Safe to reshape carbon fiber frame? - Page 3
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  1. #51
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    Quote Originally Posted by roaden View Post
    Just because your crankset has room for spacers on your bike doesn't mean all cranks have room for spacers. What does not having room look like? It means when the cranks are installed, both cranks are flush to the bottom bracket bushings. There is no side-to-side leeway.
    You need to sell or give away any tools you have and never touch a bike again. Guess what, if you shim your crank spindle and re-install, your crank+shim will be flush up against your BB bushings again - just this time it will be 1-2mm farther away from the chainstay so your chainrings won’t rub. There isn’t and shouldn’t ever be any dead space between your crank and the BB bushings - with or without shims.

    I’m actually starting to think this might be a troll. No real person could be this dumb.


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  2. #52
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    Quote Originally Posted by roaden View Post
    I like the way you think. Some people here just assumed sanding a frame wouldn't work without even attempting it.
    I wouldn't try and create clearance by removing material from the frame myself, what I asked is if you tried spacers before taking your sandpaper to frame.
    Too old to ride plastic

  3. #53
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    Quote Originally Posted by OldChipper View Post
    Guess what, if you shim your crank spindle and re-install, your crank+shim will be flush up against your BB bushings again - just this time it will be 1-2mm farther away from the chainstay so your chainrings won’t rub. There isn’t and shouldn’t ever be any dead space between your crank and the BB bushings - with or without shims.
    Hmm. Now, that doesn't make sense. If your cranks were flush to the BB bushings to begin with and you added 2mm of spacers, where did you take 2mm away from to create the space? Does that mean the bushings are compressible and you just forced them to compress 2mm in width? Or does that mean the non-drive side crank is now clamping on the BB spindle with 2mm less bite. (I have Shimano hollowtech II crankset, by the way). Since there's a pin on the non-drive crank to slot into a hole in the bb spindle, does this mean the pin is no longer pushed in? Is this even safe?

    Anyway, this sounds interesting. I admit I didn't try the spacers solution since I didn't have spacers to begin with on the non-drive side that I could have moved to the drive side. I'll try adding spacers. If I could shift the cranks at least 2mm to the drive side that would be great and would put the chainline back close to the original. I have a crank power meter on the non-drive side and the non-drive crank is also pretty close to the chainstay, but i think 2mm further in won't be a problem.

  4. #54
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    Quote Originally Posted by roaden View Post
    Hmm. Now, that doesn't make sense. If your cranks were flush to the BB bushings to begin with and you added 2mm of spacers, where did you take 2mm away from to create the space? Does that mean the bushings are compressible and you just forced them to compress 2mm in width? Or does that mean the non-drive side crank is now clamping on the BB spindle with 2mm less bite. (I have Shimano hollowtech II crankset, by the way). Since there's a pin on the non-drive crank to slot into a hole in the bb spindle, does this mean the pin is no longer pushed in? Is this even safe?

    Anyway, this sounds interesting. I admit I didn't try the spacers solution since I didn't have spacers to begin with on the non-drive side that I could have moved to the drive side. I'll try adding spacers. If I could shift the cranks at least 2mm to the drive side that would be great and would put the chainline back close to the original. I have a crank power meter on the non-drive side and the non-drive crank is also pretty close to the chainstay, but i think 2mm further in won't be a problem.
    None of this matters now. You have ruined your frame.

  5. #55
    'brifter' is f'ing stupid
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    Quote Originally Posted by roaden View Post
    Hmm. Now, that doesn't make sense. If your cranks were flush to the BB bushings to begin with and you added 2mm of spacers, where did you take 2mm away from to create the space? Does that mean the bushings are compressible and you just forced them to compress 2mm in width? Or does that mean the non-drive side crank is now clamping on the BB spindle with 2mm less bite. (I have Shimano hollowtech II crankset, by the way). Since there's a pin on the non-drive crank to slot into a hole in the bb spindle, does this mean the pin is no longer pushed in? Is this even safe?

    Anyway, this sounds interesting. I admit I didn't try the spacers solution since I didn't have spacers to begin with on the non-drive side that I could have moved to the drive side. I'll try adding spacers. If I could shift the cranks at least 2mm to the drive side that would be great and would put the chainline back close to the original. I have a crank power meter on the non-drive side and the non-drive crank is also pretty close to the chainstay, but i think 2mm further in won't be a problem.
    Let me try to explain this in a way that you might be able to understand.

    Shimano makes all their cranks to the same dimensions. ALL of their crank axles are the same length. The axle on the drive side is supposed to go into the non drive side crank arm a certain amount, you know this because of the safety tab w/ the pin that goes into the hole in the axle.

