Can I Run Hydraulic Brakes on my fatbike in Winter?

(Editorial note: In addition to writing this blog, I’m the SuperMod of the Fat Bikes page on Facebook, which currently has over 10,000 members.  From time to time, the page gets repeated questions from members, and accordingly, we are developing a Fatbike FAQ page to answer those questions.  I’ll be hosting that here.  Helpful Fatbike related topics will be posted on here, and linked to a master link of the FAQs.  This is the first of those posts).

Many entry-level fat bikes come with mechanical disc brakes.  One of the very first questions that gets commonly asked by those new to winter biking is whether they can use hydraulic brakes on their fatbike, in winter.

The answer: Yes.

Have a nice day.

 

Ok, just kidding.  We’ll give some more content.

Why run mechanical disc brakes in winter?  When perfectly adjusted, they have good braking power, and you don’t have to worry about hydraulic fluid–so say the proponents.  Why not to run them?  There’s a myriad of reasons:

  1.  If not perfectly adjusted, they don’t have good braking power.  In winter, when the pads will likely have water/crud/ice on them, that can majorly detract from braking power.
  2. If they get wet and then freeze, the mechanical components do not work well, and they can either freeze up (no brakes) or freeze tight (no movement).  Both are bad.
  3. Over time, when exposed to salt, snow, slush, etc., the mechanical components rust/seize/wear badly.  In my experience, unless you’re really on top of it, you can ruin a set of mechanical calipers in a single season.
  4. With a really good set of cables/housing, the cables should be fine.  But with a cheap set, you’re in trouble, as the cables will bind when it is cold out, and then you’ll be back to #2 (no brakes or seized brakes).  Also, even with a good set of housings, mishaps can take your brakes out.  For example, last winter I was riding a frozen river and broke through.  The right side of my handlebar was dunked in the water.  Water got into the housing, froze during the ride, expanded, and split the housing.  I lost shifting, because it took out my rear derailleur housing.  Because I used hydro brakes, my brakes were fine.  With mechanical brakes, I would have lost brakes and shifting.
  5. Generally speaking, mechanical brakes require more attention in inclement conditions than do hydro brakes.  (IMO, mechanical brakes are always more work…but that’s because I like my brakes to function perfectly, and with mechanicals, you’re always chasing the right tuning).

So what about hydro brakes?  Can they be run in the cold?  Absolutely.  In my experience, over several years of fat biking in the winter, hydro brakes are far more reliable, resilient and durable.  They’re better suited to winter than mechanicals.  They are sealed, and can withstand being dunked, frozen, and ridden further.  From time to time, if you get them really wet, they may ice up.  The solution is to pedal a bit and hold the brakes down lightly…they’ll self-clean and clear off the ice.  Set them up once, and go.

Whenever this topic comes up, the inevitable question is: Shimano or SRAM?  The answer: whichever you prefer.  I’ve run AVID and Shimano brakes.  I prefer Shimano, because they function more reliably, are easier to bleed, and frankly, require less attention.  After initial setup, I’ve never had to bleed my Shimanos…across a number of bikes (both drop bar and flat bar hydros).  With Avids, a lot more attention was required.  For example, my Beargrease originally came with Avid XX brakes.

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I replaced those with Shimano XTRs, because of recurrent air/bleeding issues.

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The next thing you will hear is: “Avids use DOT brake oil and Shimanos use mineral oil.  Mineral oil freezes at a warmer temperature than DOT oil, so you should use Avids so that the oil doesn’t freeze up when riding.”  While it is true that mineral oil has a higher freezing point than does DOT brake fluid, this point is irrelevant in all but the worst conceivable conditions.  I’ve run my Shimanos in temperatures below -35F.  (Quick note: that’s actual temperature, not windchill.  Windchill is the perceived temperature on exposed skin, based on wind and temp; it is irrelevant to mechanical things such as brakes, which do not perceive temperature.  So when talking about mechanical items, stick with actual temp, not windchill).  Even at -35, I had no issues with the brakes being sticky, sluggish or frozen.  That was the case, even after several hours of outdoor biking, when everything was fully acclimated to the cold and fully as cold as it was outside.  That was the case after hauling my bike on an exterior bike rack in those conditions, and then riding it.  That was the case even after being set in the snow on a break, and then picked back up and ridden.  From my perspective, the greater resilience of Shimanos (and lessened need for bleeding) means that they are less likely to have contaminants enter the brake system…and I’d be more worried about the contaminants freezing than the fluid freezing.  Of note, I haven’t run the latest generation of Avid brakes, which I understand are greatly improved.  But unless you’re regularly riding in temps much colder than -35, I’d suggest you pick whichever hydro brakes you prefer and run them, without worrying about mineral vs. DOT brake fluid.

So, in short: If you want to run hydro brakes, they’ll work in the cold, and they’ll almost certainly work better than mechanical brakes.  The fluid won’t freeze up–unless you’re riding in really extreme conditions.  My personal experience extends to -35F, and I’ve read of others using them successfully down to -50F.  Buy a set you like, set them up properly once, and go for it!

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One thought on “Can I Run Hydraulic Brakes on my fatbike in Winter?

  1. Is there an actually a single answer to this? Everyone’s winter conditions are different, and what works one place might not work well elsewhere. For example in my very dry and cold climate in Fairbanks Alaska I have seen more trouble with all types of hydros and very few issues with classic bb7 cable brakes. For folks living in climates with “wetter” winters, cable brakes are probably more trouble prone, as would be any place with lots of salt.

    On the hydro front, it is more complicated than just the fluid used – the seals also need to be able to function well at cold temps. In my climate it is pretty common for the seals to leak a bit of air when it gets cold, leading to spongy brakes that eventually stop “braking”.

    (I also posted something similar to the Facebook group).

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