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  1. #1
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    Shimano M785 and M596 in the cold on a fatbike: how do they perform??

    I'm not trying to start a new debate on Hydro vs. Mech on a fatbike here. Personally I've been running MT2's on my bike this season and it's been -20 at night and 0 during the day for the last month and I've had awesome performance out of them. I LOVE my new XT brakes on my MTB and want to run them on my fatbike. I've read a little chatter about old Shimano brakes exploding in the cold and statements like, "Shimano says they're only intended for 20degree and above". I would love the hear a little feedback from people who are actually running the new Shimano brakes on their Fatbike. Let me know how they work!

    THX

  2. #2
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    From what I have read the only reason Shimano hydros might not be the best in cold temps is the mineral oil. I have not seen enough ride reports in the to say that in fact the cold affects this type of fluid more, but have heard of a few who have no problems in some pretty chilly temps.

  3. #3
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    What is the freezing temperature of mineral oil

    I would think that the lowest useful temp would be below that, but still...it would it just wouldn't be a good idea.

    Here's way more info than you probably need:
    Low Temperature and Viscosity Limits
    Oh noes. I'm going to drink the Kool-Aid.

  4. #4
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    I have this XTR dual control brakes on my bike and they are working just fine at about 20deggres, except for two rides I did on the mountains at about zero degrees where they felt a little sticky and the lever was ultra firm, no lost of fluid or any permanent damage that I can tell.

  5. #5
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    I had a set of the newest generation XTR Race. Got them when they first came out...and I was one of the ones that had leaky lines and a leaky piston....which Shimano quickly fixed.
    I rode them a few times when temps were in the high teens.
    They felt notchy and sluggish when the lever was pulled....especially the first few times they were used on the ride, or after long sections or not using them. The front piston would sometimes drag a little, could hear the disc rubbing...but would finally retract.
    They always worked...just didn't feel like they normally do.

  6. #6
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    FYI. Your MT-2's use mineral oil. I have MT-8's, they are the lightest around but the lever is uncomfortable unlike all the other Magura models as the lever tappers toward the tip and they pump up, that is the biggest issue I have with them. Don't have experience with Shimano's in really cold temps.

  7. #7
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    I ran XT's through out a winter in Anchorage not that long ago. I'd say no way, If you're riding in temps that cold. Not only did the levers feel stiff, but the fluid in the calipers would expand as well. Causing the pistons to grab the rotor. Think riding with your brakes actuated. Just my experience.
    c

  8. #8
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    Interesting...I live in Calgary and we experience temperatures of -30c and for whatever reason a set of Tektro Auriga's that also use mineral oil work great in the winter. Knock on wood but I have had no issues yet. The other day I took my xtr 785 trail brakes out in -5c and they seemed to work great with no drag.

  9. #9
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    I don't think the real issue is with mineral oil.
    I'd say it's the way the different materials expand/contract when it's cold.
    And if you have any moisture in the fluid......
    I have had a set of Avids....that always worked fine before and after...work really poorly when it was around 25-30.

  10. #10
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    Quote Originally Posted by ANYRIDE View Post
    I ran XT's through out a winter in Anchorage not that long ago. I'd say no way, If you're riding in temps that cold. Not only did the levers feel stiff, but the fluid in the calipers would expand as well. Causing the pistons to grab the rotor. Think riding with your brakes actuated. Just my experience.
    c
    The only liquid I know of that expandswhen subjected to cold temperatures is water, when it freezes.

  11. #11
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    Quote Originally Posted by danaco View Post
    The only liquid I know of that expandswhen subjected to cold temperatures is water, when it freezes.
    You are correct...in a perfect world.
    But in the dirty...and wet... world of MTBing.....water can get inside a brake system.
    Mineral oil does not absorb water like regular brake fluid does....but you will often find beads of it in the system when you do a complete bleed.
    and, as I mentioned above....you also have dissimilar materials contracting/expanding at different rates....so some brakes act more funky than others when it's cold.

  12. #12
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    I changed out the mineral oil in my XT brakes to Pentisin CHF 7.1 and have had no problems since. This seems to be working great this winter so far and I have had no issues. You do loose some of the braking power, I just have to squeeze a little harder than normal, but they do brake well.
    RICOH for LIFE

  13. #13
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    Magic,
    Which XT brakes do you have? I bought some R1/RX brakes for my 9zero7 and they are working OK but have the typical Formula pad retraction issue which gets worse in the cold. I would love to put XT on there but have personally seen several sets of Shimanos dump their fluid out the caliper piston seal when the temps dropped below 20F. I don't think the Pentisin will fix this issue, but if it does I would love to know.
    =========================================
    Minnesota Off Road Cyclists www.morcmtb.org

  14. #14
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    I'm running 785's with no issues but single digit temps are about as cold as we get here in Nor Cal

  15. #15
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    The older 775 got stiff on me once it would hit 0 deg f.
    And I love beer!!

  16. #16
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    Ok, I have an answer

    Ok, it's been cold here, really cold here; -20 at night and we often ride at night. My friend has the new SLX brakes on his 907 and he's had no issues with them. Additionally, I spoke with my friend who works for Shimano and the older brakes had issues with the seals at cold temps causing pump and potential leaks. Apparently they've been using different seals for nearly 1 year now. I'm going with Shimano on my bike now. And really, if it's any colder than -15/20 nothing works well....

  17. #17
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    If it's -20 I'm staying inside

  18. #18
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    My boss is running 2012 XT brakes on his 907 with no issues at all. I don't usually like to speak for someone else's experiences but I'm the one he rides with and I'm the guy who builds and works on his bikes. I was skeptical of the idea of using a mineral oil brake, but for the conditions and temps we ride here (Ontario 2 hours drive north of Toronto) they've been great. Zero to -20 Celsius. Not to many -20 rides happening though.

  19. #19
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    Quote Originally Posted by majack View Post
    I changed out the mineral oil in my XT brakes to Pentisin CHF 7.1 and have had no problems since. This seems to be working great this winter so far and I have had no issues. You do loose some of the braking power, I just have to squeeze a little harder than normal, but they do brake well.
    I will assume you need to squeeze harder is because the viscosity is much higher than the spec'd mineral oil, is a sticky liquid substance or the viscosity increases from the cold temperatures. If the viscosity is similar it should make no difference.

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