Shimano hydraulic disc brakes (BL-M396) leaking (I think) in very cold temps
03-08-19, 06:04 PM
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Shimano hydraulic disc brakes (BL-M396) leaking (I think) in very cold temps
My winter bike is a 2015 Scott Sub Speed 10, which has Shimano BL-M396 hydraulic discs.
I commute daily in Minneapolis, where we have cold winters, with commuting temps sometimes below -5ºF (-20ºC).
I've started to believe that that at very cold temps, somewhere below 0ºF, the Shimano brake system starts to leak. Maybe it's the seals shrinking or perhaps going hard, but in any case, after exceptionally cold days, I seem to end up with air in the brake lines, and squealing, juddering brakes (and oily looking calipers and rotors).
It took a couple seasons of commuting to figure out why my brakes were acting up like this, and I had replaced both the rotors and pads in earlier attempts to fix the problem, thinking they were at fault. But now I'm fairly certain it's due to fluid leaks.
Anyone else experienced this? Are other hydraulic systems better suited for cold temperatures, or should I be looking to replace this with a cable system?
Cheers,
robo
I commute daily in Minneapolis, where we have cold winters, with commuting temps sometimes below -5ºF (-20ºC).
I've started to believe that that at very cold temps, somewhere below 0ºF, the Shimano brake system starts to leak. Maybe it's the seals shrinking or perhaps going hard, but in any case, after exceptionally cold days, I seem to end up with air in the brake lines, and squealing, juddering brakes (and oily looking calipers and rotors).
It took a couple seasons of commuting to figure out why my brakes were acting up like this, and I had replaced both the rotors and pads in earlier attempts to fix the problem, thinking they were at fault. But now I'm fairly certain it's due to fluid leaks.
Anyone else experienced this? Are other hydraulic systems better suited for cold temperatures, or should I be looking to replace this with a cable system?
Cheers,
robo
03-08-19, 07:52 PM
#2
Non omnino gravis
Mineral oil apparently cannot freeze solid, but gets pretty thick below 0ºC, to the point where it "gels." This would certainly explain your brakes behavior below zero. Brakes using DOT fluid will not experience thickening or freezing, but have to be maintained more regularly due to the hygroscopic nature of DOT fluid.
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03-09-19, 08:45 AM
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Mineral oil apparently cannot freeze solid, but gets pretty thick below 0ºC, to the point where it "gels." This would certainly explain your brakes behavior below zero. Brakes using DOT fluid will not experience thickening or freezing, but have to be maintained more regularly due to the hygroscopic nature of DOT fluid.
03-09-19, 02:47 PM
#4
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Leaking out from Where?
Sure the fittings did not loosen up?, snug them down a bit?
AFAIK , because my TRP Hy Rd brake has no hoses, master and 2 slave cylinders behind the pads,
are in the same part.. the diecast caliper, So no bleeding is to be anticipated ...
AFAIK , because my TRP Hy Rd brake has no hoses, master and 2 slave cylinders behind the pads,
are in the same part.. the diecast caliper, So no bleeding is to be anticipated ...
03-09-19, 04:27 PM
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I also had the leaking problem with shimano brakes many years ago. Had them rebuilt with new seals and it kept on happening. I think it was the combination of cold and road salt that damaged the seals That's one of the reasons why I changed to BB7s. I just hated dealing with leaking fluid.
