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  1. #1
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    Turning a rotor, re surface...

    So, its done all the time for autos... why not bikes.

    i have a stack of avids that are basically mirrors.

    i was thinking a random orbital sander and some 120 grit sand paper. an old hub in a vise and go to town.... get that stopping surface back on there.

    anybody have some thoughts? or ideas?

  2. #2
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    Simply put, it won't be the same.

  3. #3
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    Quote Originally Posted by ehigh View Post
    Simply put, it won't be the same.
    yeah, i thought so. i was thinking about making a wind chime out of them. but i was just thinking.... they do it with auto's... and i know there is a lot more metal. and you can only go so thin on a car rotor...

    maybe wind chimes it is....

  4. #4
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    Don't forget to re-temper the material when you're done destroying the grain structure with your super-heating friction sanding party.

    "Mirrors" have better stopping power than "scratchy" finishes. That's why rotors don't come in "brushed" finish or have a "cheesegrater" option. It may not make a lot of sense on the surface (pun fully intended), but it is how it works.

    Read up about pad bedding on EBC's site for an explanation of why grooved (or scratched) rotors take longer to bed in and end up with less stopping force.

    Actually 'turning' the rotor would be fine... but you would end up with much less heat-dissipative mass and reduce braking performance when you need it most (at the bottom of the hill).

  5. #5
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    Quote Originally Posted by broomhandle View Post
    yeah, i thought so. i was thinking about making a wind chime out of them. but i was just thinking.... they do it with auto's... and i know there is a lot more metal. and you can only go so thin on a car rotor...

    maybe wind chimes it is....
    Brake rotors on a bike are already very thin and it just gets hairy quickly. They wouldn't dissipate heat like they should and I'd guess that they would gobble and chirp.

  6. #6
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    Quote Originally Posted by broomhandle View Post
    So, its done all the time for autos... why not bikes.

    i have a stack of avids that are basically mirrors.

    i was thinking a random orbital sander and some 120 grit sand paper. an old hub in a vise and go to town.... get that stopping surface back on there.

    anybody have some thoughts? or ideas?
    just get some 120 to 200 grit paper.....hold it between your fingers and pinch the rotor as you rotate the wheel around tens of times....

    breaks up any glazing very well.

  7. #7
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    Quote Originally Posted by axisofoil View Post
    Don't forget to re-temper the material when you're done destroying the grain structure with your super-heating friction sanding party.

    "Mirrors" have better stopping power than "scratchy" finishes. That's why rotors don't come in "brushed" finish or have a "cheesegrater" option. It may not make a lot of sense on the surface (pun fully intended), but it is how it works.

    Read up about pad bedding on EBC's site for an explanation of why grooved (or scratched) rotors take longer to bed in and end up with less stopping force.

    Actually 'turning' the rotor would be fine... but you would end up with much less heat-dissipative mass and reduce braking performance when you need it most (at the bottom of the hill).
    not really what i was talking about.

    all i asked was.... could wasted rotors, mirrors etc... be saved... i have probably 30-40 rotors that are shinny and have no stopping at all. they were used every day for over a year. they are basically wrecked....

    i just thought, instead of people trowing away all these rotors. is there any way to save any of them?

    i didnt ask about setting up or anything like that.....

    and mirrors? you can try and stop with ones that have a solid 5 days a week, years use.....

    from the factory, avid is not a reflection...

  8. #8
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    Quote Originally Posted by broomhandle View Post
    not really what i was talking about.

    all i asked was.... could wasted rotors, mirrors etc... be saved... i have probably 30-40 rotors that are shinny and have no stopping at all. they were used every day for over a year. they are basically wrecked....

    i just thought, instead of people trowing away all these rotors. is there any way to save any of them?

    i didnt ask about setting up or anything like that.....

    and mirrors? you can try and stop with ones that have a solid 5 days a week, years use.....

    from the factory, avid is not a reflection...
    Geez I ride 6 days a week.....average 6500 km/y for seven years now...

    I have a rotor that has been on the bike for over 30000 km.....still works fine.....and it has been cooked blue several times.

    Shimano not Avid?????

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    Make a cool mandala out of them.

  10. #10
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    Quote Originally Posted by jeffscott View Post
    Geez I ride 6 days a week.....average 6500 km/y for seven years now...

    I have a rotor that has been on the bike for over 30000 km.....still works fine.....and it has been cooked blue several times.

    Shimano not Avid?????

    i have a few of shimano and avids. same thing. its not just to and fro each day, its constantly moving all day from morning to night. each day.

    i feel bad chucking them. i have thought of what cool things i can make...

    ear rings for the ladies maybe?

