Front brake is useless, bleeding made no difference *UPDATED

Coxy_UK

2009 Stumpjumer HT Comp, Avid Custom Elixer R SL brakes.

My front brake has very little power in it, so little in fact that even below walking speed it will not lock the wheel.

Pads are hardly worn, and tried pads from rear incase the front ones were contaminated, no difference.

Bled the system twice, no difference.

Any ideas please?

Thanks

nicklouse

so how does the lever feel?

id you clean the rotor before fitting the pads from the rear?

Coxy_UK

Rotor and pads clean.

Lever doesn't feel as firm as it should, which would suggest a bleed was required, however 2 bleeds on and it's no better

nicklouse

is the rotor being moved by the pads?

Coxy_UK

I just bled it again as I'm sitting here frustrated about the whole thing... time off work to ride but a knacjered bike, typical.

Anyway I know I bled it perfectly, I've seen enough vids and read enough instructions to bleed it properly. When bleeding the lever, the amount of air bubbles was ridiculous, depsite having already been bled twice.

Once all bubbles had stopped, I noticed which pulling to draw any more out I could here a noise coming from withing the lever. Hard to decribe but imagine you had a balloon filled with water and the balloon has the tiniest hold in it from which water would bubble out, that would make the same noise.

I'm now convinced there's a problem withn the lever, allowing air in, explaining the noise and the re-emergence of air in the lever.

ricardo_smooth

seals in lever gone if thats the case.

Coxy_UK

Easy to buy and replace myself?

ricardo_smooth

Not the easiest of jobs tbh, can be fiddly and difficult to get things out in on piece if you don't have the correct tools. One last thing to try is to check the hose is tightly secured in the fitting.

02gf74

I've seen the video and read a couple of ways to bleed these.

when you draw the air from the caliper, you have the brake lever held to the bars?

also I found that it may need as long as 15 mins :shock: pulling on the syringe for all the bubbles to come out ... a nightmare and my fingers start to ache, but when fully bled, they are as solid as a rock

Coxy_UK

Yeah I did it as per videos and instructions, but the sucking kinda noise appears to me to be evidence of something very wrong inside.

I will take it apart to check the bladder, then that being the problem will get this;

http://www.ukbikestore.co.uk/product/13 ... -1-pc.html

chedabob

Coxy_UK wrote:

Yeah I did it as per videos and instructions, but the sucking kinda noise appears to me to be evidence of something very wrong inside.

I will take it apart to check the bladder, then that being the problem will get this;

http://www.ukbikestore.co.uk/product/13 ... -1-pc.html

You'll need a snap-ring tool IIRC.

Coxy_UK

What's really annoying is I've now realised SRAM give a 2 year warranty, and I bought the bike on the 23rd June, so now I'm just out of the 2 year mark

nicklouse

not just Sram European law states 2 years.

sounds like you have not bled the brakes correctly.

is there any fluid leaking? if no then you dont need to look at the diaphragm.

the noise you hear will be air that you have not got out yet.

Coxy_UK

I don't see how I can have not bled them correctly though, no more air bubbles were coming out at all, and did it 3 times in all.

Coxy_UK

There is no fluid leaking though, so does this mean it's utterly impossible for the diaphragm to be knackered?

Rule74Please

Do you ride it on the Road?

You could have oil on the pads. This sounds like what it is (sight unseen)

To see if you need to bleed just pull the lever hard (stationary) and if it falls a second time you have air in the system.

Most people bleed brakes for the wrong reasons. It is a sealed system so air cannot get in unless you have a leak or have replaced the fluid

Thewaylander

nicklouse wrote:

not just Sram European law states 2 years.

sounds like you have not bled the brakes correctly.

is there any fluid leaking? if no then you dont need to look at the diaphragm.

the noise you hear will be air that you have not got out yet.

Listen to Nic, the other thing is if a seal is a bit buggered, normally after the blead the brake will feel good the first pull, then deteriate as oil comes out the seals, if it feels shoot first pull likely hood is you haven't bled them correctly.

Avids i found to be a pain to blead, but once done to be very solid, and not to bad maintenance

andermt

Currently having a similar issue.

Avid Elixir S on an Giant Anthem X3.

Were great all last year, never missed a beat. Went in for a service to see it through the summer and the LBS changed the rear pads, was okay the next few rides then was just rubbish, seemed to lose all pressure and had no power.

Took it back and they rebleed the brakes, seems better for ride immediatley afterwards but were back to being useless a few days later. Took it back again, with the same result. went back a 3rd time, this time they fitted a standard Giant brake temporarily while they sent the Avid off to Sram, apparantly no fault found.

Refitted it felt better but not perfect, improved over a 25mile ride. Yet again a week later it's back to being fairly useless (i.e. lever pulls almost back to the grip with little brake power).

In the meantime I replaced the front pads myself and they are still 100% okay, so decided to change the pads and discs on the rear to see if that helps. Took the rear pads out and they are shot, cracked, chunks missing out of them etc and these are supposedly about 6 weeks old. Fitted the new pads and noticed one difference, when I fitted the front ones I had to press the pistons back to get the pads to fit over the disc, when changing the rear I didn't need to which I found strange. Pistons looked like they were fully back (inside the caliper)
The new pads have made no difference (not that I expected too much)!

Any thoughts on what this might be as getting fed up with not being able to use the bike properly and have a trip to Glentress planned very soon?

bennett_346

Rule74Please wrote:

Most people bleed brakes for the wrong reasons. It is a sealed system so air cannot get in unless you have a leak or have replaced the fluid

But also water can be drawn in over tme also reducing the effectiveness of the fluid.

Coxy_UK

I bought a better bleed kit (one I used before was a £10 cheapy eBay job) hoping it would help with decent seals etc...

A masive no. Bled system ok, but when finished with each pull of the lever it got closer to the handlebar, until about the 4th pull it went all the way and stayed there. It's now just a floppy lever.

I have not noticed any fluid leaking anywhere.

nicklouse

if the lever is going to the bar more then you have a leak. or a MASSIVE amount of air. Or you are just doing it wrong.
most likely 1 or 3.

Coxy_UK

I'm very confident I'm not doing it wrong, seen all the vids and read manuals, it's a simple process. Something has clearly gone inside. I once read if bar pulls ok then pulls to bar and stays, a seal has gone.

I'm hoping this can be resolved by ordering the internal service kit.

mattrgee

If you remove the actual lever from the affected brake you will be able to see down to where the pushrod meets the snap ring and washer. Check the snap ring hasn't been dislodged as this will allow air into the system.

I'd be surprised if you were still bleeding it wrong after 3 attempts. As nicks suggests, you may have leak which would explain air being in the system each time you bleed them.

If you need to dismantle the lever you will need a pair of internal snap ring pliers. Halfords sell a pair for about £10.

Coxy_UK

Thanks, will have a look tomorrow and update.

Coxy_UK

Took abpart the lever today to discover some damage inside.



The white plastic washer type thing was completely in bits.

The black rubber o-ring thing has a slit through it.

What dp these bits do and would they of caused my initial problems, or have been caused by them? What do these bits even do?

nicklouse

that is the main seal that causes the brake to operate.

the cause of your problems. it would normally show with some leakage asweel.

Coxy_UK

I didn't notice any leakage, but I guess it's good news, new internals then bleed and should be sorted.

Shame nowhere has the internal kit in stock, I've been told next batch wont be in the country until Thursday.