When the mercury dropped in NYC a few weeks ago I had a recurrence of mechnical mystery that beset me last year when winter set in. In November of 2009 I had been awarded a bike as part of the Globe Experience Project. I partially chose the bike I did because it had disc brakes and I had never owned such brakes before.
I thought since I experienced this problem again this year it might be good to repost in case others out there experience the myster of sticky disc brakes. I posted the intital entry along with the follow up. Enjoy!
One of the reasons I chose the Globe model I did (now the Vienna is over on the Specialized site) was that it had disc brakes. I had never so much as ridden a bike with disc brakes and I have a tendency to burn through traditional brake pads pretty quickly. I was replacing the pads on my other bikes about twice per year and was hoping the disc version might last a bit longer and perform better.
Upon getting my Vienna I was pleased with the brakes, but not blown away. They worked fine and all, but it was not like a quantum leap in performance. I should note that I ride on roads, not on muddy trails. I can imagine that the disc brakes are especially effective in muddy conditions.
Anyway, I noticed a slight issue with the brakes and want reader input. The mercury has been on the downswing in NYC lately and the first time I rode in the snow last week the rear disc brake went all sticky on me about half way through my ride home. By this I mean the brake handle basically froze up and was non-responsive. If I pulled super duper hard I could get the rear disc to engage, but only with a very, very firm squeeze. I thought it quite strange but when I got up the next morning the brake was fine.
Then, on today's ride (perhaps 20 degrees with stiff winds dropping the wind chill close to zero) I experienced the same issue. About half way through the ride the rear brake went all sticky on me. About five minutes after bringing the bike inside I checked it and it was back to normal.
So my question to you experienced disc brake owners out there - is this normal? What advice might you have for me? I have Avid BB5 brakes and the product page is here, user manual is here and a picture of the back brake is below.
The puzzling thing to me is that the rear brake has gone sticky twice, but the front brake has been just fine. Let me know your thoughts in comments.
A key comment posted to the this original entry was the following:
The cable run leaves the end of the housing at an upward/rearward angle, facing the muck being thrown off the rotor during braking or falling from the fender. This now warmed water is falling into the housing, and freezing at the bottom of the loop. The bb7 calipers have a rubber boot that helps to block some of this, but it's not perfect. I'm unsure if the boot can be purchased separately and fitted to the bb5 caliper, but this is bikehacks, so I'm sure you can pull something off.
The hack I ended up using to test if water was indeed the problem with my sticky rear disc brake involved no tools, just a shoe. I wasn't stoked about taking my brake apart to test if there was water in the cable, mostly because the cable housing is attached to the bike by zip ties and I would have had to loosen the cable and cut the zip ties to test theory. While this chore is not all that difficult, I simply did not want to go through this only to find that there was no water in my cable housing.
I then thought what I might do is cut a small hole in the low point of the cable to see if water would drain out of the hole. That's when the light bulb went on in my head - gravity was really all I needed to test to see if water was in the cable housing. If gravity could direct water into the housing, it could also direct it out.
I tilted my bike so the front tire was facing the ceiling of my apartment, leaned the handlebars against the wall and stuck a shoe underneath the rear tire to keep the bike from moving. Take a look:
I bent down to examine the rear brake and sure enough, water started to drip out of the housing. I jiggled the cable a bit and a few more drops came out. In this case, gravity was the hack, aided by a shoe. I left the bike like this overnight, took my bottle of Tri-Flow and stuck the small straw in the housing and squirted in some oil, and then took some grease and packed it in around where the cable enters the housing. Hopefully this will keep me in business. My first day back on the road, with temps around 20 degrees, I had no problems with the brake engaging.
I know I could take the cable out and grease it up (those who fear that rust will be a problem probably would lean this way) however I think with the Tri-flow, even if rust does start to eat away at the cable, the cable will need replacing much sooner than rust setting in and causing a problem.
Since I had the same problem occur again this year, it probably would be wise of me to take the cable out, grease it, and then put it back in. Either that, or come up with some sort of boot to help keep water out of the cable housing.
If you have had any brake mysteries or you have some brake hacks or advice feel free to send them along to us for posting.