Bad brakes

[kilo3]

You do you.

I'm just sick of the BS surrounding brake fluid and everyone blindly repeating the same lackadaisical fear mongering manufacturers suggest but NEVER even bother to test the damn stuff.

Sure sells a lot of brake fluid I suppose.

[petshark]

I've done the front and rear again and pulled 2 to 3 reservoirs through the system. The result is excellent, both feel a lot firmer and I have am totally happy. No more bad brakes for me.

21 hours ago, Lone Wolf said:

Personally I wipe a small ring of grease around the brake nipple and zero air can get in, it dramatically reduces the bubbles you see - and the ones you see are from the brake system not outside atmosphere. This is a legit issue. Speed bleeder nipples come with a pre-applied sealant around the threads to combat this problem, and they sell a bottle of liquid to re apply because it wears off the threads. I just use the grease.

I tried so use grease around the bleeder nipples but only had white lithium, vaseline or copper grease lying around. Went with the lithium but I don't think it worked. I saw so much air pass by on the front right hand side front that I'm not sure if this was all from the previous bleed gone wrong or that it was sucked in through the threads. I suspect it was the latter.

[Lone Wolf]

I own a lot of tools. 3 different torque wrenches so there is a "sweet spot" in the middle of the range for big, medium, and small fasteners. I have a digital caliper. The Motion Pro chain breaker, and recently got the No Mar tire changer so I don't have to use tire irons anymore. I have a Fluke digital multimeter. I have the Morgan carb tune and sync my own bikes. I am kind of a tool freak. 

In your line of work you may have access to moisture testing equipment, and a background to understand it, which is awesome.

I don't. And although I do buy tools that I may only use once (just changed steering bearings on older bike) I really don't feel the urge to get a moisture meter.

For my background, I once restored a 50 Chevy truck and had to bore out the slave cylinders due to corrosion. The brakes were fantastic. Then I let it sit too long and some of the parts rusted up again. Maybe the metals are better now and less prone to corrosion, but that was my lesson that brake fluid (that I had put into a bone dry system) can absorb water.

Master cylinders tend to have a rubber membrane under the lid. It will essentially seal the brake fluid from atmosphere - yet after time moisture does get in the fluid. I suppose from the small area of atmosphere below the membrane. Eventually there are bubbles in the system. I am not an expert, but would imagine that H20 subjected to repeated heat of braking may release some oxygen. I don't know where else those bubbles or sponge feeling would come from if there was no air leaking into a closed system.

It's really not my battle, and certainly no battle with you, but I don't have a problem with fresh brake fluid. Motor oil is different, as they mention in the NAPA article I posted. I just don't take any chances with brakes - I even face east every time I pour fluid in the master cylinder.

[Lone Wolf]

10 minutes ago, petshark said:

I tried so use grease around the bleeder nipples but only had white lithium, vaseline or copper grease lying around. ...I saw so much air pass by on the front right hand side front that I'm not sure if this was all from the previous bleed gone wrong or that it was sucked in through the threads. I suspect it was the latter.

This SIL-Glyde is the proper grease for moving parts in a brake system, but really you can use anything to just seal around the threads. I have used wheel bearing grease then wiped it off when done. 

You have to put it where the tube connects to the bleeder nipple as well. Smear it around the end of bleeder nipple, push the clear hose over that, and it should be sealed. Wipe it 360 degrees around the bleeder nipple threads on the caliper before loosening the bleeder nipple. At that point there is no place for air to be introduced. The difference is night and day if you are using a vacuum bleeder but also makes a difference with old school tube in a bottle. Not my idea, I got it from watching a bunch of youtube videos including for car brakes.

[petshark]

1 hour ago, kilo3 said:

You do you.

I'm just sick of the BS surrounding brake fluid and everyone blindly repeating the same lackadaisical fear mongering manufacturers suggest but NEVER even bother to test the damn stuff.

Sure sells a lot of brake fluid I suppose.

I'm open to the idea that this is fear mongering but at the same time also believe that there are many controversial statements that get a life of their own, "big corporations" sometimes can fool us, but the same goes for "internet truths" and conspiracies. That is the downside of having so much information at our fingertips.

Anyway, this intrigues me so I did some research and tried to find any reported myths but couldn't find any, just hundreds of people in the industry repeating the same thing (which does not prove anything). I then tried to find scientific data and studies and found this one by Leica Microsystems Inc, Educational and Analytical Division in NY quite interesting.

