Brake Fluid

[StuNVA]

I only had some Dot4 Blue fluid laying around so used it on the bike, whats the diff between the DOT3 yellow and the blue DOT4 and should I bleed it out and put the yellow stuff back in it ?

[BANDITROD]

mate if you are after good quality stuff get yourself some Dot 5.1 motul its not expensive and it is heaps better that dot 3 or dot 4 and as far as mixing fluid its a no no i always bleed out the old stuff when due for a change otherwise you run the risk of it not doing its job when you need it too mate thats just my 2 cents worth anyway

[BANDITROD]

oh and another thing mate never use fluid that has been sitting for a while unless it still has the seal under the cap intact cos it will obsorb water even with the lid on

[StuNVA]

Thanks will do. When doing the front do you do one caliper at a time or both at the same time ?

[davio]

yer bandits right ,m i dont know much but mixing is a big no no

[davio]

i seem to remember the dot figure has some thing to do with temp range , but im prob wrong ,,,, anyone else?

[davio]

longest run first is the rule but yer 1 at a time

you have to be sure the fluid is compatible or u can cause the seals to swell and the brakes will sieze (did it to a landcruiser and my boss was PISSED) the rule of thumb is stick to whatever fluid it recomends on the m/c cap and when bleeding start with the caliper furthest from the m/c then do the closer one

[Jockney Rebel]

as a hydraulics bl;oke i can offer u this advise
1.yea the dot number relates to temp
2.there are two distinct types of brake fluid .mineral based[absorbs moisture ..not just water] and silicone based ,,[dosent absorb moisture]
3.the reason why brake fluid differs from normal hydraulic oil is the temp ramges it has to deal with
[normal HVI 68 would boil at about 2/3rds the temp brake fuild does] as the fluid in ur brakes absorbs moisture its boiling point reduces proportionally according to the amount of moisture in it ,this moisture boils and creates a gas and as we all know gasses ARE compressable and therefore defeats ur hydraulic system also as it cools down again it creates a vapour lock rendering ur brakes useless [all this can happen in a matter of minutes ].this is why you should always use fluid from a sealed container because even the air in the bottle after uve put the lid back on has moisture in it

[StuNVA]

ok....I put some 5.1 in it today, bled it through untill it was all the right colour so no more 4 in the system. The brake still has too much play before it gets hard. I'm 99% sure there is no air in the lines. I'm thinking the rotor might need replacing, not sure, doesnt look that bad, will download a manual and check the specs. The local Kwaka guy told my son to ride around with the brake slighly on until it gets smokey, then bleed them a little again, I thought WTF, is this guy serious or what.

[BANDITROD]

you will find mate that once the fluid warms up your brakes will be fuckin awsome

[Tempest]

use a zip tie to hold the brake lever in and let it sit overnight. will help 'firm up' the lever

[StuNVA]

Just zip tired it, we'll take it out tomorrow morning and put some heat in it and see what happens......ho ho ho