My aluminium front fork steerer {carbon forks} snapped off.

[hillspecial]

Hi all,

on Sunday, 25th April 2009, I was out on the bike, we had been doing well over 40 mph down some hills overlooking Ingleborough, later when we were on the flat leaving Garstang doing less then 20 mph when my aluminium fork steerer on my carbon forks snapped off just above the top headset bearing - the handle bars came away in my hands and I fell off my bike, landing on my right shoulder and head, breaking my collar bone {clavicle} and my Giro helmet was broken in several places. I also sustained cuts and bruises. I was taken to A&E by ambulance, 'gas and air' and morphine en route - bike just about written off.

**The bike is only about 3 years old, never been crashed, perhaps done 10,000 miles tops, has aluminium frame and carbon fibre forks, the fork blades having an aluminium 'fork steerer'. This snapped off at where the steerer comes out of the top headset bearing. 8mm carbon spacer twixt headset and ahead handle bar Extension. Never known this happen on steel forks. I'll be back on my steel bike in a few weeks !!

Just about to buy a new steel road frame, perhaps a Mercian, with old fashioned threaded headset and quill stem. Wot do u think? . Or, are steel a-head fork steerers potentially stronger than threaded ones , as threading reduces the diameter of the wall of the tube ?

My bones r gonna to 4 to 6 weeks to mend, missing pay at work too !

Sunday 10.35 am now in the UK, normally out on the bike now, nay we were booked to go away to the Lakes Sat, Sun, Mon as Bank Hol weekend, had to cancel.

Oh and yep, much thanks to my Giro Helmet !!

Paul.

Hi all again thanks for all of your comment and good wishes.

Just been looking on line to see about buying new forks for my two 1980s reynolds 531 frames - just to be on the safe side.

One of my 1980s 531 frames {& frorks} has done well over 100,000 miles; much touring each summer in the UK and Europe, 20 years of club runs, plus YHA and camping weekends, cycling to work and plenty of 'rough stuff'.

So, even though they are 531 forks, I'm gonna take them out and look for any signs of cracks.


Spotted some forks for sale on line - see link below. These forks are SJSC are not 531, but should be OK - certainly stonger than carbon / aluminium and a safer bet than my high milage 25+ year old 531 forks ?

http://www.sjscycles.co.uk/src/froogle/ ... -15588.htm

Cheers Paul.

Hi again,

wow, just read, re-read and read again what Chris says -I'm deff going back to steel frorks with steel steerer and also replacing my 25 year old plus 531 forks too.

As I've some time on my hands I read the CTC e-mail this week and the links re wearing helmets. I'm glad I had my helmet on when my head hit the deck. The CTC e-mail links to a 'study' by a university academic, who claims, through his own observations, that cyclists are more likely to be hit by cars / other road traffic when wearing a helmet, so its safer not to wear one?

[rogerzilla]

With a new frame, go for 1 1/8" A-head - the parts are more likely to be available in 10 years' time.

I've never had an aluminium steerer and I wouldn't. Even my Cannondale (with aluminium forks) has a steel steerer - they learned that alu steerers break in the early 1990s, and recalled a lot of Pepperoni forks.

[james01]

Sorry about your injuries,best wishes for a full recovery, and thanks for the informative post. You've confirmed my doubts about aluminium in this critical stress area.

[hubgearfreak]

Just about to buy a new steel road frame with olde fashioned threaded headset and quill stem. Wot do u think?

My bones r gonna to 4 to 6 weeks to mend, missing pay at work too !

you're dead right to. (or not dead, as the case may be)
frame weight is 1/3 of bike weight. and bike weight is 1/10th of bike and rider weight. skimping a few grammes at the expense of safety is a bit silly

hope you make a swift and full recovery

[Mick F]

Poor you! Get well soon.

My bike is steel. I like it. I do have a Vitus frame in my workshop which is a joy to ride. Very light and comfortable despite having aggressive geometry. It is totally alu, and bonded too, not welded.

The thing is, it has a quill stem and 1" steerer. I feel that an alu steerer is ok providing it is quill. An Ahead system surely puts more strain on the steerer as it pokes out the top.

Am I right in this?

[Spinners]

Getting an aluminium seatpin stuck in a steel frame recently and then seeing how easy it was to mangle it and see it fracture, tear and rip made me realise that it's probably not the greatest material to use for a steerer tube, for a lardy type like me at any rate (even when allowing for the greater wall thickness on the steerer).

[hillspecial]

Poor you! Get well soon.

My bike is steel. I like it. I do have a Vitus frame in my workshop which is a joy to ride. Very light and comfortable despite having aggressive geometry. It is totally alu, and bonded too, not welded.

