Author Topic: Aluminium Steerers  (Read 2182 times)

pdm

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Aluminium Steerers
« on: 16 February, 2018, 11:27:01 am »
What is the current evidence for the safety (or otherwise) of modern Carbon forks with Aluminium steerers?

I do know there were occasional reports of problems with cracking aluminium steerers ~5-10 years ago but I have not heard of the problem continuing with any frequency more recently.

Anecdota:
ITM did a recall on their all carbon fork about 5 years ago because of potential failures and replaced them with "equivalent" Aluminium steerer forks which were claimed to be more robust. (I had 2)
I am a large heavy rider (95-100kg) and have done over 100k km on 3 Aluminium steerer forks with no problems.
Steel forks I had on a touring bicycle purchased in 2003 failed catastrophically after 20k km (2 years) :(

Any thoughts, evidence??

Torslanda

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Re: Aluminium Steerers
« Reply #1 on: 16 February, 2018, 02:12:55 pm »
No evidence. Thoughts as follows.

Never seen a failure as described. Either it's happening lots and people aren't posting about it because they're dead or it's not happening much...

The vast majority of alloy/carbon forks have carbon blades bonded to an alloy crown and the steerer bonded in above. Some 'full carbon' forks are made the same way but with a carbon steerer.

Giant, Trek, Specialized et al all use the same type of forks. I don't believe there is an inherent weakness in the design but there are undoubtedly varying degrees of quality control in the production processes used by different manufacturers.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

LittleWheelsandBig

  • Whimsy Rider
Re: Aluminium Steerers
« Reply #2 on: 16 February, 2018, 02:20:41 pm »
It is pretty rare for there to be a complete fracture. It isn't unknown for bonding to partially or fully fail though, which leads to relative movement (e.g. creaking) between fork components (steerer, crown, blades). I've seen one example where the steerer remained connected to the crown by the brake bolt. Once the brake was removed, I could pull the steerer out of the crown. That was a long time ago though. If there is creaking, try really, really hard to find and eliminate the cause. If there is a visible crack in the clear coat or glue, the fork is almost certainly toast. If you can't eliminate a creak in a bonded fork, I'd always replace it.
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Torslanda

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Re: Aluminium Steerers
« Reply #3 on: 16 February, 2018, 02:23:42 pm »
Quote
If there is a visible crack in the clear coat or glue, the fork is almost certainly toast. If you can't eliminate a creak in a bonded fork, I'd always replace it.

This.
VELOMANCER

Well that's the more blunt way of putting it but as usual he's dead right.

Re: Aluminium Steerers
« Reply #4 on: 16 February, 2018, 02:34:23 pm »
IIRC Chris Juden wrote a fairly damming article about them for the CTC website after examining one where the carbon/aluminium bond had failed catastrophically.
I can't now find a copy of that, but a quick look round threw up just as many reported examples where 'all carbon' forks failed.


zigzag

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Re: Aluminium Steerers
« Reply #5 on: 16 February, 2018, 05:01:16 pm »
it happens, but very very rarely* - carbon forks are overbuilt more than frames, i.e. if there is a frontal impact the frame will fail/crack/wrinkle first. if i was heavier, or sprint/climb out of saddle very often i'd probably go for full carbon forks, or install a carbon sleeve inside a steerer tube for peace of mind.

* when it does it is most likely an unfortunate defect in the alloy, every component has a slight probability of manufacturing defects

Re: Aluminium Steerers
« Reply #6 on: 16 February, 2018, 08:49:08 pm »
...... I don't believe there is an inherent weakness in the design but there are undoubtedly varying degrees of quality control in the production processes used by different manufacturers.

there is also a massive difference in the service conditions that such forks see.  I've seen all kinds of forks break in all kinds of ways, but not enough of any one type personally to say for sure that X is rubbish and Y is not.  I would say that in the UK, all weather/winter use greatly increases the chances of there being corrosion at the bond line, whether it be carbon to aluminium  joints or  aluminium to aluminium.

 One of the most horrifying breakages I have heard of was in a cannondale fork, with an aluminium steerer bonded to an aluminium crown. A corrosion-assisted fatigue crack started at the rear of the steerer, (not that the owner inspected the part, but the crack would have been hidden from view within the joint), and grew until the inevitable happened which was that the fork parted company and dumped the rider in the road. The rider ended up with broken bones but survived. Others riding defective forks have not been so lucky.

Somewhat worryingly one of the most common types of  bicycle recall in the USA over the last decade or so has been in carbon forks. This category includes those with aluminium steerers.  How many breakages there have to be in order to trigger a recall I don't know.  At least one plant in China making such forks has itself gone bust, presumably as a consequence of one recall too many.

I think it is important to note two things;

1) there is a risk/consequence thing going on here; even if there is a very low risk of failure, because the consequences are so dire, it is unwise to treat forks like other bike bits. If there is the slightest doubt about them, bin them; they can fail without warning. Also

2) it is a good idea to distinguish between failures of conception and failures of execution. The vast majority of fork breakages seem to occur due to the latter rather than the former. Bonded joints are particularly susceptible to poor QA.  However it is fair to say that any fork with an aluminium steerer is likely to fatigue at some point, it is just a matter of when; aluminium is commonly believed to have no fatigue limit. The fatigue life will be greatly shortened by such commonplace things as surface damage and corrosion, which are not allowed for when the approval tests are conducted.

Bottom line; inspect your forks carefully and replace them if you have the slightest doubt about them, or they are just old/high mileage. 

FWIW it is clearly possible to make a bad set of steel forks, even, but IME when steel forks fail, they exhibit clearly visible cracks and/or give due warning of imminent failure (eg by bending) rather than just snapping like a carrot.  In this respect they behave differently from many other forks when they fail.

cheers

Re: Aluminium Steerers
« Reply #7 on: 16 February, 2018, 08:58:33 pm »
Ask George Hincapie

Tail End Charlie

Re: Aluminium Steerers
« Reply #8 on: 16 February, 2018, 09:09:12 pm »

Karla

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Re: Aluminium Steerers
« Reply #9 on: 16 February, 2018, 09:18:26 pm »
I'd be more worried about muggins here overtorquing a bung in a carbon steerer.  I've done it before  :facepalm:

Cudzoziemiec

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Re: Aluminium Steerers
« Reply #10 on: 16 February, 2018, 09:26:39 pm »
I overheard a mechanic in an LBS saying that Specialized had to recall the entire stock of 2018 Allez due to carbon fork faults before they'd even officially gone on sale. The problem seems to have been they engineered it down to a ridiculously minimal weight. But presumably they didn't have an aluminium steerer.
Riding a concrete path through the nebulous and chaotic future.

Re: Aluminium Steerers
« Reply #11 on: 17 February, 2018, 12:23:37 am »
What is the current evidence for the safety (or otherwise) of modern Carbon forks with Aluminium steerers?

I do know there were occasional reports of problems with cracking aluminium steerers ~5-10 years ago but I have not heard of the problem continuing with any frequency more recently.
 
 
I recently discovered that the fork on my beloved Kinesis UK bike has been recalled for problems with the bonding between the aluminium and the carbon parts. Apparently the problem was discovered when a cyclist died because of this :-(
 
The affected fork model was produced until 2009, which is quite some time ago, but the problem first discovered in 2015. The fork has aluminium crown and the lower part of the steerer is aluminium, while the top of the steerer and the fork blades are carbon.


 
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Regards