Dot 5

[Bogdan]

A Rockster owner who doesn't do forums asked me to query you as to Dot 5 and it's possible use in our brake systems. Apparently said 5 is silicon based instead of glycol; it's not hydroscopic and therefore lasts....yes...forever - no more fluid changes. It would be nice, but I think if we could use it I would have heard about it. Anyway...hopefully, those that understand this stuff will post and I'll pass it on.

[Sunbeemer]

DOT 5 is incompatible with DOT 3 & 4 brake fluids and causes precipitates when used in said brake systems that will literally gum up the works. There have been a few posts about this in the past (cyclerob's comes to mind), and you can search through the archives for it.

That said, I think there is also a DOT 5.1 brake fluid that is not incompatible with brake systems that previously used DOT 3 & 4, but again, you can research that in the archives.

edited 1 time to fix incorrect label. Thanks Riceburner!

[riceburner]

As said above - DOT5 is incompatible. DOT5.1 is allegedly compatible.

Personally - I'd just stick with DOT4, it's perfectly good enough for the performance of the Rockster (and I should know).

FWIW, I ran 3 Rocksters over 13 years (2 weeks, 2 years, and the third for the rest of it), and while I changed the brake fluid a few times (which is not hard), I changed the clutch fluid once on the 3rd bike (and then only because I was stripping the entire clutch assembly anyway). I never had any problems with the clutch fluid (the clutch itself had an issue*, but it wasn't fluid related).



* a fairly unique one that I've not heard of anyone else seeing, so don't worry about it.

[Bogdan]

. I do wonder why more guys aren’t using this mysterious 5a/5.1 ?

[Bogdan]

OK....I've been told that 5 is silicon and 5.1 is glycol and advised not to mix them up. So we're back where we started with hydroscopic fluid.

[riceburner]

OK....I've been told that 5 is silicon and 5.1 is glycol and advised not to mix them up. So we're back where we started with hydroscopic fluid.

Is it really an issue?? Yes it's hygroscopic*, but if you're actually suffering from that, then there's something else wrong with your brake system.

I'd advise a good check over, replacement hoses (braided) and new crush washers all round, that will sort you out for a year or two's riding.



* yes - with a 'g'.
(I like the english language, it makes no sense whatsoever sometimes, and then you find the reason for the wierdness and go 'oh!'
https://www.quora.com/Is-hydroscopic-a- ... ygroscopic )

[BadToTheBown]

DOT 5 is incompatible with DOT 3 & 4 brake fluids and causes precipitates when used in said brake systems that will literally gum up the works. There have been a few posts about this in the past (cyclerob's comes to mind), and you can search through the archives for it.

That said, I think there is also a DOT 5.1 brake fluid that is not incompatible with brake systems that previously used DOT 3 & 4, but again, you can research that in the archives.[/size]

+1 Evacuate your DOT 3/4 and put in 5.1. Higher boiling point and will be much harder to heat up enough to fade.

[UberZogster]

I have a couple vehicles that use DOT 5 fluid and still change it every few years. It gets just as nasty as the others so I wouldn't consider it a "forever" fluid by any means. Don't know if your buddies bike has ABS but DOT 5 can't be used in an ABS system because it will foam. DOT 5.1 is a glycol-based fluid just like 3 and 4 and therefor compatible with them. The difference between 3, 4, and 5.1 is the boiling point but 4 should be more than high enough for street use. I've only needed 5.1 in my track vehicles.