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  1. #1
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    how can you tell Chrome moly from high tensile steel?

    How can you tell Chrome moly from high tensile steel?

    I'm considering buying a vintage bike and would of course like to get chrome moly if I can.

  2. #2
    Senior Member BikeManDan's Avatar
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    Can it even be told? A tubing sticker would be the giveaway

    After that I think its just best guess based on weight. Maybe can make assumptions based on tubing wall thickness too

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    Senior Member barba's Avatar
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    Lift it.

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    Isn't there a "ping" test?

  5. #5
    Campy NR / SR forever cadillacmike68's Avatar
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    Quote Originally Posted by Blue Order View Post
    Isn't there a "ping" test?
    Yeah, it's called Rockwell or Brinell hardness testing - but you need specialized equipment.

    Or you can look at the tubing label.
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  6. #6
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    If it rides well, do you care?

    Most often, cheap tubing got the short shift of workmanship and expense of fittings, stamped rather than forged dropouts etc.

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    Senior Member Bikedued's Avatar
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    Weight is a big deciding factor. I can usually tell by thumping the middle of a main frame tube with a fingernail. A butted chromoly frame will make a high pitched ding, while a High tensile non butted frame will usually make a dull thunk. Usually the finish work on a nicer bike will be better too. And yes, a tubing sticker works wonders too, lol.,,,,BD

  8. #8
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    Tap it...Listen feel. High ten tubing blows. Use the knuckles on the tubing, do you feel any spring? It should have some ring to it on your fingers. Look for a tubing decal. Look for ordinary sloppy lugwork. Look for cottered cranks. Look for dorky chainguard/spoke guards. High ten bikes are dime a dozen.

  9. #9
    Senior Member ollo_ollo's Avatar
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    In my experience (51cm-56 cm lugged frames), a bare frame in Hi Tension steel can typically weigh seven pounds or more. Reynolds 531, Columbus SL, Chromor, Aelle are in the 4-5 pound range.
    visit my homebuilding blog: www.monoplanar.blogspot.com

  10. #10
    Grumbly Goat Bushman's Avatar
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    Quote Originally Posted by SoreFeet View Post
    High ten bikes are dime a dozen.
    hehehe, sellers on Craigslist seem to think otherwise....LMAO!!
    You ride a bike, we GET IT, no need to rant about it or look down on others....its JUST A BIKE...get over yourselves.

  11. #11
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    So it should be generally heavier and more rigid, that's why it dings.

    Thanks for the advice.

  12. #12
    Senior Member Bill Kapaun's Avatar
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    Gauss

  13. #13
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    Quote Originally Posted by .42. View Post
    So it should be generally heavier and more rigid, that's why it dings.

    Thanks for the advice.
    No, Hi-Ten is heavier and more rigid, that's why it thuds.
    Chromoly is lighter, more flexible and dings when thumped.

  14. #14
    Senior Member Bikedued's Avatar
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    Seems like CrMo would be more rigid and lighter. and high ten would be flexible and heavy.,,,,BD

  15. #15
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    Quote Originally Posted by Bikedued View Post
    Seems like CrMo would be more rigid and lighter. and high ten would be flexible and heavy.,,,,BD
    Did I get it backwards? Maybe I'm confusing rigid with a more solid feel with Hi-Ten.

  16. #16
    tcs
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    Quote Originally Posted by McDave View Post
    No, Hi-Ten is heavier and more rigid, that's why it thuds.
    Chromoly is lighter, more flexible and dings when thumped.
    Nope. Hi-ten and chromoly have pretty nearly the same density, and similar Young's modulus. A heavier wall tube is heavier and more rigid. A thinner wall tube is lighter & more flexible.

    Now, hopefully you'll never run into a thin wall Hi-ten frame! However, there are a few chromoly straightwall frames out there that are pretty portly.

    Bare piece of tube? In a materials lab you could check hardness as mentioned above, or pull a sample for UTS. In your home shop, you could give spark testing a go.

    HTH,
    TCS
    "When man first set woman on two wheels with a pair of pedals, did he know, I wonder, that he had rent the veil of the harem in twain? A woman on a bicycle has all the world before her where to choose; she can go where she will, no man hindering." The Typewriter Girl, 1899.

    "Every so often a bird gets up and flies some place it's drawn to. I don't suppose it could tell you why, but it does it anyway." Ian Hibell, 1934-2008

  17. #17
    Senior Member Bikedued's Avatar
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    Or you could just not buy a bike that has been repainted and/or stickers removed. Plenty of them still around.,,,,BD

  18. #18
    Squirrel solveg's Avatar
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    Quote Originally Posted by tcs View Post
    Now, hopefully you'll never run into a thin wall Hi-ten frame! However, there are a few chromoly straightwall frames out there that are pretty portly.
    Now, what if you have a chromoly-stickered frame that doesn't say it's butted, but it's much* lighter than another frame that you know is straight chromoly. Could it be thin wall chromoly, and is there a problem with that similar to thin wall hi-ten?

  19. #19
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    I'm confused now. I guess it's down to workmanship and rigidity of the frame.

  20. #20
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    The most practical way to determine the tubing in an unmarked frame is via the seat post diameter. The lower the tensile strength of the tubing, the thicker the tube walls will be, resulting in a smaller seat post diameter. Typically, hi-tensile steel frames use seat posts under 26.0mm. Cr-Mo is generally 26.0 and over, with anything 26.8 and over generally being butted.

    Of course there are some exceptions and doubts when you get a measurement that is in one of the crossover zones and the outcome does not necessarily apply to stays and forks, which were often downgraded from the main tubes, to save a few dollars. Last, this rule of thumb cannot be applied to frames with noin-standard sized frame tubes, such as many of the boom era French frames, which used undersized diameter tubing and have correspondingly smaller seat posts.

  21. #21
    juneeaa memba!
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    And Cinelli's (and a few other high end italians) use internal reinforcing at the seat lug, resulting in a columbus SL tubeset with a 26.4 seatpost.

  22. #22
    tuz
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    If you rely on thumping the frame you might as well wave your hands around it and smell it

    Kidding. Hi-ten tubes are generally straight gauge and thus heavier. I think it's softer (easier/cheaper to cut and braze)

    I would follow T-mar's advice. Hints from the workmanship: thick, long, uncut lugs, stamped dropouts, sloppy brazing (blobs of brass around brazing area seen under the paint) indicate hi-ten. Components might give you a hint as well.
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  23. #23
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    Quote Originally Posted by tcs View Post
    Nope. Hi-ten and chromoly have pretty nearly the same density, and similar Young's modulus. A heavier wall tube is heavier and more rigid. A thinner wall tube is lighter & more flexible.
    Ok, we both said basically the same thing then. The heavier Hi-Ten has thicker walls making it more rigid.

  24. #24
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    The cheap high tensile steel wouldn't be as strong as an alloy, and while the walls are thicker, it still might not be as rigid...right? Depending on how much thicker it is, I guess...

  25. #25
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    Quote Originally Posted by kramnnim View Post
    The cheap high tensile steel wouldn't be as strong as an alloy, and while the walls are thicker, it still might not be as rigid...right? Depending on how much thicker it is, I guess...
    Maybe we should go ask this in the Mechanics forum and see how big of a pissing contest they can get in over it? ROFL

    (did i say that out loud?)
    Last edited by McDave; 08-30-07 at 07:06 PM.

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