Disc Brake Issues

[P.A.K.]

Hi guys.

 

Im a bit dissapointed. I took my old and trusty Scott Reflex to a LBS to have them check my weak brakes, among other things. The rotors also touched the brake pads when the wheels spin. Its Avid hydraulic brakes.

 

So the guys replaced the rear brake pads. Now they touch the rotor even more, and still break pretty weak compared to what it used to be.

 

What can a technically inclined person like myself try to restore braking power and stop the rotors from touching the pads?

 

EDIT: Sorry for the misspelled title. I can't seem to edit it with Tapatalk

Edited January 10, 2012 by P.A.K.

[BergForce]

Take it back and tell them to sort out the brakes and remember to bed the new pads. Else replace the brakes with a brand that actually works - Shimano.

[Capricorn]

first of all, them brakes need to be bled. PROPERLY. If you can do it yourself, do it, cos most LBS just dont seem to understand when u suggest they bleed avid's just one more time past 3 - 4 bleeds.

Also check that the rotor still properly flat. A spin of the wheel and a keen eye will spot any wobble in the rotor indicating it's bent, or has a kink in it. They do bend sometimes, and just bending it back will do the trick.

 

Also ensure the brake pistons are pushed ALL the way back in. Reinsert pads, Realign the caliper, and go test the sucker.

[kosmonooit]

If the callipers are well used, then they might need to be taken apart serviced with new seals etc because dirt and gunge can get inside between the pistons and the housing, and make the piston movement sticky, so the spring tension cant hold the pads apart. That can be done DIY but I would say advanced DIY, and sometimes special tools are needed, best contract the importers/agents and get a recommendation as to whom to take them to. Replacing pads is a non-brainer, sometimes shops all to keen to do that even when no needed.

 

Bleeding them is essential from them to work properly, that can be done yourself. You just need a few things and make you get stock of the right oil for the brakes. Check out you-tube for some tuts. Dont know about spares for the Avids, but Hope you can get all on-line and all parts are reusable.

Edited January 10, 2012 by kosmonooit

[Johan Bornman]

A couple of points.

 

1) Bleeding has nothing to do with your problem. Bleeding is only required to sort out spongby brakes.

2)Avid brakes are crap.

3) Replacing the caliper pistons and square rings will help for a while.

4) Avid brakes are crap.

5) They don't take oil, but hydraulic brake fluid.

6) Avid brakes are crap.

7) They have to springs to push the pistons back. In fact, there is no mechanism to push the pistons back other than a bit of flexibility in the piston square ring (rubber). Those springs you see on the pads are only anti-rattle pads.

8) Avid brakes are crap.

[Smiles]

got to agree with avid brakes not being my favourite - i'm pretty sure that as an accountant, even I could design something better.

 

but having said that, you should be able to get them to stop rubbing the rotor. maybe have a look at youtube about proper set-up

[Capricorn]

JB: the bleed will fix the lack of power. ill put a considerable amount to that assertion. Based on personal experience. All avid brakes prior to the redsigned elixir models were unfortunately quite prone to trapping air. Hence why avid moved the bleed port in the 2012 models and dumped the juicy range.

 

and no, they not crap. At least not on a functional level. JB would do well to qualify his disagreement with avid without making a sweeping statement

[Johan Bornman]

JB: the bleed will fix the lack of power. ill put a considerable amount to that assertion. Based on personal experience. All avid brakes prior to the redsigned elixir models were unfortunately quite prone to trapping air. Hence why avid moved the bleed port in the 2012 models and dumped the juicy range.

 

and no, they not crap. At least not on a functional level. JB would do well to qualify his disagreement with avid without making a sweeping statement

 

 

I just don't see how a bleed can increase the hydraulic force.

 

Let's say there is air in the system. Once you've pumped the lever, you have maximum force. After a few seconds, that disappears, but two pumps of the lever and you're back to maximum force. This is not what the OP described, hence my assertion that a bleed will not solve the problem.

 

Why do I say they are crap? Well, let me start. They are extrememly prone to trapping air. Even the new ones. They are extremely prone to introducing air into a previously-perfect system with no leaks in the hoses. Other designs don't do that.

 

If you read the Avid bleed instructions it reads like a comedy. If you don't agree, lay the Shimano and Avid bleed instructions (and special tools)next to each other and compare the steps.

 

The pistons are very prone to getting stuck. The phenol resin compound they use for the pistons easily roughens up and get stuck. The fact that they use non-lubricious fluid inside there exacerbates the system. An oil-based system on that small scale overcomes the piston friction much better. I think oil is a superior fluid for brakes on this tiny scale.

