Bleedin' 'ell, guv

A lot of Elixir

Recently, I've added a couple of pairs of Avid's Elixir brakes to the RideItFixIt garage. Second hand pairs mind, that had some problems... Problems which thankfully turn out (so far) to mean "by jove, these brakes are in need of a jolly good bleeding". I've also had to bleed another pair not long ago - that's a few bleeds I've done lately.

As you might guess, I'm a big fan of Avid brakes here - especially the current models (Elixir, and no, I don't like Juicys). Decent modulation and power and good vfm. The levers can feel a bit plasticky, especially on the cheaper, models, but they work, well, and are very effective bits of kit. I've ridden some Hayes (never again) and Shimano (quite nice) brakes, I think the Avids are a tough act to beat.

So, let's take a look inside the Elixir, and I'll list a few hints and easy fixes for common problems with these things.

A trip round the Elixir lever, or how TaperBore(TM) works

Prototype Elixir lever was "a bit plasticky"

With the aid of SRAM's nice photo of this transparent Elixir lever, I've labelled the different parts, so you can see what TaperBore(TM) is and what it does. TaperBore(TM) is, to put it simply, an area of the master cylinder where the diameter of the cylinder gets a bit bigger. The O-ring on the plunger sits in this bigger section when the lever is at rest and fully extended (i.e. when you're not touching the brakes). Now, when the O-ring is in this TaperBore(TM) area, it allows fluid to flow around it. It is a sloppy fit. When the brake is applied, and the plunger moves the O-ring into the regular master cylinder part, the O-ring fits nicely... and the lever will pump fluid down the hose, and your callipers do their thing and the brakes stop your bike. Unless you're pulling a giant skid. Or something.

To sum up:

• When the brake is at rest, the whole system, from calliper to reservoir, is one single body of brake fluid. That makes bleeding the brake possible.
• The TaperBore(TM) area lets the brake lever regulate the amount of fluid in the calliper & hose.

But, wait - there's one more clever part to the levers. When you are filling the brake, the rubber bladder squishes, and allows you to get the whole system completely full. As the brake pads wear down, the pistons will need to move closer to the brake disc. As they do so, the bladder unsquishes, and the TaperBore area allows some fluid to move from the reservoir into the master cylinder, which compensates for the pistons gradually moving closer and closer toward the disc - which gets you "self adjusting" brakes. Clever, no?

It's quite a neat little design Avid have made.

Fill 'er up 

There are plenty of good guides to bleeding Avid brakes. There is no point me writing another one.

http://www.pinkbike.com/news/tech-tuesday-bleeding-avid-brakes-2010.html
http://bikefat.com/tech-tips-avid-juicy-and-elixer-speed-bleed/
http://www.youtube.com/watch?v=IoaPUw5DliA

Hang on

So I couldn't stop there - here are some tips for bleeding and fixing Avid Elixirs...

• If the brake lever it is not extended, the O-ring seals the master cylinder, and the bleed port on the lever is only connected to the reservoir - this makes bleeding impossible. If this happens, try adjusting the lever with the bite point adjust gizmo. Have a look at the plastic mock-up lever picture - the rubber O-ring needs to be in the TaperBore area. If you don't have bite point adjust, this is highly unlikely to ever be a problem.
• Sometimes, you just don't get all the air out of the brake system with the first bleed. Give it a second go before giving up and giving the brakes to your worst enemy. Or, try this - remove the calliper from the bike, and angle it so the bleed port is right at the top. The calliper is where air is most likely to become trapped, so if you can angle the calliper with the bleed port upwards, it makes it easier to get a good bleed first time.
• Bleed blocks are a must. Don't piss about trying to bleed without one.
• Avid fluid is crap (so is Hayes fluid, by the way). Buy some DOT4 from a motor factors. I spent ages degassing the Hayes & Avid fluid. The cheapest DOT4 in the motor shop required, by comparison, almost no degassing. It is a shit load cheaper, too.
• Avid bleed kits are astonishingly expensive. It is brazen the amount they want for two syringes, two clips, two bits of tube and two bleed adaptors. Ebay is your friend - loads of merchants selling bleed kits for a quarter of the cost of the official effort.
• The Avid sequence doesn't have to be followed to the letter - but it helps.
• DO NOT squirt brake fluid in your eye. A pair of those geeky safety glasses might just be an idea. And the rubber gloves, while you're at it.
• SRAM quality control is reputedly not the finest, and their brakes suffer with inconsistent factory bleeds - sometimes a bleed is necessary right after purchase.

What else? There are several common problems with Elixirs:

• Sticky pistons in the calliper can be sometimes be fixed by moving them in and out a few times, coupled with a drop of brake fluid around the edge. Hold the working piston with something, use the lever to push out the sticky piston. Push the sticky one back in again.
• The CPS magic positioning method doesn't always get things right. Do a final adjust by hand, after getting close with the CPS method.
• Noise, vibration, difficult calliper alignment and dragging brakes, that's probably a sticky piston.
• Almost everything else is down to air getting in the system and the brakes needing bleeding.

Skids

Well, that's it for this time. Getting Avid brakes working isn't actually that difficult. The bleed process can be a bit fiddly and sometimes needs doing twice to get an air free system, but how often do you bleed your brakes? Once every year or two? Small price to pay for effective stoppers.