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  1. #1
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    The factory cut a giant hole into my carbon fiber top tube

    When I removed the cable guide from the side of the top tube in my new frame I discovered a large rectangular opening. I know that a hole is necessary to route the rear brake cable through. My question is why does the hole have to be so large? It makes me a little bit nervous to know that there is such a seemingly oversized hole in the frame. Is this what you typically find when you remove a cable guide on a carbon fiber frame?

    The frame is a 2010 Lapierre Xelius.
    Attached Thumbnails Attached Thumbnails The factory cut a giant hole cut into my carbon fiber top tube-dsc0008550.jpg  
    Last edited by Deus_Ex_Machina; 12-08-2010 at 07:50 PM.

  2. #2
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    I've seen this on an aluminum bike or two. My guesses to why that hole is big...

    To provide the best/compatable interface for the guide to clamp on?
    Make re-routing, whenever necessary, easier?
    Keeping things simple in one way or another?

    This sounds a bit light-hearted, but the only vulnerability I see through that is from heavy vertical forces/loads, and well, you're not really supposed to sit on the top tube anyway.

  3. #3
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    Wow...that's shocking!

  4. #4
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    My look has a smaller one. As long as it's unaltered and it's supposed to be that way, I don't see anything that would worry me.

  5. #5
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    It makes your frame lighter.

  6. #6
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    That might be larger than the ones on some Cervelo downtubes, but not by much, and in a lower stress spot.

  7. #7
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    Quote Originally Posted by padawan716
    My look has a smaller one. As long as it's unaltered and it's supposed to be that way, I don't see anything that would worry me.
    I may install an internal carbon fiber patch to transfer loads around the opening better. The large rectangular cut is a stress riser that I would rather not have to think about while I am riding.

  8. #8
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    The hole has to be that size so that when the cable goes into the frame it won't enter it an acute angle which could lead to kinking & cause problems. If you ever watched any of the videos of the pinarello or derosa factories on youtube, you'll be surprised at how much drilling that goes on with pneumatic air drills on completed carbon frames.

    People are under the impression that carbon is uber high tech & involves voodoo black magic of the sort. Carbon construction/layup is a time consuming but relatively straight forward process that anyone with a little research could do themselves & indeed some members here have done so by building their own bikes. Technology only comes into play in the design of the frame. Large companies use sophisticated computer CAD/CAM & FEMA programs to make bikes lighter, more aero, stiffer etc.

    So I'm pretty sure that opening of that size at that location is most likely reinforced at that spot internally with extra layup like the double butting in steel frames where its thinner in the middle & thicker at the ends so to speak. So no worries, I'm pretty sure the bike designers know what they're doing.

  9. #9
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    My aluminum frame had holes that size. If they were dangerous I imagine they wouldn't do it. Not like you were riding around saying "damn my frame is flexy I wonder if there is a hole there" right?

  10. #10
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    Quote Originally Posted by Deus_Ex_Machina
    I may install an internal carbon fiber patch to transfer loads around the opening better.
    would that void any applicable warranties? Be honest, if you hadn't removed the cable guide would you even care?
    Edit Signature here---------->

  11. #11
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    Quote Originally Posted by Deus_Ex_Machina
    I may install an internal carbon fiber patch to transfer loads around the opening better. The large rectangular cut is a stress riser that I would rather not have to think about while I am riding.
    Think that's bad, consider all the internal stuff you can't see! I'd fill the hole frame up with epoxy.

    Yes, restructuring your frame with ad hoc gussetts will void you warranty. And rightly so. Everybody wants to be an engineer...

