Poorly finished steel seat tube wrecking cf seatpost?
02-04-23, 03:24 PM
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Poorly finished steel seat tube wrecking cf seatpost?
A tiny"burr" inside the seat tube of a recently purchased steel bike has caused the carbon fiber seatpost to become scratched and delaminated. The seatpost was creaking and ticking a bit when I first rode the bike and these noises increased in volume and frequency quite rapidly before I inspected.
I replaced the seatpost with an aluminium one after having the burr removed.
I replaced the seatpost with an aluminium one after having the burr removed.
- Could this have been dangerous? I know nothing about carbon fiber.
- Am I within my rights to ask the company to pay for the new searpost?
02-04-23, 06:41 PM
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Yes it could have been dangerous if it started cracking. Light scratching probably not a huge issue though.
In terms of the company you could ask them but generally I would hone it out first when I am building depending on the builder. If it were a custom frame that I bought painted and finished I would probably say yeah maybe the builder might get a call but for a mass produced frame I would say yeah probably not a bad idea to hone it out and check it over before building.
In terms of the company you could ask them but generally I would hone it out first when I am building depending on the builder. If it were a custom frame that I bought painted and finished I would probably say yeah maybe the builder might get a call but for a mass produced frame I would say yeah probably not a bad idea to hone it out and check it over before building.
02-06-23, 11:48 AM
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Did they put the carbon seat post in the bike?
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02-07-23, 06:55 AM
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You may have missed the boat. If you showed the bike shop the frame with the burr in it that caused the damage you would have a case, but once the burr was removed so is the proof and evidence of poor manufacturing methods. There are so many threads on the internet about cracking carbon bike frames and parts, I am more happy I never bought into any of it every day.
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02-07-23, 09:51 AM
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You may have missed the boat. If you showed the bike shop the frame with the burr in it that caused the damage you would have a case, but once the burr was removed so is the proof and evidence of poor manufacturing methods. There are so many threads on the internet about cracking carbon bike frames and parts, I am more happy I never bought into any of it every day.
02-08-23, 01:18 AM
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A carbon seatpost breaking can leave a razor sharp spear to get impaled on, I went to a bike shop with a similar worry and the owner told me a horror story about a guy he knew. I tuned out the injury but it was horrible, perforated his anus or stomach and needed surgery. Your ears are your friend and I think you should trust them, and they told you something was wrong.
as for who is responsible/can you get your money back? Honestly I don’t think it really matters, you’re safe and it’s not really anyone’s fault. That said you probably have a case and if it’s a big store you’re justified imo.
as for who is responsible/can you get your money back? Honestly I don’t think it really matters, you’re safe and it’s not really anyone’s fault. That said you probably have a case and if it’s a big store you’re justified imo.
02-08-23, 10:32 AM
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A surface scratch in aluminum is worse than in carbon, as the scratch in alumimun is a stress riser that can lead to a crack forming.
As long as a surface scratch does not break any carbon fibers, the strength of a carbon post is not affected.
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02-09-23, 11:45 PM
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If you pay attention to almost ANY production metal frame, you'll find all manner of issues at the seat collar. I have yet to find one with nice smooth, rounded edges at the clamping slot and on the top edge. And no bike shop building 100's of bikes a month will flex-hone a seat tube. Most shops don't even have a flex hone on the tool board.
So anyone using a carbon seat post would behoove themselves to take a really close look at their frame's seat tube clamping area. Spend some time with small files to round the edges of the slot and its rounded bottom, the top edge of the tube, as well as flex-hone the inside of the tube. Then use quality sandpaper like silicon carbide to finish the edges. (If there are any burs, then remove them manually BEFORE flex-honing, as this process doesn't actually remove offending burs, etc., it will just "smooth" them.) If you think anyone took the time to do this on your bike, you're sorely mistaken. I've done this to most of my bikes out of habit. I just like knowing there aren't sharp metal edges digging into my seat post as I clamp it and ride, regardless of seat post material.
So anyone using a carbon seat post would behoove themselves to take a really close look at their frame's seat tube clamping area. Spend some time with small files to round the edges of the slot and its rounded bottom, the top edge of the tube, as well as flex-hone the inside of the tube. Then use quality sandpaper like silicon carbide to finish the edges. (If there are any burs, then remove them manually BEFORE flex-honing, as this process doesn't actually remove offending burs, etc., it will just "smooth" them.) If you think anyone took the time to do this on your bike, you're sorely mistaken. I've done this to most of my bikes out of habit. I just like knowing there aren't sharp metal edges digging into my seat post as I clamp it and ride, regardless of seat post material.
Last edited by LV2TNDM; 02-10-23 at 12:55 AM.
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02-10-23, 10:41 AM
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fredlord-
LV2TNDM is correct. Any metal frame will have a non-round seat tube. The welding or brazing leads to an out of round condition due to heat distortion and typical manufacturing does not address this. Every metal framed bike should have the seat lug opening reamed, de-burred, radiused and honed. That will prevent marring or stress riser notching of the post and will allow for uniform and the minimum clamping force necessary on the post.
LV2TNDM is correct. Any metal frame will have a non-round seat tube. The welding or brazing leads to an out of round condition due to heat distortion and typical manufacturing does not address this. Every metal framed bike should have the seat lug opening reamed, de-burred, radiused and honed. That will prevent marring or stress riser notching of the post and will allow for uniform and the minimum clamping force necessary on the post.
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02-10-23, 12:24 PM
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Any metal frame will have a non-round seat tube. The welding or brazing leads to an out of round condition due to heat distortion and typical manufacturing does not address this. Every metal framed bike should have the seat lug opening reamed, de-burred, radiused and honed. That will prevent marring or stress riser notching of the post and will allow for uniform and the minimum clamping force necessary on the post.
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02-10-23, 08:59 PM
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For the most part, it is necessary. If you look at alloy seatposts, almost all spot zigzag lines or gouges from the lug ears or edges. You are correct that "...seat tube machining and preparation is a very rare thing", unfortunately.
For the most part, it is necessary. If you look at alloy seatposts, almost all spot zigzag lines or gouges from the lug ears or edges. You are correct that "...seat tube machining and preparation is a very rare thing", unfortunately.