It goes into great depth so I didn't read all of it but I found this part of the conclusion most useful:

Quote

The safety of a motor vehicle’s braking system is directly related to the water content of the brake fluid. As water content increases, the boiling point decreases. Water content in brake fluid increases 1% to 2% per year. A recent study has shown that temperatures of brake fluid in the wheel cylinders of vehicles can reach high enough levels to boil brake fluid containing significant amounts of water. Our study on used brake fluid confirms over 60% of the vehicles tested in Germany had brake fluid with water content above 4%. On the average 4% water reduces the boiling point by 100 degrees centigrade. The brake fluid in the vehicles which tested over 4% water could reach the boiling point under high braking load for short periods or light but continuous braking such as encountered when descending from elevation.

I would conclude from this that we should be be able to use brake oil for less than two years once opened, either in the bike or in the bottle. The bottles are small but after doing my first two bleeds I get the impression that you could do longer with a bottle than that. So the truth seems to be in the middle; no need to throw it away after three months but don't use an open bottle 1,5 year later unless you plan to bleed again after three months but that just seems silly. High profile racers will obviously take zero chances so it makes sense that Dave Moss does not want 0,5% of water in new brake oil, that does not mean that we have to do the same.

Variables like different air moisture levels will probably also play a big role and I assume that this range is the 1% to 2% per year mentioned in the study.

Checking with a refractometer is obviously best but just to find some common ground between the fear mongering and having to buy another tool for something that is not really a case-by-case thing but just something where we need to know how it works and be done with it, I think I will remember "absolute maximum usage of opened oil = 2 years" and write a date on my bottle when I open it. 

That said I had an ER6n for 7 years and never did any service except oil change and tyres and the brakes were still fine, a lot better than the Tracer when I bought it. 🤷‍♂️

[fjray]

I'd wager if you ever did the brakes on a 1800 Goldwing, all eight bleeders in the correct order, you'd put new fluid in just to insure that it wouldn't get gunked up and then it would really take some $$ to get it going again.  So yeah, bleeding every year wasn't something that I was ever going to forgo.  Think about this heavy pig of a bike, with a sweet motor, downhill into a switchback.  You don't want old fluid in there.  

[roadrash83]

On all my restoration projects I replace all the brake lines, rebuild the master cylinders and calipers. Then I get to run DOT5 Silicon fluid, its non hygroscopic (does not absorb moisture) Know all I need is fuel that does not go to crap after 3months!

[Merciless]

Does anyone know whats the piston diameter of stock caliper ? 

[2and3cylinders]

I have one of each of the below 3 types/ models (they all work the same based on water having a higher conductivity than glycol based brake fluid), and never found any fluid sample using each tester on fluid collected from a caliper flush n' bleed (low points in system is where H2O settles and causes worst corrosion) or an opened bottle after a year or more to have more than 1.5% agua.  The test paper is handy but goes bad if not kept in double zip lock tpbags with a desiccant (I do the same with open bottles of brake fluid).  There is a test paper for coolant too.  But the BOMB for changing coolant is the UView 550000!

I'm a whacky tool-a-holic too, whose been creating, fabricating, and collecting cool and special tools for 40+ years (besides essentials like a Handy Lift and NoMar tire changer), some I've only used/ needed once (I've drawn the line on digital torque wrenches or the one like Motion Pro makes that fits on a combo hand wrench, etc, as I've developed a very accurate "pretensioning" wrench in my right wrist).  So investing $30 to test brake fluid testers is a no brainer, as is buying a UView 550000 once you've used one only once!  I have their blown head gasket testing kit too.

The biggest risk to your brake system IMO (as I've mentioned twice before) is flushing / bleeding by pumping the lever (versus the vacuum or pressure methods, as MityVacs are inexpensive), so that the MC piston with its fragile rubber seals is pushed to the bottom of the bore where nasty crud accumulates which will damage the seals.

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[koth442]

20 hours ago, Lone Wolf said:

Once a container of brake fluid is open, the clock starts ticking on shelf life.
Dave Moss says if you don't use it within 3 months to toss it (due to absorb moisture from atmosphere).

I know Dave personally. He's a great guy and means well, but he can be massively overkill. He's also told me likes to take a toothbrush to his brake caliper pistons after every race weekend. 

