Avid OEM DOT fluid
On the cautious side of writing this, I would like to post some observations that i had from personal experiences with Avid brakes and making my opinion as a user and likely fanboy of Avid brakes. There is no intent to harm the brand in any way.
I own both the Juicy 7s 2009 and the Elixir CR 2011 versions. I have worked on my buddies' ultimates 2009 and elixir 7, X9 and other CRs to free their brakes of jammed pistons meaning. they are unable to retract.
with my personal pieces of 7 and CR, till today, i have never had an issue where the brakes locked up on me or having jammed pistons or jammed levers.
2 changes i made to the brakes from first day of using them.
1. Rebled to Motul RBF600 Dot 4.
2. Cables change to HEL braided cables.
The main issues my buddies faced had been:
1. piston jam
2. total jam in lever.
From the piston being jammed in place, I reckon there are 2 possible issues that stock brakes have: bled in factory with too much fluid and (this is entirely my guess) poor quality of avid oem dot fluids.
After i had rebled in the past 2 years at least 6 sets of Elixirs with Motul RBF600, the brakes till today have not have an issue.
One of the Elixirs had jammed a piston and a quick unscrew of the bleed port and a drain on a few drops of dot fluid made the brake usable again. However, i was wondering how the dot fluid expanded till the volume increased to that extend of jamming up the pistons. could it be the absorption of h2o from atmosphere that led to this expansion of fluids?
I have also rebled 4 sets of 7s with stuck pistons with motorex and mugen branded 5.1 and they never had an issue after that.
I have with me a buddy's ultimates that was never rebled from day 1 and the lever is totally stuck. i cant even flush any form of fluid through. so till now i have no idea how to restore the ultimates to work order without buying a new lever body.
I am guessing that the issue may be with the Dot fluid quality installed from the factory .
I am wondering if anyone else have made such a conclusion with their Avid 7 or Elixir brakes?
would be great if there is some opinion from the users of Avid brakes here.
I do believe water absorption is a major factor in sticky pistons. Tiny, lightweight piston seals are going to allow some fluid to pass in both directions, and the fluid will soak up water over time.
I can't speak to the quality of the DOT fluid Avid provides, but it may be possible other types of compatible fluid are somewhat less hydrophilic than the Avid stuff. I'm sure Avid is just putting their name on someone else's fluid, and that someone else is most likely the lowest bidder.
I can barely get my mouth around it.
Hey, try this:
Originally Posted by Jhanney
1. Take the hose off
2. Shove a 1.5mm Allen wrench into the lever to push the piston back
- be careful here to not slip off the piston and score the wall of the piston chamber
3. Take the lever apart and get to the piston/spring assembly
4. Remove all the seals from the piston
5. Hold the plastic against a file surface and shave a bit of material off the edges
6. Trial fit resized piston into the lever body.
7. Repeat 5 and 6 until you get only a bit of resistance, then reassemble
** when you reassemble, put some DOT grease between the lip seal and o-ring.
Just did these steps w/ a set of Juicy Carbons, and brought them back to life
If you've ever taken apart a stuck avid caliper before you'll see they're usually full of corrosion. I don't know if that's due to poor fluid that has sucked up too much moisture or just that the fluid needs to be changed more often. I use ATE super blue dot 4 in my brakes and it seems to work well.
Motul is a full synthetic isn't it? Not absorbing water is a huge plus!
I'll go with the original fluid
All DOT3, 4, 5, and 5.1 brake fluid is synthetic.
That being said, some brake fluid is better than others.
What GM uses in their cars turns to an awful black mess with many solid deposits within a few(4-5) years, While you rarely see this on Japanese, or Ford products.
You see it even less on European cars, but they also have regular scheduled change intervals.
All DOT4 and DOT3 are compatible with each other and any system that takes either, but DOT4 has to meet higher standards for boiling point, so systems designed for DOT4 should use DOT4.
DOT5 is non compatible, and does not absorb moisture, but moisture still gets in, and since it is not absorbed, it creates droplets that can cause corrosion. This should not be used in any system except the motorcycle brakes that came with it, and should be flushed regularly.
DOT 5.1 is a new fluid, that is basically a very high performance version of DOT4 fluid, and has nothing in common with DOT5 fluid. This is what AVID uses, and should always be replaced with DOT5.1, but if unavailable a DOT4 will work, and the higher end/racing DOT4 fluids are very similar to DOT5.1
edit; PS: DOT 5.1 is usually available at your local NAPA auto parts or a motorcycle dealer.
