front wheel flexes whilst climbing? cause

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bretonbikes
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Re: front wheel flexes whilst climbing? cause

Postby bretonbikes » 28 Jan 2018, 3:29pm

Brucey wrote:
bretonbikes wrote:....It seems you have several problems all combining;-) but the fact that your 'good' hub still rubs does point to the forks being at least partly to blame....


I agree. Believe it or not if the wheel itself is flexible (e.g. because of the narrow spaced flanges), a less stiff rim may result in less rim deflection between the brakes. This seems quite counterintuitive, but tests have borne this out.

I would suggest that you think about getting a replacement fork. One of the possible reasons for excessive flex in a fork is that it is falling apart.

cheers


If this is the case a Carbon fork can simply disappear in a shower of fibres - it's not a very nice failure mode... It may be that it's delaminating internally. Combine that to the affect of scratches in contributing to such failures and you have something totally unsuitable for the rough and tumble of touring (or for that matter anything but racing)...

See - http://www.rideyourbike.com/carbonfiber.shtml

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Gattonero
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Re: front wheel flexes whilst climbing? cause

Postby Gattonero » 28 Jan 2018, 3:53pm

Brucey wrote:...
I would suggest that you think about getting a replacement fork. One of the possible reasons for excessive flex in a fork is that it is falling apart.

cheers


Replacing things after a certain amount of use is a good thing, but to say that carbon-fiber forks are "falling apart" because of flex is mostly a wrong statement: if you've reached the point where the matrix of fiber+resin has disconnected, then it's a matter of minutes before the whole structure "falls apart".
Needless to say, this happens to various degrees according to the product (just like other metal structures, when badly engineered and manufactured, do fall apart) and the use. It takes a while before this happens, and when the structure is failing it will go fairly quick, but it needs to pass that point where the material has lost its resilience. I have never known composite materials to hang around with fatigue for long time, they will simply fail without much warning.
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Gattonero
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Re: front wheel flexes whilst climbing? cause

Postby Gattonero » 28 Jan 2018, 3:55pm

bretonbikes wrote:[...

If this is the case a Carbon fork can simply disappear in a shower of fibres - it's not a very nice failure mode... It may be that it's delaminating internally. Combine that to the affect of scratches in contributing to such failures and you have something totally unsuitable for the rough and tumble of touring (or for that matter anything but racing)...

See - http://www.rideyourbike.com/carbonfiber.shtml


It takes not "scratches" but deep gouges to damage some carbon-fiber forks. There's laquer and protective paint well before lots of layers of fiber, it really needs some abuse and negligence to make a permanent damage.
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

bretonbikes
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Re: front wheel flexes whilst climbing? cause

Postby bretonbikes » 28 Jan 2018, 5:31pm

Gattonero wrote:
bretonbikes wrote:[...

If this is the case a Carbon fork can simply disappear in a shower of fibres - it's not a very nice failure mode... It may be that it's delaminating internally. Combine that to the affect of scratches in contributing to such failures and you have something totally unsuitable for the rough and tumble of touring (or for that matter anything but racing)...

See - http://www.rideyourbike.com/carbonfiber.shtml


It takes not "scratches" but deep gouges to damage some carbon-fiber forks. There's laquer and protective paint well before lots of layers of fiber, it really needs some abuse and negligence to make a permanent damage.


That's not what I've been told (I admit no direct material science experience in this), nor supported by much evidence on the web - and that scratches in lacquer are the precursors of failure especially acting as stress risers or exposing the fibres directly - even though a scratch may look shallow, being transparent it may extend unnoticed deeply down to the fibres. Personally I don't know, but the comment in the article above that no frame or fork should ever be used for more than 10 years or ever if there is any external damage also causes me concern - not least because these sorts of frames tend to 'trickle down' to the less well-heeled and young where they may experience yet more damage exactly when thy are at their weakest. Of course the quality of CF varies hugely and addition of Kevlar etc can reduce the risk of catastrophic failure, but it's not a material I trust for my own use. However I am also aware that steel forks can fail and even more so that Aluminium has a problem with fatigue. My main worries with CF are this - damage is often not visible (bit like a crash helmet must always be replaced if you even just drop it) - on a steel bike you'll see dents or bent forks after a crash - if not it's OK - that's not the case with CF. And on tour, if the bike does get a ding in the fork or frame - do I carry on? On steel you're fine, on CF you are at risk. The OP seems to have a problem with that CF fork but it looks OK? that would be a worry.

I'm not anti-carbon by any means, If I were a world class time trialler I'd be on a CF bike tomorrow but I'm not...;-)

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Gattonero
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Re: front wheel flexes whilst climbing? cause

Postby Gattonero » 28 Jan 2018, 7:52pm

It sounds like you are over concerned.