    There are different bottom brackets that adapt various frames to work w/ the very much standardized Shimano axle. If your frame/bottom bracket/crank combination doesn't work properly w/ the parts as they come out of the box something is wrong. You shouldn't add shims to make it work nor should you remove material from your damn frame. I would think for most people this would be obvious. I have a feeling that your frame/bb/crank combination is not compatible but can't say for sure w/o seeing it. You need to stop what you're doing and take your bike to a reputable bike shop. After they stop laughing at you for trying to sand the frame away to get necessary clearance they might be able to fix things for you.
    #promechaniclife

  6. #56
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    Quote Originally Posted by cxwrench View Post
    Let me try to explain this in a way that you might be able to understand.

    Shimano makes all their cranks to the same dimensions. ALL of their crank axles are the same length. The axle on the drive side is supposed to go into the non drive side crank arm a certain amount, you know this because of the safety tab w/ the pin that goes into the hole in the axle.

    There are different bottom brackets that adapt various frames to work w/ the very much standardized Shimano axle. If your frame/bottom bracket/crank combination doesn't work properly w/ the parts as they come out of the box something is wrong. You shouldn't add shims to make it work nor should you remove material from your damn frame. I would think for most people this would be obvious. I have a feeling that your frame/bb/crank combination is not compatible but can't say for sure w/o seeing it. You need to stop what you're doing and take your bike to a reputable bike shop. After they stop laughing at you for trying to sand the frame away to get necessary clearance they might be able to fix things for you.
    Would you work on that bike? I wouldn't touch it with a 10 foot pole. I'm not going to be liable for anything that happens to that frame after I touched it. No way.

    I would have a good laugh though.

  7. #57
    'brifter' is f'ing stupid
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    Quote Originally Posted by 202cycle View Post
    Would you work on that bike? I wouldn't touch it with a 10 foot pole. I'm not going to be liable for anything that happens to that frame after I touched it. No way.

    I would have a good laugh though.
    True, I wouldn't touch it either. 'Fix it' could mean selling him a new bike in this case.
    #promechaniclife

  8. #58
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    I think he just likes to 'work' on bikes, probably not planning on riding that thing, are you crazy?
    BANNED

  9. #59
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    Please please post a picture.

  10. #60
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    As bad as what OP's description of what he did, it may not be as bad as one might think for the following reasons: 1) Built-in Factor of Safety 2) Structural component involved, and 3) The location/orientation of the breach. I won't bore you with the technical details, but even if the chainstay experience a complete shear failure, I do not believe it would lead to a catastrophic collapse of the rear triangle. Having said that, this would have a very different outcome if say this involved the seatstay.

    Found this posting related to the topic:
    https://forums.roadbikereview.com/ge...ke-253975.html

    Here's a video of a chainstay failure during a ride:
    https://www.youtube.com/watch?v=7zoJ4fhJmO0

  11. #61
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    Quote Originally Posted by cxwrench View Post
    Let me try to explain this in a way that you might be able to understand.

    Shimano makes all their cranks to the same dimensions. ALL of their crank axles are the same length. The axle on the drive side is supposed to go into the non drive side crank arm a certain amount, you know this because of the safety tab w/ the pin that goes into the hole in the axle.

    There are different bottom brackets that adapt various frames to work w/ the very much standardized Shimano axle. If your frame/bottom bracket/crank combination doesn't work properly w/ the parts as they come out of the box something is wrong. You shouldn't add shims to make it work nor should you remove material from your damn frame. I would think for most people this would be obvious. I have a feeling that your frame/bb/crank combination is not compatible but can't say for sure w/o seeing it. You need to stop what you're doing and take your bike to a reputable bike shop. After they stop laughing at you for trying to sand the frame away to get necessary clearance they might be able to fix things for you.
    Come on CX a 1 or 2 mm shim isn't going to fatally compromise anything. I've had to do this on both the DS and NDS on several bikes with Shimano cranks, ridden each 1000's of miles and never a problem and all the safety tabs inserted properly with no problem. With all the different cranks, frame and BB designs, CRs, FDs, etc. some combinations are going to have issues and a small tweak like this isn't going to cause problems.
    Well, you know, that's just, like, your opinion man. - The Dude

  12. #62
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    Quote Originally Posted by roaden View Post
    i sanded down a small part of my carbon bike's chainstay just behind the bottom bracket. This was to clear the new super-compact chainring that i installed. I sanded down about 1mm or a maybe a bit more. The frame had very little clearance even with the regular size chainrings, but with the new chainrings that i got, the rings are offset 2.5mm closer to the frame. The inner ring actually contacts the frame so i thought i'd sand the paint off. Turns out i had to sand down the carbon too to clear the rings and so the cranks would fully set into the bottom bracket. I didn't sand down through the carbon completely but i sanded down at least two layers from the bands that i can see. The sanded area still seems strong; there's no give when i push hard on it with my finger.

