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Thread: 5.1 shelf life?

  1. #1
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    5.1 shelf life?

    I have had 3/4 of a bottle of Motul 5.1 on the shelf for about a year. What do you think? I was always told ditch brake fluid after you open it but I can't imagine it would absorb much water in AZ w/ a tight cap. Do you think the boiling point has dropped to less then a high quality DOT 4?

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    so long the cap was on right n tight you should be just fine
    Never look down to see if your bike actually shifted.. trees look for that type of stupidity

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    Well, living in wisconsin with no real bike shops around, I usually have to order a bottle of 5.1. I've definitely needed to unexpectadly bleed my Hope Tech M4s (5.1 fluid), and in those situations you just have to make do with what ya got. If you need to bleed your brakes, and you don't have a fresh bottle of 5.1 available then yeah try the old stuff out. I would suggest putting in an order for fresh stuff though and re-bleeding in a week or two when you get the new stuff; it's not that expensive, and you know you're using proper oil then.

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    Test the bottle for moisture with a fluid strip test. Your local automotive shop should have something like this.

    http://www.brakebleeder.com/products...ake-strip.html

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    Considering it only costs around $3 for a bottle I would just replace it. You can use whatever brand the autoparts store has as long as it is 5.1 compliant (Valvoline makes a synthetic that is compatible across the board). If it has absorbed moisture you may experience brake fade when you need your brakes the most!

  6. #6
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    I went ahead and used what i had to get rolling for a ride tomorrow. Judging by the color of the old fluid it was an upgrade. I'll order some fresh tonight. I live in BFE so any 5.1 must be ordered. Thanks everybody.

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    If the cap was tight, I wouldn't worry about it at all.

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    Like others have said,

    Yeah, not to worry. I'm sure it's fine as long as the cap was tight.

    And nothing I've ever seen in a regular auto parts store is '5.1' spec. DOT4 is mixable with DOT5.1, and is largely interchangeable, but will have a lower boiling point... and that is the whole point of DOT5.1 in the first place. I've had to get it from high end motorcycle shops, or order it online. $3 a bottle, no way. Going rate is like $11 a pint around here.


    Quote Originally Posted by frdfandc View Post
    Test the bottle for moisture with a fluid strip test. Your local automotive shop should have something like this.

    http://www.brakebleeder.com/products...ake-strip.html

    $68?!?!? Dayumm... maybe if I was servicing Ferraris or something.....

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    Quote Originally Posted by pimpbot View Post
    And nothing I've ever seen in a regular auto parts store is '5.1' spec.
    Oreilly's has it in stock... Just checked their website... YMMV but worth checking out.
    Last edited by FireLikeIYA; 06-26-2011 at 12:42 AM.

  10. #10
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    I want to say that 5.1 was brought about for classic cars that didn't get driven all that often. Consumers wanted a brake fluid that was less prone to absorbing moisture since there cars sat around a lot. Given that it's only been sitting around for a year and you live in the arid land of arizona I wouldn't think twice about using it.

  11. #11
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    Quote Originally Posted by customfab View Post
    I want to say that 5.1 was brought about for classic cars that didn't get driven all that often. Consumers wanted a brake fluid that was less prone to absorbing moisture since there cars sat around a lot. Given that it's only been sitting around for a year and you live in the arid land of arizona I wouldn't think twice about using it.
    my 2 cents. I was led to believe.
    Dot 5.1 fluid absorbs water quicker than Dot 4.
    5.1 was developed for car brakes with advanced features like ABS.
    After 12 months I wouldn't use an open bottle in my car but might in my bike.
    A new bottle of Dot 4 is about $6 were I come from.
    Fill opened bottles of brake fluid with clean glass marbles to reduce the air space in the bottle for storage.
    YMMV
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    Quote Originally Posted by mitzikatzi View Post
    my 2 cents. I was led to believe.
    Dot 5.1 fluid absorbs water quicker than Dot 4.
    5.1 was developed for car brakes with advanced features like ABS.
    After 12 months I wouldn't use an open bottle in my car but might in my bike.
    A new bottle of Dot 4 is about $6 were I come from.
    Fill opened bottles of brake fluid with clean glass marbles to reduce the air space in the bottle for storage.
    YMMV
    my further E research tells me that 5, 5.1 and 3/4 are all about the same for absorbing water. But the 5/5.1 fluid is a silicon based fluid and is not compatible with the seals that are used inside ABS equipment.

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    I think you need to do a little bit more searching, as dot 5 does not absorb water. It is also not related to the dot 3/4/5.1 group of brake fluid. Dot 5.1 is a racing/high temp brake fluid, most definitely not developed for antique cars.

    Edit: re-reading your post, it seems you have dot 5 and dot 5.1 confused - they are 2 different fluids, and most of what you seem to associate with 5.1 is actually information for 5.

    ie - 5.1 is just better dot 4
    dot 5 is silicone based.

