brown brake fluid.

[glang]

Originally Posted by yorkie_chris

DOT4 absorbing water is actually part of what it needs to do, you don't want puddles of un-absorbed water hanging about. Not a problem in a carefully fettled road bike but some water ingress is a fact of life on the road. DOT4 can deal with it but non-water absorbing fluid is a bad thing IMO.

And another thing, fluid of infinite life is not needed as sooner or later you'll need to split the system to clean the pistons anyway.

Does DOT4 degrade when hot? It's designed to work at high temperatures.

Sorry guys I dont understand. How can water enter in the brake system when its always under pressure (fluid comes out of the bleed nipple even without pulling the lever)? I think normal brake fluid absorbs moisture which then does horrible things to pistons etc so a liquid that isnt hydroscopic wont. My theory is that the manufacturers luv extra the business generated by brake fliud changes but then Im just a grumpy ol sod.

Originally Posted by yorkie_chris

DOT4 absorbing water is actually part of what it needs to do, you don't want puddles of un-absorbed water hanging about. Not a problem in a carefully fettled road bike but some water ingress is a fact of life on the road. DOT4 can deal with it but non-water absorbing fluid is a bad thing IMO.

And another thing, fluid of infinite life is not needed as sooner or later you'll need to split the system to clean the pistons anyway.

Does DOT4 degrade when hot? It's designed to work at high temperatures.

iknow every body says you can get water in your brake fluid,but i to this day cant see how a sealed system that wont leak fluid at many 1000 lbs pressure can let water in but not oil out,and as far as cars go and they arnt that different to bikes whan it comes to disc brakes, i had a old mondeo for 12 years and 110k and it still had the same brake fluid in from new,(and would still be going now if some ars--ole hadnt hit it in a carpark and rit it off)as a matter of a fact i had never changed or topped up the water in the rad or changed the gearbox oil,mind you ford said the antifreeze and gearbox oil was good for the life of the car,dont know what they rec for the brake fluid.

[yorkie_chris]

Originally Posted by glang

Sorry guys I dont understand. How can water enter in the brake system when its always under pressure (
...
I think normal brake fluid absorbs moisture

Make your mind up chap

Originally Posted by suzukigt380paul

iknow every body says you can get water in your brake fluid,but i to this day cant see how a sealed system that wont leak fluid at many 1000 lbs pressure can let water in but not oil out,and as far as cars go and they arnt that different to bikes whan it comes to disc brakes,

Except how much mither you can give them when you've got 600 bhp/tonne instead of about 3.

But anyway, they do get moisture in there, I'm not sure how, possibly the in-out motion of the seal/piston carries some fluid in and out on the surface of the pistons and some gets swapped with water. Either way, the same mechanism is likely to occur with a fluid other than DOT4 and cause issues.

Someone on here has access to brake fluid tester and says a lot of bikes come in with massively wet brake fluid. Like it or lump it this will reduce boiling point, 99% of people don't use them hard enough for it to be issue.

With the price, and what is guaranteed to be fine for the existing seal materials I do not quibble about changing fluid. Especially as I recommend they be stripped to have the salt and sh*te cleared out every year or less which means changing the fluid.

[NTECUK]

Originally Posted by glang

Sorry guys I dont understand. How can water enter in the brake system when its always under pressure (fluid comes out of the bleed nipple even without pulling the lever)? I think normal brake fluid absorbs moisture which then does horrible things to pistons etc so a liquid that isnt hydroscopic wont. My theory is that the manufacturers luv extra the business generated by brake fliud changes but then Im just a grumpy ol sod.

Ok when the piston/ pad move out to contact the disc air is drawn in the vent in the resivor. and as the pas wears down the level drops so bigger air gap. so its not sealed.

[glang]

Originally Posted by NTECUK

Ok when the piston/ pad move out to contact the disc air is drawn in the vent in the resivor. and as the pas wears down the level drops so bigger air gap. so its not sealed.

That makes sense - so cos brake fluid is hydroscopic the moisture mixes with it and slowly u have a problem whereas with silicone isnt and you dont. Still wish they had put silicone fluid in mine from new, I would have paid the 20 quid difference to avoid bleeding the brakes every year!

[yorkie_chris]

Originally Posted by NTECUK

Ok when the piston/ pad move out to contact the disc air is drawn in the vent in the resivor. and as the pas wears down the level drops so bigger air gap. so its not sealed.

Well except for that rubber diaphragm that allows volume change without letting air in and out.

[NTECUK]

Originally Posted by yorkie_chris

Well except for that rubber diaphragm that allows volume change without letting air in and out.

Wich looking at every car we do a M2 on that has it doesn't work all that efficiently.ok its is better than the ones with out .

[yorkie_chris]

What's an M2?

[NTECUK]

sorry 2nd year service M1=1st.etc

Originally Posted by NTECUK

Wich looking at every car we do a M2 on that has it doesn't work all that efficiently.ok its is better than the ones with out .

as i said before about car brake fluid just looked up the service intervals for my old car,and it was 3 years or 60k,and i would say car brakes get far more abuse than a bike,lots more weight to stop most use a servo thus putting far more pressure on the system and larger loads to stop and because they are out of sight they never get the salt washed off like you can do on a bike,the discs on a car might last 80k pads about 40k not that much different to most none sports bikes such as a bandits,as to pulling to bits the caliper every year i think that is over the top,ive never stripped the caliper on any of my fleet of bikes nore have i had any trouble with them and my old N reg 1995/6 bandit 6 has done over 52k problem free miles with out having the calipers stripped.the fluid was changed only cose the brake pipes cracked and were replaced,the only calipers i have rebuilt are on my sons tzr with new pistons and seals but that was about 20years old.
and the front discs on my gt380 which has the front end off a gsx400f and they where about 25 years + old at the time