm bleeding my brakes I'll check if water sinks or floats in the fluid.
JezzaPeach:
When starting work on mine the front brake was useless, and after realising fluid had been leaking onto the disc, I replaced seals etc, which didn’t work. I then realised there was slight corrosion in the channel the piston seal sits in, and in the master cylinder bore. Barely noticeable, but I’m guessing minute traces of Dot 4 in those interfaces with the outside air attract water and then slight corrosion takes place over many years. As I couldn’t machine these I bought replacements and all now working very well, with the SBS501HF pads. They squeaked a bit, but I’ve slightly chamfered the leading edges, but also cleaned the disc with Wonder Wheels cleaner which may have helped, and if it has will use it periodically.
I just bought 250ml of ECB Dot 5 which I will not use, as I don’t want to do the full clean/rebuild (if the above is correct re the ‘interfaces’) which would need all old fluid cleaning off seals etc. (I got it for a good price £15.75 inc postage if anyone wants it for that!)
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