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Ok, so I noticed what looked like a crack in my Ritchey Superlogic seatpost. I contact Wiggle and they asked for it to be sent back. I complied. Now I knew at the time that Ritchey were just going to come back with "it's been overtighted" so I wasn't sure what I expected to achieve. Thing is I know that I've not overtighted it, it's been in my road bike torqued properly and adjusted once ro twice (and torqued properly again) in the 6 months or so I've had it. I've had problems with seatposts in the past so I've learned the hard way.
Anyway it's my word against theirs and it's not the end of the world if it's just put down to experience. Wiggle have been decent....
I just thought I'd see what others thought could have caused such an issue.
For info I always use fibre grip and 4nm maximum. It's never slipped.
[url= https://photos.google.com/share/AF1QipPfDWNEUqMjY_YsX_LQCaKXFLoDpU3LgvtF-arWNKlbLHy8FbcRV23ACK8PhXupIw?key=dEpGRzBfSTl3TW1Sd2VNSUNWcHViOTFDbXFjNDhR ]Photo[/url]
Is this it? You would have thought that if it had been overtightened then the crack would be running along the length of the seatpost surely?
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it kind of is....
It runs down the seam of the carbon and has bulged out effectively filling the split in the frame where the clamp goes. it's hard to photograph.
This shows the split better...
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Ahh yea from that angle it definitely looks like overtightening to me. Are there any sharp burrs or edges on the seat tube?
Nah it's smooth as a babies bum....
I'll have to check my torque wrench to see if it's giving the correct reading.
Who's torque were you using? The seatpost or clamp suppliers?
The lowest of the two.
Clamp says 5nm but the seatpost is listed as 12nm and I know I've never been anywhere near that.
I experienced that once. It was the was the way the clamp gripped the frame and pushed the carbon into the carbon.
Is the red line the minimum insertion, if so I'd get a longer one next time - plus how central do have your saddle, ie any layback?
No the min-insertion is way to the right of the photo.
12nm is more than shimano chainset clamp bolts!
any chance its been moving in frame (fretting) a tiny bit and its worn carbon = split
just a thought
I've had exactly the same on my roadie, a Deda Superzero. Followed torquing to the letter too. Just replaced it and noted that the max torque has been reduced to 4NM from 6, so presumably I'm not the first! I've also filed down the lips of the slot in the seat tube and turned the seatpost clamp 180deg so that it's slot is opposite the seat tube slot.
I don't think it's been moving. I've never had to re-adjust the post over a period of time. I'll have to check the frame tonight as I've replace it with a Deda Superleggero with a lower NM setting.
I'm not going to lose any sleep over especially now Wiggle have offered a 50% refund. Just have to keep a closer eye in the future.
With a crack running up the tube I'd be asking them about their layup schedule. I'd expect the outer layers on any seatpost to be bias wrapped, there's little strength to be had from fibres running straight up the post, especially when almost all the experienced load is front to back. +/- 45 degrees is order of the day.
If they're really on their game them the trailing edge of the tube should be thicker than the front and the front thicker than the sides.Assuming a relatively normal saddle position most of your weight will be over the middle/back of the saddle and hence leverage comes from behind. No matter how much you might try you just can't support as much weight on the tip of the saddle as you can the back and they should design accordingly. Look at a Thomson, their wall thickness distribution tells you all you need to know.
If they come back telling you it's just the beauty layer ask them why they don't use a beauty layer that offers structural benefits, after all it's a top flight light weight component, there's no place for 'excess' anywhere.
sq225917 - Member
With a crack running up the tube I'd be asking them about their layup schedule. I'd expect the outer layers on any seatpost to be bias wrapped, there's little strength to be had from fibres running straight up the post, especially when almost all the experienced load is front to back. +/- 45 degrees is order of the day.
Nope.
+/- 45 for torsional loads
90 for hoop stresses
0 for longitudinal ie bending, tension etc
I would expect to see a priority for 0 deg, ie up and down the length, in a seat post. But you will want some fibres in other directions for obvious reasons and all 0 would be very susceptible to crushing. You could replace some 0s with 45s if you want some more flex.
The post has a 110kg weight limit, are you close to that (including rucksacks etc)?
My opinion is it looks a bit like it has been bending due to being close to maximum extraction and having a fair bit of weight/force on it so it then failed at clamp slit where the post is not reinforced by the frame.
I'm 85kg never ridden with a backpack