Cracked seat tube

royalmile

Hi Guys

I'd really appreciate some advice on my broken bike.

I have a Cannondale Synapse Carbon, the old model with a standard seat post. Over the winter, I decided to rebuild the bike with new old stock Ultegra 6600 components. To finish the build off, I decided to go for a carbon seat post.

Before fitting the seat post, I contacted the manufacturer (of the seat post) for advice on the seat clamp torque. I provided full details of the bike and post. They recommended a torque of 12nm - It seemed quite high but I didn't doubt the 'expert advice' I was given. I heard a sickly crack from the frame as I tightened the clamp. I removed the seat post and discovered a 1cm vertical crack at the top of the seat tube as well as a crack on the seat post itself. I used a torque wrench and it wasn't anywhere near 12nm when I heard the crack. As it turns out, Cannondale recommend a maximum of 6nm. I'll not name the seat post manufacturer for now as I'd like to give them a chance to sort things out.

Has anyone experienced anything like this and are the seat post manufacturer liable for the replacement cost of my frame? I still have a copy of their email.

Any advice would be much appreciated.

smidsy

Wait and see what they say is the best advice.

No point getting all hot and bothered until you know that they refuse to do anything.

If all else fails RPD Steve on here can repair it.

Monty Dog

12Nm for the seatpost is way too high - 5Nm is all that's needed at most.
Also, torque wrenches are notoriously inaccurate

ellj22

The problem is that all parts of the assembly have a torque rating, frame, seat clamp and seatpost. The minimum torque setting for any of these components should be the limiting factor.

In my experience 5 Nm is generally ample for any part clamping carbon and carbon assembly paste is a good idea as the increase in friction it generates reduces the torque required.

Sadly when I used to work in the cycle industry I only ever saw one successful claim against a cycle brand for a part failing within torque. He way a Cytec level 3 mechanic and was using a torque wrench that had been professionally calibrated.

I wish you the best of luck, but I wouldn't hold your breath. They may replace the seatpost but I doubt they will pay out for a new frame/repair.

father_jack

yeah 12nm is way too high that's more like going into larger 6/7/8mm bolts. If you look through park tools torque settings, only the larger bolts go past 10nm.

royalmile

Thanks for your replies

Just posted a letter and copies of the email exchange to the seatpost mfr, I'll share their reply when I receive it. I'm guessing they'll probably send me a new seatpost and accept no liability for the frame damage.

The good news, of course, is I now have a great excuse to treat myself to a new bike. I see there are a few of last year's Synapse models on offer in my size 1300 for 105 or 2k for ultegra - I'm tempted!

Thanks again

ricky1980

You can get that repaired I would imagine.

royalmile

ricky1980 wrote:

You can get that repaired I would imagine.

Very good point and I'll definitely get a quote on the repair. I'm a little concerned that the crack is on the forward side of the tube immediately above the join to the top tube, and then there's the age of the frame - a 2008 model. I'm sure I read somewhere that carbon frames have a limited life anyway?

sungod

cf will last indefinitely, if it's exposed to strong uv there can be degradation of the resin, but on a painted frame i'd think there's little chance of that, especially in uk 'summers'

a cf repair expert should be able to fix it, especially as it's due to a known local overload rather than the result of a crash, they might give you an estimate from pictures but they'd need to see it for a firm price, try...

http://www.carboncyclerepairs.co.uk/index.html

pride4ever

LOL CARBON.

rolf_f

royalmile wrote:

Very good point and I'll definitely get a quote on the repair. I'm a little concerned that the crack is on the forward side of the tube immediately above the join to the top tube, and then there's the age of the frame - a 2008 model. I'm sure I read somewhere that carbon frames have a limited life anyway?

No reason why the frame won't outlast you. As long as you lay off with the torque wrenches on it that is

ellj22

Almost anything carbon can be repaired and if its at the front of the seat tube its less of a concern as most of your weight will act down the back of the seat tube.

But yea this is more than enough to justify to yourself that you need a new bike (with the repaired one as a winter or spare)!!

smidsy

royalmile wrote:

ricky1980 wrote:

You can get that repaired I would imagine.

Very good point and I'll definitely get a quote on the repair. I'm a little concerned that the crack is on the forward side of the tube immediately above the join to the top tube, and then there's the age of the frame - a 2008 model. I'm sure I read somewhere that carbon frames have a limited life anyway?

As I said earlier RPD Steve on here will be able to advise on repair.

Compared to some of his work a small seat tube crack will be a doddle.

Once repaired it will be as good as new and not affect the longevity of the frame.

andi1363

sungod wrote:

cf will last indefinitely, if it's exposed to strong uv there can be degradation of the resin

Yes the fibre will last indefinitely but the composite structure will have a fatigue endurance limit. However its not something to be concerned about in frames or forks.

