[Tone No Balone]

I am experiencing the same problems xcguy has had with his Elixir R's.

Formula Oro K18's

Here is my situation:

Vassago 16" frame SS/w track ends. I was running Avid BB7's with 160 rotors without any problems. Thought I would upgrade and purchased a set of Formula Oro K18's. 180 Front rotor/160 rear.
Did the install using Formula instructions and torqued all hardware to spec's carefully. I started with sintered pads. The front brake works great but the rear will produce an extremely loud hmmmmm and vibration up through the seatpost under hard braking just before I lock the wheel.Under high speed, modulating the brake works a bit but when I need more brake, the hmmm and vibration begins. I changed the rear pads to organic and I still get the vibration. Did multiple caliper adjustments and just about everything discussed in xcguy's thread. I even tried wrapping a strip of innertube on the left side seat stay with no success.
I also took one link out of my chain which moved my wheel forward a bit thinking that might change things...no dice. So tonight I was test riding and while moving at high speed, I reached down and just put my thumb and forefinger on my left seat stay and braked really hard and there was no noise or vibration at all!
I did call Chris @ Formula right after I did the install and he gave me some recommendations and also said give it some time to set in. Well,I have got at least a dozen rides on these and nothing has changed. It is beginning to make me crazy. I find myself laying in bed thinking "what if I try this".
I know these brakes are factory bled but I am considering doing a bleed as I noticed the inboard piston isn't protruding as much as the outboard and I have very little clearance between the rotor and the pads although the pads are not rubbing the rotor when I spin the wheel. Possibly some air in the lines at the caliper? Don't know.....
The brakes work really well other than the vibration. Wondering if I should go 180 rotor rear with mount?

Tone.

 

[louisssss]

what my mechanic did to fix all vibration was to "true" the rear rotor. he used the park tool and bent it up a bit and it has 95% gone away.

 

[miles wadsworth]

Have you tried swapping the rotor with another?

 

[AZ]

Recenter the caliper before you bleed . If the brake is not spongy there is no need to bleed . As Louisssssss posted make sure the rotor runs true . Make sure the rotor is clean , you can use non chlorinated brake cleaner or alcohol . Good luck .

 

[Tone No Balone]

Miles....The rotor is suspect. It is new and looks straight but I still suspect the damn thing!

The lever feels firm so no bleed necessary?

 

[miles wadsworth]

No bleed, that part should be fine, good luck.

 

[SteveUK]

Get the brake tabs faced. If it still vibrates, cut a length of inner tube, wrap it around the stay and secure it with a cable tie.

 

[gmcttr]

Make sure the inboard piston is not sticking and is moving as much as the outer. If it moves freely, push both pistons back into the caliper and re-center/align the caliper.

If the noise and vibration still occurs, try using the old Avid rotor.

 

[Tone No Balone]

Get the brake tabs faced. If it still vibrates, cut a length of inner tube, wrap it around the stay and secure it with a cable tie.

Steve.....I did the inner tube wrap on the left side seat stay tightly and that didn't help. Haven't faced the brake mount tabs but the BB7's and adapter mount I had on before didn't vibrate at all.

gmcttr.......I will try swapping out the rotor and use the old avid rotor to see what happens next.

Tone.

 

[SteveUK]

Haven't faced the brake mount tabs but the BB7's and adapter mount I had on before didn't vibrate at all.

The main reason for the CPS set-up used on the Avid brakes (including the BB7) is to eliminate the need for frame facing.

 

[Tone No Balone]

Is the CPS set up on avids the concave washers which allow the top of the caliper to pivot inwards or outward, not just left to right? It seems as though the Formulas are similar in design. not sure.

 

[SteveUK]

Is the CPS set up on avids the concave washers which allow the top of the caliper to pivot inwards or outward, not just left to right?

Yes, the same as those found on V-brake pads. The Formula calipers are like all PM calipers, are they not? Elongated slots to allow caliper movement inboard/outboard? This won't account for misaligned brake tabs, though.

 

[alexalecu]

I know that it may sound crazy, but try a different quick release for the rear wheel.

I used to have the same problems with my rear brake (a Hayes 9 Carbon) on my hardtail about 2 years ago - just the rear brake, as the front one was just fine. When braking on the rear, I could feel VERY STRONG vibrations in the frame and hear the brake howling (I cannot find other word to best describe the sound made by the brake).

I did a search in this forum for possible solutions and found a couple of threads at that time describing the same problems as mine, and a long list of possible solutions, ranging from using plastic (soft) washers between the caliper and the frame to using new rotors with a different shape.
The cheapest and fastest was to replace the quick release with a different one, which is what I did: I replaced the WTB QR with a Shimano XT, which, miraculously, fixed the problem. No more vibrations / howling coming from the rear brake since then.

 

[timehoc]

Thread subscribed. I have the exact same problem with my K24s. Howling resonating through the frame when I brake hard at > 15mph.

 

[Tone No Balone]

Yes, the same as those found on V-brake pads. The Formula calipers are like all PM calipers, are they not? Elongated slots to allow caliper movement inboard/outboard? This won't account for misaligned brake tabs, though.

That's correct Steve. Formula's have elongated slots for inboard outboard movement. When I get home this afternoon I am going to try a different rotor. Facing the brake mount might possibly be what it needs! Visualize a misaligned brake mount. The brakes work fine until I ask for hard braking power then the hmmmm/vibration starts. Pads may not be pressing against the rotor evenly?

Alexalecu....That crossed my mind about the QR. I currently am using an American Classic QR. I think I have a Kore and a Shimano QR which I will try.

Thanks for the support you guys. I don't feel so all alone with this problem.

 

[alexalecu]

Alexalecu....That crossed my mind about the QR. I currently am using an American Classic QR. I think I have a Kore and a Shimano QR which I will try.

As I have mentioned already, the QR I replaced was a WTB, which coincidently is the same as your American Classic QR, except for the logo
On the other hand, that QR is now on my wife's bike, which has an Avid BB7 rear brake - not a problem so far.

 

[gmcttr]

And I thought it was only Avid brakes that made noise and vibrations. At least that is what a lot of posters on this board would have you believe.

 

[Tone No Balone]

update

OK, I just finished wrenching and here's where I stand!

First I tried the Kore quick release.......no go whaaaaaa.

Next the Shimano quick release....nada........

checked the hub for bearing play and its solid, nice and smooth.

Last....pulled the Formula rotor and put the Avid rotor on.....hmmmmmm/whaaaaaaaa! no dice!

going to the shop tomorrow to have the brake mount faced!

I'm going riding anyway!

Tone.

 

[gmcttr]

If you originally had sintered or metallic pads, try them with the Avid rotors as well. You never know what combination might work.

 

[Tone No Balone]

If you originally had sintered or metallic pads, try them with the Avid rotors as well. You never know what combination might work.

Thanks for that....I'll put that on my unchecked list....the short list.

Tone