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  1. #1
    Recovering Weight Weenie
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    Tips on trueing rotors...anyone?

    I know there are some shadetree mechanics around here who've got some MacGyver-esque method of making flat again what had been made wobbly.

    I tried the caveman approach, just using some vice-grips, with no luck.

    Any hot tips?

  2. #2
    Penis Goat!
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    I just use a small or medium (6"-8") adjustable wrench, open slightly larger than the width of the rotor, not clamped to it. I keep the wheel on the bike, which is upside-down, and run it through to see where it needs adjusting. Then I pull the problem section in the opposite direction, using the wrench, and I keep on until it's pretty true. It's worked fine for me.

  3. #3
    Recovering Weight Weenie
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    Quote Originally Posted by GirchyGirchy
    I just use a small or medium (6"-8") adjustable wrench, open slightly larger than the width of the rotor, not clamped to it. I keep the wheel on the bike, which is upside-down, and run it through to see where it needs adjusting. Then I pull the problem section in the opposite direction, using the wrench, and I keep on until it's pretty true. It's worked fine for me.
    Cool, I'll go attempt.

  4. #4
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    no vice grips

    clamping on it with a vice grip could leave a bur on the roter. that could make things worse. is it really that bad, i never did it to my hayes brakes the 2 years i had them...

    scott

  5. #5
    I am the owl
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    Small adjustable wrench and a pencil. Stare down the rotor, slowly spin the wheel until you either don't see light between the rotor and the pad OR you hear the pad contact the rotor. Mark with pencil, tweek with wrench. Repeat as necessary.
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  6. #6
    Just Ride!
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    In the past I have taken a piece of 1x2 wood about 12" long and cut a slot in it with a skill saw. Just use this as a lever, the wood is gentle on the rotor.

  7. #7
    29 some of the time...
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    Crescent wrench or one of the old school brake alignment tools. The brake tools are about the same as the disc specific tools. I am more of the use what you got opinion on straightening rotors since it isn't a task that needs to be tackled too often.

  8. #8
    One gear to rule them all
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    Quote Originally Posted by Padre
    I know there are some shadetree mechanics around here who've got some MacGyver-esque method of making flat again what had been made wobbly.

    I tried the caveman approach, just using some vice-grips, with no luck.

    Any hot tips?
    Bicycle Research makes a tool (LC-1), that is designed to straighten chainwheels. I have found that it works great on rotors. I have also tried the the adjustable wrench trick. I have used both tools at the same time, too. Good luck.
    Last edited by 32seventeen; 12-21-2004 at 07:54 PM.
    Todd............. If you can't be kind, at least have the decency to be vague

  9. #9
    Recovering Weight Weenie
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    This place is a verifiable bastion of quality mechanical info.
    Thanks gents.
    I've tried the crescent wrench approach already tonight.
    I had already pulled the rotor of the wheel, so determining where is was out was a bit tougher.
    I'll reinstall it on a wheel to get a better view.
    Kudos!

  10. #10
    meatier showers
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    I can't believe it

    Nobody said to use your bare hands? Amazing. That's what I always do. Rotors are extremely malleable. It doesn't take much pushin' to make 'em perfect again. I leave my bike in the stand and use the caliper as a runout gauge. Personally, I'd never put a metal device around my rotor and tweak it thataway... it seems like I'd be much more likely to bend the rotor in the plane between brake track and rotor bolts. Whenever I use my bare hands to eliminate rotor wobble, I'm confident the adjustment in rotor warp is occurring at the hub, rather than the next weakest place -- where the rotor spokes meet the brake track. I've straightened my rotors infrequently over the past 4-5 years and have yet to be disappointed in the bare hands method.