  12. #12
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    I'm sure Lapierre didn't bother to check that the large hole there wouldn't cause problems. I'm sure there's probably some crazed guy in charge of "random hole cutting" who hacks away at frames all day while singing songs from Moulin Rouge. I'm positive their designers/engineers are two-bit hacks who don't have a clue how to design a toothpick, let alone a bike frame.
    Other countries need to stop hatin' or we'll unfriend them. - Christine

    Apparently I left my reading comprehension glasses in my ass. - DrRoebuck

    Still, it felt great and I felt like I was sitting on some kind of vibrator -Touch0Gray

  13. #13
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    Quote Originally Posted by PlatyPius
    I'm sure Lapierre didn't bother to check that the large hole there wouldn't cause problems. I'm sure there's probably some crazed guy in charge of "random hole cutting" who hacks away at frames all day while singing songs from Moulin Rouge. I'm positive their designers/engineers are two-bit hacks who don't have a clue how to design a toothpick, let alone a bike frame.
    I appreciate what you are saying. I am not suggesting that the designers purposefully specified a dangerously oversized opening. It is possible that the hole was cut incorrectly in the first try, and then oversized to correct the initial error. Things like this happen in factories sometimes.

    In a perfect world nobody ever makes a mistake. In the real world...

  14. #14
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    Quote Originally Posted by Deus_Ex_Machina
    I appreciate what you are saying. I am not suggesting that the designers purposefully specified a dangerously oversized opening. It is possible that the hole was cut incorrectly in the first try, and then oversized to correct the initial error. Things like this happen in factories sometimes.

    In a perfect world nobody ever makes a mistake. In the real world...
    I've worked on a lot of bikes. That opening is in no way "oversized". That's a pretty standard hole size for internal cable routing.
    Other countries need to stop hatin' or we'll unfriend them. - Christine

    Apparently I left my reading comprehension glasses in my ass. - DrRoebuck

    Still, it felt great and I felt like I was sitting on some kind of vibrator -Touch0Gray

  15. #15
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    If the frame is covered under warranty then what is the concern. If the hole is a problem and the frame fails you will receive a new frame. If not your riding happily along and replacing cables is not an exercise in frustration. Keep in mind that if one frame tube fails there are 3 other tubes to keep the bike from completely disintegrating.

    Kind of like this!
    Attached Thumbnails Attached Thumbnails The factory cut a giant hole cut into my carbon fiber top tube-broken-bike.jpg  

  16. #16
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    Holes should actually be molded into a carbon frame, never cut. If you look at some high end companies like Parlee, they refuse to compromise the fibers by cutting them. This creates a significant weakening of the tubes and, depending on where and how the cuts are made, can create stress risers, just like in metal frames.

  17. #17
    Larry Lackapants
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    Quote Originally Posted by Deus_Ex_Machina
    When I removed the cable guide from the side of the top tube in my new frame I discovered a large rectangular opening. I know that a hole is necessary to route the rear brake cable through. My question is why does the hole have to be so large? It makes me a little bit nervous to know that there is such a seemingly oversized hole in the frame. Is this what you typically find when you remove a cable guide on a carbon fiber frame?

    The frame is a 2010 Lapierre Xelius.
    Don't know how tight the cable guide sat in but i can immagine that the cable guide plays a part in solidifying that point. i.e. with cable guide ok, without cable guide some cracks could develop starting from there. But maybe I'm wrong, I wouldn't know about these since i'm riding metal frames
    "There are only 3 motivating factors that change human behavior; pain, fear or ambition. Which button do you want to press?" Steve Hogg

  18. #18
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    Quote Originally Posted by Deus_Ex_Machina
    I appreciate what you are saying. I am not suggesting that the designers purposefully specified a dangerously oversized opening. It is possible that the hole was cut incorrectly in the first try, and then oversized to correct the initial error. Things like this happen in factories sometimes.

