njlonghorn

For the second time in 3 years, I snapped the bolt that connects my saddle to the seat post. Both times it happened during a seated climb, which I suppose is when the forces are greatest. But I haven't ever heard of this happening to other cyclists, much less twice.

Should I assume this is just a fluke, or do I need to be looking into titanium bolts?

Amt0571

I've seen this happen. Not twice in 3 years though.

Jokes aside, how much do you weigh?

3alarmer 

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...it's not uncommon at all to snap a Campagnolo seat post clamp binder bolt, but this is the first I've heard of this one. Are you large enough to have your own zip code ?

shelbyfv

Try a different style of seatpost?

Crankycrank

What seat post? Photos would be helpful.

Iride01 

Are you certain there is a gap left between the clamp and the surface it meets? If no gap, then you might be over torquing the bolts and fracturing them just enough to think the seats secure and then they break when normal ride forces are encountered.

I used to similarly break bolts for seat post clamps trying to tighten them enough to keep the seat from falling. Either the slot in the steel tube of my bike would be closed up under the clamp or the clamp would be fully closed. Thankfully I knew about them breaking before riding.

cyccommute 

Sometimes a broken seat bolt can lead to a legend.

njlonghorn

The first time it happened, I weighed around 185 lbs. Currently, I'm more like 220.

lol. That's what I was looking for.

In my defense, well over half of my weight gain has been muscle. Unfortunately, pecs, delts, and traps don't offer much help when cycling.

What styles are there? Mine came with my bike (2006 Cannondale Quick 5).

I'll post photos shortly. I have to go out to the garage and take some.

I know nothing about clamps or gaps, Is the clamp the mostly rectangular metal part that sits on top of the seat post and has grooves that the saddle rails slide along?

njlonghorn

Amazing story! Thanks for sharing it.

Amt0571

Well, you're not featherlight, but even at 220lbs this should not happen. I have ridden with heavier riders and their seats kept attached to the post for years without issues.

Maybe your seatpost is made in a way that causes fatigue on the bolt, or maybe this has been extremely bad luck.

As I said I have seen this happening a couple of times, but not on the same person and definitely not on a "short" period of time.

Iride01 

Probably. Depending on what post you have. Some are stamped steel plates that might bend a little under the bolt and make contact with the surface they are being bolted too before sufficient force is put on the saddle rails to hold it secure.

Do you think that you are having to use a lot of force to tighten the bolt to hold your saddle?

If so, then it's likely a change to a better seat post might be needed anyhow. Once the clamp plate is bent, there isn't a satisfactory fix for anyone that doesn't lean toward having experience as a machinist or metal fabricator.

Steve B.

There are a dozen 2 bolt designs out there. I use Ritchey,

I would suggest maybe just just take off the bolt, take it to a good hardware store and buy a spare or two. Or three it seems. Keep them in your saddle bag, as this is what would be called a "mission critical" part.

dsbrantjr

If it is just a normal threaded bolt, not a specialized bolt with a shoulder or other features I would look for a grade 10.9 or 12.9 bolt (assuming metric) of the same size. Class 12.9 (1220MPa) are stronger than typical titanium (1030MPa) in ultimate tensile strength.

ridingfool

try a Thomson seat post a little expensive but doubt you will break that one . I am about 230 on a good day and use them on 2 of my bikes never a problem yet with them.

njlonghorn

Here’s the seat post from above.

After my posts above, I realized there was a second metal piece wedged between the saddle and the rails. They fit together and form a clamp, so I’m clear on that part now.

Iride01 

Probably just tightening them too much. Many people over-torque bolts falsely thinking more tight is better.

njlonghorn

I looked at the Inside of the bottom half of the clamp more closely, and there are some little lines there (see photos). They seem like surface scratches to me because you can barely feel the lines, and they don’t go from one side to the other. But might these be signs of fatigue?

DiabloScott

This is not a weight issue - although that doesn't help. Heavy riders will tend to break saddle rails, not seatpost bolts.
Did you just replace the bolt after the first break? (not a new post?) - if so that might point toward a seatpost defect if it happened again.

Possibilities:
Complete random quirk or bolt defect two times in a row: 30%
Installation error (over torque or improper saddle position eg): 30%
Saddle/seatpost mismatch: 10%
Seatpost defect: 5%
Something else: 25%

So I would advise a new seatpost, purchased and installed by your bike shop. Be sure to tell them the story - they like hearing stuff like this and might be able to find something interesting, and might be able to guarantee you a good result.

njlonghorn

After looking at the parts, I think I understand what you are saying. The clamp consists of two metal plates, one of which goes above the seat rails and the other of which goes below. The bolt goes through the un-threaded hole in the seat post, then through the un-threaded hole in the bottom half of the clamp, then through the threaded hole in the top half of the clamp. When tightened, the two halves of the clamp shouldn't touch each other, but instead should be tightening against the rails from top and bottom. Correct?

If so, I'll have to get a new bolt to test this.

njlonghorn

This sounds like me.

njlonghorn

The first time, I was half way up Mt. Okemo in Vermont, and coasted down to the LBS / ski shop at the base. They found a matching bolt on a used saddle. I suppose it is possible that the bolt was compromised before I ever got it, but this seems unlikely given the rarity of the issue. It seems more likely that there is a common causal link arising from me or my bike.

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My statistics professor years ago taught me to be suspicious of data that comes out in unnaturally round numbers. Kidding aside, thanks for the breakdown. It may not be precise but it does give me a window into your thinking.

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I just may head in that direction -- but I'm trying to save up for a better bike and I hate putting money into this one. It wasn't an expensive bike to start with, and probably has a value pretty close to 0 after 15,000 miles or so of wear and tear.

Steve B.

The only seat post bolt I've ever broken was a titanium bolt on a Thompson. Fortunately it was a 2 bolt but I came to the anecdotal conclusion that these were no stronger that any steel version I had used prior or since.

Trakhak

The best seat clamp designs must be protected by patents, because there sure are a lot of iffy cheap OEM one-bolt seatposts out there, including the one in the pictures of the OP's bike.

As several people have suggested so far, junk that one. The most reliable seatposts I've come across all use a two-bolt design.

smashndash

That looks a lot like the bikesdirect seatpost my friend had. The bolt would keep coming loose so I had to keep absolutely wailing on it. Eventually I just replaced his seatpost with a $20 one I had lying around. Afaik he never had issues again. I say junk it and get something else. The one I used was this:https://www.citygrounds.com/products...MaAuH8EALw_wcB

Leebo

^^^^^ This. Thomson. I'm a little over 230.