Adjusting Avid Elixir 5 brakes - disc not centered between pads

[nickdos]

Recently got a new bike with Elixir 5 brakes. The rear disc rubs slightly on the inside surface and the lever is a bit tighter than the front one. Shining a light up the brake pads I can see the disc is closer to the inside pad than the outside one.

I attempted to realign the brake following the instructions by loosening the two hex bolts holding the brake to the bike frame, then depressing the brake lever and tightening the bolts back up. Although this improved the issue it did not fix it entirely. I've repeated it a couple of times but when I tighten the bolts the housing shifts back to being slightly off centre from the disc.

I'm guessing that I'm right at the edge of the available movement the brake attachment bolts are allowing for my brake. Is there anything else I can try or should I simply take it to the shop to get fixed (still under warrantee)?

Thanks

 

[0psi]

When you are doing up the two bolts holding your caliper on do so a little at a time, say an 8th of a turn at a time on each bolt.

So loosen the bolts, spin the wheel, slowly apply the brake. Repeat and hold down the brake lever quite firmly. then while still keeping the brake lever depressed, do up the bolts so that they are just firm and then turn each one an 8th of a turn at a time till they're done up.

Chances are your rotor won't be dead centre but close enough is good enough. As long as the rotor isn't rubbing and the caliper is aligned with the rotor correctly you should be fine.

 

[Dales Cannon]

If that doesn't work the only option is to push the pistons back into the calliper and then centralise the calliper on the disc.

 

[nickdos]

When you are doing up the two bolts holding your caliper on do so a little at a time, say an 8th of a turn at a time on each bolt.

[snip]

Chances are your rotor won't be dead centre but close enough is good enough. As long as the rotor isn't rubbing and the caliper is aligned with the rotor correctly you should be fine.

Thanks for that, I'll try it tonight.

I've already got it to the point where the wheel will now spin for quite a while with a very gentle push (can still hear the faint rubbing sound though), so I'm close to the "good enough" point. Hopefully a fraction of a mm more and I'll be there. I also figured once the brakes wear a little it'll improve slightly too.

 

[Agostino]

I use a feeler gauge, and put a similar thickness on either side between the pad and rotor this centers the caliper. Then I tighten the bolts up, I find this method always works.

For those that don't know what a feeler gauge is, its used to set the gap on your spark plugs, will cost you about $10 or possibly cheaper.

http://www.fine-tools.com/s309613a.jpg

Hope this helps

 

[nickdos]

Just a fiddle with them again...

I also tried using a very thin piece of cardboard as a "feeler gauge" as suggested above. Doing this I discovered the gap between the pads is much tighter on the rear than for the front brakes (easily slipped in compared with very tight for rear). This is echoed by the feeling of the brake levers - much less movement for the rear brake.

Will Dales suggestion of:

If that doesn't work the only option is to push the pistons back into the calliper and then centralise the calliper on the disc.

help re-set the distance between the pads or is it a problem only a bleeding will fix?

If yes, can someone provide a little more detail on how to do this?

 

[MTBcrash]

If the pistons look to be out an even amount each side then the caliper is working fine.
If that's the case then in my opinion you would be best to get some shim washers like the ones in the links below and put them between your brake mount adapter and frame. Because they are shims, they are exactly the same thickness so will keep the mount/caliper in line with the frame.
Doing this will set the caliper in towards your spokes giving you a bit more clearance between rotor and pads on the inside.

I bought some from another seller on EBay (I think it was EBS Brakes??) which had a variety of thicknesses in the packet and they've come in very handy. You could probably get them elsewhere if you look around.

http://cgi.ebay.com/Magura-Caliper-...Cycling_Parts_Accessories&hash=item2562e368cf

http://cgi.ebay.com/Disc-Brake-Cali...Cycling_Parts_Accessories&hash=item25611f9971

http://www.chainreactioncycles.com/Models.aspx?ModelID=356

 

[nickdos]

Thanks for that MTBcrash.

I think I've got the caliper centered well enough on the frame. But I've now realised there is an issue with the pads being set too close together - which meant there was hardly any room for error in setting the caliper position.

How easy is it to reset the "resting" distance between the pads. Can I do it without bleeding?

They are way too close right now and as a result the brake lever has hardly any movement in it. I think I need a spacer to do this (just watched the Avid bleed video on youtube)...

