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Rotors: How Much Effect On Lever Feel?

Discussion in 'Downhill & Freeride' started by Tenacious Doug, Dec 28, 2005.

  1. Tenacious Doug

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    After much wrestling to get that crisp shimano feel from my brakes I am one by one trying to get rid of possibilites from the mush feel I am still getting at the lever. The setup is a pretty standard shimano Saint setup, callipers and rotors with sintered pads and standard hoses, however I am running the wavy "braking" rotors (badged up in the UK as Aztec) as opposed to the standard shimano ones as I wanted a 180mm 6 bolt setup, and shimano only make this rotor in centrelock. I have bled till I am blue in the face, swapped pads, levers etc but still have more mush at the lever than with my previous shimano brakes (with standard rotors) and any customers bikes that I have serviced or setup with these brakes, which must be 4 odd years of working on Shimano brakes, or however long since they came out.
    The only thing I am wondering is if the rotors are the weak point and causing a bit of mush at the levers, possibly as the pad may not have full contact with the rotor at any one time due to the fluctations in diameter of the disc. Braking power etc is all fine, it is just the feel of the brake that is driving me up the wall, which bugs me as one of the main reasons for me buying Shimano is because of the great lever feel they normally have.
     

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  2. Transcend

    Transcend My Nuts Are Flat

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    It's more likely that the rotor is slightly warped, or that you have a crack in the seal at the level, then the rotor shape having any impact on braking feel.
     
  3. Tenacious Doug

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    The rotors are perfectly true and callipers properly alligned. The brakes have probably had 20-30 hours riding time in them and have shown no signs of leakage. I have also tried the system with different levers which gave no improvement
     
  4. amateur

    amateur Turbo Monkey

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    Which lines are you using? Try swapping those, you may have a leak in the inner tube.
     
  5. F.O.G

    F.O.G Monkey

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    I run Braking Rotors with Shimano XT 4-pots and they have great lever feel. I run 8 inch rotors on all my bikes, and they are really to powerful for the 4x bike.
     
  6. Tenacious Doug

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    Using standard Shimano lines, which I have always had good results with, and I am comparing my brakes against other ones with standard shimano lines. Not discounting the possiblity of a leak, it just seems a bit unlikely that both front and rear would be suffering from a leak from new, seeing as both are lacking a crisp bite at the lever.

    The plan was to upgrade to goodridge before soon anyway!
     
  7. Changleen

    Changleen Paranoid Member

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    Not quite in the same vein, but I once switched to wavy discs on a motorscooter and it had the effect of making the brakes feel mushier.
     
  8. OGRipper

    OGRipper Turbo Monkey

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    Assuming you are getting full pad contact, the rotors shouldn't make a big difference as far as lever mush goes. Sintered pads tend to feel a little softer to me than the metallic so that could be it. Honestly, no disrespect, but it sounds like you have air in your system somewhere, or maybe contaminated fluid. Bleeding alone may not do it, you might need to flush out all the old fluid and try again. Pay extra attention to the calipers, as air can get trapped in there pretty easily.

    You could always try 'em out with shimano or hayes 6" or 8" rotors and see if it improves lever feel.
     
  9. Tenacious Doug

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    No disrespect taken, and over the last however many bleeds I have been telling myself that I just must be doing it wrongly but I have flushed, flushed and flushed again. Bled from top down, bottom up, with bleed kit and without bleed kit. Only reason I am asking about the rotors is I have done this so many times with complete success and these ones (it had to be my own ones!) are proving to be a real nightmare and I just cant put my finger on it.
     
  10. OGRipper

    OGRipper Turbo Monkey

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    Are you talking about new levers?
     
  11. Zutroy

    Zutroy Turbo Monkey

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    The only thing i can think of that would effect the feel would be if the rotor thickness changed.
     
  12. OGRipper

    OGRipper Turbo Monkey

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    Yeah but that would just change the contact point, not make mush no? I keep coming back to air in the system, contaminated fluid, or maybe a worn lever piston or something.
     
  13. dhkid

    dhkid Turbo Monkey

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    are your pads worn out or new? coz when you bleed your brakes, you can end up with a slight vacumm(sp?) in your system, so each time you you press the brake leaver you are pumping oil into the system first to compensate for the vacumm then only it will give the solid feel you are looking for.
    so what you can do is, if the pads are new, push the pistons all the way in and use the shimano yellow biscut, if they are worn out, just leave the pads in and use the red biscut on them. after you have done that, add oil throught the bleed nipple, just make sure you suck some oil out first so that any air would not get into the system, then just add some oil, then your system should give the solid feel that you are looking for. hope you understand what i mean.
     
  14. Udi

    Udi RM Chief Ornithologist: “I Brake for Birds”

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    Religious shimano brake user here.

    In my experience even if you do a scrappy bleed with any of the shimano brakes, they solid up after a good day of runs.

    I run saints on my DH bike, and when I first bled them, I found following the manual as closely as possible produced the best results. Bleeding up didn't work well at all (as in - don't do it), so I would suggest gravity bleeding, and pumping the fluid through by compressing the lever while having the bleed nipple only open 1/8 of a turn. Obviously top up the resovoir as often as neccessary, air is bad :). Read the manual for more specific details.

