Wilwood what fluid

[Jim mk2]

Hi have a set of dynalite callipers to fit what fluid can I use ? 
 

regards Jim 

[Vista]

I'd have thought any Dot 4 or Dot 5.1 brake fluid would be fine?

[Mash]

11 hours ago, Vista said:

I'd have thought any Dot 4 or Dot 5.1 brake fluid would be fine?

If you've had one in the system, do you need to flush the other out completely? Just wondering, because my Wilwoods had been used when I got them....😕

[katana]

Either doesn't do well with cross contamination so best flush system with what you propose to use. I think Dot 4 tolerates Dot 5.1 better as the latter doesn't absorb water but best to flush completely IMO

[Vista]

1 hour ago, katana said:

Either doesn't do well with cross contamination so best flush system with what you propose to use. I think Dot 4 tolerates Dot 5.1 better as the latter doesn't absorb water but best to flush completely IMO

Dot 5.1 does absorb water, more so than Dot 4 in fact. I also think you can mix Dot 4 and Dot 5.1, it's Dot 5.0 that can't be mixed with either

Not my words but:

DOT 5.1 is more hygroscopic than DOT 4 and therefore absorbs more moisture, it will need to be changed more often. However, the benefit of 5.1 with its higher boiling point, is that it can experience higher temperatures than DOT 4 before it starts to affect braking efficiency

You can mix Dot 4 and Dot 5.1 as they're both glycol based (more details here) but as you don't know what was in them before at all, I'd flush them thoroughly with your chosen fluid prior to fitting

[Ray]

DOT 5 is silicon brake fluid, and its this that cannot be mixed with any other, and the system has to be totally cleaned prior to using, 

its main benefit is, if you spill it, or get a leak, it dosnt harm the paintwork, and reportedly you never have to change the fluid either, and at the price of it im pleased with that as well

have read reports that some seals in older designed systems dont like it, but ive not had a problem as yet, other places say ideal for classics that dont get used much

not readily available in shops though, usually need to buy it online

being purple in colour, it goes very well in a purple car 😀

 

[colr6]

I was told NOT to use the DOT 5 in older cars so have never used it. The 5.1 version can be mixed with dot 4 without any issues. It gets me all this modern fluid that needs to be changed at regular intervals, back in the day of supposed old fashioned crap it never got changed nor was it part of the service schedule. So in short the modern stuff absorbs water and boils it’s brains out. So much for modern technology.

[katana]

Sorry I knew the silicon stuff was #5 - didn't know 5.1 was a completely different variant ! That's confusing!

As regards modern tech - its the fact that brake pads are now so hard they wear the discs out faster, its the same with clutches ! ! Flywheels are treated as a wear / service item! Sometimes I believe we are going backwards rather than forwards!

[Ray]

2 hours ago, colr6 said:

I was told NOT to use the DOT 5 in older cars so have never used it. The 5.1 version can be mixed with dot 4 without any issues. It gets me all this modern fluid that needs to be changed at regular intervals, back in the day of supposed old fashioned crap it never got changed nor was it part of the service schedule. So in short the modern stuff absorbs water and boils it’s brains out. So much for modern technology.

i read not to put it in pre 1980 cars  as the seals wont like it, yet ive had no issues and know people been using it for years in classics without issues, but i probably wouldnt put it in a daily tbh, im assuming the seals that didnt like it werent cleaned properly

it does have a big downside to bleeding as well, as it airates very easily, so much so you can very easily airate the reservoir just topping it up, so you bleed it and 24 hours later the air has come to a head in parts of the system

nick did have an issue with the level in the reservoir going down dramatically, but no leaks in the system at all, so again can only put that down to air in the fluid 

tbf the pair of us used it for its colour, my blue one has DOT 4 ATE racing fluid in because its blue lol, but thats not road legal now, they labeled the last of the tins as such then stopped making it, so thats now horrendous prices if you can find it