Author Topic: Carbon frame cracked around seatpost (Read 20513 times)

jhob · « **on:** 11 May, 2015, 02:31:33 pm »

Just discovered this today:

Outside:

Inside (crack extends right through):

Clamp was always tightened to 5Nm using torque wrench and carbon paste was used.

Not good eh? I would consider this un-rideable at the moment. I've got in touch with the manufacturer about sorting it out. Will see what they come back with.

Leaves me without a bike for the moment though, gutted.

Sympathy and advice welcomed

Little Jim · « **Reply #1 on:** 11 May, 2015, 05:22:28 pm »

Commiserations, that doesn't look good, although I can't see how it could have failed like that unless the seat post is too small so that as you tighten the clamp it cracked the tube, or too short. Neither of those seems that likely though.

Obviously you need to see what the manufacturer has to say first but there are companies that do carbon repairs so that would be worth looking at - google is your friend. I am assuming that the crack is in the seat tube above the join with the top tube, and if so that should not affect the structural rigidity of the bike, just the ability to keep the seat post in position, so a repair should be possible - I read an article last year about a company in America that specialised (they claimed) in repairing bike frames for the big teams with much bigger cracks in them than yours, but they didn't say what the repairs cost!

Hot Flatus · « **Reply #2 on:** 11 May, 2015, 05:40:56 pm »

what brand is it?

Veloman · « **Reply #3 on:** 11 May, 2015, 05:43:46 pm »

This might be useful:

http://carbonfibrerepair.com/recent-work/#cycling

and these:

http://www.carboncyclerepairs.co.uk/contact-carbon-bike-technics_3.html

jhob · « **Reply #4 on:** 11 May, 2015, 05:44:57 pm »

Quote from: Little Jim on 11 May, 2015, 05:22:28 pm

Commiserations, that doesn't look good, although I can't see how it could have failed like that unless the seat post is too small so that as you tighten the clamp it cracked the tube, or too short. Neither of those seems that likely though.

Obviously you need to see what the manufacturer has to say first but there are companies that do carbon repairs so that would be worth looking at - google is your friend. I am assuming that the crack is in the seat tube above the join with the top tube, and if so that should not affect the structural rigidity of the bike, just the ability to keep the seat post in position, so a repair should be possible - I read an article last year about a company in America that specialised (they claimed) in repairing bike frames for the big teams with much bigger cracks in them than yours, but they didn't say what the repairs cost!

That was what I surmised too, can't quite understand how it happened. I just checked the seat post with calipers and it's 31.55mm in diameter, which I would have thought was within tolerance for a 31.6mm tube.

I am looking at my options, and carbon repair is one. Not quite sure how much that will cost as of yet and might not be viable. We shall see...

jhob · « **Reply #5 on:** 11 May, 2015, 05:46:22 pm »

Quote from: Flaatuus on 11 May, 2015, 05:40:56 pm

what brand is it?

It's a Dengfu.

jhob · « **Reply #6 on:** 11 May, 2015, 05:46:44 pm »

Quote from: Veloman on 11 May, 2015, 05:43:46 pm

This might be useful:

http://carbonfibrerepair.com/recent-work/#cycling

and these:

http://www.carboncyclerepairs.co.uk/contact-carbon-bike-technics_3.html

thanks!

Hot Flatus · « **Reply #7 on:** 11 May, 2015, 05:48:01 pm »

Quote from: jhob on 11 May, 2015, 05:46:22 pm

Quote from: Flaatuus on 11 May, 2015, 05:40:56 pm
what brand is it?

It's a Dengfu.

Don't tell zigzag

My guess is Dengfu will offer you an unrealistically high repair charge, or offer to sell you another

jhob · « **Reply #8 on:** 11 May, 2015, 05:55:47 pm »

Quote from: Flaatuus on 11 May, 2015, 05:48:01 pm

Quote from: jhob on 11 May, 2015, 05:46:22 pm
Quote from: Flaatuus on 11 May, 2015, 05:40:56 pm
what brand is it?

It's a Dengfu.

Don't tell zigzag

My guess is Dengfu will offer you an unrealistically high repair charge, or offer to sell you another

Is there history here with the company?

I shan't be buying another bike from them...

Hot Flatus · « **Reply #9 on:** 11 May, 2015, 06:09:12 pm »

Quote from: jhob on 11 May, 2015, 05:55:47 pm

Quote from: Flaatuus on 11 May, 2015, 05:48:01 pm
Quote from: jhob on 11 May, 2015, 05:46:22 pm
Quote from: Flaatuus on 11 May, 2015, 05:40:56 pm
what brand is it?

It's a Dengfu.

Don't tell zigzag

My guess is Dengfu will offer you an unrealistically high repair charge, or offer to sell you another

Is there history here with the company?

I shan't be buying another bike from them...

Its just a very good example of why I hold the views I expressed in this thread:

https://yacf.co.uk/forum/index.php?topic=89772.msg1845295#msg1845295

Don't get me wrong, stuff breaks, but if you've bought it direct from China you're fucked if you expect any sort of meaningful comeback.

rafletcher · « **Reply #10 on:** 11 May, 2015, 07:45:09 pm »

If you get no joy, then drilling a small hole to stop the crack propagating should be fine.

jhob · « **Reply #11 on:** 11 May, 2015, 07:47:25 pm »

Quote from: Flaatuus on 11 May, 2015, 06:09:12 pm

Quote from: jhob on 11 May, 2015, 05:55:47 pm
Quote from: Flaatuus on 11 May, 2015, 05:48:01 pm
Quote from: jhob on 11 May, 2015, 05:46:22 pm
Quote from: Flaatuus on 11 May, 2015, 05:40:56 pm
what brand is it?

It's a Dengfu.