The thing is, it has a quill stem and 1" steerer. I feel that an alu steerer is ok providing it is quill. An Ahead system surely puts more strain on the steerer as it pokes out the top.

Am I right in this?

Hi Mick, well the more I think about, I can only conclude the same as you. With an 'ahead' sysyem, all the pulling / twisting force applied by the rider at the handle bars, will be transmitted to the steerer and applied at just one point to this 'thin walled aluminium tube'. Plus I'm 6 foot 2 inch, about 15 stones and have wide {46 cm ?} drops and a longish extention from the steerer to the bars, so all in all a lot of force, exp when pulling at the bars going up hills. Even 'resting' my wight on the bars, as I cycled along the flat would have been stressing the steerer and then, with no notice at all, it just sheered off, hence my close encounter with the tarmac!!

[irc]

Sorry to hear about your crash but I'm glad the result wasn't any worse.

I'm about 6ft3 and more lardy than is good for me - circa 17 stone. I don't have any racing bikes so I've not had to make the same choices as you. I am aware that I'm at the upper end of the design weight for bikes. When I recently got a tourer built up to my own spec I tried oversize 31mm diameter drop bars. The standard bars on my old bike would flex noticeably when I put any great effort into the pedals. The new bars feel reassuringly solid and with a double layer of bar tape are still comfortable. Less flex on critical alu components has to be a good idea if comfort is still acceptable

I think it is worth considering what bars and stems are used if you are bigger than average. The risk of failure may be low but it might only take one .............

[rogerzilla]

A lot of fore-and-aft flexing goes on at the fork crown due to road bumps, and this also flexes the steerer (this is why top headset races get pitted, although they don't carry as much weight as the bottom race). Failure is probably just due to fatigue, and alu has no fatigue limit. Steel does, and steel steerers are surprisingly heavy and thick, especially at the crown end, so should last a lifetime if brazed properly. Rule no.1 of bike component design should be: don't assume a lighter material can be substituted for steel when the dimensions can't be changed. Also see Ti pedal spindles, BB spindles and saddle rails, all of which are "contra-indicated" for the heavier rider.

[hamster]

A frightening thing to happen. Get well soon!

[CJ]

Poor you! Get well soon.

My bike is steel. I like it. I do have a Vitus frame in my workshop which is a joy to ride. Very light and comfortable despite having aggressive geometry. It is totally alu, and bonded too, not welded.

The thing is, it has a quill stem and 1" steerer. I feel that an alu steerer is ok providing it is quill. An Ahead system surely puts more strain on the steerer as it pokes out the top.

Am I right in this?

Sorry no. In order for an aluminium alloy tube to even come close to the fatigue strength of a typical steel bicycle steerer tube, it has to be made a bigger diameter and with thicker walls - even when the best aluminium alloy available for that purpose is chosen. Aluminium is really poor in fatigue, and fatigue is what kills forks - even good steel ones eventually.

Alloy frames have fatter tubes for a good reason, but the outer diameters of steerer tubes are dictated by the dimensions of other components that were standardised when steel was the only material choice. All the designer can do is make the walls thicker. To equal the stiffness of steel (flexibility is not an advantage in steerer tubes) he'll have to make them three times thicker, so the weight advantage of aluminium disappears. And even so, the fatigue resistance will remain far inferior to the likes of 531.

In the threadless design, it is at least possible to make the walls thicker - all you need is a smaller star-fangled wotsit. And that's how they make them when aluminium is used, but not usually three times as thick, so you get a more flexible and much less reliable steerer tube. But a 1.125in diameter threadless alloy might be just about reliable enough compared to a 1in threaded steel.

In the threaded design however, you can't even thicken the walls, since the quill has to go in there, at least at the top. Thicker lower down is possible, where the stress is greater, but you still have to deal with a stress concentration at the end of the stem.

Nope: the only way I'd like to have an alloy steerer and a quill stem is if the inside of the steerer were 7/8in diameter, i.e. sized for the sort of stem that goes with a 1in headset, whilst the outside was threaded for a 1.125 in headset!

[vorsprung]

What about a completely carbon fork with a carbon steerer, or one like I have with "full carbon steerer on an alloy crown" see here for more details

http://www.kinesisbikes.co.uk/product.php?id=19

[travelling]

There is a good discussion on the thorn forums about carbon forks might be of interest to a few

[pq]

My fixed bike has a 10 year old pair of Columbus Carve forks which have an alu steerer. Maybe I ought to get my credit card out, but with 1" forks, there aren't many options these days.

[rjb]

I thought the recent article in Cycle clips http://www.ctc.org.uk/DesktopModules/Ar ... &mid=13417 might have provoked a response from someone so here goes to restart it. Is anyone else concerned? Has anyone a solution to this problem?