Carbon frame cracked around seatpost

[jhob]

Seemingly Cannondale were pretty shit from reading that thread, offering only a discount on a new frame and blaming the seatpost.

HongFu (realised it's HongFu, not DengFu I bought the bike from) have replied requesting more photos, which they now have.

I at least have my backup plan if nothing happens with HongFu.

Been a bit put off carbon now, think I'll start saving the pennies for a Van Nicholas...

[chesterbull]

If you are after a repairer HQ Fibre Products in Norfolk have a good reputation on the TT forums.  They've repaired a sheared chainstay for a clubmate and a disc wheel that I cracked.  http://www.timetriallingforum.co.uk/index.php?showtopic=32930

[Paul]

Is the internal diameter of the tube consistent or does it get wider below the clamp area? What sort of clamp did you have?

(Afraid I can't help, I'm just interested in how this might have happened.)

[Chris N]

Been a bit put off carbon now, think I'll start saving the pennies for a Van Nicholas...

Because Ti frames never crack, right?

[jhob]

Is the internal diameter of the tube consistent or does it get wider below the clamp area? What sort of clamp did you have?

(Afraid I can't help, I'm just interested in how this might have happened.)

Appears to be consistent, although I have not specifically checked.

Here's an image showing the clamp and general area:


and why not have one of the whole bike:

[Hot Flatus]

Seemingly Cannondale were pretty shit from reading that thread, offering only a discount on a new frame and blaming the seatpost.

HongFu (realised it's HongFu, not DengFu I bought the bike from) have replied requesting more photos, which they now have.

I at least have my backup plan if nothing happens with HongFu.

Been a bit put off carbon now, think I'll start saving the pennies for a Van Nicholas...

Let's hope for a positive response from Hongfu.

Don't be put off carbon. I've heard of more Ti failures than I have carbon. I have 4 cf bikes and 2 ti, by the way. No failures yet.

Van Nic have a bad rep for cracks, but a good rep for honouring warranties.

[DrMekon]

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.

Trek did me a generous discount on a new frame when I went into a car and my frame didn't break.

[mrcharly-YHT]

My gut feeling is that this is a crack caused by compression and would be prevented by having a much larger hole at the end of the slot.

[P Walsh]

If anybody knows of a material that is 100% reliable for cycle use, please let me know. I've had steel and titanium saddle rails snap, and I have known both those materials fail when used for frames. I have had two alloy seat posts snap. And I have heard of carbon failures. I don't like the look of carbon (it looks like plastic) but I would not jump to the conclusion that it is always a liability. If I were buying a carbon frame I would look for strength and I would avoid overly light frames and forks. And I would prefer a manufacturer with a reputation for putting things right.

[jhob]

Interestingly one of the carbon repair companies got back to me with a quote.  They offered 2 solutions: build up the carbon around the crack, or use a metal shim and reduce the width of the seatpost - the same solution I was looking at doing myself.

Their quote made it uneconomic for me to get it repaired, at any rate how hard can it be to epoxy a metal shim in place with a bit of araldite?

[zigzag]

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

only just seen this. it is unfortunate that it's happened, but can be easily fixed with epoxy and a shim and is not dangerous at all (it's dangerous if the seatpost breaks near the clamp and you fall down on a pipe ). i'd be interested if they really offer warranty replacement, but if it had happened to my frame i'd just fix it myself and be back on the road asap. it will take less time than stripping the bike down and posting the frame somewhere.
i don't believe in bike warranties as they are too much hassle - it's best to have a bike that is least likely to break and if (in the unlikely case) it breaks, fix it or get a new one.

[yoav]

I suspect that the main (or only) difference between cheaper unbranded Chinese carbon frames and the more expensive well known brands are the warranties (to justify the higher prices).

[Paul]

Is the internal diameter of the tube consistent or does it get wider below the clamp area? What sort of clamp did you have?

(Afraid I can't help, I'm just interested in how this might have happened.)

Appears to be consistent, although I have not specifically checked.

How much seat pin is there below the '60' mark?

