DOT4 or DOT5...??

[bugjuice]

k, so I think the brakes need bleeding/changing.. At the moment, I think there's a wee bit of moisture in there, which is causing a touch of brake fade when they warm up, and the fluid is starting to go off-colour too, so might as well. So tomorrow, off to buy some fluid, some tubing and a syringe..

Obviously the recommended, or standard, is DOT4 liquid.. but I've been told that DOT5 has a higher boiling point, and slightly better 'feedback' when it comes to the crunch..

Any for/against points here?

[bane]

Just did both bikes today - used DOT 5 (both bike manuals recommend DOT 4).
As you mentioned DOT 5 has higher boiling point, both neat, and when wet.
With the type of bike I have, and the kind of rider I am, probably a waste of $2 (over DOT 4) - but hey its only money!

[MacD]

DOT 4 and DOT 5.1 fluids are glycol-based, DOT 5 fluid is silicone-based. Supposedly DOT 5 (silicone) fluids shouldn't be used in systems that weren't designed for them as the various components (seals etc) can be damaged.

So, you may be OK with DOT 5.1, but not DOT 5, assuming your system was designed to be used with a glycol DOT 4 fluid.

There's lots of info out there on the interweb, but it resembles the "which oil" discussions!

[bugjuice]

If you want to wait untill Tuesday (when I'm back at work) I may stumble across some #*cough*# tubing and #*cough*# a syringe.

Otherwise if I saw this thread earlier I done a recall today.. WooHoo time and a half!

Who was the biker chick up at the NS Yoga room on Barry's Point Road this morning BTW???

And who knows the biker that got smacked by a cage in Pt Chev this morning too.. busted legs and pelvis.. multiple fractures ouch!!

ouch.. hope the dude is gonna be ok..

yeah, no rush.. the biggest *cough* syringe and a tube that'd be *cough* about the size of my nipple.. *cough* or the calipers nipple.. *cough* and something for this damn cough..


MacD - I forgot there was 5 and 5.1. The bike is only a year old, and the system design around two or so, so I guess it'll be ok. But I'd be keeping a close eye on it if I did change it. I'm also searching the intermaweb on the topic, but I'm just cream-crackered at the moment, so probably do a better job tomorrow..

[bugjuice]

I reckon the guy (Mr Hudson) that designed oxygen tubing knew that we needed to bleed our bleedin brakes from time to time and made them surprisingly EXACT in size.

These comments are in no way related to the above post.

sweet, he must have rode bikes too..

[bane]

So, you may be OK with DOT 5.1, but not DOT 5, assuming your system was designed to be used with a glycol DOT 4 fluid.

was DOT 5.1 I used. - bottle states "not suitable for mineral based systems". However the DOT 4 bottle also said the same thing...

[Pixie]

was DOT 5.1 I used. - bottle states "not suitable for mineral based systems". However the DOT 4 bottle also said the same thing...

Mineral based systems are those that need the hydrualic fluid they use in Citroens, some KTM's are like this.
Neither Glycol and Silicone are mineral.
As the DOT number increases the Hygroscopic nature of the fluid decreases,so it absorbes less moisture.A DOT 5.1 may have a lower boiling point,but it will maintain that b.p. for a longer period than a lower DOT rated fluid.As a fluid absorbes moisture the b.p. drops

[Coyote]

I went for the Castrol 'Advanced Formula' DOT 5.1. It must be better, it's 'Advanced!'

[Bonez]

I went for the Castrol 'Advanced Formula' DOT 5.1. It must be better, it's 'Advanced!'

It's called marketing hype.

[Hitcher]

As with most things in life, just because you can doesn't mean you should...

[bane]

As with most things in life, just because you can doesn't mean you should...

wish someone would tell that to Paris Hilton!

[Brains]

Stick with DOT4, yeah yeah DOT5 does sound better, but you'll have to replace it more often - every six months or so, I forget the reason, but it simply doesn't last as long.

[mjvduc]

1st of all you should not mix or use any silicone based brake fluids in DOT 3/4 designed systems!!!!!

DOT 5 (silicone) is not hygroscopic, meaning it won’t absorb water from the air!! Every time your brake is getting really hot and then cold condensation occurs and DOT 5 fluid cannot absorb this water and you will loose your pedal feeling.

I use DOT 5.1 (glycol based) since 1997 and never had any problems.


HD and some other American produced grasshoppers may use the silicone rubbish

mjvduc