Brake Fluid

[sezian]

I have some "Castrol Motorcycle" Brake fluid that says good for DOT 3 / 4 requirements

What's the difference between this and normal DOT 4 brake fluid 

Does it mean I can only use this in my motorcycle and not my car 

[Silverstripes]

Price 

Look at the specs as I would imagine its only the label that's different 

[UncleGary]

One can use DOT 4 in older vehicles specifying DOT3. DOT4 has a little more high temperature resistance so better for disk brake vehicles supposedly.

[sezian]

The other thing that puzzles me is we're told to change brake fluid every couple of years -  Because it's hygroscopic meaning it can absorb moisture from the air, but were does the air come from there is no air in any brake system (car or bike) except for the minuscule amount at the top of the master cylinder it's a sealed system effectively

Is there really a reason to change this fluid so often, is it another money making job for dealers, what happens if I don't change it - I can't see my brakes suddenly stop working and if there would be deterioration in performance it must be so small I don't think you would ever notice 

Would the cleaver people please explain 

[bucksfizz]

I'm no clever person, but I do not change the brake fluid every two years.
With my 2009 Street Triple R, I change the brake fluid and coolant every three years.
Both fluids appear in excellent condition, and I never have any braking or cooling troubles.
I wonder why Triumph recommends DOT 4 brake fluid.
I have a couple of classic disc-braked bikes, and I use DOT 5 silicone brake fluid - this I never have to change being non-hygroscopic.
Also, DOT 5 fluid doesn't damage paintwork in the event of a spillage or leak.

[Grumps]

Originally Posted by sezian

The other thing that puzzles me is we're told to change brake fluid every couple of years -  Because it's hygroscopic meaning it can absorb moisture from the air, but were does the air come from there is no air in any brake system (car or bike) except for the minuscule amount at the top of the master cylinder it's a sealed system effectively

Is there really a reason to change this fluid so often, is it another money making job for dealers, what happens if I don't change it - I can't see my brakes suddenly stop working and if there would be deterioration in performance it must be so small I don't think you would ever notice 

Would the cleaver people please explain 

I have often wondered this. For many years, even in master cylinders without diapfragms we didn't change fluids - hardly ever.

My vote goes to money-making

[chico]

Whether you use dot 3 or 4, don't ever mix it with dot 5. They are incompatible. It's like mixing oil and water.

Chico

[UncleGary]

Originally Posted by bucksfizz

I'm no clever person, but I do not change the brake fluid every two years.
With my 2009 Street Triple R, I change the brake fluid and coolant every three years.
Both fluids appear in excellent condition, and I never have any braking or cooling troubles.
I wonder why Triumph recommends DOT 4 brake fluid.
I have a couple of classic disc-braked bikes, and I use DOT 5 silicone brake fluid - this I never have to change being non-hygroscopic.
Also, DOT 5 fluid doesn't damage paintwork in the event of a spillage or leak.

DOT 5 brake fluid is not suitable for ABS equipped bikes. As to the wisdom of changing it every two or three years, I have noticed that there are contaminants and that the old fluid is not water clear. Does that matter? I don't know but it is easy and cheap to change so I do.

[healdem]

whether you change the fluids at 2 or 3 years is I suspect largely irrelevant. If Triumph were a huge concern they could have an R&D function which examined such topics. However the 2 or 3 years is de facto an arbitary limit. the origianl manufacurer of the brake fluid or the brake calipers may have an opinion. there may be soem chart somewhere that states that the expected working life is n years. someone may have decided to reduce that on elfnsafety grounds. no doubt Triumph and others will be coverign their asses by either accepting the fluid or caliper makers spec and possibly chopping of bit to be on the, allegedly,  safe side.

the downside of people chopping off a bit to be on the safe side is that you can get very odd numbers, quickly diverging from reality or understandign.


Many years ago my ex boss who worked on the Anglicisation of the F4 Phantom said that by the time the specificiation for the Phantom has passed from the original service requirement up the chain oif command, through the MoD Procurement process, and everyone had added a few percent here, removed a few percent there the UK Phantoms would have out performed the then available missiles, not just any plane in terms of rate of climb, speed in level flight, service ceiling and god knows what else.

So the brake fluid isn't that expensive, nor is the antifreeze additive so why not just do it, rather than put it off and off. its like the person wh was talking about extending the life of the chain by chopping of a couple of links when it was nearly shagged.. its a false economy. just do it on time and you know its within the manufactuers specs. Afterall its not as if the brakes are at all a critical system 

[tommyt]

So BMW charge £45 to change the brake fluid on my wife's X3 and they tell me that it has to be done every two years. Do they actually change it? I don't know but I suspect not. I don't really understand because, when I had my Triumph Dolomite, changing brake fluid was never mentioned so I didn't bother! Now it seems to be an essential part of "the service" but I'm really not convinced.

TT