[EPeff]

Hello everyone,

I was directed to this section of the forums after having no luck in the Brake forum or Specialized forum, and I'm looking for a frame building super guru wiseman or wisewoman who may be able to guide me (and many others) on the path of a quiet ride.

I'll keep the issue somewhat short and simple... (there are 150+ posts on this in the Specialized forum, so I am paraphrasing quite a bit)
All 2009/2010 Specialized Stumpjumpers affixed with hydraulic brakes (Avid Elixir standard) create a resonant frequency in the rear stays that transfers into the whole frame, causing vibration and a loud loud annoying howling noise from the rear brake. Specialized points the finger at Avid, Avid has been trying to come up with fixes, but it isn't the Avid brakes, it is the frame. This is proven because different makes/models of brakes have been tried, and they all do the same thing.
Here are some of the non-working fixes so far.....
-New solid non-vented G3 rotor from Avid (noise/vibration then came back)
-Switch from metallic to organic pad (noise/vibration then came back)
-Switch from organic to new metallic pads (noise/vibration then came back)
-Switch from new metallic pads to new organic pads (noise/vibration then came back)
-New vented G2 rotor from Avid (noise/vibration then came back)
-New, different brand rotor, any make/model at all (noise/vibration then came back)
-Upgrade from Elixir R to Elixir CR (noise/vibration then came back)
-Adjusting, truing, cleaning, balancing, reinstalling, checking, adjusting (noise/vibration then came back)
-9 trips to the LBS (noise/vibration then came back)
-New Shimano brake adapter (noise/vibration then came back)
-One user installed Formula RX brakes (noise/vibration then came back)
-One user suggests spraying expanding foam into the rear stays (not tested yet)
-One user wrapped the opposite chainstay in innertube (noise/vibration is muffled)
-One user ziptied lead fishing weights onto the rear brake caliper (noise/vibration is 90% eliminated)

Alright, so other than those last two fixes, another real fix doesn't exist. Avid has put together at least 4 different "fix kit packages" to send to the LBS, and they never work. Any amount of tweaking with the brakes themselves is useless. It is the combo is hydraulic brakes with this frame.

So why I'm here... I want to run two ideas by some of you who know materials and perhaps even a bit about vibration dampening.

1) Spraying the frame's rear stays with expanding foam (Great Stuff) - it will probably void the warranty, which sucks. Will this help? Could the expanding foam expand so rapidly that is cracks a stay?

2) Using Ti bolts for the rear brake caliper and caliper mount. My thought is that the different density/mass of Ti might not transfer this frequency into the frame, or at least deaden it a bit. Obviously aluminum fasteners are not an option here. I was also thinking about some other type of material to use for the washer for the caliper adapter. Similar to phenolic material used for car intake manifolds to prevent the cylinder head from transferring heat to the intake manifold... maybe there is a specific material washer that would help eliminate the transfer of vibration into the frame?

and

3) Do you have any other suggestions of how to eliminate this issue (without adding weight via inner tube or lead weights to the bike). These 09/10 Stumpjumpers may not be the nicest bikes in the entire world, but there are many owners like me, who had a budget, and bought the best bike they could afford. Putting lead fishing weights on a $2k bike is just ridiculous. Its not a fix, its a lead band aid.

Many people are dealing with this issue, and there no fix is in sight from Spec or Avid, so your help would be greatly appreciated!

Thank you and take care

 

[mikael_nr1]

Sure the caliper mounts on the frame are not out of alignment?

 

[crux]

This is a fun one. I had this happen to a guy and nothing would cure the issues. THe vibration was so bad you could feel it in the seat. It was a FS bike and even after facing the tabs the vib remained. New brakes same model were tried and vib. remained. Went thru quite a few different attempts. What finally fixed it was getting a different brake adapter. Think we put on a Formula one and it went away. Prior to that we did a shimano, hope and Magura Adapter and the noise & vibration remained.

This will be annoying, but swap out one component at a time till the noise is gone.

I'd also check the frame for potential cracks in the area. However small that could be a potential source, but unlikely.

 

[jay_ntwr]

I'm assuming all these trials are with 160mm rotors too huh? Have you tried either a 180mm or a 140mm?

 

[RoyDean]

try changing brake disc diameter?

 

[RoyDean]

Got me by a minute, jay...

 

[Walt]

Lots of bikes do this with Avids

I know for a fact that Turners and Ventanas have this problem with several models of Avid brake. There is a HUGE thread about Avid brake squeal floating around somewhere...