  14. #14
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    Quote Originally Posted by customfab View Post
    my further E research tells me that 5, 5.1 and 3/4 are all about the same for absorbing water. But the 5/5.1 fluid is a silicon based fluid and is not compatible with the seals that are used inside ABS equipment.
    I have the upmost respect for "customfab" posts

    In this case you are not 100% correct. 5 and 5.1 are completely different.

    5 is used mainly by the US Army (apparently they have asked to stop using it) and Harley Davidson.

    5.1 is designed for use with ABS. You are correct some 5.1 has a longer life span. A 5.1 long life is available to buy.
    www.synlube.com
    Long Life up to 10 years, normal 5 years. I would think it wise to flush mountain bike brakes sysyems more often than that to get any dirt out of the system that gets past the seals. Have a look at the color of the fluid removed during some flushes.

    wikipedia Brake_fluid

    the-great-dot-brake-fluid-controversy
    stealth316.com brakefluid.htm
    allmorgan brakefluids

    I still think (happy to be shown I am wrong) 5.1 absorbs water faster than 4 or 3. I am unable to find this on the net. I may have picked that information up from this forum so it may be incorrect. The fact that "long Life" lasts up to 10 years may mean fact is incorrect. It seems this long life is popular with antique car owners. My readyness to believe 5.1 absorbs water faster than 4 is that any thing high performance usually comes at a cost. 5.1 costs more than DOT 3 and 4 fluid, one trade off for more performance. So when told it absorbs water faster ie didn't last as long. I was happy to believe it as it seems like a fair trade off for more performance.
    Last edited by mitzikatzi; 06-28-2011 at 02:39 PM.
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  15. #15
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    Dot 3,4 or 5.1 work in Hope brakes.
    Don't waste your money. Buy the cheap Dot3 for $2 at AutoZone. I do.
    Use that bottle for years. A tiny bit of moisture isn't going to matter on a bicycle.
    Clean fluid is always better than dirty fluid.

  16. #16
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    http://en.wikipedia.org/wiki/Brake_fluid
    I'm going to stick w/ fresh 5.1. I like my brakes to work at their best. Thanks again everyone.

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    Quote Originally Posted by mitzikatzi View Post
    5.1 is designed for use with ABS.
    Dot 3/4/5.1 are all designed to work with ABS. It is more just a way to classify boiling points. Almost all cars are spec'd for Dot 3 but higher performance cars will be spec'd for Dot 4. Mercedes is the only car that I know of that specs 5.1. It doesn't hurt to go up in range but it isn't advised to go down. Dot 5 is incompatible with Dot 3/4/5.1 and shouldn't be used in systems designed for such... it will cause seal failure eventually.

    That long life brake fluid sounds interesting... I have used another fluid made by Valvoline that was a synthetic and claimed to be compatible with Dot 3/4/5.1 AND 5. I just found out that they stopped producing it after only a few years in production which makes me a little nervous because that is what I have in my DD right now!

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    Quote Originally Posted by egebhardt View Post
    Dot 3,4 or 5.1 work in Hope brakes.
    Don't waste your money. Buy the cheap Dot3 for $2 at AutoZone. I do.
    Use that bottle for years.
    A tiny bit of moisture isn't going to matter on a bicycle.
    Clean fluid is always better than dirty fluid.
    True- the moisture content of years old brake fluid is much more of a concern with the temps generated in car brake systems.

    Valvoline makes a DOT 3/4 compatible synthetic fluid that will work fine (and I have read is used OEM in many bike brakes). If someone is worried about it, tightly close the bottle and store it in a Ziploc storage bag.

    http://www.valvoline.com/products/br...brake-fluid/28

  19. #19
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    Quote Originally Posted by The_Rizzle View Post
    I think you need to do a little bit more searching, as dot 5 does not absorb water. It is also not related to the dot 3/4/5.1 group of brake fluid. Dot 5.1 is a racing/high temp brake fluid, most definitely not developed for antique cars.

    Edit: re-reading your post, it seems you have dot 5 and dot 5.1 confused - they are 2 different fluids, and most of what you seem to associate with 5.1 is actually information for 5.

    ie - 5.1 is just better dot 4
    dot 5 is silicone based.
    Yup, so many fluids to keep track of. It's pretty confusing to have the 5.1 be a part of the 3/4 family but 5 is something completely different. Plus I was trying to remember what I had read in a road and track article years ago. Thanks for putting the correct info out there.

  20. #20
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    Take from this what you will but...
    I haven't changed my brake fluid in my 92' Toyota truck since I bought it in 1996.
    And I would bet money that it is probably original factory fluid.
    So almost 20 years on the same Dot 3 fluid...
    The brakes work very well and I drive 6 different vehicles on a regular basis and have a good idea on decent brake performance.

    My take is that brake fluid can last a long time in a closed system.

  21. #21
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    ^ Your trucks brake system is trashed because you neglected it. Guarantee it. Its just waiting to fail, and its going to cost you a master cylinder and probably a set of calipers all around.