  11. #11
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    A mobile or chime sounds like an idea. Maybe make a small clock if you have one with 6/12 spokes. FWIW, Sram is sponsoring a used parts into art fundraiser. Sounds like a good cause for your stack o' rotors

  12. #12
    gran jefe
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    try it out. what do you have to lose?

  13. #13
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    I hit mine with an abrasive pad, on the drill the other day. Rebed the setup an it's like new...

    Scotchbrite medium worked great for me, just make sure your running the disc perpendicular to the rotor face, you don't want the scratches to be directional...

  14. #14
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    not done with bikes as it's not cost efficient for one also they are already so thin. If you turned them their structural stability would no doubt be compromised.
    SS ==> Nut up or Shut up!

  15. #15
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    ummm...maybe you should look into a different type of pad???....that many rotors...crazy....

    How are you riding every day, all day, for basically a year?...just curious...

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    pics of stack or it didn't happen

  17. #17
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    Quote Originally Posted by broomhandle View Post
    i have a few of shimano and avids. same thing. its not just to and fro each day, its constantly moving all day from morning to night. each day.

    i feel bad chucking them. i have thought of what cool things i can make...

    ear rings for the ladies maybe?
    I am confused on how the rotors are no good... I think the rotors should be good until they reach the minimum thickness stamped on the side. If you are suggesting that they are no longer porous because of the shine then maybe try giving them a light sanding. I have never had that issue but I think they should still be good.
    Killing it with close inspection.

  18. #18
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    i "resurfaced" an avid rotor using metal etch-worked well and I am still using it after 2 seasons of pretty heavy riding. I'm not saying it's right-or wrong-but it worked for me. results may vary.

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    Quote Originally Posted by broomhandle View Post
    i have a few of shimano and avids. same thing. its not just to and fro each day, its constantly moving all day from morning to night. each day.

    i feel bad chucking them. i have thought of what cool things i can make...

    ear rings for the ladies maybe?
    Okay

    So you don't want to sand them fine....

    When you are ready to chuck them pm me I will take them off your hands.

  20. #20
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    im not the one doing the ridding.

    they all start out as brand new Avid bb5's and brand new rotors. as well as some shimano avlio's.

    ive been doing this for about 8 years, its the same thing.

    trust me. new avid pads all the time, the rotors last about 1-2 years.

    i have tried sanding, bla bla....

    i didnt expect the Spanish Inquisition...

  21. #21
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    Quote Originally Posted by broomhandle View Post
    im not the one doing the ridding.

    i didnt expect the Spanish Inquisition...
    I think everyone is just curious/surprised because most might go through a rotor after 3 - 4 years....most guys don't have 30 - 40 rotors worn out sitting around

    cool coasters??

  22. #22
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    Resurface 2 of them on one side...

    ...sandwich 2 thin rotors together with resurfaced sides facing out...

    This coming from a guy who runs V-brakes and has worn rims out to the "see through" point, then re-welded them, and machined them, and kept riding them!

  23. #23
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    Quote Originally Posted by NEPMTBA View Post
    Resurface 2 of them on one side...

    ...sandwich 2 thin rotors together with resurfaced sides facing out...

    This coming from a guy who runs V-brakes and has worn rims out to the "see through" point, then re-welded them, and machined them, and kept riding them!
    what? for reals?

    no way! haha

  24. #24
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    Quote Originally Posted by Shark View Post
    I think everyone is just curious/surprised because most might go through a rotor after 3 - 4 years....most guys don't have 30 - 40 rotors worn out sitting around

    cool coasters??


    yeah, its just from over the years. and billions of new bikes.

    i have already chucked a tub of them in recycling. a few years ago.

    maybe i can make ninja stars out of them....

  25. #25
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    Naw, just mess'in about the rotors...

    ...the V rims? Well sometimes ya gotta do what ya gotta do no mater how ugly...LOL

  26. #26
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    shurikens! +1
    2008 Trek Fuel EX 8

  27. #27
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    Quote Originally Posted by broomhandle
    i didnt expect the Spanish Inquisition...
    Well, people don't like the idea of riding on improperly surfaced superthin rotors. And before you go on about you don't intend on riding them read what you wrote:
    Quote Originally Posted by broomhandle
    So, its done all the time for autos... why not bikes.
    i was thinking a random orbital sander and some 120 grit sand paper. an old hub in a vise and go to town.... get that stopping surface back on there.
    Now why in the world would you want a "stopping surface" if you aren't gonna be stopping with them?

