In need of an even pair of disc rotors

Discussion in 'Bicycle Repair' started by battery, Mar 18, 2014.

  1. battery

    battery Member

    Can anyone please tell me where to get a set of disc rotors that are true but cheap. I am on unenjoyment and have little money to work with. My rotors are uneven and slowing the bike around turns is a serious concern! Or is there a trick to shaving them even possibly?
     

  2. FurryOnTheInside

    FurryOnTheInside Active Member

    Cheap disc rotors will "always" warp with heavy use, and are unsuitable for motorised use (IMHO from my experience with off-road bicycles), so I wouldn't recommend investing more money in cheap rotors. You get what you pay for in disc rotors.

    So what can you do without money?
    Firstly are your brake levers currently adjusted to their maximum reach (distance away from the handlebars when fully released)? There should be room to lengthen the brake lever pull by quite a bit before you run into issues with the lever hitting the handlebar and preventing application of full braking force.
    How to lengthen brake lever pull: Move the pads away from the rotor using the barrel adjuster alone if they are dual-sided calipers. With a single side brake caliper where only the outside pad moves when you pull the lever, the inner pad is stationary but it is adjustable. There is a grub screw on the inside, which you can reach with an allen key through your wheel from the right hand side. Turn this grub screw anticlockwise until you see that the inner pad does not rub. Then set the open/released/"at rest" position of the outer pad using the barrel adjusters at either/both ends of the brake cable. Bikes set up by incompetent bike mechanics (i.e. those working in most big stores) come with the barrel adjusters already set to their minimum, so before being able to use the barrel adjusters you will have to slacken off the cable a little. (The proper way to set up a disc brake cable when initially building up the bike is to set the barrel adjusters to almost their maximum, then clamp the cable so the pads rub the disc, then reduce the cable tension using the barrel adjusters. Setting the barrel adjusters even half way in would only be correct if pads wear as fast or faster than rotors warp, which is not the case with cheap disc brakes. IDK why most bike mechanics can't get this right, it's a real pet hate of mine!)

    If you can't get the pads to clear the rotors even with the pads position adjusted, or if doing this adjustment means you cannot pull the lever fully before coming into contact with the handlebars, then you will have no choice but to try to straighten the rotor. You can't completely straighten a rotor, or even close; but if the rotor is very badly warped then you should be able to get some improvement by bending using a large adjustable wrench or possibly a long screwdriver. Whether you do this while the disc is mounted on the hub (quick but perhaps risky) or in a vice is up to you to decide, but I would mark the areas that need bending and do it in a vice, re-fit, re-mark, back in vice and bend again until I see an improvement.
     
  3. FurryOnTheInside

    FurryOnTheInside Active Member

    Now I'm wondering why you mention "around turns".. Do you have a problem with a flexy frame or fork? Or did you mean braking for a turn?
     
  4. battery

    battery Member

    that is not the issue at all. I bought a cheap bike and the cheap rotors are out of balance out of the box. we have a lot of sand and salt on the road here. jerky brakes will cause me to slide. the front fork jerks back and fourth too. the guage is uneven.
     
  5. FurryOnTheInside

    FurryOnTheInside Active Member

    Oh, damn.. took me ages to write that. :(
    If the material is uneven thickness, return them to the shop!
    Also check your headset.
     
  6. battery

    battery Member

    Its a wal mart bike and I already butchered it by putting the motor on it. I been looking around I think Im going to go with a shimano rotor. they are pretty inexpensive and should be true.
     
  7. Fabian

    Fabian Well-Known Member

    The Shimano 8" Rotor is an amazingly stable disk rotor, even when a lot of heat is pumped into it.
     
  8. battery

    battery Member

    I have a 6" on there. cant afford to upgrade just yet. but out of balance 6" rotors are worse than 6" even rotors. I'm upgrading one peice at a time.
     
  9. Racie35

    Racie35 Member

    That the bike slows when turning(via brakes dragging) would suggest some things giving either forkwise or bearings.....maybe
     
  10. battery

    battery Member

    no if I ease on the brakes around a turn the uneven rotors will **** the bike back and fourth. I got a 160mm avid rotor comin in next week at my local shop. he said it will be even and cheap. only $25.
     
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