    Fluid has no impact on feel or performance of a brake system. Its either working, or its boiling and goes mushy. You could fill your brakes up with water and get the same braking performance.. until it overheats. Most people dont heat the brakes enough to boil out the water and cause problems, so they just figure everything is fine and not in need of service.

    After a couple years the fluid has reached its capacity of absorbing water, so you have pools of water rusting out your calipers, master cylinder, abs bits.. and eventually the lines and fittings. Thats the major reason to keep your fluid fresh, to stop rusting.

  22. #22
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    Quote Originally Posted by One Pivot View Post
    ^ Your trucks brake system is trashed because you neglected it. Guarantee it. Its just waiting to fail, and its going to cost you a master cylinder and probably a set of calipers all around.

    Fluid has no impact on feel or performance of a brake system. Its either working, or its boiling and goes mushy. You could fill your brakes up with water and get the same braking performance.. until it overheats. Most people dont heat the brakes enough to boil out the water and cause problems, so they just figure everything is fine and not in need of service.

    After a couple years the fluid has reached its capacity of absorbing water, so you have pools of water rusting out your calipers, master cylinder, abs bits.. and eventually the lines and fittings. Thats the major reason to keep your fluid fresh, to stop rusting.
    20 years bro, 20 years... Still works like a champ... I guarantee it...
    Most people would be stoked to get 20 years out of their vehicles brake system components even with changing the fluid regularly.

    Pools and pools of water... Oh My!

  23. #23
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    Food for thought...

    From a Feb. 14th 2011 Pinkbike article on Hayes V-series rotors. " Bicycles are of course lighter than most all other vehicles with disc brakes, but in the ultra weight conscious bike industry, the mass of the rotor is minimized creating extreme usage conditions that match or exceed the harshest motor racing environments. "

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    I use one of these at the motorcycle shop, found it cheaper on one of the tool trucks that frequent our shop.

    http://www.jegs.com/i/JEGS%20Perform...0002/-1?CT=999

    As for anyone not changing break fluid for 20 years....you probably have no viable input on this topic!

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    Quote Originally Posted by wormvine View Post
    20 years bro, 20 years... Still works like a champ... I guarantee it...
    Most people would be stoked to get 20 years out of their vehicles brake system components even with changing the fluid regularly.

    Pools and pools of water... Oh My!
    I was in the same thought process as you until I over heated my brakes and ended up in the middle of an intersection a couple of years ago. My pedal basically went to the floor. The fluid was 8 years old and I was coming off an interstate doing 75mph. About a year prior to this I was informed by an auto shop that the fluid should be replaced. Having never bothered replacing brake fluid before I blew it off as a sales pitch. Since this incident I started replacing my brake fluid every 2-3 years. Your old fluid boiling point decreases with age gradually so you may not notice a decrease in performance but I bet you will with new fluid. It is kind of like automatic transmission fluid... You may or may not notice a difference when you change it but if you dont you are looking at premature failure.

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    Quote Originally Posted by murd View Post
    Food for thought...

    From a Feb. 14th 2011 Pinkbike article on Hayes V-series rotors. " Bicycles are of course lighter than most all other vehicles with disc brakes, but in the ultra weight conscious bike industry, the mass of the rotor is minimized creating extreme usage conditions that match or exceed the harshest motor racing environments. "
    Total BS....while on a rare occasion a rotor may get blue hot...it is nothing like the red hot for 3 hours on a formula one circuit.

  27. #27
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    Quote Originally Posted by jeffscott View Post
    Total BS....while on a rare occasion a rotor may get blue hot...it is nothing like the red hot for 3 hours on a formula one circuit.
    Your comparing carbon ceramic brakes to stainless rotors with sintered metallic pads. Apples to Oranges. Now comparing bicycle disc brakes to Nascar or ALMS GT might be a closer comparison.

    Most consumers use there brakes similar to a normal passenger car. Moderate stops separated by plenty of cooling time. That cooling time would render the brakes of a modern F1 car almost useless.

  28. #28
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    Quote Originally Posted by FireLikeIYA View Post
    I was in the same thought process as you until I over heated my brakes and ended up in the middle of an intersection a couple of years ago. My pedal basically went to the floor. The fluid was 8 years old and I was coming off an interstate doing 75mph. About a year prior to this I was informed by an auto shop that the fluid should be replaced. Having never bothered replacing brake fluid before I blew it off as a sales pitch. Since this incident I started replacing my brake fluid every 2-3 years. Your old fluid boiling point decreases with age gradually so you may not notice a decrease in performance but I bet you will with new fluid. It is kind of like automatic transmission fluid... You may or may not notice a difference when you change it but if you dont you are looking at premature failure.
    I hear ya man. Its not like I don't want to change my fluid. I am not deliberately holding out replacing the fluid. It just worked out that way. Lots of other vehicles and toys to maintain. It's just an example of how long the fluid can last in a closed system.
    Maybe I should get Blackstone labs to do an oil analysis to see how it compares to fresh DOT 3.
    Anyone have a venturi brake bleeder I can borrow?

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