[jhob]

Is the internal diameter of the tube consistent or does it get wider below the clamp area? What sort of clamp did you have?

(Afraid I can't help, I'm just interested in how this might have happened.)

Appears to be consistent, although I have not specifically checked.

How much seat pin is there below the '60' mark?

Just measured it and there is 14cm below the '60' mark, so plenty.

[P Walsh]

Your post (which you have measured) is close to perfect diameter, very slightly undersize. Is the inner seat tube a little oversize?

[jhob]

Your post (which you have measured) is close to perfect diameter, very slightly undersize. Is the inner seat tube a little oversize?

I'll not be able to accurately measure the inside of the tube as the calipers can't extend far enough into the tube and taking a reading at the top probably wouldn't be a valid measurement because of distortion caused by the crack.

However it does feels like it's a good fit - not at all loose and with a light friction when inserting the post.

[DaveP]

If you feel that the post is a decent fit, how about simply using epoxy resin to bond it into place? Seems likely to make a more substantial reinforcement than a shim (which would still involve a degree of compression around the new seat post)

I do appreciate that posts can be valuable chattels in their own right, and that even riders with thoroughly well sorted positions occasionally need to make adjustments, when changing saddles for example.
But whatever you do is going to be a compromise, so best to consider all possibilities 

[jhob]

If you feel that the post is a decent fit, how about simply using epoxy resin to bond it into place? Seems likely to make a more substantial reinforcement than a shim (which would still involve a degree of compression around the new seat post)

I do appreciate that posts can be valuable chattels in their own right, and that even riders with thoroughly well sorted positions occasionally need to make adjustments, when changing saddles for example.
But whatever you do is going to be a compromise, so best to consider all possibilities 

I think that would be a step too far for me, especially when the epoxyed shim idea should work equally as well in providing strength to the affected area, whilst also allowing for future adjustment.

[Paul]

Here's an image showing the clamp and general area:

Is there also some damage further up the tube, just below the clamp on the right left hand side (as we look at it)?

If it's not a mismatch between the tube and pin then could it just be a weak section, or that the clamp isn't the right shape/size, or is over-tight? I speculate about that because the pin looks to be more scored than I would expect where it was clamped. 

[jhob]

There is a bit of an indentation just below the clamp, but that's just a feature of the frame.

I can see the bit you're referring to.  That does look a bit cracked, you're right.

Clamp is definitely the right size, I'm pretty certain I've never over-tightened it.  I have a torque wrench and always use that.

Still waiting to hear back from HongFu.  At any rate, the metal sleeve fix will cure all damage up there at once.

[Paul]

If everything is the right size and it's all been treated and tightened properly, then something else is wrong.

In my (lay) opinion the cf tube is not up to scratch. I wouldn't be confident of a glue and shim fix. I'd be inclined to ditch the frame and the pin.

[P Walsh]

I had to buy a new clamp for a titanium frame about 18 months ago, and I chose a Thomson clamp because it seemed more thoroughly designed than others, requiring less torque to hold the post. The bolt has a slightly odd angle to it that is claimed to work better. And with a carbon post the bolt goes at the front (away from the slot). It is very well made, and might just help after your repairs.

[jhob]

I had to buy a new clamp for a titanium frame about 18 months ago, and I chose a Thomson clamp because it seemed more thoroughly designed than others, requiring less torque to hold the post. The bolt has a slightly odd angle to it that is claimed to work better. And with a carbon post the bolt goes at the front (away from the slot). It is very well made, and might just help after your repairs.

Thanks for the advice, just ordered the thomson collar.  Sounds like a good investment for any future bike too.

HongFu have gone quiet so I'm just going to make the repairs with the shim myself.

Does anyone have advice for a decent, but reasonably priced, 27.2mm seat post?

[Jurek]

I have a used titanium one which, I'm pretty sure is 27.2 (I'll check this evening) - I'm open to offers, assuming you wanted to move away from C/F.

[Biggsy]

Does anyone have advice for a decent, but reasonably priced, 27.2mm seat post?

If you don't mind aluminium: Deda RSx 01

Or Deda RSx 02 - 10g lighter