I’ve never had hydraulic brakes before. I’ve had no issues so far (coldest so far -1F, -18C) but today I’m going to ride @ -8F, -22C. I wondering if anyone knows at what point temp would be low enough to cause braking issues. (PS – same question re Di2 cold temp limits)
At those temps, your brakes will be the least of your concerns! Bike brakes use the same fluids and basic designs as car and motorcycle brakes, which work just fine at extremely cold temps. Stay warm and have fun!
bnystrom wrote: Bike brakes use the same fluids and basic designs as car and motorcycle brakes, which work just fine at extremely cold temps. Stay warm and have fun!
Shimano uses mineral oil which freezes at a much higher temp than DOT oil that Sram uses. I've never used my Shimano brakes in cold temps, but I hear they start getting sluggish around 15 but still work even as the temps get colder.
I stick with mechanical on my fat bike, but won't put di2 on it.
The mineral oil that Shimano uses is the same type of hydraulic fluid used by Volkswagen, Audi, BMW and a few other car manufacturers. In fact, that's what I use in our Shimano brakes, as it's much less expensive to buy it by the liter at an auto parts store than it is to buy it from Shimano, Finish Line or Magura. It works fine at low temps and the only difference is that it's dyed green instead of red or blue. A couple of options are:
Febi Billstein 06162
Pentosin CHF 11S
Both of these are good to -40 F.
As for summer use, while on vacation in 2019, I descended Mt. Tamalpais on my gravel bike with no braking issues, as well as doing several shorter dirt and road descents around Mill Valley, Santa Cruz and Livermore. So, it works just fine in hot weather and extreme braking conditions.
Thanks much for the info! Can confirm I had no issues with either hydraulic braking or Di2 shifting at -8F. Warmer weather ahead so I'll need to wait until next winter to test lower temperatures.
Volsung wrote:My Di2 concerns are with the functionality of lithium ion batteries. Its possible to keep my phone next to my body at -28F but not a Di2 battery.
Do you ride at -28F? With a giant phone running a heater app?
Phones will shut off at a certain point, but if you keep it in a pocket or a pogie it will stay warm enough. If you put it in a frame bag it won't turn on for a while until it warms back up.
I've had Niterider headlights die permanently due to the cold. They have a great warranty and will fix the light and send it back though so they're still all I use. Their recommendation is to not expose them to cold temps, but I'm not willing to move to a different state because of bike headlight inconvenience.
Both examples are just a limitation of Li ion storage.
Here's an article on mineral oil vs DOT in the cold. Obviously stopping a car will heat up the fluid faster than stopping a bike in addition to running an engine and heater vs the heat generated by one human body, so this is just a comparison of bike brakes. https://www.velonews.com/gear/technical-faq-disc-brakes-cold-weather/
Also heres my old fat bike at -28° on a ride to see if St Anthony Falls on the Mississippi had frozen. It hadn't, if you're curious. Lots of steam everywhere though
Yeah, my garmin has been freezing lately when I have it attached to my bars.
Brake wise - I have more problems with pads than hydralics.
Last year, a well intentioned mechanic really really cleaned my pads and disks in the fall, and they didn't work for crap all winter long. the vibration and shudder was horrible. They didn't bed in properly until spring. Doesn't seem like it takes much to get some nasty squealing in the winter (I'm on Organic pads)
I had a Garmin for years and had battery issues in cold weather. Switched to Wahoo and it's been great, not sure why the difference (-8F is lowest I've tried). Still shows lots of charge left at end of ride. No screen dimming, etc.