    --Sparty
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  11. #11
    intentionally left blank
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    Quote Originally Posted by Sparticus
    Nobody said to use your bare hands? Amazing. That's what I always do. Rotors are extremely malleable. It doesn't take much pushin' to make 'em perfect again. I leave my bike in the stand and use the caliper as a runout gauge. Personally, I'd never put a metal device around my rotor and tweak it thataway... it seems like I'd be much more likely to bend the rotor in the plane between brake track and rotor bolts. Whenever I use my bare hands to eliminate rotor wobble, I'm confident the adjustment in rotor warp is occurring at the hub, rather than the next weakest place -- where the rotor spokes meet the brake track. I've straightened my rotors infrequently over the past 4-5 years and have yet to be disappointed in the bare hands method.

    --Sparty
    my understanding is that you never touch rotors with your bare hands - unless you hit them with rubbing alocohol and burn that off afterwards.

    i guess that's more of a priority for the pads, but it stands to reason that you'd apply that to the rotors too.

  12. #12
    SS Grrrrrrrl
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    Quote Originally Posted by GirchyGirchy
    I just use a small or medium (6"-8") adjustable wrench, open slightly larger than the width of the rotor, not clamped to it. I keep the wheel on the bike, which is upside-down, and run it through to see where it needs adjusting. Then I pull the problem section in the opposite direction, using the wrench, and I keep on until it's pretty true. It's worked fine for me.
    I second this approach. I use it all the time. Be sure to wipe the wrench arms with rubbing alcohol prior to using and it's probably not a bad idea to wipe down the rotor with rubbing alcohol when you're all done trueing.

  13. #13
    Medium?
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    A story

    My son and I were fooling around on bikes at the school, and I dropped off the right side of a concrete wall and "landed" on my 7" avid rotor on top of the wall. It was bent taco-style at about 75 degrees. I had to walk home thinking about the $50 it would cost to recover.

    A couple hours later I was unpissed enough to take another look at it, take it off the wheel, and start whacking it with a 5 lb sledge hammer. With that as an anvil, and a framing hammer I got it pretty straight. With another hour of work on and off the wheel I got it straight enough to ride.

    I've been riding it ever since.

    It rubs a tiny bit in my Hayes caliper, but the Avid caliper has enough throw to miss it completely. I tweak it sometimes with a crescent wrench if it needs it. I don't bother wiping or alcohol. I'm pretty sure that "don't ever touch your rotors with your bare hands" thing is overstated.

  14. #14
    I am the owl
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    Quote Originally Posted by Fast Eddy
    I'm pretty sure that "don't ever touch your rotors with your bare hands" thing is overstated.
    Well, I wouldn't touch it after you've been riding, especially downhill! But for reasons other than those stated above.
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  15. #15
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    except...

    Quote Originally Posted by dirtcrab
    I second this approach. I use it all the time. Be sure to wipe the wrench arms with rubbing alcohol prior to using and it's probably not a bad idea to wipe down the rotor with rubbing alcohol when you're all done trueing.
    Avid recommends that you don't use alcohol on their rotors because their pad compound makes an awfull squealing sound if you do (i have personally heard it! ).
    but clean tools and hands are a must.
    Spinning and Grinning...

  16. #16
    Its only 1" on the map!
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    Quote Originally Posted by riderx
    Small adjustable wrench and a pencil. Stare down the rotor, slowly spin the wheel until you either don't see light between the rotor and the pad OR you hear the pad contact the rotor. Mark with pencil, tweek with wrench. Repeat as necessary.
    I have used the same approach but with two wrench one to tweak with and the other about 45 degrees away to isolate the torque to the area I am working on.

  17. #17
    semi-evolved simian
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    Quote Originally Posted by OneGearGuy
    Avid recommends that you don't use alcohol on their rotors because their pad compound makes an awfull squealing sound if you do (i have personally heard it! ).
    That explains a LOT. Nothing quite like the "symphony" of front and back Avids producing slightly different pitched squeals. Urghh. Mind you, it does stop me using the brakes quite so much, which is possibly a good thing

  18. #18
    SS Grrrrrrrl
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    Quote Originally Posted by OneGearGuy
    Avid recommends that you don't use alcohol on their rotors because their pad compound makes an awfull squealing sound if you do (i have personally heard it! ).
    but clean tools and hands are a must.
    Interesting. It causes no such noises on my Magura Marta's.

