Discussion
It is OK to mix and match brake fluid brands? I know some people frown on this for motor oil - I was just wondering about brake fluid.
I think the Cerb is DOT4 (please correct me if I am wrong) but wouldn't hae a clue to the brand and I want to top up the master cylinder to stop it drying out while the brakes are off.
I think the Cerb is DOT4 (please correct me if I am wrong) but wouldn't hae a clue to the brand and I want to top up the master cylinder to stop it drying out while the brakes are off.
Cerbs will often have DOT5, as far as I’m aware (it’s not recommended but) there are no big problems mixing even DOT4 & 5 never mind brands, just if you had DOT 5 & you topped up with 4 you’d lower the boiling point.
You don’t really need to worry about it drying out, brake fluid wont evaporate very quickly, if at all. The only problem with it is that its hydroscopic (it absorbs water moisture) & water = rust. You be best off just waiting till it’s all back together & flushing it all though with new some DOT5. For the moment the most important thing is to stop any dirt getting into any open pipes.
You don’t really need to worry about it drying out, brake fluid wont evaporate very quickly, if at all. The only problem with it is that its hydroscopic (it absorbs water moisture) & water = rust. You be best off just waiting till it’s all back together & flushing it all though with new some DOT5. For the moment the most important thing is to stop any dirt getting into any open pipes.
Edited by Luckyone on Tuesday 4th June 19:01
Luckyone said:
Cerbs will often have DOT5, as far as I’m aware (it’s not recommended but) there are no big problems mixing even DOT4 & 5 never mind brands, just if you had DOT 5 & you topped up with 4 you’d lower the boing point.
You don’t really need to worry about it drying out, brake fluid wont evaporate very quickly, if at all. The only problem with it is that its hydroscopic (it absorbs water moisture) & water = rust. You be best off just waiting till it’s all back together & flushing it all though with new some DOT5. For the moment the most important thing is to stop any dirt getting into any open pipes.
OK, cheers for for that. When you say DOT5 do you mean 5.1 as I though DOT 5 wasn't recommended (although it sounds like you know far more than me).You don’t really need to worry about it drying out, brake fluid wont evaporate very quickly, if at all. The only problem with it is that its hydroscopic (it absorbs water moisture) & water = rust. You be best off just waiting till it’s all back together & flushing it all though with new some DOT5. For the moment the most important thing is to stop any dirt getting into any open pipes.
TimJM said:
OK, cheers for for that. When you say DOT5 do you mean 5.1 as I though DOT 5 wasn't recommended (although it sounds like you know far more than me).
Yes sorry 5.1, it used to say on the back of the bottles what you could & couldn’t mix, but that’s going back some. To be more clear if you are unsure of the DOT then it’s better to flush & change all the fluid, if you know you’ve got DOT4 its fine to top up with more DOT4 of a different brand for the short term.
DOT 3,4 and 5.1 are based on poly glycol compounds.
DOT 5 is silicon based. You can't mix silicon and poly glycol. DOT 5 is more compressible than PG compounds, which can result in a sluggish or spongy pedal. Because it does not absorb water, any water remains as globules, which can vaporise when heated under heavy braking giving a bad effect on braking efficiency.
I doubt whether DOT 5 would ever be recommended in a Cerb.
DOT 4 is probably the most common spec; DOT 5.1 has higher specification still and is for fast road and occasional track day use.
Personally I use Carbonne Lorraine DOT 4 Racing Brake Fluid. You'll never get it to boil and with decent aeroquip hoses always gives a firm pedal under 'pressing on' driving.
DOT 5 is silicon based. You can't mix silicon and poly glycol. DOT 5 is more compressible than PG compounds, which can result in a sluggish or spongy pedal. Because it does not absorb water, any water remains as globules, which can vaporise when heated under heavy braking giving a bad effect on braking efficiency.
I doubt whether DOT 5 would ever be recommended in a Cerb.
DOT 4 is probably the most common spec; DOT 5.1 has higher specification still and is for fast road and occasional track day use.
Personally I use Carbonne Lorraine DOT 4 Racing Brake Fluid. You'll never get it to boil and with decent aeroquip hoses always gives a firm pedal under 'pressing on' driving.
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