    In a perfect world nobody ever makes a mistake. In the real world...
    i really can't believe that all this time and effort has been spent worrying about this. does the cable guide fit in the hole reasonably well? or is the hole way too big and you risk losing the guide in the frame? if it fits properly, it's fine.
    as for cutting or drilling into carbon...gimme a break, it's done all the time. the lay-up schedules for frames take into account where holes for bottle cage mounts and cable routing will need to be and the area is reinforced.
    sherpa, can you tell me how you can 'mold' a hole for a water bottle mount? and brblue...that plastic cable guide in no way reinforces the frame. it's just sitting there, guiding the housing.
    i work for some bike racers...
    2013 Trek Madone 5.9 w/ '12 SRAM Red
    2010 Cervelo T1 sprint bike
    Ruger 10-22TD
    Smith&Wesson M&P 15-22
    Smith&Wesson M&P 9
    oh, those belong in another forum

  19. #19
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    Quote Originally Posted by PlatyPius
    I've worked on a lot of bikes. That opening is in no way "oversized". That's a pretty standard hole size for internal cable routing.
    That is reassuring, sort of.

  20. #20
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    Quote Originally Posted by roadie01
    If the frame is covered under warranty then what is the concern. If the hole is a problem and the frame fails you will receive a new frame. If not your riding happily along and replacing cables is not an exercise in frustration. Keep in mind that if one frame tube fails there are 3 other tubes to keep the bike from completely disintegrating.

    Kind of like this!
    Will the warranty give me new carbon fiber teeth?

  21. #21
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    Quote Originally Posted by Sherpa23
    Holes should actually be molded into a carbon frame, never cut. If you look at some high end companies like Parlee, they refuse to compromise the fibers by cutting them. This creates a significant weakening of the tubes and, depending on where and how the cuts are made, can create stress risers, just like in metal frames.
    That's how I would have done it if I were designing and manufacturing the frame.

  22. #22
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    Quote Originally Posted by roadie01
    If the frame is covered under warranty then what is the concern. If the hole is a problem and the frame fails you will receive a new frame. If not your riding happily along and replacing cables is not an exercise in frustration. Keep in mind that if one frame tube fails there are 3 other tubes to keep the bike from completely disintegrating.


    Kind of like this!
    What the heck happened there - was that a joke or was it real?

  23. #23
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    Quote Originally Posted by roadbike_moron
    What the heck happened there - was that a joke or was it real?
    Looks like a garage door kissed it to me.
    Other countries need to stop hatin' or we'll unfriend them. - Christine

    Apparently I left my reading comprehension glasses in my ass. - DrRoebuck

    Still, it felt great and I felt like I was sitting on some kind of vibrator -Touch0Gray

  24. #24
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    Quote Originally Posted by cxwrench
    sherpa, can you tell me how you can 'mold' a hole for a water bottle mount?
    Sure. In the actual mold, there are inserts or protrusions where the carbon plies fit around, creating a hole in the finished product. It creates a significantly stronger product with much higher durability. For the water bottle mounts, some companies put bolts in place and you simply lock down the cages with the nuts.

    Anyways, the whole weakening of carbon by having holes drilled into it is something that is gaining momentum. Remember your wheel sponsor from last year, Edge Composites (now ENVE)? They were able to create a significantly better product than the two companies their executive and engineering team came from (Reynolds and Lew) because they went the extra steps to mold the holes in the rims instead of drilling like everyone else. They built their entire business model for their rims on this methodology. No broken fibers and weakened areas. Consequently, weren't you able to build wheels with no tension limits and no rider weight limits with very few, if any, broken spokes? Feel free to tell me if that's wrong and the rims were no better than average.

    Now, on an overbuilt carbon frame, will a frame with holes drilled into break in 18 months? Probably not. But it's not as strong as one with no holes drilled. As a result, a frame with broken fibers from drilling can be lighter without sacrificing long term durability.
    Last edited by Sherpa23; 12-09-2010 at 07:21 PM.

  25. #25
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    Quote Originally Posted by Deus_Ex_Machina
    I may install an internal carbon fiber patch to transfer loads around the opening better. The large rectangular cut is a stress riser that I would rather not have to think about while I am riding.
    I'd leave the bike designing to the bike designers. The hole size and shape looks pretty darn deliberate to me. And as somebody else said, you may nullify your warranty by making any such modification, even if you think it makes the frame better.
    It ain't rocket surgery. Buy everything on sale, pedal when you have too, coast when you can, and get home in one piece. Keep going forward - there is no reverse.

    OGWB

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