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Crimp in seat tube

Old 05-14-22, 12:35 PM
  #1  
Jwebbike
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Crimp in seat tube

I have a slight crimp in my seat tube. Happened from towing a kid trailer on my bike. I have a photo but I can't upload it till I have posted 10 times. Happy to send it if you message me or whatever. Thanks again!!!
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Old 05-14-22, 12:39 PM
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Seat tubes are pretty sturdy and unlike many parts not too costly for replacement on most bikes.
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Old 05-14-22, 12:41 PM
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Is it the seat tube or the seat post? Seat posts are replaceable, seat tubes are part of the bike frame
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Old 05-14-22, 12:42 PM
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Originally Posted by alcjphil View Post
Is it the seat tube or the seat post? Seat posts are replaceable, seat tubes are part of the bike frame
It's the post. Part of the frame.
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Old 05-14-22, 12:45 PM
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Originally Posted by Jwebbike View Post
It's the post. Part of the frame.
A seat post is not part of the frame. It can be removed and replaced
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Old 05-14-22, 12:47 PM
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Originally Posted by Jwebbike View Post
It's the post. Part of the frame.
Let's try again. The seat post is the part that attaches to the saddle (seat) and slides down into the frame. The seat tube is the part of the frame that the seat post slides into.
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Old 05-14-22, 12:47 PM
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Originally Posted by alcjphil View Post
A seat post is not part of the frame. It can be removed and replaced
Sorry. I mis typed whatever it is called. It's part of the frame. Just before the split. Tube. It's the seat tube.
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Old 05-14-22, 12:55 PM
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Words matter!
Probably the only problem with a crimp or dent in your seat tube is if it interferes with the seat post getting to the correct position. If there is no interference, then it's nothing to worry about.
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Old 05-14-22, 12:58 PM
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Originally Posted by sweeks View Post
Words matter!
Probably the only problem with a crimp or dent in your seat tube is if it interferes with the seat post getting to the correct position. If there is no interference, then it's nothing to worry about.
Great to hear! The seat slides in just fine! Thank you so much!
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Old 05-14-22, 01:06 PM
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@Jwebbike's Album:

https://www.bikeforums.net/g/user/554397
https://www.bikeforums.net/g/album/24979979



Two more photos just added for more perspective:



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Old 05-14-22, 01:09 PM
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Originally Posted by sweeks View Post
Words matter!
Probably the only problem with a crimp or dent in your seat tube is if it interferes with the seat post getting to the correct position. If there is no interference, then it's nothing to worry about.
Photo was just updated, would you mined triple checking? It would make my, and my wife's brain happier.
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Old 05-14-22, 01:12 PM
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What type bike is this? Maybe need a full pic of the bike from the side.



https://cimg9.ibsrv.net/gimg/bikefor...2a31fafdb7.jpg
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Old 05-14-22, 01:19 PM
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Ok, so it looks like an older MTB or Hybrid.

Probably a STEEL frame.

And a rear monostay seat stay that got crimped.

It looks like a pretty gnarly crimp.

It is certainly a structural component of the bike. But, I'm not sure one could say whether it would have an imminent failure.

Repairing it would be difficult. You might be able to expand it somewhat with auto body tools coming in from under the brake bridge if that is open. Perhaps build an anvil out of a steel shaft that would fit into that area.

However, my choice would be to simply leave it alone and keep an eye on it for initiating of cracking.

Your trailer should either connect to the seat post (the aluminum or steel part where the seat attaches), or to an optional cargo rack.
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Old 05-14-22, 01:30 PM
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Old 05-14-22, 01:32 PM
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I agree with CliffordK Just ride it and watch it. Don't use it for BMX competitions! <grin>
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Old 05-14-22, 01:39 PM
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Ok, two more photos added (above) to give more perspective.

As expected, some kind of monostay hybrid/MTB.

With the seat mast, there is no room to clamp on to the actual seat post, unless the seat could be comfortably raised an inch or so.

The Burley Moose and Trailercycle Hitch are designed to solve the problem somewhat.







However, I'm not sure if I'd want to tow with anything attached to the seat stay with your bike anymore.

The more you work that seat stay, the more likely it will eventually fail.

Attaching to the seat post is likely OK.
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Old 05-14-22, 02:23 PM
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As noted, that's not your seat tube; it's part of the "seat stay", which in turn is part of the "rear triangle".
This frame element is mainly under compressive loading, so should be resistant to fatigue cracking; it's also readily available for frequent inspection.
I'd ride it with no worries, but I'd look at it once in a while. Even if it fails, it's not likely to do so in a catastrophic manner.
It's pretty well deformed; I would guess it's an aluminum frame, which puts it into a somewhat more troublesome category... though low risk. Of course, you can test it with a magnet; if it's steel there's almost literally no concern.

The "seat stay" is the left side of the rear triangle in this image. Orange is high-stress; blue is low-stress.
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Old 05-14-22, 03:27 PM
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Man, you really hammered on that thing. Waaay too much torque.

At any rate, you can probably ride it an keep an eye on it. Repairing it is not an option since the bike is worth far less than the cost of repair.
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Old 05-14-22, 06:07 PM
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Another vote for just leaving it and keep an eye out for cracks developing at the damaged areas. Not worth the cost of trying to repair it. Your kid may graduate college before it fails with any luck.
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Old 05-14-22, 07:02 PM
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I've never used a trailer but anyway, that tube should never have been used for that. That's why it crushed. If it makes it so you can't ride straight with no hands, then chuck it.
IMO get the kid his own bike. Those outriggers are not safer. I've seen lots of 3 year olds riding without trainer wheels lately. Hell, they are even doing BMX races at that age.
And anyway, WTH is with that Texas longhorn bar?? You are really asking for getting smacked by a truck.

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Old 05-16-22, 07:49 AM
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Originally Posted by GamblerGORD53 View Post
I've never used a trailer but anyway, that tube should never have been used for that. That's why it crushed. If it makes it so you can't ride straight with no hands, then chuck it.
I agree with these comments in GamblerGORD53 's post - the trailer almost definitely should be clamped on the seat POST (the removable part to which the saddle is clamped) which generally has much thicker walls than any tube on the bike frame. This is also SOP for clamping a bike in a repair stand - clamp anywhere on the frame and you run a very big risk of damaging whatever tube is clamped, ALWAYS clamp the seatpost. Even with super lightweight carbon seatposts, don't clamp the frame - there are 'dummy' seatposts available that can be swapped in in place of the good seatpost and clamped. These won't help with clamping a trailer, though.
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