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  1. #1
    cbx
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    Formula Rear Grinding feeling/noise?

    Hey All,
    I have a new set of fully broken in Formula K 24's. On some recent rides, I felt a sporadic grinding in the lever...it also was accompanied by a grinding sound. I thought it was dirt and the environment I was riding in, but found even after full cleaning and running my bike in a non sandy environment, it still did it. Took it to the shop who installed and they said that after wear in chances are the caliper was out of center. They adjusted, improved the feel but noticed one side was dragging when I got home. I recentered the caliper and no drag, but the feel of grinding is back a bit. It's almost as if I can feel the pad reacting to the vents in the rotor in the lever. Very bizarre. Anyone know what I can do to center with no drag but no grinding as well?

  2. #2
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    Reputation: SteveUK's Avatar
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    Take a look through the top of the caliper when you pull the brake lever. Does one piston/pad move further/quicker than the other? Does the rotor appear to move/flex when the lever is pulled? Even if the caliper is perfectly aligned over the rotor, if one pad touches the rotor before the other you're likely to get noise and a decrease in performance.
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  3. #3
    cbx
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    Just did a squeeze test...the rotor is dead still, pads appear to move exactly at the same pace/distance. Looks perfect to me.

  4. #4
    cbx
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    As not to say the problem is solved...still have a bit of a grinding feel

  5. #5
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    I just put up a post today about having issues with my new K24s. Is yours causing the whole back end of your bike to vibrate and make a ton of noise?

  6. #6
    cbx
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    No not really...just a grinding sound I can feel a bit in the lever. Power is pretty good but the noise and grind feel has got to go.

  7. #7
    cbx
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    Well, I give up. Just took her out for a test ride and the rear is still "grindy". Perfectly centered too, with no rotor drag. Is it possible the stock pads just suck?

  8. #8
    ride hard take risks
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    Before you throw in the towel can you post a pic of the set up??
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  9. #9
    cbx
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    Sure...here's a pic I just snapped. Any detail you are looking for in particular? I am running an Avid 140mm rear rotor. Forgive the image quality.
    Attached Images Attached Images

  10. #10
    cbx
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    Since they're new, perhaps the rotors need a good cleaning since the break in period?

  11. #11
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    Not looking for anything in particular just if your not wrenching on something a pic can possibly help.

    Grinding noises are some what common on OE pads, Semi Metallics usually less if any noise. The rotors on most OE setups are thin to minimize weight which can create a vibration through out the bike which we feel as a slight vibration or disturbing feel. My guess without being there would be Sintered pads grinding on the rotor which can be considered standard.
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  12. #12
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    Suggestions:
    -take pic of pads, inside of caliper w/o pads
    -swap front and rear pads and see which end has grinding if any
    then we'll go on from there

  13. #13
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    You can call Perigeum Development at 707 765 2770. They are great to deal with. They are one of Formulas US reps
    Lead by my Lefty............... right down the trail, no brakes.

  14. #14
    cbx
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    Called today...they are closed for Sea Otter. Will try them back tomorrow to see what if any light they can shed.

  15. #15
    ride hard take risks
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    Quote Originally Posted by cbx
    Called today...they are closed for Sea Otter. Will try them back tomorrow to see what if any light they can shed.
    Might give them an extra day, 4 dayz at the Otter drive home unpack and back to work. 5 dayz of emails and phone call messages to respond to.
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  16. #16
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    I had the same issue with stock pads and rotors after a muddy/wet race. I sanded, cleaned and buffed the rotors and pads to no avail. I ended up getting some sintered pads and new set of rotors (different brand but not for this reason). Issue gone for full life of pads. I think that the organic compound is too soft and gets contaminated easily. Only way to get rid of the problem is abrasion, but then you don't have any pad left. I've had the brakes since Dec08 and I'm already in need of a 3rd set of pads. I figured I would at least make it till the summer...I'm going to try a 3rd setup to see if I can get better pad life.

  17. #17
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    Quote Originally Posted by pwork
    I had the same issue with stock pads and rotors after a muddy/wet race. I sanded, cleaned and buffed the rotors and pads to no avail. I ended up getting some sintered pads and new set of rotors (different brand but not for this reason). Issue gone for full life of pads. I think that the organic compound is too soft and gets contaminated easily. Only way to get rid of the problem is abrasion, but then you don't have any pad left. I've had the brakes since Dec08 and I'm already in need of a 3rd set of pads. I figured I would at least make it till the summer...I'm going to try a 3rd setup to see if I can get better pad life.
    I found to organics to wear fast too. The sintered pads lasted me just under 4 months in the winter. I'm happy with that. Coming from magua martas, which were organics, I was swapping pads every month.
    Lead by my Lefty............... right down the trail, no brakes.

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