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Front end vibration

Discussion in 'Tech' started by DWhyte91, May 24, 2016.

  1. DWhyte91

    DWhyte91 Well-Known Member

    Yep. The top ~1" of the rod got bent when I was removing the tool that pulls up on the cartridge. I got distracted and almost dropped the tool, tried to catch it and bent the top of the rod that was sticking out that the cap sits onto. We had it sliding in and out with just a slight bit of friction after trying to straighten it.

    I had the issue last weekend and the second last round last year. I was positive it was the rotor but it just doesn't add up. Tried to order new ones and they aren't available for a few weeks so that leaves me with my oem set. We'll get it narrowed down in the first session but there's only 2 for Friday so we've got to be on the ball. I'll have my second front with a tire and my oem rotors on it ready to go so it'll be a quick swap.
     
  2. DWhyte91

    DWhyte91 Well-Known Member

    My geometry has changed from last year as well as the spring rate. It only happens coming into/through allens braking hard vertically and trail braking and the last corner before the straight when trail braking. Even into the hairpin it's ok where speeds are a bit similar (slow).
     
  3. Spitz

    Spitz Well-Known Member

    You're making a lot of assumptions by putting rotors on a piece of glass, other than being seriously bent you're not going to see anything. I can feel vibrations in a car with rotor runout of anything more than about .007". Definitely swap them out to verify. Start with the easy shit first.
     
  4. DWhyte91

    DWhyte91 Well-Known Member

    I am and will. But, here's my thought, if the rotor is as warped as it feels at say 20mph, at 150 the bike should self destruct or shake so violently it wouldn't be ridable. I should atleast have a pulsating in the lever should I not?
     
  5. Banditracer

    Banditracer Dogs - because people suck

    I would think if it was rotors you'd feel a pulse in the lever and it would do it all the time.
     
  6. DWhyte91

    DWhyte91 Well-Known Member

    At high(er) speeds the brakes are fine. I'm still going to try a different wheel with my oem rotors first if my new whee bearings didn't fix it. Then if that doesn't solve it were going with damper rod/suspension issues.
     
  7. Spitz

    Spitz Well-Known Member

    So many weird situations have run through this shop I could make a book of shit and no one would believe anything written. :D I've felt low speed vibrations which felt much better at higher speeds. Maybe the frequency changes to where you don't "feel" it as much, it may very well be present however. Example- this is a balance issue but along the same lines, my clothes washer can start with an unbalanced load and spin up to 1000rpm where it evens out somewhat, It doesn't walk itself its way across the floor. Same with tire balance, there is speeds at which the unbalance counteracts itself. I'm just mentioning to not discount it which you're not but other people read these tip threads and its just out there for the masses as well as you. Like I said, easy stuff first before you create a problem that isn't there.
     
    DWhyte91 likes this.
  8. DWhyte91

    DWhyte91 Well-Known Member

    It was the rotors.
     
    MELK-MAN likes this.
  9. Banditracer

    Banditracer Dogs - because people suck

    Glad you got it sorted. Been checking the timing thru the day, looks like some decent sized grids. Also hot as hell.
     
  10. DWhyte91

    DWhyte91 Well-Known Member

    Ya the grid is pretty decent in pro sbk and the field is deep.
     
  11. MELK-MAN

    MELK-MAN The Dude abides...

    totally depends on how bad a warp. and it sure doesn't take much to feel under braking, but not at the lever.
     
  12. They in the mail yet?
     
  13. DWhyte91

    DWhyte91 Well-Known Member

    It seems once the rotor gets hot is when we have the issues

    I'm racing. Monday or maybe Tuesday.
     
  14. RM Racing

    RM Racing Tool user

    Rotors with cuts milled in them (Galfer and others) will pulsate at 20mph but do nothing at 150. If you are just ticking the buttons of the rotor with a caliper or pad, the same thing will occur.
     
  15. Gino230

    Gino230 Well-Known Member

    Is there anything we can do with these tweaked rotors? I have had 3 sets on 2 different bikes get warped or end up bend or whatever in the last season. It's usually pretty slight, I only feel it when I first touch the brakes, as I come into them harder it goes away. I swear they are flat but once I get to the track they are at it again.

    Nothing fancy, the Brembo stockers on the 848 and the 848 LW conversion.

    I'm guessing it happens when they get banged around off the bike, or ? I'm not a very hard braker so I doubt I'm overheating them.
     
  16. MELK-MAN

    MELK-MAN The Dude abides...

    i have never had luck getting em straight Gino.. even sent some brembo oversized rotors out to a place that 'specialized' in straightening. never were right. i gave up on buying expensive rotors, as the stock r6 rotors are REALLY good in my opinion. yes, they seem to get banged around occasionally during tire changes is also an opinion i have. it would be ideal to remove the rotors every time you get a new tire (like they do in motoGP with mega$$ rotors), i just don't have patience for it.
    Had a vibration here at summit point this weekend on my marchesini wheel rotors, and having 4 other stock wheels, they get a lot of abuse. I tried using a dial indicator and screwdriver to get a little better. no go. new rotors.. amazing. for $220 a pair with a decent discount, i just replace once a year or so, or whenever they get a little vibration after i verify with the dial indicator there is some run-out.
     
  17. DWhyte91

    DWhyte91 Well-Known Member

    They aren't overly slotted. I would actually say they might be less then the oem rotors.

    I used the stock rotors this weekend. If I'm going to continue to use them I need a much more aggressive pad. I had to use twice the effort I normally would to get the bike stopped. That gets tiring.
     

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