I will join in with the rest of the replies - swap out brake parts until it goes away. I don't think frame mods will help.

-Walt

 

[Guitar Ted]

We had a similar issue while testing a Giant XTC 1 29"er. Hydro-formed frame, Avid brakes. A lead fishing weight killed the noise. We felt it was due to the tabs on the frame to mount the adapter that were too thin, allowing for a vibration.

Eventually we switched out to a new set of brakes and as far as I know, that cleared up the problem. (I do not have the bike here now to verify this)

 

[shirk]

Norco had a very similar issue with either the Fluid or the Fluid LT. They ended up changing the seat stay and adding a small gusset and it fixed the issue. I'll have to dig around NSMB to find the details.

 

[unterhausen]

I propose connecting the NDS seat stay to the NDS chain stay with two hose clamps and a spoke

 

[shovelon]

Had the same problem with my Serotta softail. Hayes hydrualic 22mm mounts.

Switched to organic pads, was better but progressively got worse. Out of frustration, I soaked pads in White Lightning. No power but no niose. Eventually came back.

Friend gave me some Stans alum rotors. Put them on, lubed pads with white lightning to break in the rotors, and problem solved. Power is decent too.

I think the alum rotor dampens the vibration.

 

[customfab]

I'd be willing to throw some great stuff in their. I did it with an aluminum bar once and it was noticeable. I don't know why it would void your warranty either, not like you modified the structure of the frame. Dynamat may be another option. Might go down to a car audio shop and see if they can give you some scraps to play with.

 

[EPeff]

I should have come here first all along. Some great suggestions.

One of the suggestions from the other thread was the new Shimano brake adapter... but I didn't think about using other brands as well (Hope, Magura, Formula, etc). Again, following the idea of different mass/density/shape material between the frame and brake to help deaden the vibration.

Here is my next steps; (each step following the next if that previous step doesn't work)

Shimano brake adapter which arrives in 2 days...
then Hope, then Magura, then Formula adapters...
Dynamat (a little price the same shape as one side of the brake adapter - aka; Clean)
180mm front and back rotors... (potentially 2-piece)
great stuff expanding foam in the rear stays...

Thanks again everyone, you have been a great help.r

 

[bobbotron]

Great stuff

If you do go the Great Stuff route, you should practice using it on something you don't care about first, like filling a small diameter pluming tube or something. The directions say something like "don't fill the void over half full" - they mean it! It is a great product, but it really does expand. I think a lot of people who use that stuff over fill the first time, and either have something pushed out of the way, or have to cut off a huge expanded blorb of GS after the fact. Or both! A little goes a long way.

 

[SC RockLobster]

throwing it out there

what about a carbon brake adapter. carbon should be great for this app.

 

[EPeff]

what about a carbon brake adapter. carbon should be great for this app.

I have no knowledge of carbon brake adapters. Is this a joke, or is this even real?

I'm weary of using any carbon on my bike (heard too many stories, I'm a clyde, just my choice I guess...) but I wouldn't be adverse to this if it were actually a real product and has a proven track record.

Maybe even a Ti adapter?

Anyone know if either of these exist?

Google searching came up fruitless.

Thanks much

 

[giantbikeboy]

Had the same problem with my Blur and the Juicy Sevens. Tried everything and nothing stopped the howling. Put some new XTs on it and problem solved. Put the Sevens on my 575 and they are quiet as can be. Brake/frame combo?

 

[Megashnauzer]

there was some stuff made by loktite that went on automobile disk brake pads to stop squealing. i bought it years ago for that problem with a honda i had. anyway i had howling from a set of avid brakes that wouldn't go away. i put this stuff between the rotor and the hub before i bolted it on. i also put it on the back of the pads before inserting them in the caliper. it didn't make the problem go away entirely but it knocked it back quite a bit. the stuff is like orange silicon. it's cheap and might be worth a try.

 

[EPeff]

Brake/frame combo?

Exactly.

Unfortunately with my specific frame it seems most brands/makes/models will cause the same issue.

So did I get fooled into thinking carbon/Ti disc brake adapters are real? Doesn't seem logical for CF, but maybe Ti.

Thanks for your responses.

 

[Francis Buxton]

I would seriously try a little strip of Dynamat. Its entire purpose is to reduce vibration resonance. It did a great job in the trunk of my 72 Nova with a 12" sub when I was in high school.