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DOT4 to DOT 5 Silicon
Lobo:
Thanks all… very informative.
Trig, all brake seals (Master, front callipers, rear slaves) are <3 yo and not on their way out (I assume). Honestly, I’ve had enough monkey’ing around under her; I finish each day grimy and aching - getting too old for this malarkey. = don’t wanna dismantle the braking system. So… do ya reckon I could comprehensively flush the system with DOT 5 Silicon, and perhaps repeat in a month - would that do the trick?
I can’t afford ‘fails’ - the car has zero useful engine braking, and regularly comes down the local ‘mountain’ with engine @ max revs and brakes being ridden fairly hard (when she had 4x drums it was even more exciting with the burning smells). I’m awfully aware there’s no plan B at such times - fairly nail biting 😂.
K2-K6:
To answer the otiginal question, no I wouldn't change over as noted with original system still in place.
The risk is small, but you don't know the outcome, and none can state that clearly. That's for using the pre-used front end system and flushing the dot 4 out.
Don't know if there's enough upside in going to dot 5 to make it worthwhile, but each case is going to be different for each owner.
It's really just the corrosion potential as far as I understand it, none of the other properties seem to be large enough to hold sway really.
Current popular projection would have it that dot4 is so unstable as to be useless, that's just not the case and proven over so many years.
The bicycle world is absolutely stark staring nuts over this stuff, with plenty of opinions seeming to spill out of that sphere.
They have mineral oil as well in the equation, the exponents of which suggest anyone using dot 4 will die :) its amplified out of all proportion, and with many transferring that thinking to other vehicles. Those two are definitely, absolutely incompatible for interest.
Reading about one recently on mtb forum, Aus based car truck technician, got a test kit for checking water ingress and boiling point in brake fluuds, banging on to his father about having 9 year old dot 4 in his Toyota truck, thought he maybe at risk of dying ;D partly a joke in his writing, tested that fluid and surprised to find water inclusion very low, with boiling point well above minimum threshold.
As Ted notes, it's the arrangement around mastercylinder and how that is vented that gives the only scope for water ingress in practical terms. Decent system design will help with long term performance.
Converted systems dot 4 to dot 5 can scavenge any existing moisture of systrm if not going from dry assembly. Ending up at tge calioer ultimately. Specific gravity of most oils is lower than water.
Also the mtb crowd routinely seem to jet wash their calipers etc at about 50 trillion psi and may risk getting water past the piston seals that way. It wont ordinarily get through there in systems well maintained and not subject to external pressure.
JezzaPeach:
Lobo is the system servo assisted just out of interest?
McCabe-Thiele (Ted):
--- Quote from: JezzaPeach on January 20, 2023, 03:37:12 PM ---Lobo is the system servo assisted just out of interest?
--- End quote ---
With that disc front brake upgrade it should have some sort of pedal booster set up I would have thought.
K2-K6:
--- Quote from: McCabe-Thiele (Ted) on January 20, 2023, 07:19:39 PM ---
--- Quote from: JezzaPeach on January 20, 2023, 03:37:12 PM ---Lobo is the system servo assisted just out of interest?
--- End quote ---
With that disc front brake upgrade it should have some sort of pedal booster set up I would have thought.
--- End quote ---
Thats more dependent on mc and caliper bore sizes that should have bought more pure brake power in absolute terms.
The downhill scenario demands more cooling capacity than shear brake torque, that's normally through vented disc route. Can't see what's there in photo.
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