    Is this going to be safe to ride?
    [font=arial black]Who in there right mind sands down a carbon from well into carbon... and then ask's "is this going to be safe to ride"? .... NO!
    Last edited by ROAD&DIRT; 02-12-2020 at 07:01 AM.
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  13. #63
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    Quote Originally Posted by ROAD&DIRT View Post
    [font=arial black]Who in there right mind sands down a carbon from well into carbon... and then ask's "is this going to be safe to ride"? .... NO!
    By sanding it down before asking he didn't have to ignore any advice that suggested he didn't do what he was going to do anyway.
    Too old to ride plastic

  14. #64
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    Quote Originally Posted by OldChipper View Post
    Come on CX a 1 or 2 mm shim isn't going to fatally compromise anything. I've had to do this on both the DS and NDS on several bikes with Shimano cranks, ridden each 1000's of miles and never a problem and all the safety tabs inserted properly with no problem. With all the different cranks, frame and BB designs, CRs, FDs, etc. some combinations are going to have issues and a small tweak like this isn't going to cause problems.
    No, it won't. That said I have never seen a frame w/ the correct bottom bracket and a Shimano crank need a shim of any kind. Not once. I've seen them the opposite, nearly wide enough that the safety tab won't engage, but not loose. When people talk about needing to use shims that aren't supplied w/ whichever component they're using it always leads me to thinking the same thing...I'm sure you can guess what that is.
    #promechaniclife

  15. #65
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    Quote Originally Posted by cxwrench View Post
    No, it won't. That said I have never seen a frame w/ the correct bottom bracket and a Shimano crank need a shim of any kind. Not once. I've seen them the opposite, nearly wide enough that the safety tab won't engage, but not loose. When people talk about needing to use shims that aren't supplied w/ whichever component they're using it always leads me to thinking the same thing...I'm sure you can guess what that is.
    Is everything alright? You seem uncharacteristically restrained today.

  16. #66
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    before and after painting pics
    Attached Images Attached Images

  17. #67
    'brifter' is f'ing stupid
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    Quote Originally Posted by roaden View Post
    Is everything alright? You seem uncharacteristically restrained today.
    All good. The weather is global climate change wonderful for Feb, can't wait to get on the Fuel EX this weekend. Maybe even play some tennis and start working on my tan a bit early this year.
    #promechaniclife

  18. #68
    What the what???
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    Quote Originally Posted by roaden View Post
    before and after painting pics
    I owe you an apology. I really thought you were just trolling us. But, no, you actually are just that ridiculous. Best of luck.
    Given his penchant for nicknames, and his aversion to reading, I've decided to shorten Donald J. Trump to it's essence: Dump*

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  19. #69
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    Dude.. that is not a little sanding.. you went through 3 layers of carbon, in what is more than likely 5 or so layers, in a very high stress area.......

  20. #70
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    Seeing as it's painted, have you built it back up and ridden it yet? How about a ride report?

    Maybe report back every 500 miles or so, after the initial ride report, I'm sure everyone is anxious to hear how things work out for you.
    Too old to ride plastic

  21. #71
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    I read somewhere 7 layers is minimum recommended, and can go as high as 12 to 16 layers in high stress areas.

  22. #72
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    No, not ridden yet. It's touching again after painting, but I have spacers on order. Will add some spacers before I ride it. Hopefully I can fit 1mm, but even 0.5mm should be enough. I need to bring the chainline back out also since right now the derailleur is still very slightly rubbing the chain when in the lowest gear (low limit is completely open).

  23. #73
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    Sounds like it's time to make some room for wall art
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  24. #74
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    No guarantees but unless you're a Clydesdale I'd say that's probably safe to ride. People freak out here over cracks in clearcoat... Most of the stress is probably on the top and bottom of that chain stay not on the side. Ride it in a soft grassy field and sprint all out throwing the bike back and forth. Make sure to video tape it just in case for our amusement.
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  25. #75
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    Quote Originally Posted by DrSmile View Post
    No guarantees but unless you're a Clydesdale I'd say that's probably safe to ride. People freak out here over cracks in clearcoat... Most of the stress is probably on the top and bottom of that chain stay not on the side. Ride it in a soft grassy field and sprint all out throwing the bike back and forth. Make sure to video tape it just in case for our amusement.
    video tape? you're dating yourself.

    You've hit on something important - rider weight (and power) matters. Nobody has asked and I haven't even mentioned it, but I'm 145 lbs. If a frame has tolerances to handle the likes of Peter Sagan sprinting, it probably can handle me with 2 plies of carbon tied behind its back so to speak.

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