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  1. #1
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    Does Mineral Oil or DOT Fluid work better?

    Are there advantages to using Mineral Oil or DOT fluid? Would you consider this when buying disk brakes? Or does the brand of disk brake matter more.

  2. #2
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    Hydro brakes are designed to use one or the other. You can not switch. Buy the brake, not the fluid.
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  3. #3
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    Quote Originally Posted by Spectre
    Are there advantages to using Mineral Oil or DOT fluid? Would you consider this when buying disk brakes? Or does the brand of disk brake matter more.
    DOT fluid's biggest advantage is it doesn't boil. However DOT 3&4 will absorb water, but DOT5 won't being Silicone based. DOT fluid is nasty, paint-stripping stuff.

    Shimano brakes seem pretty reliable so I wouldn't be put off by their use of mineral oil. Just spec the right brake and size rotor for the job and brake fade won't be an issue...

  4. #4
    Ole
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    Actually...

    Quote Originally Posted by Haggis
    DOT fluid's biggest advantage is it doesn't boil. However DOT 3&4 will absorb water, but DOT5 won't being Silicone based. DOT fluid is nasty, paint-stripping stuff.
    Actually, DOT can also boil, but the boiling temperature is pretty high, up to 270 C (518 F). The big advantage over mineral oil, is that it does indeed absorb water. Over time, some moisture will find it's way into the system. With mineral oil, that water will sink to the lowest point, the caliper, and sit there as a drop of water. As soon as the temperature reaches 100 C (212 F), the water boils, and you have catastrophic loss of brake pressure (puming the lever quickly several times will give you the pressure back. Then hold it until the bike stops, and wait for brakes to cool down). With DOT, the water is absorbed into the fluid, lowering the overall boiling temperature from 270 C to say 250 C. There is a reason NO-ONE outside the bicycle business uses mineral oil in braking systems.

    DOT 3, 4 and 5.1 are alle glycol based. DOT 5 is silicone based and mainly used in heavy motorcycles like Harley. DOT 3, 4 and 5.1 can all be used in the same systems, but should not be mixed. DOT 5 is a completely different game, and does not work with the others.

    DOT - American Department Of Traffic. At some point in time, it was deemed that oil was not a safe fluid for brakes, and the DOT set out to standardize a fluid that was safe yo use.

    Ole.

  5. #5
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    I use Valvoline Synthetic brake fluid. Conditions the seals a bit, making them last longer. Allows for better retraction because it's thermally stable and has a better lubrication quality to it. The BP is higher than anything an MTB bike will ever create. It's also cheap at about $5USD per quart.

    If you can't find that, you can always find ATE Super Blue brake fluid, which is similar and more in tune for racing. European cars use this stuff out of the factory. A bit more expensive.

  6. #6
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    But isn't it ironic that the biggest and baddest disc brake in the business, and one of the oldest - the Magura Gustav - is a dedicated DH brake and I can assume it's capable of abosrbing as much heat as any bike disc brake and it still uses mineral oil.

    Maybe the Magura engineers know more than we do and they don't listen to theories and opinions.

    BTW - the T in DOT is Transportation.

    Mike T. (mcm # 717 & FOG)
    Mike The Bike's home wheelbuilding info - dedicated to providing Newby wheelbuilder information and motivation.

  7. #7
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    mineral oil doesnt absorb water and wont strip your paint,That has nothing to do with performance, if you flush your fluid regularly and clean up an spills the DOT fluid will handle the heat better. There are people that have gotten brake fluid up to boiling.

  8. #8
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    Mineral oil is used because it's user friendly in bike applications. It is expensive but will not outperform DOT fluid. DOT fluid is thinner and more thermally stable than the mineral stuff. It allows the pistons to retract easier=less drag.

  9. #9
    WOY
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    Maybe some company uses their own mineral based oil because

    1, less compatibility issues (eg mixing DOT 5 with DOT X.1, different brand having different seal swelling properties etc)

    2, market their brake to used their own brake fluid and make more $$$ in the process

  10. #10
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    Quote Originally Posted by WOY
    Maybe some company uses their own mineral based oil because

    1, less compatibility issues (eg mixing DOT 5 with DOT X.1, different brand having different seal swelling properties etc)

    2, market their brake to used their own brake fluid and make more $$$ in the process
    so you are saying that people that use mineral aren't smart enough to read the labels?
    DOT fluid is not proprietary if people choose to buy brake fluid from the brake manufacturer then thats there business. I use the same stuff I use in my car.