    BTW car rotor resurfacing is a machining technique - more akin to drilling than sanding. They're cutting off the grooves in the rotor with a hard bit, not grinding with an abrasive.

  28. #28
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    Quote Originally Posted by broomhandle View Post
    i didnt expect the Spanish Inquisition...
    Nobody expects the Spanish Inquisition.

    I like the clock idea, personally.

  29. #29
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    Quote Originally Posted by broomhandle View Post
    i didnt expect the Spanish Inquisition...
    Nobody expects the Spanish Inquisition.

    I like the clock idea, personally.

  30. #30
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    Resurface mountain bike rotors - YouTube
    Did it on stock shimano rotors. I used 250 sandpaper and it did help after I've done brake-in. It also helped with the squeal. But It didn't last as long as buying a new rotor.

  31. #31
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    Yes, you can turn your rotors. I've done it a few times.

    The first time I turned a rotor, I made a fixture for the lathe and used a carbide tool to take a light cut. I found that chatter was excessive. Next I used a toolpost grinder. The finish was a lot better, but not to perfection as I would like. Those are the rotors that I'm running right now, and I've got 1000+ miles on them.

    Since then, I've made another fixture that will hold rotors solidly against a faceplate, so I should be able to take a heavier cut with no chatter.

    So my advice is to figure out a good way to hold the rotor that will minimize chatter. I wouldn't use a cutting tool, such as carbide or hs. I grinding is superior for this application. If you have access to a surface grinder, that would be the best and fastest.

  32. #32
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    Well... "best" would be a blanchard grinder...

    I still wouldn't. If you just want the brake pad material out of them, use a selective chemical stripping agent.

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    There is no need to use any fancy tools to resurface your rotors.

    Just find an old pair of brake pads, glue some sand paper on them and put them back into your caliper.

    Now just do a couple of laps in the parking lot while dragging your brakes and your rotor will be resurfaced. Also works on rainy days if your use wet sand paper.

  34. #34
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    yes, I stopped buying regular pads and started using folded up sheets of sandpaper a couple of years ago. my rotors never get glazed, and the brakes emit a pleasant shushing sound as i stop. as you mention, on rainy days be sure to use wet-or-dry paper.

  35. #35
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    Give them away to other riders who will use them. Theres nothing wrong with your rotors, but if you dont want to use them, just give them away to someone who will.

    Scuffing them by hand is the proper method. Scuff, clean, and they're fine again until minimum thickness. Absolutely no need for any sort of machining.

    Car rotors are machined because they warp... no other reason. If your car needs brakes, the rotors *do not* need to be machined or replaced as long as they dont shake and are above minimum thickness. The specs are listed in all repair manuals, and it might save you some car repair money .

  36. #36
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    Quote Originally Posted by One Pivot View Post
    Car rotors are machined because they warp... no other reason. If your car needs brakes, the rotors *do not* need to be machined or replaced as long as they dont shake and are above minimum thickness.
    Or if they are grooved, exhibit surface cracking, or have minor surface pitting from corrosive brake dust.


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  37. #37
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    I did forget to add thickness variation, but thats sort of warping. Grooves kinda fall under thickness variation.

    Either way, its kind of the same thing. Simple pad replacement is common and factory approved by most brands.. the pads dont really ruin a rotor to the point where some sort of layer needs to be chopped off. I deglaze rotors with an abrasive pad, but its really just scuffing the surface, which is good enough.

    We can straighten out bike rotors with a tool, so the warping issue is kinda off the table. Bust the glaze off and use fresh pads and you're solid! If this guy has 40 good rotors hanging around, he might as well give them away instead of trashing them.

  38. #38
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    Quote Originally Posted by anthonyk View Post
    Nobody expects the Spanish Inquisition.
    i was waiting for that.

  39. #39
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    Quote Originally Posted by One Pivot View Post

    Car rotors are machined because they warp... no other reason. If your car needs brakes, the rotors *do not* need to be machined or replaced as long as they dont shake and are above minimum thickness. The specs are listed in all repair manuals, and it might save you some car repair money .
    yes, i know that. I was just saying they are machined...


    what has this post become. where is the delete everything button?

  40. #40
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    I too find it odd you have all those "bad" rotors. I've never felt that a rotor went bad. I often will spin the tire while holding fine grit sandpaper on the rotor. Spray with brake cleaner and off you go. Only reason I think rotor would be bad is if it was too thin or bent beyond repair.

