Not an oil thread

[Dads_FJ]

Not an oil thread but should be just as good as one... per the Yamaha TDM850 service manual, "change your brake hoses every two years and your brake fluid only when your brakes are dissembled".





So the question begs, how often do you replace your brake hoses and fluid?

[1tinindian]

My 82 Suzuki still has the original hoses, oh my!

[Pat Conlon]

IIRC, on the FJ, Yamaha recommends to replace the brake lines at the 4 year mark. I did mine back in '89.

I don't have access to my manuals, can someone check my memory on this? ^^

I run DOT 5 which does not absorb water (non-hygroscopic) and I live in a dry climate, so I flush the systems out every 2 years. Because DOT 5 is lighter than water (floats on water) I unbolt and flip my calipers and clutch slave upside down and zip tie them a day before I flush, that way any accumulated water will pool around the bleed nipples. While holding them upside down, open up the bleeder and out comes any water.
I've noticed that after wet weather riding, for some reason water can and will accumulate in the clutch slave, not so much in the R-1 calipers.

On DOT 3/4 which absorbs water, you don't have to do this.
Any water in the system will be suspended in the fluid and thus, will flush out with the fluid.

[TexasDave]

My 82 Suzuki still has the original hoses, oh my!

My 84 FJ also has the original hoses which are working just fine by the way.

Dave

[ribbert]

So the question begs, how often do you replace your brake hoses and fluid?

A good way to remember when to change the brake hoses on your bike is to do them the same time you replace them all on your car (and disassemble wheel cylinders/calipers and master cylinder for cleaning, flush fluid and replace, remove and scrub discs etc)

Noel

[Pat Conlon]

Yea, 3 things could have occurred....
1) those Yamaha engineers are idiots.
2) Yamaha folks are greedy bastards who just want to sell you parts
3) Yamaha's legal counsel advised them to say that to cover their ass.

Really, the oem rubber lines are good for twice the length of time they recommend....no wait... I mean the oem lines are good for 10 times the length of service life they recommend......just round it up to the life of the bike of the bike, just like all the other rubber parts. Remember, it's just the brakes.

You got 30 year old tires with good tread on them? Look fine on the outside? No problem!

You feeling lucky today?

[Earl Svorks]

    Just thinking aloud on the DOT3/4 brake fluid and the water it may absorb and the scary idea of ones brakes becoming non existent if and when that water should come to boil. Now, if the brakes are being applied, hard, it is possible (as I recall from trade school theory) that hydraulic pressure can go as high as 1,000 psi. Under that pressure, at what temperature does water boil? Will it boil at all if it has become one, chemically bonded with the glycol base of the brake fluid ?  With glycol coolant, the boiling point is higher when cut 50 % with water.     Further, if the DOT 5 fluid does allow the water to remain intact, why is there no fear of it boiling in a caliper ?
     Cheers
    Simon

[ribbert]

Yea, 3 things could have occurred....
1) those Yamaha engineers are idiots.
2) Yamaha folks are greedy bastards who just want to sell you parts
3) Yamaha's legal counsel advised them to say that to cover their ass.

Really, the oem rubber lines are good for twice the length of time they recommend....no wait... I mean the oem lines are good for 10 times the length of service life they recommend......just round it up to the life of the bike of the bike, just like all the other rubber parts. Remember, it's just the brakes.

You got 30 year old tires with good tread on them? Look fine on the outside? No problem!

You feeling lucky today?

Whoaaaaa.... Who got off the wrong side of their FJ this morning.  

If brake hoses become US from use they should, if anything, be changed more frequently on cars than bikes.

And no Pat, luck doesn't come into it and I don't have a cavalier attitude to brakes, but I do have a lot of experience.

Noel

[Pat Conlon]

Noel, are you aware of Any car manufacturer that specifies a 4 year service life on their oem brake lines?

Didn't think so. Still, you keep comparing motorcycles to cars.

Change your bike's oem rubber brake lines when you change your car's is bad advice and certainly not the advice of experts.

[ribbert]

Noel, are you aware of Any car manufacturer that specifies a 4 year service life on their oem brake lines?

Didn't think so. Still, you keep comparing motorcycles to cars.

Change your bike's oem rubber brake lines when you change your car's is bad advice and certainly not the advice of experts.

No I'm not, nor any other motorcycle manufacturer. Nor am I aware of any brake hose manufacturer who does. Yamaha don't even make their brake hoses and I'm not aware of any hose manufacturer who specifies 4 years. I suspect the likely origin of the 4 years is the hose makers have given Yamaha an already conservative number and they've halved it for good measure.

I use cars as an example because they are around in larger numbers, do higher mileages, the fleet is considerably older and the hoses operate in a harsher environment. This makes it much easier to gauge longevity and the rate of breakdown before becoming unsafe.

As I said, if anything, car brake hoses deteriorate faster than motorbike hoses.

