Avid, Juicy 7: caliper; piston and seal replacment.

I'm having to replace the seals and pistons in an old set of Avid, Juicy Seven calipers. I've had the opportunity to use a lot of different hydraulic brakes over the years and I really like the modulation and actuation of these brakes.

The slotted mounting holes and concave and convex washers allow for flawless setup...assuming the pistons are actuating, which the performance in these calipers has eroded over the last 8 years (heat, cold, dirt, and road salt), which leads us to today.

 

The first thing you need is an Avid rebuild kit for your calipers (contents pictured in orange square). Not only does it supply you with the pistons, piston seal, and o-ring seals, but also the 4 bolts, bleed port screw (torx 10), and clips.
When you rebuild the caliper it's not a bad idea to flush out the old fluid. I got Avid, dot 5.1 brake fluid. Any 5.1 or 4.0 will work. The higher the number, the higher the boiling point. It's hard to find 5.1, or at least around where I live. Most automotive places carry dot 4.0 and since I don't ride down mountains 4.0 would be fine if I was in a pinch.

Most automobiles take dot 3.0, so it is the most widely available, but it is not recommended. Also you might find dot 5.0 and that is silicone based and not recommended. Also some systems take mineral oil like Shimano Deore XT. Don't use that either if you system calls for dot fluid.

I also got new Kool Stop brake pads. There is usually a choice between Organic and Sintered. Organic is softer, so it bites better, but it wears faster. Sintered brake pads are harder, bit less than organics, but wear longer. It's a personal choice.

Also pictured above are the syringes for the bleed kit. Avid Juicy Sevens suggest bleeding the system with 2 syringes.

Here they are taken apart. Looks they might need a little clean up. Now all I have to do is get the pistons out. Let me make this clear. You just don't pull these out. Before you get to this step, you should pump on the brakes while it's all still together to get the pistons as far out of their bores as possible. I got a good start on one side, but one piston was stuck in it's bore.

The trick now is to use compressed air to pop the pistons out of their bores. Here I rigged a shock pump with a Rock Shox air valve adapter that fits prefect. This might take as much as 250psi. so have your hands and everything clear for them to POP! out.

Ahhhh everything cleaned and replaced. Don't forget to lubricate the seals and pistons with some of that dot fluid for easy action.

Reassembled and in it's place. Now to fill and bleed the brakes. Rather than recreate the wheel Park Tool has a wonderful How-To.
http://www.parktool.com/blog/repair-help/avid-reg-juicy-caliper-brake-bleed-service