Braided lines

[bugjuice]

mmmm.. i was under the impression that even tho they carried similar properties, you still shouldn't mix them up.. I'll stop by Ripco and have a read.

As for the water thing, yeah DOT 5.1 absorbs more, but I change it every 6 months anyway, so don't care. Keeps the brakes feeling sharp..

[Postie]

Good old "how stuff works.com"

The U.S. Department of Transportation issues specifications for brake fluid. The three main types of brake fluid now available are DOT3, DOT4 and DOT5. DOT3 and DOT4 are glycol-based fluids, and DOT5 is silicon-based. The main difference is that DOT3 and DOT4 absorb water, while DOT5 doesn't.
One of the important characteristics of brake fluid is its boiling point. Hydraulic systems rely on an incompressible fluid to transmit force. Liquids are generally incompressible while gases are compressible. If the brake fluid boils (becomes a gas), it will lose most of its ability to transmit force. This may partially or completely disable the brakes. To make matters worse, the only time you are likely to boil your brake fluid is during a period of prolonged braking, such a drive down a mountain -- certainly not the best time for brake failure!

As a DOT3 or DOT4 brake fluid absorbs water, its boiling point decreases. It can absorb water from the air, which is why you should avoid opening your car's brake fluid reservoir. For the same reason, you should always keep containers of brake fluid tightly sealed.

DOT5 fluid does not absorb water. This means the boiling point will remain relatively stable, but it also means that any water that does get into your brake system will tend to form pure water pockets, which could cause brake corrosion.

Two other important things about brake fluid: DOT3 and DOT4 eat paint, so don't spill it on your car. Also, none of the different types of brake fluid should be mixed. They can react badly with each other and corrode your brake system.

(below text from http://www.stoptech.com/tech_info/wp...fluid_1a.shtml )

Historically, DOT 5-level performance (specifically boiling points and viscosity) could only be achieved with silicone-based fluids. However, modern compounding has created glycol ether-based fluids which now meet DOT 5 bogeys in these key areas. Consequently, the DOT 5.1 moniker was created to differentiate between these two very different chemistries which both meet DOT 5 performance requirements.

In so many words, DOT 5.1 fluids are simply DOT 4-type fluids which meet DOT 5 performance requirements. Because of this, they typically can be mixed with DOT 3 or DOT 4 fluids without concern. In some circles, they are even referred to as ‘DOT 4 Plus’ or ‘Super DOT 4’ fluids because they are more similar to a conventional DOT 4 fluid by chemistry than they are to a conventional DOT 5 fluid. In fact, DOT 5.1 is essentially comprised of Borate Esters.



the big advantage of the DOT 5.1 fluids is that they contain all of the nifty water-absorbing characteristics of the DOT 3 and DOT 4 fluids while simultaneously providing for very high boiling points and relatively stable viscosity over a wide range of temperatures. The best of all worlds, you could say. The table below sums it up quite nicely.

PROPERTY DOT 4 DOT 5 DOT 5.1
Dry BP (F)@ 0.0% H2O 446 509 509
Wet BP (F)@ 3.7% H2O 311 356 356
Chemical Composition Glycol Ether / Borate Ester Silicone Based Glycol Ether / Borate Ester

[Motu]

Apart from the fact that the water content of the fluid boils,these repeated heating and coolings,and other compounds it finds in the fluid - the water content turns acidic.Another way to say it is...it turns into an electrolite,and turns your brake system into a battery,removing metal from here,and depositing it there.This is how you get corrosion pits in master and wheel cyls.

I test brake fluid with a multimetre - positive to earth and neg into the resivour....anything over 300 millivolts means the fluid has absorbed too much water.The same thing happens to your coolant,it turns into an electrolite...anything over 600 millivolts and dump it.

[Ghost Lemur]

Thanks for the tip Motu. That one's going in the knowledge base.

How frequently would you suggest testing it?

[imdying]

What is DOT 5?
DOT 5 fluid, it has a silicon base.
You must never put this in your bike, unless (like some Harley Davidsons) it came with it factory.
It will make your seals (that have previously been in a glycol based fluid) swell, or otherwise deteriorate.

And the other brake fluids?
DOT 3/4/5.1 are all interchangable, they have a glycol base.

The higher the DOT number, the higher the wet boiling point. The higher the DOT number, the more hygroscopic it is, which means the faster water is absorbed by it. More hygroscopic merely means you need to change it more often. 5.1 fluid should be changed every year. Most road riders will not boil DOT 4, so they don't need to change to 5.1. Having said that, it's a cheap upgrade.

Why did they make DOT5
DOT 5 fluid isn't hygroscopic at all, it was developed for the US army. IIRC, Castrol had much to do with its development, and they no longer bother developing it further. It has been, at times, popular with people restoring old cars because it has less effect on paint (although it's a prick to repaint anything that has had it spilt on it). It was also popular with them because it's unhygroscopic nature resists rusting old cast iron cylinders.

Can you put DOT 5 fluid in your bike?
You can do anything if you're motivated. You shouldn't, but you can. You should ideally get seals designed for use in Silicon based fluids, either off the shelf, or more likely custom made.

You can however get seals for glycol, and soak them in DOT 5 fluid. If they don't swell in a week, they will probably be fine to use. If they do, get some more and try again.

The thing is, some compositions of rubber made for glycol fluids will function ok in DOT 5 fluid, some will not, trial and error. Personally, you'd be mug to try, silicon fluid it a cunt.