  41. #41
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    Quote Originally Posted by thehotrodpig View Post
    I too find it odd you have all those "bad" rotors. I've never felt that a rotor went bad. I often will spin the tire while holding fine grit sandpaper on the rotor. Spray with brake cleaner and off you go. Only reason I think rotor would be bad is if it was too thin or bent beyond repair.
    yes i know. sand paper dose not do much on these, a few i have done that, i have saved a few and they work, not like new but they work. the ones i am talking about are the ones that are mirrors. and are pretty thin. sand paper does not take the mirror out. thats why i was asking about a sander.

    i can not believe this has gone on to 2 pages.... haha

    i guess a lot of you guys dont use your brake rotors "constant" from sun up to sun down 5 days a week. its not like these are from a weekend bike.....

  42. #42
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    Well if they are pretty thin I would obviously not sand or turn them or even try to use them. They are worn out. Make something cool out of them.

    I am not sure I would be concerned about the ones that are mirror like but thick enough. I would lightly sand them and run with them. They should work fine. Could there be something else wrong with your brake setup that you are going through so many rotors? I think the theme here is that most others are not experiencing rotors going bad like you are. Wearing thin I can see but just glazed over should not be a big issue. Perhaps there is another issue.

  43. #43
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    Quote Originally Posted by broomhandle View Post
    i guess a lot of you guys dont use your brake rotors "constant" from sun up to sun down 5 days a week.
    No, the time I use my rotors in any given ride is usually a pretty small proportion of the total ride time. Maybe you should adjust your brakes so they aren't on all the time?
    Those who can give up essential liberty to obtain a little temporary safety, deserve neither. - Ben Franklin

  44. #44
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    Quote Originally Posted by Bad Idea View Post
    No, the time I use my rotors in any given ride is usually a pretty small proportion of the total ride time. Maybe you should adjust your brakes so they aren't on all the time?
    haha

  45. #45
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    Perhaps your brake pads are too hard and they just rub off metal instead of working like they should? Are you using sintered?

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    Quote Originally Posted by broomhandle View Post
    yes i know. sand paper dose not do much on these, a few i have done that, i have saved a few and they work, not like new but they work. the ones i am talking about are the ones that are mirrors. and are pretty thin. sand paper does not take the mirror out. thats why i was asking about a sander.

    i can not believe this has gone on to 2 pages.... haha

    i guess a lot of you guys dont use your brake rotors "constant" from sun up to sun down 5 days a week. its not like these are from a weekend bike.....
    What type of sand paper are you using? I think it's possible that the surface of those rotors could be harder than some garnet sandpapers.

    I can't imagine that silicon carbide or aluminum oxide sandpaper wouldn't be able to remove the mirror finish. Once the finish is gone, the rotor can re bed the brakes.

  47. #47
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    Quote Originally Posted by Millfox View Post
    Perhaps your brake pads are too hard and they just rub off metal instead of working like they should? Are you using sintered?
    I was thinking that or it could be the opposite... Rotors are too hard. Either way it doesnt sound like the pads and rotors are playing well with eachother.

    One of my cars has performance brakes on it. The pads and rotors are designed to wear together as a system. Both need to be replaced for a brake change (@$700 every 30-50k ). The rotors cant be turned as they will reach their min thickness. I replaced the pads with something else because its the wife's car and I dont want drop that kind of dough. The braking performance is now on par with a Camry but who cares. You could be using the wrong pads for the rotors or if they are factory pads then maybe try a different brand of brakes as the ones you have obviously ar not working for you.
    Killing it with close inspection.

  48. #48
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    Quote Originally Posted by broomhandle View Post
    not really what i was talking about.

    all i asked was.... could wasted rotors, mirrors etc... be saved... i have probably 30-40 rotors that are shinny and have no stopping at all. they were used every day for over a year. they are basically wrecked....

    i just thought, instead of people trowing away all these rotors. is there any way to save any of them?

    i didnt ask about setting up or anything like that.....

    and mirrors? you can try and stop with ones that have a solid 5 days a week, years use.....

    from the factory, avid is not a reflection...
    If you have that many why don't you try a few different home-brew solutions and report back? You have nothing to lose really

  49. #49
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    BREAKING NEWS, A great thing to do with old rotors is turn them into Ninja throwing stars..
    If you have kids they will love them or you might like just taking them outside n throwing them round yourself, they are killer throwing stars.

    Just take you grinder out and grind all the sections out leaving lethal segments to do the damage.
    You can even grind them to make them razor sharp, honestly you could pretty much cut somebodies head off with them.

    If you really wanna get into the spirit, dress as a ninja, and hang about 20 off your black belt n roam the neighbourhood looking for targets to put holes in......
    Dont ever let the truth get in the way of a funny story....

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