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Trek Domane 4.5 - cracked seat tube

andyebandyeb Posts: 407
edited December 2015 in Workshop
Today I noticed a small crack spreading from the slot in the seat tube on my Trek Domane 4.5, which has a carbon fibre frame. The seat clamp has only ever been tightened with a torque wrench, to the required torque setting.

Has anyone else heard of similar issues, or know if this is a common problem with this frame? I’m hoping to claim on the frame warranty, so would be particularly keen to hear from anyone else with similar experiences.

The bike is about 18 months old and has done ~6400 miles.

Posts

  • crikeycrikey Posts: 362
    Trek do a very good lifetime warranty for the original owner, but that appears to be a way over tightened clamp. You can see that the tube has buckled under the stress.

    Time to talk to your Trek dealer, but I wouldn't be surprised if you have to explain how that happened.

    All is not lost though; I suspect that is an eminently repairable situation.
  • keezxkeezx Posts: 1,314
    Seems a seatpost that doesn't fit correct in the frame.
    A clamp alone cannot buckle the frame that way if the post fit.
  • andyebandyeb Posts: 407
    keezx wrote:
    Seems a seatpost that doesn't fit correct in the frame.
    A clamp alone cannot buckle the frame that way if the post fit.

    That's what I'm thinking too. It is still the original seat post which came with the bike. It's almost like the seat post is either too small, or the seat tube has been manufactured too large, so that the seat tube has to deform excessively to clamp the seat post. And that may have been what caused the crack.

    The seat tube is designed to be an unusual shape - circular at the top, but becomes a wide oval as it extends towards the very wide bottom bracket. Hence it's not a piece of stock carbon tube - it must have been specifically moulded during frame manufacture.
  • keezxkeezx Posts: 1,314
    Didn't you notice it until recently?
    No frame/bike should leave the factory this way.
  • andyebandyeb Posts: 407
    keezx wrote:
    Didn't you notice it until recently?
    No frame/bike should leave the factory this way.

    I've noticed the excessive deformation before, but the crack in definitely new - I regularly check the bike over following cleaning/maintenance.
  • andyebandyeb Posts: 407
    Quick update on this: Trek quickly replaced the whole frame under warranty, however the very next day the replacement frame developed the same crack!!! It's now back with the dealer awaiting warranty assessment :(
  • noodlemannoodleman Posts: 852
    This is weird! To me it looks like a manufacturing problem but i would imagine there would be thousands of frames with the same issue, resulting in a recall. Let us know what they say.
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  • andyebandyeb Posts: 407
    noodleman wrote:
    This is weird! To me it looks like a manufacturing problem but i would imagine there would be thousands of frames with the same issue, resulting in a recall. Let us know what they say.

    Agreed - I'm either suffering chronic bad luck, or something is definitely amiss here.
  • apreadingapreading Posts: 4,532
    andyeb wrote:
    Quick update on this: Trek quickly replaced the whole frame under warranty, however the very next day the replacement frame developed the same crack!!! It's now back with the dealer awaiting warranty assessment :(

    Is the seat post narrower than it should be then?
  • andyebandyeb Posts: 407
    apreading wrote:
    andyeb wrote:
    Quick update on this: Trek quickly replaced the whole frame under warranty, however the very next day the replacement frame developed the same crack!!! It's now back with the dealer awaiting warranty assessment :(

    Is the seat post narrower than it should be then?

    I measured with my digital callipers in 3 places and the measurements are 26.98mm, 26.98mm, 27.07mm.

    According to this (slightly dated) list http://sheldonbrown.com/seatpost-sizes-m-z.html#t Treks OCLV carbon frame historically have used 27.2mm. So that might be the problem right there?!

    EDIT: Seems the 2015 Domane (mine is a 2013) definitely uses 27.2mm seat posts: <http://www.evanscycles.com/products/trek/domane-45-2015-road-bike-ec068737&gt;
  • apreadingapreading Posts: 4,532
    Hmm, would an extra 2mm bend on the seat tube cause this much stess? I dont know. Is it the original seat post, supplied with the bike? If so then I would ask the question of Trek. If not then I would put the original seatpost back in quick before they point the finger at you...!
  • andyebandyeb Posts: 407
    apreading wrote:
    Hmm, would an extra 2mm bend on the seat tube cause this much stess? I dont know. Is it the original seat post, supplied with the bike? If so then I would ask the question of Trek. If not then I would put the original seatpost back in quick before they point the finger at you...!

    It's 0.2mm we're quibbling over here, but looking at the way the seat tube deforms around the seat post slot, I'm inclined to believe this is potentially the root cause of the issue.

    And yes it's the original Bontrager carbon fibre seat post.
  • apreadingapreading Posts: 4,532
    Good point - I would have thought that 0.2mm is neither here nor there but based on the problem you are having, would at least point to it being a contributory factor. Can you measure the inside of the seat tube with your calipers to see if this is substantially more than 27.2mm?
  • DCS450DCS450 Posts: 2
    Have noticed exactly the same fault today on my 2013 Trek Domane 4.3 when cleaning/lubing before a group ride.

    Again 18 months old, lower mileage, not really noticed any deformation before.

    Standard seat post, as supplied, never overtorqued, (set by them when they fitted a new saddle).

    Interesting that the first question from the LBS, is this the correct seatpost! Followed by has it been over tightened?

    To which I replied, well it is the seat post you supplied me and you were the ones who set the torque when you fitted my new saddle.

