Disc brake locked on

natrix

Earlier this year I replaced the rear Avid Juicy 3 disc brake on my old Specialised Rockhopper with an Avid Elixir 1 disc brake. Everything was fine, the brake worked well and I spent a week with the family tootling around the Forest of Dean, brakes working fine.

The bike had intermiitent use over the past few months (sometimes with a tagalong attached), but was left in the garage for probably a month unused. Went to get on it yesterday to find that the rear brake was now locked on, both pads firmly against the disc. There is no movement in the brake lever. It is as if the hydraulic fluid has somehow expanded.

Anybody got any ideas???

cooldad

Take the wheel out. Massage the seals with hydraulic fluid. (Remove pads) Use a big srewdriver or something to force the calipers back (best to put the pads back in, then if you trash anything it's the pads, not the pistons). Repeat if necessary.

If it works clean well with isopropyl alcohol, replace pads.

If not buy Shimano. (Sort of joke)

Antm81

I had the same problem with elixir 3s if I stored the bike in the shed, seems the seals are censored , allowing the fluid to absorb moisture. Weirdly never happened indoors. Quick fix was open the bleed port on the caliper, letting out a small amount of fluid.

natrix

Thanks Ant, I'll go for the quick fix

The Rookie

More likely fluid expansion due to heat, given the time of year? Bear in mind that initially fluid absorption actually reduces the brake fluid volume not increases it (before you take the mickey, check it).

JBA

[url=http://www.bikeradar.com/forums/viewtopic.php?p=19631416#p19631416]The Rookie[/url] wrote:

More likely fluid expansion due to heat, given the time of year?

This^^^.

When I had Avids they would always get tight when the ambient temperature went up for a few days.

cooldad

I'll bow out gracefully, I missed the no movement of the lever.

But I'll stay with buy Shimano.

The Rookie

We had a handful of these last year. Always seems to be Avids and not Shimano or others.

natrix

fluid absorption actually reduces the brake fluid volume

Bizarre, do you have a link for that?? (I've tried google with no success)

The Rookie

No, did all this way back, about 10 BI (Before Internet), try it yourself easily with water and sugar (or salt), as you initially dissolve the material in the molecules cling to and pull in the water molecules towards themselves thus reducing the total volume occupied (water level goes down), you get the same effect with anything that readily dissolves into anything else.

larkim

http://www.nuffieldfoundation.org/practical-physics/volume-change-dissolving-salt-water