Question about Avid Juicy 7's
I pulled my bike out last weekend after it sat all winter long( busted my shou8lder snow skiing). The rear brake was locked, I pulled on the lever and fluid started to come out of the resevoir. I checked all the nuts and bolts to see if they were loose, they were all tight. I suspected that moisture got into the line and made the system over-full.
I took it into to my lbs and they told me it was just over filled, and they removed some fluid. I explained to them my theory of water leaking into the brake lines and that at speed, the water would heat up and dissipate, leaving a, now, underfilled brake line. They did not see this as being an issue.
Who's right here?
P.S. I would like to sort this out without doing a trial by fire.
Originally Posted by saidrick
the water will possibly heat up and maybe turn to gas? i have no idea how hot fluid gets in a bike. but i dont think it will be able to escape, instead it will just probably give you some brake fade from the now present gas.
i would probably do a complete bleed to be on the safer side.
It is a bit surprising that a brake that performed well last year (presumably?) would all of a suddent turn out to be "overfilled" this year. Water wouldn't be at the top of my list of suspects, but as the previous poster suggested, bleeding would eliminate that concern.
If you provide a little more info about the brakes (age, type of riding) perhaps someone will have a some bright ideas.
Something sounds fishy, brakes don't get overfilled by just sitting there. I doubt it could absorb enough water from the air to make it overfilled either, and even if it did that would point to a problem that needs to be fixed. Just draining off some fluid does not fix the problem.
Yeah, hydro brakes are filled with evil spirits, and just like in the Victorian era, they need to be bled to heal properly.
My guess is the fluid absorbed water.
I'm tuning up a friends bike that he hasn't ridden in over a year because of injuries, and the brakes (Juicy 7's) had major rotor drag, and It was not possible to push in the pistons. I'm sure it wasn't like that when he parked the bike.
Letting out some fluid fixed the problem, but I figured the fluid had absorbed a lot of moisture over the year, so I gave them a fresh bleed, and they are perfectly fine now.
I highly suggest you bleed.
The DOT fluid in hyraulic brakes absorbs water and expands, so it's very possible that a seal allowed moisture in and expanded the fluid in the system. If you read through the Avid bleed procedure, I think it mentions not laeving the DOT fluid open to air for this reason. I read if you leave a near full jar open on a humid day, it will over flow from the absorbed moisture.
DOT brake fluid is hydroscopic. Meaning it absorbs water. If its "overfilled" the system needs to be bled to get that moisture out of the brake system. Since it requires such a small amount of fluid, any additional fluid introduced into the system will give cause for concern, as you have found out.
Have the LBS or even better, YOU, give the system a good bleed. Problem solved.
Yeah, just like a sponge...
Belgian beer and Scotch whisky.