  19. #19
    mudnthebloodnthebeer
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    Greasy fingers

    Quote Originally Posted by Adrian
    my understanding is that you never touch rotors with your bare hands - unless you hit them with rubbing alocohol and burn that off afterwards.

    i guess that's more of a priority for the pads, but it stands to reason that you'd apply that to the rotors too.
    I'm not sure how much a fingerprint would degrade performance (unless said finger had gone directly from the peanut butter jar to the rotor). I eat a lotta PB, so I use a clean shop rag when I work on my rotors. I've gotten better results using finger pressure (just small nudges, not trying to get it all the first time) than I have with the wrench method, which seems a little like trying to true a wheel by just working on the worst spoke.

  20. #20
    Medium?
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    Why not?

    Quote Originally Posted by riderx
    Well, I wouldn't touch it after you've been riding, especially downhill! But for reasons other than those stated above.

    Photo credit: Biking Viking

  21. #21
    I am the owl
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    Sweet photo.
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  22. #22
    meatier showers
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    The defense rests

    Quaffi baby, you said it perfectly.

    Avoiding the best method to true a rotor for fear it might get a bit of oil on it would be like buying a new car and parking it in the garage forever and throwing the keys away because driving it would cause it to wear out.

    I always wash my hands before I manipulate a bent rotor. In the four + years I've used my hands to true my rotors, residual body oil has never proved a problem. Seems to me that anyone riding up and down serious hills would burn the body oil off within a few minutes of descending anyway. That is, unless they have a real sweating problem I suppose.

    --Sparty


    Quote Originally Posted by quaffimodo
    I'm not sure how much a fingerprint would degrade performance (unless said finger had gone directly from the peanut butter jar to the rotor). I eat a lotta PB, so I use a clean shop rag when I work on my rotors. I've gotten better results using finger pressure (just small nudges, not trying to get it all the first time) than I have with the wrench method, which seems a little like trying to true a wheel by just working on the worst spoke.
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    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  23. #23
    DAS
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    crescent wrench

    I always had trouble adjusting the rotor by hand. I started using a crescent wrench and got them to true up nicely.

    also, all the out of true problems I've had with my rotors have been to shipping the bike, as in packing it up in a bike box. So I would advise whoever is listening (no one?) to be extra careful while packing up disc wheels.

  24. #24
    meatier showers
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    You're right, DAS

    Okay so the car analogy was a medeocre one, I admit that. It would be more appropriate to analogize it to throwing the baby out with the bath water.

    Besides, DAS, your experience with tools and bike repair are legendary here on MTBR.

    Hmmm... shipping my bike... something I've never done and never intend to do. Sounds to me like it's asking for trouble.

    --Sparty



    Quote Originally Posted by DAS
    I always had trouble adjusting the rotor by hand. I started using a crescent wrench and got them to true up nicely.

    also, all the out of true problems I've had with my rotors have been to shipping the bike, as in packing it up in a bike box. So I would advise whoever is listening (no one?) to be extra careful while packing up disc wheels.
    disciplesofdirt.org
    Remember who
    you wanted to be.

    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  25. #25
    Penis Goat!
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    Quote Originally Posted by Sparticus
    In the four + years I've used my hands to true my rotors, residual body oil has never proved a problem.
    That may be, but all I know is that last year, I rode my bike onto campus for a little while. I could do nose wheelies no problem on the way there. When I got there, a friend decided to start grabbing ahold of my brake rotor. On the way home, I couldn't lock the front brake.

    After taking the pads to work and having a friend torch them with an oxy-acetylene torch, they worked great. I can perform nose wheelies once again.

    That's my story, and I'm stickin' to it!

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