 

[MTBcrash]

Sent you a PM which might help

 

[0psi]

If the pistons look to be out an even amount each side then the caliper is working fine.
If that's the case then in my opinion you would be best to get some shim washers like the ones in the links below and put them between your brake mount adapter and frame. Because they are shims, they are exactly the same thickness so will keep the mount/caliper in line with the frame.
Doing this will set the caliper in towards your spokes giving you a bit more clearance between rotor and pads on the inside.

Negative captain. Those shim washers are designed for use with IS mount calipers, if you need to do this with a post mount brake then there are bigger problems.

You may be able to reset the pistons using either a big flat screwdriver, a ring spanner or my personal favourite, an 8mm allen key. Remove your pads and slide the allen key the whole way through the caliper so you can grab it on both sides of the caliper. With a flat side of the allen key against the piston and your thumbs on the caliper, gently pull, working your way back and forth along the piston. This should work assuming you don't have excess fluid in the system.

 

[MTBcrash]

Negative captain. Those shim washers are designed for use with IS mount calipers, if you need to do this with a post mount brake then there are bigger problems.

Forks have 'IS' or 'post' mount, he is asking about the REAR caliper/mount.

Pretty sure most if not all frames have an IS design at the rear requiring an adapter to mount the caliper on to. Also fairly sure most hydraulic calipers are post mount design with only a few cable disc brakes being an actual IS mount.

'Those' washers can be used between the mount and the frame to push the mount inwards and subsequently move the caliper inwards. In this particular case he has identified that this is not the problem, but if it were it is an easy way to fix it.

 

[Landon]

Elixir Pad Clearance

Yeah, I feel your pain. As a general rule, most Elixir brakes out of the box will have less pad clearance on the rear brake than the front. I would love to hear a definitive reason for this issue from the SRAM techs, but here are some things you can try that will help.

1. Bleed the brake with one of the new Avid Pro bleed kits (not the cheap standard kit), or have the brake bled by an experienced mechanic. Even though the caliper piston seals are responsible for retracting the pistons, there would be a certain vacuum effect from the lever piston. The taper bore system uses an o-ring to drive fluid and not a cup seal like most other brakes. Due to the length of the hose and the increased capacity of the rear brake system to trap air, this vacuum effect can be reduced in the rear brake I reckon. Removing as much air from the rear brake as possible has increased pad clearance from my experience. SRAM have improved their factory bleeds over time, but some problems still occur.

2. Remove all excess fluid from the rear brake system. You can remove all excess fluid from the system by installing the pads and inserting a pair of Avid Elixir pad spacers from the top and bottom of the caliper. Use the two pad spacers like a wedge against each other. This will force the pads back and hold them back. With the Elixir 5, you're going to want to lay the bike on its side so that the lever bleed screw is pointing up. Hold a rag around the bleed screw and loosen it with an Avid T10 tool. A small amount of fluid should spray out into your eye. No, it will just well up around the bleed screw and you can safely wipe it away. If no fluid comes out, and you can't see any fluid at all after removing the bleed screw completely, that's bad.


3. If they're new brakes, the pistons will free up a little with use. You can lubricate the exposed area of the pistons with a little brake fluid if you pump them out of their bores slightly. The next step is caliper disassembly and seal lubrication with a little SRAM DOT grease.

After you've improved the pad clearance and taken the bike on a few rides to smooth the new pads, it should be easier to get the brake drag free. Always aim to centre the caliper body over the disc as a first priority. To do this you will probably need to work the pistons a little to have them centred in the caliper. A beefy plastic tyre lever is the best tool I've used for this job.
The caliper alignment techniques mentioned above are all very useful. It is sometimes necessary to use shim washers between the adaptor and frame to place the caliper within its adjustment range. Thankfully, this isn’t a common thing. It is indeed very helpful to tighten the CPS bolts lightly at first, check the alignment and then adjust with a little force to the caliper if required. Tighten the CPS bolts in stages.

 

[nickdos]

Just an update...

I took the bike out for a short ride at Mt Stromlo on Sunday (loop #2) and gave the brakes a good workout coming down through the Luge, etc. At the end the rear brake did have more movement in it but I haven't looked at the calipers to see if the gap is bigger. The disc is no longer rubbing on the pads so I've decided to do nothing more for the time being. I might get it looked at on the next service...

Thanks for all the advice