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Seatpost Bolt / Clamp Housing Stripped!

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Seatpost Bolt / Clamp Housing Stripped!

Old 09-23-22, 09:38 PM
  #1  
Ratspeed
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Seatpost Bolt / Clamp Housing Stripped!

I am disgustipated. Has anyone ever encountered this before? This bike I haven't had for a month, I tried tightening the seatpost with a torque wrench and the steel stripped into a fine taper. It's one of those notched bolts that locks into the mechanism. I'm not even sure what to call this piece, but it's on the frame, and now I can't get a proper torque to keep the seatpost from sliding down.

For future reference: What is the proper torque to set these to?

More importantly: How the frick can I fix this?



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Old 09-23-22, 09:59 PM
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BITD this wasn't all that rare, nor was it common either.

Odds are that the bolt key was never properly seated, and once it started turning, it simply cut it's own path.

The first takeaway here, for the OP and anyone reading this, is that blindly turning nuts, even with the best tools, and even adhering to specified torques has the potential to screw (no pun) things up. As a mechanic you need to keep your eyes open and be attuned to what's happening. If the turning bolt was spotted early in the process, the damage would have been much more limited.

Fortunately, there's an easy way past this (in this instance). The OP can simply buy a cap screw, or hex head bolt, so he can hold one end while turning the nut. Or he can buy one of those double ended hex head binder bolts like these.
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Old 09-23-22, 10:04 PM
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No way! I've never seen this before! Never!!! !!!
!!! !!!
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Old 09-23-22, 10:07 PM
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I'd just go to Ace Hardware, buy the biggest SS hex head bolt that will fit through, a SS nut I liked, a few washers to sit on the outer flanges and use two wrenches. (Might want some wedgelike washers to distribute the load. I'd be looking through my odd parts for wedge shaped whatever I could cut and drill into washers.) I just did this on an old Miyata racing bike that spent real time left out in the rain. Threaded Campy-like seatpin stripped out early on.

Edit: and once again, FB beat me to it!
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Old 09-23-22, 10:08 PM
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Originally Posted by FBinNY View Post
BITD this wasn't all that rare, nor was it common either.

Odds are that the bolt key was never properly seated, and once it started turning, it simply cut it's own path.

The first takeaway here, for the OP and anyone reading this, is that blindly turning nuts, even with the best tools, and even adhering to specified torques has the potential to screw (no pun) things up. As a mechanic you need to keep your eyes open and be attuned to what's happening. If the turning bolt was spotted early in the process, the damage would have been much more limited.

Fortunately, there's an easy way past this (in this instance). The OP can simply buy a cap screw, or hex head bolt, so he can hold one end while turning the nut. Or he can buy one of those double ended hex head binder bolts like these.
Thanks for that. I actually remember the moment it happened. It was seated properly in place, and when I turned the wrench I heard and felt a sudden "give." I didn't know it had stripped, and I was able to obtain a good torque at first, so I thought nothing wrong until today when I removed the bolt, nut and washer completely and saw this mess.

The thing that strikes me is I have that 33-year old gazelle with a similar mechanism and I've never had this trouble. The steel on that bike is far superior to this. The Gazelle has stainless steel underneath, where this steel doesn't look or feel anything like it. It feels way softer.

I found those binding bolts like you linked, after I posted this, and that does look like a viable solution. But, do you recommend I find a tapered washer as well, to fill in the gap? Or should I just leave it hollow?

I'm also wondering, should I try to find some beveled washers? If I put the binder bolt on there, the torque would apply unevenly due to the angle of the housing.


Last edited by Ratspeed; 09-23-22 at 10:20 PM.
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Old 09-23-22, 10:20 PM
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Originally Posted by Ratspeed View Post
......But, do you recommend I find a tapered washer as well, to fill in the gap? Or should I just leave it hollow?
Ideally the head will span across the top. Otherwise, I suggest a structural washer (a thicker machined disc vs. the typical flat washer), to take the load. Even if you could find or make a conical washer to fill the gap you wouldn't want too. The compression driving the cone inward will tend to spread the ear outward, possible cracking it.
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Old 09-23-22, 10:22 PM
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Originally Posted by FBinNY View Post
Ideally the head will span across the top. Otherwise, I suggest a structural washer (a thicker machined disc vs. the typical flat washer), to take the load. Even if you could find or make a conical washer to fill the gap you wouldn't want too. The compression driving the cone inward will tend to spread the ear outward, possible cracking it.
Yeah, the conical thing, that was my thought too. Force applied incorrectly. Okay, thanks.
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Old 09-23-22, 10:25 PM
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Originally Posted by cxwrench View Post
No way! I've never seen this before! Never!!! !!!
!!! !!!
Dost I detect a slight sarcasm? Not that it's unwarranted. This was probably the most newbie'ish mistake I could have ever made, heh.
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Old 09-23-22, 10:28 PM
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Originally Posted by ratspeed View Post
dost i detect a slight sarcasm? Not that it's unwarranted.

SLIGHT!!!!! Have you learned nothing?
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Old 09-24-22, 06:52 AM
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We have a bin full of 6 mm bolts and nuts at the shop for this reason.
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Old 09-24-22, 03:50 PM
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Could some of the "spherical" washers used for brake shoes be adapted for this application? The bolt diameter might be too small though. Just a thought/
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Old 09-24-22, 04:50 PM
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Why the shim?? Get the right size post for starters.
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Old 09-24-22, 05:27 PM
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Originally Posted by GamblerGORD53 View Post
Why the shim?? Get the right size post for starters.
You're talking about the seatpost? What do you mean it's not the right size?
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Old 09-24-22, 05:31 PM
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Here was my fix, at least for now. Marine-grade Stainless Steel M8 bolt, two extra washers, and the two washers and nut that came with the bike.

Ace doesn't have much of a selection of Stainless Steel Metric items. They had no beveled washers or structural steel washers. They did have a nice bushing that could have added some extra strength but it was zinc-coated, not stainless. It's holding the seat up at least, for now!

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Old 09-24-22, 07:18 PM
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Hopefully it;s just lighting and camera angle, but the left ear seems partly collapsed, and possibly touching it's opposite member.

If the ears touch anywhere, that will prevent proper clamping of the tube and you'll be over tightening to try to hold the post.

Take a look, and if it's not touching, all is good and you can file the above for future reference. Meanwhile, don't worry that it looks bad and that most of the pressure is at the base of the ear. That's actually in your favor since it minimizes stress on the ear itself.
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Old 09-24-22, 09:19 PM
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Originally Posted by Ratspeed View Post
You're talking about the seatpost? What do you mean it's not the right size?
you look to have a sleeved seattube.
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