[BBB]

3 hours ago, 2and3cylinders said:

The biggest risk to your brake system IMO (as I've mentioned twice before) is flushing / bleeding by pumping the lever (versus the vacuum or pressure methods, as MityVacs are inexpensive), so that the MC piston with its fragile rubber seals is pushed to the bottom of the bore where nasty crud accumulates which will damage the seals.

I’ve read this a few times before and can never figure it out. I’ve looked at cutaway diagrams of master cylinders and still can’t see how this would work.

How does pumping the lever move the seal to a different position than any normal movement? All pumping does is raise the system pressure when there is air in the circuit; conversely it can’t raise the pressure in a pure liquid.

Why do you think crud accumulates in the bottom of the bore and why doesn’t it simply get pushed away each time you pull the brake lever?

I’m genuinely confused here so would appreciate explanations.

[Lone Wolf]

32 minutes ago, BBB said:

How does pumping the lever move the seal to a different position...

In normal operation, the brake lever doesn't easily move all the way to the handlebar.
At some point the fluid pushes the brake pads against the rotor, and the movement within master cylinder halts right there.

On an old engine that needs to be bored out due to wear, you can see where the piston rings hit top dead center, and the bottom of the stroke. Above and below the area traveled by the piston and it's rings, the cylinder will be normal. It can be difficult to remove the old piston out of the worn engine because the rings hang up at the ridge formed at the location where normal travel ends. You get that old piston out, take the engine block to the machine shop where they bore out the cylinder a small amount. You purchase oversize piston and rings. Good as new.

Same concept for brake system. During normal use the piston in the brake master cylinder only goes back and forth in a specific range of movement. You crack open the bleeder nipple in the caliper and start pulling the lever all the way to China, and the piston is now moving beyond it's normal area and depending on the age of the system could be hitting things stuck on the walls of the bore that interfere with the rubber seal. Could cause damage to the seal.

Edited January 27, 2021 by Lone Wolf

[kilo3]

Dave Moss would replace the master cylinder every 3 months, I mean it's only 15 bucks. 😁

[2and3cylinders]

5 hours ago, Lone Wolf said:

In normal operation, the brake lever doesn't easily move all the way to the handlebar.
At some point the fluid pushes the brake pads against the rotor, and the movement within master cylinder halts right there.

On an old engine that needs to be bored out due to wear, you can see where the piston rings hit top dead center, and the bottom of the stroke. Above and below the area traveled by the piston and it's rings, the cylinder will be normal. It can be difficult to remove the old piston out of the worn engine because the rings hang up at the ridge formed at the location where normal travel ends. You get that old piston out, take the engine block to the machine shop where they bore out the cylinder a small amount. You purchase oversize piston and rings. Good as new.

Same concept for brake system. During normal use the piston in the brake master cylinder only goes back and forth in a specific range of movement. You crack open the bleeder nipple in the caliper and start pulling the lever all the way to China, and the piston is now moving beyond it's normal area and depending on the age of the system could be hitting things stuck on the walls of the bore that interfere with the rubber seal. Could cause damage to the seal.

Well said!  BTW, I've lightly honed MC bores as part of a rebuilds, and once managed to coat a rough bore with epoxy and have it function for several years more.  

[petshark]

On 1/27/2021 at 1:01 PM, 2and3cylinders said:

The biggest risk to your brake system IMO (as I've mentioned twice before) is flushing / bleeding by pumping the lever (versus the vacuum or pressure methods, as MityVacs are inexpensive), so that the MC piston with its fragile rubber seals is pushed to the bottom of the bore where nasty crud accumulates which will damage the seals.

 

20 hours ago, Lone Wolf said:

During normal use the piston in the brake master cylinder only goes back and forth in a specific range of movement. You crack open the bleeder nipple in the caliper and start pulling the lever all the way to China, and the piston is now moving beyond it's normal area and depending on the age of the system could be hitting things stuck on the walls of the bore that interfere with the rubber seal. Could cause damage to the seal.

This also got me thinking.. would you agree that if I see no crud at all in the MC and if I bleed by using the lever at least once a year on an almost new bike that there is little chance that there is anything in the bore that could hurt the seals? I can certainly see that with my ER6n without any brake service in 8 years there probably would be some crud there. But by doing this frequently from the start it should be ok, no?

Edited January 28, 2021 by petshark