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Discussion Starter · #1 ·
... or you might end up with an unintended dropper post....

a friend wanted to get an epic gravel ride in before the weather turns and the light fades. I decided to throw a new seat and seatpost on my gravel bike (first poor decision) right before the ride, knowing I would probably need to make some adjustments along the way.

Well, at our first rest stop, I decided to raise the seat a tad, and overtightened the seatpost clamp (probably a little extra adrenaline at the beginning of a long ride).

Normally, I take a portable torque wrench with me in situations like this. I had plenty of space in the bags. I just forgot and got a little over zealous. I'm normally meticulous with my bike maintenance/service.

The result was a split in the seatpost, and no amount of 'just a little tighter' was going to make it stay up. Initially the split showed up as just a small crack at about the 4cm mark, but the seat was slipping down and chased the split up to the top of the seatpost. I was worried about damaging the frame with the seat being all the way down, so...

What was supposed to be an epic all day gravel ride turned into a 20 mile trip with a miserable 10 mile ride back to the car, riding OUT OF THE SADDLE (yes, my quads are very sore today).

Tire Bicycle part Automotive tire Bicycle frame Bicycle tire
 

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Yikes! Hope you didn't cause any damage to your frame. That would have REALLY sucked.
 

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I once broke a seatpost and had to ride eight miles back out of the saddle. It was aluminum, and a Thomson no less. On a greenway ride. That post had thousands of miles on it, mostly gravel and some trail miles. Shit happens, carbon or aluminum.

So OP, did you split the post when you initially tightened it, and subsequently you couldn't tighten it sufficiently to hold the post? Could you have sat on it putting the seat all the way down? 6 Nm is the common torque for carbon frame/carbon posts, which isn't much. Remember if you're using one of 'quick' torque tools set to this, it takes a bit of effort to reach that torque but you have an extremely small moment arm. Those tools are about two inches across. So if you're tightening with a longer lever, grip the tool much closer to the bolt, not at the end of the lever, and that will help prevent what happened.
 

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Wow. I never thought carbon was a good material for bicycles, and the information like this never stops coming in to back that up. One of the guys I ride with is getting a new expensive carbon bike because the frame on his last expensive carbon bike broke by the rear dropout while riding, another friend has a cracked carbon road frame sitting in his junk-pile too. I put thousands of miles each year on four steel frame bikes with steel and aluminum components that are from 25 to 50 years old, and I am guessing all I will ever have to do to any of them is to throw new chains and tires on them once in a while and keep them lubed, have fun watching most of the crowd spend their time and energy on whatever corporations decide to market to them.
 

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Here's a trick to help keep your seatpost from slipping. I've been doing this for years. (no I'm not Thor Hushovd)
Add a second clamp onto the seatpost.
It doesn't prevent you from ham handed over tightening. But you don't have to worry about making the main clamp as tight in the first place. It just needs to be snug enough to keep it from rotating.
It's virtually impossible for it so slide down.

 

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Have you tried carbon paste?
That's the only thing that kept my seatpost from sliding down on my carbon bike.
 

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Discussion Starter · #10 ·
I always use finish line carbon paste when installing seats/seatposts.

In this case, no amount of carbon paste was going to keep a cracked seatpost from slipping down.

I have only had one bike that had a finicky (not wanting to stay up) seatpost. That was a BMC RoadMachine with a D shaped seatpost, so the 2nd clamp idea wouldn't have worked for that.

As far as the bike I was riding when I cracked this seatpost, the seat and seatpost were just fine. No problems with it slipping, right up until I cracked it with an over zealous bolt cinching. At that point, it was a lost cause.
 

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In this case, no amount of carbon paste was going to keep a cracked seatpost from slipping down.
Oh no, no, no, of course not. You weren't actually thinking of using a cracked post, were you?
 

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Discussion Starter · #12 ·
Lol, pay attention...

I cracked the seatpost while making a mid ride adjustment 10 miles into what we supposed to be a 100+ mile gravel ride.

I didn't realize it was cracked until it started slipping down a few minutes later. At that point I had to turn around and ride 10 miles back to my van, mostly out of the saddle.

I'm not asking for help, or advice. I know why it broke (my own poor judgement). It's already been replaced and the bike is working just fine with the new seatpost.

I feel like the original post was written fairly clearly, but I understand it's a little bit long for an Internet forum post.

The TLDR is, I broke my seatpost over tightening it after stopping to make an adjustment.

The seatpost wasn't slipping before it cracked. It wasn't defective, or in need of extra clamps. It had been installed and doing it's job perfectly since I originally installed it in 2016,.

IT CRACKED BECAUSE I DIDN'T USE A TORQUE WRENCH AND OVER TIGHTENED IT.
 

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Lol, pay attention...

I cracked the seatpost while making a mid ride adjustment 10 miles into what we supposed to be a 100+ mile gravel ride.

I didn't realize it was cracked until it started slipping down a few minutes later. At that point I had to turn around and ride 10 miles back to my van, mostly out of the saddle.

I'm not asking for help, or advice. I know why it broke (my own poor judgement). It's already been replaced and the bike is working just fine with the new seatpost.

I feel like the original post was written fairly clearly, but I understand it's a little bit long for an Internet forum post.

The TLDR is, I broke my seatpost over tightening it after stopping to make an adjustment.

The seatpost wasn't slipping before it cracked. It wasn't defective, or in need of extra clamps. It had been installed and doing it's job perfectly since I originally installed it in 2016,.

IT CRACKED BECAUSE I DIDN'T USE A TORQUE WRENCH AND OVER TIGHTENED IT.
Understood.
 
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