Good on paint, not hygroscopic, any bad points about DOT 5
Can be a bitch to repaint any area that has had it spilt on it, although silicon isn't as much of a problem these days as it has been (better paint preps now).
When fluid enters the system (it will via the heat cycling if nothing else) it pools in the system. Rather than lowing the boiling point overall, slightly degrading performance, the pools will boil off, causing big air bubbles and major brake fade.

You want me to Loctite what?
Yes, loctite the assembly areas on the braided lines. This is where the braided line meets the banjo assembly. If that comes undone, you're dead. They should also never ever be disassembled and reassembled, so loctite them up good (yes, people have brought me calipers off bike to recon, with the banjo piece attached... they didn't undo the banjo bolt, they undid the banjo to hose connector instead... plonkers).

The caliper bolts, a small amount of low strength loctite is cheap insurance, but not required.

The banjo bolts, a small amount of low strength maybe cheap insurance, but is not required.

So braided lines, worth it?
If they're not correctly stamped, they're illiegal on the road, and will fail a WOF. They degrade on the inside... you don't know if they're fagged or not. I've seen the inner lines give out, no more brakes, and that kids is not cool. They're primarily a racing component, designed to be replaced after a certain number of hours. They're quite safe used that way, as tracks have run offs, and they're replaced when they're old. As for performance increase... subjective, if you're not a demon on the brakes, you may be disappointed.

So rubber is safer then?
I have seen a rubber hose with a damaged inner take over 5000psi on the outer lining itself. Sure it bulged up something chronic, but it didn't kill the driver.

But they expand when they're hot!
Yes, you will get some expansion when the hoses are old. When they're new, the expansion is negligible for road riding. Its worth noting that whilst replacing braided lines after a certain amount of usage is recommended, your manual probably says replace your rubber lines every 3 years too.

But factory rubber lines are way too expensive
If you're stuck for rubber lines, or don't like the cost of new ones, I can make new lines out of a proper motorcycle specific low expansion rubber hose for a modest price. Always ring your dealer though, they might not be that bad. I don't deal in braided lines as a rules, too many problems with WOF agents not knowing what is legit and what isn't, and failing perfectly legal ones as a result. There has been futher instruction from the LTSA on this matter as of late, so this should be less of a problem. If you want top quality braided lines, crimped, none of the screw together bullshit (none of this are legal AFAIK), get Goodridge.

[imdying]

I test brake fluid with a multimetre - positive to earth and neg into the resivour....anything over 300 millivolts means the fluid has absorbed too much water.The same thing happens to your coolant,it turns into an electrolite...anything over 600 millivolts and dump it.

You are a cunning man

[imdying]

Umm aint DOT 5.1 a new mix that aint as good as 5 but has some of the longer lasting properties of 4.

You will find all the racing type of fluids are 5.

This is not correct.

[imdying]

mmmm.. i was under the impression that even tho they carried similar properties, you still shouldn't mix them up.. I'll stop by Ripco and have a read.

As for the water thing, yeah DOT 5.1 absorbs more, but I change it every 6 months anyway, so don't care. Keeps the brakes feeling sharp..

You should never mix fluids as a rule, it's bad practice. However, for the purposes of flushing a system with new fluid, 3/4/5.1 are interchangeable.

You should never ever put 5 into a system that has had a glycol based fluid, unless you replace every rubber component (including hoses and check valves) with components designed for silicon, or components that have been soaking in silicon for a significant period of time (to prove their compatibility).

[SuperDave]

Bugger the ones I've bought are the screw together type but they do look good quality but then again what do I know? I'll be fitting them tomorrow so I'll see how it all goes. Thanks for all that info imdying and thanks for answering the question regards the loctite - I purchased the necessary one today.

[SuperDave]

Just fitted them lines this afternoon and went for a short test run - seem to be working prefectly fine and a noticable increase in stopping power. But what I like the most is how the lever feels now, hopefully it will stay like it is now.

[imdying]

Bugger the ones I've bought are the screw together type but they do look good quality but then again what do I know? I'll be fitting them tomorrow so I'll see how it all goes. Thanks for all that info imdying and thanks for answering the question regards the loctite - I purchased the necessary one today.

The quality isn't necessarily in question, just their ability to be certified. Because they can be disassembled (which is bad) and reassembled, they need to be recertified every time... if they could be certified in the first place, ha!

[SuperDave]

I didn't realise that these wouldn't pass WOF - I did ask and was told that they were fine. Oh well no problem, I'll just go to the guy I bought the bike off and get my WOF from him, he'll pass it not sweat

[Colapop]

I was having a yarn to a guy today and he was saying that braided lines that have nut type fittings will not pass a warrant. They have to have crimped connections from now (or soon) onwards.

[imdying]

I didn't realise that these wouldn't pass WOF - I did ask and was told that they were fine. Oh well no problem, I'll just go to the guy I bought the bike off and get my WOF from him, he'll pass it not sweat

Yep, they don't necessarily have to pass legitimately And seeing as you're well aware of the risks involved, and won't disassemble them at the hose to banjo connector, it's a risk that's been sufficiently mitigated.

As colapop says, crimped lines only can be certified for use in NZ roads.

[SuperDave]

Okay so there are no screw in type ones that do comply?

I've just had a look at them and the following is stamped on the lines
DOT B.H. SAE J 1401 01/06 3MM. H.L

Does that mean anything?

I'm a bit ticked off, I did ask at the shop if these lines would pass WOF and if they were all okay and I was definately told that there wouldn't be any problem.

Sorry I'm asking again just want to make sure exactly where I stand here.