Deda says only love is stronger than carbon

From Deda:
Carbon lasts longer than metal.Only love is stronger than carbon.Bonding is a different story.I believe that a good glue (epoxy) can last for 2000 hours of work, or about 800 days, not in continuous daylight, and below 35 Celsius.Whenever a carbon “part” has crashed, even if you cannot see a failure, if there is any reasonable doubt about having surpassed the elongation limit, the part must be replaced.
–Fulvio Acquati
Deda Elementi

From Kestrel:
On the lifespan issue, of course the person should contact the manufacturer regarding specifics on the product in question. For carbon forks in general, there should not be any limited life span, as carbon composites themselves are not subject to fatigue failures as metals are. So the fatigue life of a properly made carbon composite is “infinite”. Example, in Kestrel’s case, our forks (as with all our carbon products) have a lifetime warranty and are designed and tested to last a “lifetime” of use for the given product.

What should be more of a concern, again as it would be with a metal structure, is the kind of abuse and/or damage the fork has seen. It’s the old “inspect in case of crash, impact or other suspected damage” deal. If any fork is known to have been crashed or impacted I’d look it over real close and, if any damage is present or suspected, I would play it safe and assume the worst. Get it checked out immediately by the manufacturer.

If a carbon part – in this case a fork – is properly designed, properly manufactured and has not been damaged due to crash/impact/abuse, there is no reason it should not last just as long (or longer) than a metal component.
–Preston Sandusky
Sand Point Design (Kestrel Bicycles)

From Columbus:
Carbon forks can be long lasting but one has to take care of other aspects than metal ones.

A fiber composite material has higher mechanical characteristics than metals (higher tensile strength, higher fatigue life, higher stiffness) but it has even different behavior due to its “non-homogeneous nature”. This means that the fork project is really a “critical point” for life span, moreover the final user has to check the composite fork with attention to different aspects compared to metal one. In fact, for composite material the areas of coupling with other parts are critical (headset bearings, stem clamp, gap cap),composite has different impact behavior so for each shock is important to check fork, finally composite is sensitive to ambient agents (solvents, temperature over 90°C etc).
–Riccardo Carpinacci
R&D department, Columbus, Cinelli and 3T

From Look:
There is no limitation because carbon has a natural flexibility. It can be used a hundred years while maintaining the same stiffness.
–Ming Tan
Look Bicycles

From Reynolds:
After considerable testing and thought on the matter we find the question of “fork life” in terms of time to be a tough question to answer. Our fatigue testing would indicate that well built composite forks are far superior to metal forks with cycle counts running hundreds of thousands of cycles rather than tens of thousands. These tests are also run at much higher loads than metal forks can withstand further demonstrating the durability of composite materials. Based simply on fatigue life a well made and properly installed composite fork should last virtually indefinitely if the bike is not crashed or otherwise abused.
Mike Lopez
Reynolds Composites

From Easton:
There are two failure modes that could cause a fork to fail, fatigue or impact. Questions about life span are really questions about fatigue life. How many cycles can a fork survive before it is tired and worn-out? The good news is the fatigue life of carbon fiber is immensely more than that of metals. While the writer expresses concern about his carbon fork lasting as long as a metal component, there is nothing to worry about in terms of fatigue life on a composite fork.

The most likely cause of failure for a composite fork would be impact damage sustained from crashing. Most of the time any damage to a fork from a crash will be visible. Cracks can be seen. We would recommend that the fork be periodically inspected visually at the drop out area and along the fork legs to look for cracks or depressions in the material. Any fork that shows signs of cracking should not be ridden and replaced immediately.

In general terms, a component made from carbon fiber will far out-last a component made from metal.
John Harrington
Easton Sports

royalmile

Thanks everyone for the information and contacts on carbon frame repairs and life. Just looking through the posts and links, it seems that carbon frames may be more repairable than other materials? My seat-tube crack actually seems very minor so I'm definitely going down the repair route. The crack is hidden behind the seatpost collar so the repair should be invisible.

Cheers

royalmile

Just had two opinions from specialist repairers:
1. CBS - They can't repair the frame because the crack is in the area normally covered by the seat clamp collar.
2. Carbon Fibre Repair - claim that they can fix the crack by taking the material right down and replace the damaged area with new fibres. The finished job will be the same internal and external diameter so no problems with the clamp. Estimate £100.00+VAT including an ultrasound check of the frame. The price seems ok, has anyone used Carbon Fibre Repair?

ride_whenever

Give HQ fibre products a ring.

andi1363

royalmile wrote:

Just had two opinions from specialist repairers:
1. CBS - They can't repair the frame because the crack is in the area normally covered by the seat clamp collar.
2. Carbon Fibre Repair - claim that they can fix the crack by taking the material right down and replace the damaged area with new fibres. The finished job will be the same internal and external diameter so no problems with the clamp. Estimate £100.00+VAT including an ultrasound check of the frame. The price seems ok, has anyone used Carbon Fibre Repair?

This is bollox. The fibres are continuous in certain directions so to remove a broken fibre from a fully cured composite is impossible.

Not saying the repair will be no good but the fibres will not be continuous any more.

royalmile

andi1363 wrote:

This is bollox. The fibres are continuous in certain directions so to remove a broken fibre from a fully cured composite is impossible.

Not saying the repair will be no good but the fibres will not be continuous any more.

I agree and given the age and relatively low value of the frame, I think I'll break this bike for parts and scrap the frame. Perhaps I should get rid of that torque wrench on eBay too!

smidsy

No joy from RPD Steve?

What size is your frame? if its a 54 I may be interested.