    Do that properly, make sure everything is clean and oil free, and go out and give them a day of dh runs. By now they should feel solid, but if not another thing I found helped was - tie the levers closed overnight or for a few days if you are not riding. I use wire but i'm thinking zipties will work well here. Simply tie the lever to the grip and tighten as much as you can before the ziptie gives, and leave it like that.

    The M06 sintered pads that come with the saints provide a pretty solid feel as well, and once they bed in they are an excellent pad. So rule that out as the culprit.

    I doubt the rotors would cause any issues - but if you suspect them and have the money to throw around - a set of 203mm XT rotors would be perfect. Try everything else I suggested first though.

    Also ensure that your hoses are setup properly, nothing loose and nothing leaking. Slide the plastic caps off the hose ends at the lever and make sure theres no oily residue. Alignment is another important one - the disc should be perfectly centered in the 5mm wide slots in the calliper when installed, and the pads should be bedded in square as well. The latter will take time if you screwed it up the first time, but I doubt you did.

    All round i'm yet to use a better brake - the saints bite hard, have a nice solid lever feel, and bags of power. So good luck - and don't give up on them.
    -Udi
     
  15. konastab01

    konastab01 Monkey

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    Doug i ran 203 wavy rotors on saints during the year and also got this mushy feeling but when changed back to standard shimano rotors and rebled they where magic.
    Dont quote me on this but can you not run Hope rotors on Saint brakes if you cant get a hold of a shimano.I know they have a smaller braking surface but Its not much Im sure
     
  16. DirtyMike

    DirtyMike Turbo Fluffer

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    N rotors Wont make a difference in your brake feel.... like another had said just change the contact point.....Which levers Do you have?... I i were to guess i would Guess they were theOld style Seperate from teh shifter not the silly wanna be road style were the brake lever if your shifeter right?.... But You never know... i run a front derailer so i have shifters both sides <E13 DRS Best way>

    Anywho i ask Because i Saw a couple recalls on the New style levers that were Bypassing fluid internally in the Master portion
    ________
    Blondibondar
     
    #16 -   Dec 29, 2005
    Last edited: Aug 25, 2011
  17. zedro

    zedro Turbo Monkey

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    well most brake levers are regressive in nature, so further you have to push the lever in the less power you'll get. Hayes are notorious for this when people set their levers too close to the bar. Comparing my Avid and Hayes rotors the difference in thickness is pretty significant, so it is a possibility
     
  18. Tenacious Doug

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    It is Saint levers and Saint callipers, no flip flops here!!
     
  19. Tenacious Doug

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    Despite being convinced by replies on here that it probably wasnt an issue I managed to get hold of a 180mm 6 bolt hope rotor to try with them.........and immediately the mush was gone and the firm bite point I had expected with the brakes was there, tried it front and back and both were greatly improved with the standard rotor. It was the only change I made to the setup, no more bleeding, same pads, same callipers and levers, so it can only be the change of rotors. So a set of 180mm Hope floating rotors is next on the shopping list!

    Thanks for all the replies guys, lots of good info.
     
  20. OGRipper

    OGRipper Turbo Monkey

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    Wow, interesting. Other than the wavy action, what else is different? Any significant difference in thickness?

    I have a set of avid juicies that came with wavy rotors, I could feel the pulsing and immediately switched to round shimanos, much better. But I didn't notice a change in the mush factor.
     
  21. Tenacious Doug

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    I think the Hope are possibly marginally thicker, didn't pay much attention though and dont have them in front of me. Still a bit confused about it, I know people using these brakes with wavy rotors and having good results, though I know for sure that at least one of them is using Goodridge hoses which I guess may compensate for any mush being caused by the rotor??? Who knows, all I know is that I am excited that my brakes are finally sorted!
     
  22. DirtyMike

    DirtyMike Turbo Fluffer

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    How much thicker is the rotor?.... Just curious Myself.... And does it seem the contact is Much higher?..... Might need a Micrometer to see the difference...... Would be nice to have info for future needs if i sewe this with some friends not on RM
    ________
    New Condo Pattaya
     
    #22 -   Dec 30, 2005
    Last edited: Aug 25, 2011
  23. Tenacious Doug

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    Not sure, but will check.
    Both rotors are at work and I am off till the 6th of January :thumb:
     
  24. zahgurim

    zahgurim Underwater monkey

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    I know the rotors you are talking about, they are crap. I used to run them myself.

    They look something like the Hope gothic, but are poorly designed. The pad/rotor contact patch goes from a very minimal contact area to a large contact area, causing a very wierd feeling at the lever.
    I was running them with Hope 6tis, and when I applied a lot of power they actually caused the wheel to vibrate, much like an ABS anti lock system. I think Avid had a problem like this with their wavy rotors they first supplied with the Juicy brakes. When I changed back to a round rotor the problem dissapeared.

    The rotors are poo, toss them.