Pat, I was a Licenced Vehicle Tester for many years. This is a Govt issued licence for the purpose of carrying out vehicle inspections and issuing Roadworthiness Certificates, a legal requirement with every change of ownership and vehicle registration. This is no kick the tyres quickie inspection. It is a couple of hours work in a well equipped workshop. I have inspected thousands of cars and hundreds of bikes. The inspection is over the top to the point of being ridiculous but even so, brake lines were (and still are) only subject to a visual inspection.

The most worrying motorbike brakes to me are some of the routing, clamping, abrading and lengths of owner fitted braided lines I have seen.

Pat, I think you and I will just have to respectfully agree to disagree on this one.

Noel

[Pat Conlon]

......I suspect the likely origin of the 4 years is the hose makers have given Yamaha an already conservative number and they've halved it for good measure.

Ok, so if Yamaha halved a conservative number (Yamaha specifies 4 years) that conservative number is 8 years, say the brake hose manufacturer's halved their number (8 years) just to be safe, so the actual service life number on the hose is 16 years....? Let's add 10 years to that, just because, make it 26 years.

Noel, as an expert LVT, do you not agree that 30 years is just a 'tad' outside the service life of the oem rubber hoses?

In my signature line, I advise changing the oem brake hoses because they are over due for replacement.

I stand by that statement and I'm not standing alone. I have a lot of company saying the same thing.

Lastly, motorcycle brake lines have UV exposure, something cars don't have.

[CutterBill]

Yea, 3 things could have occurred....
1) those Yamaha engineers are idiots.
2) Yamaha folks are greedy bastards who just want to sell you parts
3) Yamaha's legal counsel advised them to say that to cover their ass.

There is a 4th possibility... The number in the manual is a mistake.  It's not the first mistake I've found in the FSM.

I will agree that a 2 year service life for brake hoses is overkill.  But no more than 10 years, certainly.
Bill

[carey]

Just thinking aloud on the DOT3/4 brake fluid and the water it may absorb and the scary idea of ones brakes becoming non existent if and when that water should come to boil. Now, if the brakes are being applied, hard, it is possible (as I recall from trade school theory) that hydraulic pressure can go as high as 1,000 psi. Under that pressure, at what temperature does water boil? Will it boil at all if it has become one, chemically bonded with the glycol base of the brake fluid ?  With glycol coolant, the boiling point is higher when cut 50 % with water.     Further, if the DOT 5 fluid does allow the water to remain intact, why is there no fear of it boiling in a caliper ?
     Cheers
    Simon

Simon,

I'd have to pull out an old text book to find you an exact answer, but the boilers at work were about 650 psi and the feedwater temp was around 500+deg F. 

The thing to remember, when pressurized water above 212 deg F suddenly experiences no pressure, it flashes to steam and expands about 1000 times.  In a brake system, as soon as you release the brake lever, the brake fluid/water wouldn't be under 1000 psi. 

I don't think the water bonds with the fluid as much as it mixes into an emulsion.

As far as changing brake lines, I usually sell the bike before the lines need replaced 

[balky1]

If something is hygroscopic that means it mixes or bonds with water (usually bonds water by a meaning of hydrogen bonding or van der Waals forces). It does not create an emulsion. Emulsion is a type of colloid in which 2 phases never mix, but are dispersed in one another in a form of small droplets (u can make it with oil in water if you shake vigorously, but leave it be and soon you will again have two distinct phases).
That is true for water boiling what you said. But that would assume water is a separate phase in DOT 3/4/5.1, what it isn't. It is mixed and hydrogen bonded. The fact that boiling point is lowered with more water in the fluid remains. So I suppose the thing you talked about would happen, but with a slightly different variables (temp and pressure) than for a clean water phase. I did see a flash point temperature noted on the brake fluid casings.

[FJ_Hooligan]

Recalling a project first proposed by Jeff Hoffman (which he never got around to doing), when time came for my son to do a 6th grade science project we chose to boil brake fluid.

I've lost the data, but we had a control specimen which was a sealed container of DOT 3 fluid.  During the test, we diluted the fluid with varying percentages of water, mixing it in and allowing a period for it to stabilize and absorb.  Something like 1%, 3%, 5%, 10%, and 20% solutions were tested.  One other thing we did was pour an amount of fluid into an open container and let it sit in the garage for about 2 or 3 months (thus allowing it to naturally absorb water from the atmosphere).

When time came to do the boiling, I was kind of amazed.  First we boiled the control sample from a factory sealed container.  It was cheapo Walmart DOT 3, but as I remember, it didn't actually boil until about 450 degrees F!  By that time it was smoking quite a bit when it finally boiled. This was all at atmospheric pressure.  Boiling the various samples, we plotted a curve of boiling temperature versus %water contamination.  Again, the details escape me but I remember that it only took a small amount of water contamination to significantly reduce the boiling temperature down into the mid 200 degree F.  Anything above about 10% contamination basically had the approximate boiling point of water. 

It was kind of neat to identify where the open container fell on the curve.  Being exposed to the atmosphere for a few months the fluid had absorbed about 8% water which was significant in affecting the boiling point.