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  1. #1
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    MTB Carbon frame question. Defective or not?

    Hey guys,

    I bought a new MTB Carbon frame form a web bike shop, I noticed 2 defective spots on it.

    1. There is a scratch (straight line) in front of the headtube. Hard to tell if its is deep and cracked or just a surface scratch and since it is a carbon frame it worries me.

    2. The rear post mount disc brake threads is clogged with paint making it unusable as it is. By that I mean without removing the paint somehow. Had numerous frames but seeing this for 1st time.

    I would like to read your thoughts on this, is this considered a defective frame that need replacement or not?
    Even if the scratch is just purely aesthetically and not deep.







    Thanks,
    George

  2. #2
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    Contact company you bought from and see what they say. Scratch from what I can see doesn't look that bad, but can't really tell from pic. It has to compromise the actual fibers to be a problem. The brake posts look they just need to have threads chased. Some frames aren't finished as nice and you need to chase all the threads and mating surfaces like the BB and headset. A good bike shop mechanic can take care of that. You can probably take care of the posts threads yourself, just find the correct thread tap/chase at hardware store and run it through yourself.

  3. #3
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    The scratch is superficial. The threads just need cleaning out with a tap. Nothing to worry about it.

  4. #4
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    The scratch is PROBABLY superficial. How can you possibly be confident enough to make that statement based on the photo? Way too many variables to make a definitive statement.

    EDIT: As a matter of fact, it looks like a spider leg is coming off the main "scratch" about halfway down. What's that all about?

  5. #5
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    Thank you for your answers.

    I can feel the scratch with the finger nail. I tried the coin tap method and can't hear any difference in sound. Checked the inside of the headtube the connection of the two pieces seems fine. So I guess the scratch is not so deep after all. But I am truly picky with new stuff. Is a small cosmetic scratch like this and unfinished threads enough reason for a product replacement?

    The threads could be fixed as you suggested with tap/chase tool. Sadly I don't own any tool, so in order to fix it I will be charged by my local bike shop.

  6. #6
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    looks like a scratch on headtube. that area is gonna take
    hits from someone sloppily boxing up frames...may have been set on the floor and
    hit some piece of grit there...



    it is common to need to chase and face brake mounts from paint booth
    you need a brake post facing tool to shave them flat and also clean threads

    the frame was likely cheap(er) because it is partly unfinished in that regard
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  7. #7
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    If you aren't comfortable with the condition of the frame you received you should call the place you bought it and tell them that you are rejecting and returning it. You can't really expect us to talk you into feeling better about it. Don't mean to sound harsh, but it's kind of like taking a picture of a lump in your chest and asking us if we think it's cancer or if you shouldn't worry about it. You are probably perfectly safe on that frame, or maybe not. The brake mount overspray is nothing but a finish quality detail. The scratch or crack - your guess is probably better than ours because you can see and touch it. Did you see if all compound out?

  8. #8
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    Quote Originally Posted by Hops143 View Post
    If you aren't comfortable with the condition of the frame you received you should call the place you bought it and tell them that you are rejecting and returning it. You can't really expect us to talk you into feeling better about it. Don't mean to sound harsh, but it's kind of like taking a picture of a lump in your chest and asking us if we think it's cancer or if you shouldn't worry about it. You are probably perfectly safe on that frame, or maybe not. The brake mount overspray is nothing but a finish quality detail. The scratch or crack - your guess is probably better than ours because you can see and touch it. Did you see if all compound out?
    No worries man, I understand your point.
    I already contacted the shop, they replied it's OK and has no problems.
    That's why I started this thread to read some views on this matter.

    Sorry the English is not my first language what does this mean " Did you see if all compound out?

  9. #9
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    No need to apologize. Your English is excellent. That sentence was confusing because it contains an error on my part. I meant to type "Did you see if it WILL compound out?". There are liquids called Rubbing Compounds that have various levels of abrasives in them that you use to remove scratches from painted surfaces. I would try 3M Imperial Rubbing Compound or whatever your local car store (like Autozone) has. If you can rub the scratch out then you will know it wasn't a crack.

  10. #10
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    Ah OK I got it. I though for a moment to use a sandpaper and remove the paint to see how deep it is. But then rejected the idea and told to myself why should I need to do that? to a brand new frame and especially to the most visible part of it. So I contacted the shop to ask them for a replacement but they response was late and all frames gone OUT of Stock.

  11. #11
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    Quote Originally Posted by Basser View Post
    Ah OK I got it. I though for a moment to use a sandpaper and remove the paint to see how deep it is. But then rejected the idea and told to myself why should I need to do that? to a brand new frame and especially to the most visible part of it. So I contacted the shop to ask them for a replacement but they response was late and all frames gone OUT of Stock.
    toothpaste on a toothbrush is abrasive enough to be a hobo-rubbing compound

    try that. it will remove gloss so be careful with it.
    "Put your seatbelt back on or get out and sit in the middle of that circle of death." - Johnny Scoot

  12. #12
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    I had a similar looking crack in the clear-coat on my bike. I initially thought it was a scratch, but it could not be removed with scratch remover. I sent a picture to my shop who sent it to the bike representative. The bottom line I had a new frame within 2 weeks and the manufacturer paid to have every thing transferred from the old bike to the new frame. I wasn't too worried about the crack, but my dealer said the crack in the clear coat could indicate an underlying issue and the manufactuer did not want to risk a failure. The bike was only about 6 months old.

  13. #13
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    Quote Originally Posted by plummet View Post
    The scratch is superficial. The threads just need cleaning out with a tap. Nothing to worry about it.
    A sharpie will fix that scratch.

  14. #14
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    Quote Originally Posted by Hops143 View Post
    The scratch is PROBABLY superficial. How can you possibly be confident enough to make that statement based on the photo? Way too many variables to make a definitive statement.

    EDIT: As a matter of fact, it looks like a spider leg is coming off the main "scratch" about halfway down. What's that all about?
    The white scratch is simply a mark in the clear coat. It has not reached any structural fibres and therefore represents no integrity issues. Furthermore there is no indication of any subsurface delamination or impurities.

    Scratches deep enough to affect strength physically show broken fibres, have a black colour of torn carbon. A white scratch with no abraided carbon is simply cosmetic.

  15. #15
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    Quote Originally Posted by 127.0.0.1 View Post
    toothpaste on a toothbrush is abrasive enough to be a hobo-rubbing compound

    try that. it will remove gloss so be careful with it.
    Or a "cut and polish" car wax. You can probably buff it out without sanding. Sanding will dull the clear coat around the surrounding area

  16. #16
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    Quote Originally Posted by plummet View Post
    Or a "cut and polish" car wax. You can probably buff it out without sanding. Sanding will dull the clear coat around the surrounding area
    Personally, I'd just use a glaze if it is that big of deal to the OP. No, it won't remove it but it will hide it. Two factors go against a cut and polish on a carbon frame: potential for high localized heat and the fact that the clear is probably already thinner than a piece of paper.

    Sent from my SM-N950U using Tapatalk

  17. #17
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    Thank you all for your replies. I learned new things and glad it's not a big deal after all.

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