DOT to DOT (Brakes/Clutch)

[Mr Cake]

Whats the right DOT for topping up my brake/clutch reservoirs? It says something weird on the reservoir caps, like "use DOT 3.5 (or is it 3 *divide sign* 5, or 3-5)" WTF do they mean!?

Dave

[CK & AK]

Al says use DOT 4 - get it at any motorfactors, Dave.

[Albie]

Use any fluid between variants of 3 to 5. Most are 4 but obviously they are graded as per quality or type of usage. or so my mate said at vauxhall when gave me my freebies.

[snakey]

I was told NOT to use DOT 5 as the chemical make-up of it can destroy the seals in the braking system (having a lot of fun at the moment trying to sort the brakes out on the 750 sport, and getting through a lot of DOT4)

Pete.

[superlight3]

Generally Ducati (or any manufacturer) will recommend DOT 3 or 4, which are mineral based oils.

DOT 5 is generally a synthetic fluid, usually silicone based.

Now, history tells us that using DOT 5 in Brembo products (brakes, clutch master & slave cylinders etc) will ruin the seals.

However.....

I've been using DOT 5 silicone fluid (Goodridge and Puntolene) for over 10 years (100k miles) in Ducati brake and clutch systems with no problem whatsoever. In fact, since I've changed over to DOT 5 in the clutch circuit, I've never had a slave cylinder seal go 'pop' or the loss of any fluid, or the fluid turning black.

The advantage of DOT 5 is that it won't attack your paintwork (not that modern brake fluids do much harm anyway) and that being 'non-hydroscopic' it won't absorb water and so is quoted as being able to last the life of the bike.

The downsdie to all this is that if you wish to go over to DOT 5, you'll have to totally strip the hydraulic circuit of all traces of DOT 3/4 before filling with DOT 5, as the two are not compatible.

Well, that's my experience anyway. :)

Perhaps someone else has other ideas.

Cheers.

Lee.

[Mr Cake]

Thanks guys and gals.

Dave

[CK & AK]

Lee - you are quite right in what you say about DOT 5

- but IF moisture does get into the system - through the atmosphere - it can't be absorbed into the fluid (which is good) but the down side is that the water stays as 'globules' - which is not good.

This water has a lower viscosity - but will still work as a hydraulic. However, any metal parts could poss then rust from the inside out.

Alan