Last edited by autodoctor911; 12-25-2012 at 11:31 AM.
Upon further research, I have found that the higher grades of ether based brake fluid(DOT4,5.1) can absorb less moisture, and so should be changed more often. Their main advantage is higher boiling points when dry or especially when wet(they have absorbed as much moisture as they are able to).
If your brake fluid boils in a closed system, like most bicycle brakes are, you get locked up brakes. In a car, with an open, reservoir system, they don't lock up, they get spongy, because the excess volume can go past the m/c piston, but the gaseous brake fluid is compressible.
So, a fluid flush with the appropriate fluid is the best repair.
DOT4, or DOT3 fluid may work for longer before the amount of moisture they can absorb is exceeded, but may boil at a lower temperature.
DOT5.1 will not boil till a hotter temperature, but it's moisture absorption can be exceeded earlier, causing corrosion in the system.
I am sure AVID has considered all of this, and chosen the right fluid for the job. But then, there are DOT4, and DOT3 fluids that may be better than 5.1 at dry boiling point, but not meet the wet boiling point, which may work better overall than the 5.1
I have seen that in the shop a handful of times. The fix was to adjust the reach screw. At some point, the reach adjuster moves the master piston (though it doesn't seem like it should, but it does) just enough to block the flow of fluid when bleeding. Fiddle with the adjuster till the fluid starts to flow. I think the main offender in our shop is the elixer 5/7? I can't remember which direction you need to turn it, just experiment.
Originally Posted by Jhanney
Sticky pistons can come from a week return spring in the master cylinder as well as dirty and "dry" seals. We use SRAM's Pitstop DOT Grease on master cylinder and the caliper piston seals.
This one ounce of DOT grease is enough to last one user the length of his lifetime: Amazon.com: PitStop DOT Disc Brake Assembly Grease, 1 Ounce: Sports & Outdoors
Weighing in on the DOT fluids..if you don't like the Avid OEM, just use any aftermarket, high quality DOT. I've seen Super Blue and Motul around. Our distributors are constantly out of Motul 5.1. They get it in and it is gone within a week. Any reputable motorcycle shop should have more than one choice. I'm no chemist but race fluids should be a touch better than OEM--but that is by no means exclusive.
Last edited by SomethingRelatedToBiking; 01-18-2013 at 11:24 AM.
Reason: had to add link
I have 2009 CR's, Juicy 7's and 2012 Elixir 5's (plus BB7's). Only issues I've had (on the rear of both the Juicy 7 and Elixir 5) was a sluggish inboard piston which I guess was due to dirt/brake remnant build up.
To fix it:
I removed the wheel and brake pads, inserted a 10mm box wrench between the pistons and applied a bit of pressure to the outboard piston (to force the inboard to move at a similar rate) while gently pressing the brake lever.
Once it the pistons moved out to expose ~4mm or so, I blasted the inside of the caliper with brakekeen and dried it thoroughly. Then I put a few drops of brake fluid around where the piston meets the caliper.
I pushed the pistons in manually with the box wrench and then moved them out a couple of times until both pistons started moving similarly.
Possible though I'm not totally convinced. I installed the (brand new) Elixir 5's three months ago in October and the Elixir CR's have been running trouble free since 2009. I didn't modify brake fluid in either. If they start sticking again I'll replace the brake fluid.
Originally Posted by wiammaren
Car and M/cycle brakes get a rubber 'foreskin' around the end of the piston to keep the water out. Capillary action pretty much assures water will be on the other side of the seal in wet conditions and that's where the problem starts. IMO,
Originally Posted by wiammaren
I see these blingy megadollar brakes coming out but what we really NEED is a seal. I know, this is the bike business that took half a century to put sealed bearings in derailleur pulleys [ Can't be done!] and half the rest of bike moving parts, so nothing new.
So instead we extend the pistons out and clean and lube with brake fluid. I've made a habit of checking that all four pistons move freely and evenly about once a week and have happy [Avid!!] brakes but this isn't acceptable for the consumer to have to know/deal with.
Is there some reason I'm missing why what is SOP on every other brake system is MIA on bicycle brakes?