Snapped the saddle rail bolt on my seatpost

[ekib]

__PG__

I would propose another possibility. That is that the bolt may have actually been loose.
A loose bolt can fail very quickly from fatigue.

Apparently about %85 of bolt failures are due to fatigue.

Have a look here if you're interested;
Saddle bolt failure



ekib.

[Mulger bill]

What sort of post was it? Someone may have spares gathering dust.

[Stepr]

had this problem a while back. you could either find some spares at the local tip shop. or go to a nut and bolt supplier and get an 8mm socket head screw.

[__PG__]

__PG__

I would propose another possibility. That is that the bolt may have actually been loose.
A loose bolt can fail very quickly from fatigue.

Apparently about %85 of bolt failures are due to fatigue.

Have a look here if you're interested;
Saddle bolt failure
ekib.

Surely if the bolt was loose I'd notice the saddle creaking and moving around?
No idea what the post originally was, all the markings/logos on it rubbed off years ago.
Have scored an old 2nd-hand post from a mate as a temporary fix. Am planning to go into the LBS for a quick saddle fit and then will look at how much setback I need.

[ekib]

_PG_,

yes you're right, you would expect to notice a loose seat post bolt.
Or perhaps you wouldn't,
From the article,
"Because the lower part of the clamping system is serrated, it is not free to move if the bolt is only slightly loose."



I might try loosening my seatpost bolt and see, or maybe I'll loosen someone else's seatpost bolt

Ekib.

[pacra]

I have had a saddle bolt failure (ala catastrophic, unfortunately for me at the time).
I got the bolt checked at Monash Engineering and it showed

1 Work hardening very similar to the failed bolt in the article leading to a critical crack then failure.
2 but also when the bolt was measured under magnification it had necked over time (years) from continual tightening.

As you cannot detect necking with the naked eye the moral of the story seems to be to lightly lubricate the bolt at regular periods and possibly consider replacing the bolt every couple of years.

The bolt that failed was an alloy bolt on a Chorus seat post. Steel bolts would be more durable.

[toolonglegs]

I have had 5 or so go over the years... since switching to Thomson posts I have never had a failure.
All of my bikes have Thomson posts now, but I find they do have an annoying problem over time of changing shape or wearing ever so slightly around the clamping area... real PITA especially on mtb and CX bikes when they slip down a touch... hence I now have dual clamp seat post clamps... finally I am happy .