Don't tell zigzag

My guess is Dengfu will offer you an unrealistically high repair charge, or offer to sell you another

Is there history here with the company?

I shan't be buying another bike from them...

Its just a very good example of why I hold the views I expressed in this thread:

https://yacf.co.uk/forum/index.php?topic=89772.msg1845295#msg1845295

Don't get me wrong, stuff breaks, but if you've bought it direct from China you're fucked if you expect any sort of meaningful comeback.

With the benefit of hindsight, I would now agree with you.

At the time I bought the frame last year I was skint but needed a new frame so price was a major factor. I did my research and DengFu repeatedly came up as having excellent customer services and frames that were well liked and appeared reliable. I hedged my bets that the chances of having an issue were low. Looks like I might have lost that hand.

We'll see what response I get from them anyway....

Hot Flatus · « **Reply #12 on:** 11 May, 2015, 07:59:22 pm »

Well, good luck and I hope it works out well. Keep us posted.

Hot Flatus · « **Reply #13 on:** 11 May, 2015, 08:01:53 pm »

Quote from: rafletcher on 11 May, 2015, 07:45:09 pm

If you get no joy, then drilling a small hole to stop the crack propagating should be fine.

Not sure that is wise. You'll be drilling through the fibres and compromising them. I don't think I'd want something so close to my ballsack likely to shear off into a shard.

Veloman · « **Reply #14 on:** 11 May, 2015, 08:08:18 pm »

I assume the worst case scenario would be the collar area shearing and the seat post suddenly descending into the seat tube. Rather like having the seat post clamp loosening.

jhob · « **Reply #15 on:** 11 May, 2015, 08:11:03 pm »

I've just had a thought for a repair if DengFu aren't any help:

Epoxy the crack up to stop it spreading. Get a 31.6 - 27.2 metal shim (could even epoxy that to the frame). Use a 27.2 seatpost.

That should be safe and secure shouldn't it?

Veloman · « **Reply #16 on:** 11 May, 2015, 08:13:48 pm »

What have you got to lose? (Based on the assumption further failure would result in a seat post sliding down)

Canardly · « **Reply #17 on:** 11 May, 2015, 08:33:09 pm »

Commiserations looks like you have just been a tad unlucky. Hope it is sorted.

jhob · « **Reply #18 on:** 11 May, 2015, 08:33:34 pm »

Quote from: Veloman on 11 May, 2015, 08:13:48 pm

What have you got to lose? (Based on the assumption further failure would result in a seat post sliding down)

Voided warranty.... going to wait first to see if the warranty is actually worth anything in practice...

mrcharly-YHT · « **Reply #19 on:** 11 May, 2015, 10:15:15 pm »

Quote from: Flaatuus on 11 May, 2015, 08:01:53 pm

Quote from: rafletcher on 11 May, 2015, 07:45:09 pm
If you get no joy, then drilling a small hole to stop the crack propagating should be fine.

Not sure that is wise. You'll be drilling through the fibres and compromising them. I don't think I'd want something so close to my ballsack likely to shear off into a shard.

Agreed. The drill technique is for metal to stop crack propogation. CF is a woven fibre, totally different.

For it to have gone like it has, I suspect bad materials design as well as poor manufacturing.

jhob · « **Reply #20 on:** 11 May, 2015, 10:42:01 pm »

Just been reading that a number of cannondale MTB frames have failed in a similar fashion:
http://forums.mtbr.com/cannondale/jekyll-carbon-seat-tube-crack-828418-2.html

Feline · « **Reply #21 on:** 11 May, 2015, 10:50:14 pm »

Quote from: jhob on 11 May, 2015, 08:33:34 pm

Quote from: Veloman on 11 May, 2015, 08:13:48 pm
What have you got to lose? (Based on the assumption further failure would result in a seat post sliding down)

Voided warranty.... going to wait first to see if the warranty is actually worth anything in practice...

I would be seriously worried that what you have to lose could severely effect your significant other (if you have one!) and future child bearing abilities .....
Total failure doesn't bear thinking about. Don't risk it!!!

jhob · « **Reply #22 on:** 11 May, 2015, 10:56:30 pm »

Quote from: Feline on 11 May, 2015, 10:50:14 pm

Quote from: jhob on 11 May, 2015, 08:33:34 pm
Quote from: Veloman on 11 May, 2015, 08:13:48 pm
What have you got to lose? (Based on the assumption further failure would result in a seat post sliding down)

Voided warranty.... going to wait first to see if the warranty is actually worth anything in practice...

I would be seriously worried that what you have to lose could severely effect your significant other (if you have one!) and future child bearing abilities .....
Total failure doesn't bear thinking about. Don't risk it!!!

Total failure would be no worse than seatpost slipping down - I could then just pretend that it's a bmx!

Future childbearing abilities (or lack thereof) have already been taken care of!

The inner sleeve and epoxy idea I am pretty confident will work in the event that don't get a repair/replacement. I'm not expecting one so this will likely happen sooner rather than later.

Lesson learnt here anyway...

mrcharly-YHT · « **Reply #23 on:** 12 May, 2015, 08:41:46 am »

Quote from: jhob on 11 May, 2015, 10:42:01 pm

Just been reading that a number of cannondale MTB frames have failed in a similar fashion:
http://forums.mtbr.com/cannondale/jekyll-carbon-seat-tube-crack-828418-2.html

Had a brief read of that thread. Cannondale and Trek mentioned.

Failure in the same place.

I think this suggests a fundamental design flaw in the seatpost/clamp area.

Hot Flatus · « **Reply #24 on:** 12 May, 2015, 08:45:26 am »

The difference being that Trek and Cannondale will be extremely interested in this issue in order to rectify it. To the point of wanting frames sent back.

I'd be amazed if Dengfu care.