 

Ironically, brake dust is its biggest enemy.

 

Lastly, those poofter levers with their sloppy pivots don't impress me. A ten-year old Shimano brake's pivots still hinge crisply. Avids seem to last one season before needing an overhaul.

 

I think there are several better systems out there. The old Avid tests where they show the boiling point of oil vs DOT fluid is moot. 99% of people never get to a point where 12 extra degrees of C would help them.

 

Do a casual survey of the number of Avid complaints on this forum compared to the other big brand.

 

The fact that they work, and work for you, doesn't reflect the collective experience (experience in what the consumer receives) out there.

 

Your mileage clearly differs and I'll respect that.

[Swift01]

I have to say I run elixir CR brakes on my bike. Having moved from V-Brakes I thought they were the bomb until I had them 6 months. Talking of heating up, they are crazy. Running G3 rotors, organic pads, well bled, but as soon as you use them a bit too much they start to feel like the pads have worn out and the discs are scratching. Upsets me because the GF got a set of Marura Loiuse Bat brakes, running Storm SL rotors and the preformance pads. Boy can those brakes stop well. She has been running them for a year now, only re-bled them once and they are still working like new. No scratching feeling etc. So yeah Avids I have to say may not be the best brakes in town........

 

Saying all that, I would at least get the brakes cleaned, bled etc. The rotors can bent straight if they are not too bad. I hope thats the reason, as you said they have been to the LBS, so the SHOULD have trued the pads the the rotor correctly.......

 

If the brakes are still not working, consider that the rotor could be toast. Not sure what rotor you are using but if it has been over used or over heated in the past it seems to loose it's braking power. The GF had that on the Magura brakes before she bought proper Marura rotors. She had Aligator rotors on, brake were ok (nothing like they are now but way better than her previous Deore brakes). Did a race where there was huge amounts of mud. Ever since then the brakes were worse than the old Deore brakes. Even new pads didn't change a thing. The rotors were only 3 months old, but as soon as we changed the rotors the brakes were like brand new. Seems something happened to the rotors with the mud etc.

[rouxtjie]

Also didn't have the best experience with two sets of Avid Elixir brakes. I am convinced the Dot5.1 fluid eats up internal o-rings and getting spares were tough, bleeding them was also a nightmare. Went shimano and I am happy as a pig in ....

[Capricorn]

actually jb its about recovering the braking power and its been my recent experience that pumping the lever doesnt help in the sligjtest. lever just kept lowering till it parked on the bars. but a proper bleed did resolve it. compleltely. so sorry im sticking with the bleed working. a proper bleed.

[The Drongo]

A couple of points.

 

1) Bleeding has nothing to do with your problem. Bleeding is only required to sort out spongby brakes.

2)Avid brakes are crap.

3) Replacing the caliper pistons and square rings will help for a while.

4) Avid brakes are crap.

5) They don't take oil, but hydraulic brake fluid.

6) Avid brakes are crap.

7) They have to no springs to push the pistons back. In fact, there is no mechanism to push the pistons back other than a bit of flexibility in the piston square ring (rubber). Those springs you see on the pads are only anti-rattle pads.

8) Avid brakes are crap.

 

9) Your pistons are probably 'welded' to the 'square rings' ie. seized

10) Avid brakes are crap.

11) You can bleed Shimano 'properly' in 1/5th of the time.

12) Avid brakes are crap

 

...completion of sweeping statement.

[SeaBee]

I don't have Avid's, but running out of patience on mine. Just out of curiosity - what do you guys seem to favour as a decent braking system? Seems Shimano is right up there... What else is advised?

[rouxtjie]

I don't have Avid's, but running out of patience on mine. Just out of curiosity - what do you guys seem to favour as a decent braking system? Seems Shimano is right up there... What else is advised?

Formula or Hope will be my next set

 

Very happy with my Shimano XT set though

[Sammajoor]

the heading should read " disc BRAKE issues"

[Swift01]

@ SeaBee I am quietly waiting for a good set of Magura Brakes to pop up on the hub. After testing the difference between the Avids and the Marura you can't compare. I believe the new range of Shimano's are quite good, but I have never tried them so can't personally comment. I just know that everyone you talk to that have the Magura Loiuse Bat brakes just talk how strong they are at stopping. The only secret is only stick to Magura parts like brake pads and rotors. Don't try mix n match.