  11. #11
    WOY
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    [QUOTE=iopturbo]so you are saying that people that use mineral aren't smart enough to read the labels?

    Not at all, all I meant is that big S and big M say/design their bike brake to use their own proprietary fluid so it is more of a controlled environment. Also user of these brake has to buy their fluid which is usually more expensive so the company is marking more money in the process.


    [QUOTE=DOT fluid is not proprietary if people choose to buy brake fluid from the brake manufacturer then thats there business. I use the same stuff I use in my car.[/QUOTE]

    Although there are specifications for the DOT brake fluid as outlined by the US DOT, the swelling component is not the same for fluid from different manufacturers (from memory the DOT swelling component is given by a range). I believe because bike disk brakes have much tighter tolerance than say cars, the swelling and lubricating factor is more critical.

    I use the same fluid for my bikes (2 pair of mono minis, 1 set of Hayes), brakes and clutch for my street car and track car – Mutol 5.1.

  12. #12
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    Quote Originally Posted by WOY
    Although there are specifications for the DOT brake fluid as outlined by the US DOT, the swelling component is not the same for fluid from different manufacturers (from memory the DOT swelling component is given by a range). I believe because bike disk brakes have much tighter tolerance than say cars, the swelling and lubricating factor is more critical.

    I use the same fluid for my bikes (2 pair of mono minis, 1 set of Hayes), brakes and clutch for my street car and track car – Mutol 5.1.
    you race cars? too bad you are in australia or I would challenge you to a race. what do you race? I race LMP and can am cars

  13. #13
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    Quote Originally Posted by Ole
    There is a reason NO-ONE outside the bicycle business uses mineral oil in braking systems.
    Ole.
    Actually, Citroen used mineral oil in their braking, steering, and hydraulic suspension systems for years, through a variety of series (D, SM. and CX).
    Last edited by 2xPneu; 02-22-2005 at 10:47 AM.

  14. #14
    pj.
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    Yep, one system for brakes, powered steering and hydraulic suspension. Pump failure on my Citroen BX, is one of my more memorable experiences.

  15. #15
    Ole
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    I knew...

    Quote Originally Posted by 2xPneu
    Actually, Citroen used mineral oil in their braking, steering, and hydraulic suspension systems for years, through a variety of series (D, SM. and CX).
    I knew that comment of mine was going to come back and bite me. Ok, no-one outside of the toy industry uses oil in their brake system. :-)


    Ole.

  16. #16
    pj.
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    LOL Citroen had a penchant for novelties – being whacked out on olive oil and red wine does strange things to the mind. I sometime wonder what happened to their bod that decided 4 wheels and a steering wheel was a good convention to follow – probably shunned out of the France.

  17. #17
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    Rolls Royce too

    Quote Originally Posted by Ole
    I knew that comment of mine was going to come back and bite me. Ok, no-one outside of the toy industry uses oil in their brake system. :-)


    Ole.
    Rolls Royce also use mineral oil in their brakes. Expensive toys

  18. #18
    pj.
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    really, didn’t know that….probably stops one’s chauffer from stopping to quickly, spilling one’s champagne.

  19. #19
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    The very rubber used in the seals will decide what fluid the system can use. I highly doubt any bike brake mfg had their own seal polymer concocted. I've no idea what is the best choice for mineral oil, but when I worked for wilwood's R&D we used EDPM for our seals.

  20. #20
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    I changed the mineral oil out of my XT's due to the fact I have grimeca brakes as well.
    I now use BelRay dot4 (they seem to ok after several months)
    That way I can mix and match parts.
    Performance is the same but I dont have to worry about different fluids

  21. #21
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    You will at some point begin to have seal failures.
    Quote Originally Posted by desrcr
    I changed the mineral oil out of my XT's due to the fact I have grimeca brakes as well.
    I now use BelRay dot4 (they seem to ok after several months)
    That way I can mix and match parts.
    Performance is the same but I dont have to worry about different fluids

  22. #22
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    Quote Originally Posted by lebikerboy
    You will at some point begin to have seal failures.
    Is this opinion or experience speaking
    IMO they use mineral oil because non-caustic.
    I will let you know when/if it happens(seal failure)

  23. #23
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    I've seen it before at the shop. It will happen.
    Quote Originally Posted by desrcr
    Is this opinion or experience speaking
    IMO they use mineral oil because non-caustic.
    I will let you know when/if it happens(seal failure)

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