    Waiting to hear Trek's response, slightly enocouraging that they replaced andyeb's frame.

    My first thought was an undersized seatpost.

    Have noticed that the latest Domane 4.3 has a seatpost with less offset, (current post 20mm, latest version 8mm) maybe this indicates a design/manufacturing problem to try and limit the amount of set back?

    Still this should not really be necessary as the whole seat tube/post is designed to flex.

    However, I will ask why the change has been made and whether they should change the seatpost as well.

    Not that I would want an 8mm offset as I already have my saddle set back nearly to its limit.
  • andyebandyeb Posts: 407
    Quick update: Trek replaced both the frame (again) and the seat post, although there weren't any suitable Bontrager seat posts available so they paid the bike shop to source and fit an equivalent. So they used an FSA carbon post.

    A few weeks on and the fault has not yet recurred.

    So I conclude the original fault was an undersized original seat post and I suspect there are probably a lot of other Domanes out there with this crack.

    @DCS450 - I would push to get your seat post changed too, mentioning this forum post and my experience.
  • dabdabdabdab Posts: 2
    Another here with EXACTLY the same issue. I've discovered exactly the same seat post crack on my 2013 model Domane 4.3

    There definitely seems to be an issue with the seatpost supplied with 2013 models, as shown here http://www.evanscycles.com/products/trek/domane-43-compact-2014-road-bike-ec041047 the 2013 model had "Bontrager Carbon, 20mm offset" but 2015 models now have "Bontrager Carbon, 2-bolt head, 27.2mm, 8mm offset" http://www.trekbikes.com/uk/en/bikes/road/endurance_race/domane/domane_4_3_compact/
    It would appear Trek have acknowledged that the offset was too much ?

    Another interesting point to note is that the higher spec 5.0 & 6.0 series frames have a totally different seatpost arrangement, where the Seatpost clamp is much higher up the frame. Presumably this is to move the clamp further away from the flex point of the iso coupler ?
    http://www.trekbikes.com/int/en/bikes/road/endurance_race/domane/domane_5_2_compact/#
  • apreadingapreading Posts: 4,532
    The design on the 5 and 6 is totally different - its a sleeve fitting over the seat tube rather than a post fitting inside it. This seems to be the direction on top models from other makes too. I dont think it is specifically anything to do with the cracking problem here.

    The reduced offset could be because of a redesigned geometry on the frame too - so that the saddle is further back already and requires less offset. This is just a suggestion of a possible other reason, I have no knowledge if that is the case. Looking at the frame, visually it seems no different - would need to look at the specs for the geometry to tell for sure. The seat post is a completely different design too - not just a change in offset. Interesting...

    From what I understand above though, the problem is not to do with offset creating excess bending force but more because the seat post does not fill the tube so clamping with sufficient force to hold it in place is constricting the seat tube too much.
  • DCS450DCS450 Posts: 2
    Agree that the series 5 and 6 design is totally different, especially as it avoids any slots and the attendant stress concentration points.

    Also agree that it looks more like a poorly sized seat post causing to much local deflection. Except:

    No change in geometry between my 2013 4.3 and the 2015 model. Trek's spec sheet shows current the 2015 4, 5 and 6 series sharing the same geometry, but with a 8mm and 20mm offset respectively?

    The new Emonda range also shares the same geometry across the ranges, but again those with a slot and internal seat tube have 8mm offset, SL and above have the 20mm offset on the seat mast.
    Had a look round the bike shop yesterday and noticed that the carbon S range Emonda now has 3 slots, one at the front, and one each side (biased to the rear of the frame). No slot at the point of highest stress.

    All the aluminium versions have also been changed to an 8mm offset on the seat post including the Madone, surprising for a race version.
    Looks like a blanket change across the board to change all internal style seat posts.

    The joys of far east manufacture with batch sizes so large that frame changes are difficult to intoduce, but a seat post change is much easier to implement.

    Guess we will never really know.

    However, cannot fault Trek's quick response, as they have agreed today to give me a new frame. As andyeb says I will get my LBS to check/replace the seat post; still need my 20mm offset though.
  • dabdabdabdab Posts: 2
    Another positive vote for Trek's warranty response here too!

    Trek agreed to swap the frame without any hassles, and even managed to hunt down a better colour frameset than their initial choice presented as the only colour choice they had available in the UK. LBS have now swapped out the frame and replaced the Seatpost (with an Easton Carbon post).

    Well happy to have my bike back again, even though she looks rather different in her new colours.

    Like the rest of you i'll be watching the seat tube like a hawk from now! Fingers crossed that's the end of it though.
  • I've had the same issues twice and a third time is coming up.
    I purchased the Trek Madone 5.2 in 2013 and noticed a crack at the same location as the OP about 12 months later. After a little debate I received a new frame from Trek. Then in March/April 2015 the exact same thing happened. No debate, I received a new frame once again. Now, December 2015, I can see the same thing happening. As of now it seems it's only the paint that's been cracked, but the shape is exactly the same as previous cracks and I don't trust it one bit. Will take it back to the store before it's a complete crack ... I have to say I lost all faith in this frame/seatpost solution. It's very weak! I've always used the correct torque, always a bit below the max. And I don't change the height of the seat very often ... when I just found out I changed the height for the 2nd time since I got the new frame ...
  • andyebandyeb Posts: 407
    Rwlinda: what seat post do you have and has it been changed yet? The problem has not recurred for me since the original factory fit seat post was replaced. In my case it the series of cracked frames were caused by an undersized seat post.
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