I've "decomissioned" hundreds of CF forks on a "legal" basis, and let me tell you as much as they were deeply scratched and been straight and sound for the age/impact survived, it needs two strong men and two pieces of pipe to break them. They don't break that easy, in fact I prefer to cut them with a hacksaw as it takes too much to break them by hand :shock:
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

bretonbikes
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Re: front wheel flexes whilst climbing? cause

Postby bretonbikes » 28 Jan 2018, 10:18pm

Gattonero wrote:It sounds like you are over concerned.

I've "decomissioned" hundreds of CF forks on a "legal" basis, and let me tell you as much as they were deeply scratched and been straight and sound for the age/impact survived, it needs two strong men and two pieces of pipe to break them. They don't break that easy, in fact I prefer to cut them with a hacksaw as it takes too much to break them by hand :shock:

I bow to your experience;-) Just don't know how so much bad press has built up?

Brucey
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Re: front wheel flexes whilst climbing? cause

Postby Brucey » 28 Jan 2018, 10:31pm

FWIW the majority of carbon fork failures I have seen personally have arisen from degradation/weakness in/near adhesively bonded joints. They quite often get rather wobbly before they break completely, but they can break without any warning whether they were obviously wobbly beforehand or not.

Another possible reason for excessive wheel rim movement is that the fork is simply not very well engineered, and just isn't stiff enough, for your style of riding.

In any event replacing it seems like a pretty reasonable idea to me. Forks don't cost a fortune, don't last forever and a bad one will put you in hospital or in a wooden box. Breaking a blade is bad enough but if the steerer goes you are in the deepest poop imaginable. You can choose the new one to be as strong and as stiff as you like.

cheers
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NATURAL ANKLING
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Re: front wheel flexes whilst climbing? cause

Postby NATURAL ANKLING » 28 Jan 2018, 10:34pm

Hi,
Ah....somethings not right, needs fixing for sure.
If You Don't Try You Don't Do.....Don't Do You Don't Get...I'm Still Trying....Well Very..
You'll Find Me At The Top Of A Hill...............Somewhere...After Dark..

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Gattonero
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Re: front wheel flexes whilst climbing? cause

Postby Gattonero » 28 Jan 2018, 10:37pm

bretonbikes wrote:
Gattonero wrote:It sounds like you are over concerned.

I've "decomissioned" hundreds of CF forks on a "legal" basis, and let me tell you as much as they were deeply scratched and been straight and sound for the age/impact survived, it needs two strong men and two pieces of pipe to break them. They don't break that easy, in fact I prefer to cut them with a hacksaw as it takes too much to break them by hand :shock:

I bow to your experience;-) Just don't know how so much bad press has built up?


Pretty much ALL the failures are in regards of the joints -as said just above- with the join between steerer and fork crown being the most stressed and the one that would fail first. I'm yet to see some composite forks where the crown/steerer are intact and the blades have come off. Not that is a relieve, just sayin'
It is by riding a bicycle that you learn the contours of a country best,
since you have to sweat up the hills and coast down them.
Thus you remember them as they actually are...

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Re: front wheel flexes whilst climbing? cause

Postby martinn » 31 Jan 2018, 10:14pm

So, I spoke to the nice people who made my wheel originally, and asked if rebuilding the wheel with a Shimano N80 hub instead. They agreed and are only charging for the new spokes.
So could this help with reducing flexibility of the wheel

Martin

Brucey
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Re: front wheel flexes whilst climbing? cause

Postby Brucey » 31 Jan 2018, 10:19pm

Gattonero wrote: .... I'm yet to see some composite forks where the crown/steerer are intact and the blades have come off.....


I've seen several sets do exactly that.

cheers
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Brucey
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Re: front wheel flexes whilst climbing? cause

Postby Brucey » 31 Jan 2018, 10:38pm

martinn wrote: ...So could this help with reducing flexibility of the wheel...


well any hub with bearings that are not falling apart is going to be an improvement...?

cheers
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Samuel D
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Re: front wheel flexes whilst climbing? cause

Postby Samuel D » 31 Jan 2018, 11:14pm

Was it resolved whether the flex was the wheel, the fork, the bearings, or even the quick-release skewer allowing the axle to move in the drop-outs?

The Shimano hub has more widely spaced flanges so will be a bit stiffer for the same spoke count, type, and tension.

martinn
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Re: front wheel flexes whilst climbing? cause

Postby martinn » 4 Feb 2018, 4:25pm

Ok changed the QR skewer in the known to be good hub, and there is still some movement but only about 2-3mm lateral deflection each side.
The "bad" hub, by pushing on the axle, I could get this to visably move. This had 5mm plus lateral deflection each way with the same skewer fitted.

So I think bad hub is really bad, but the forks must also be playing a part. On reflection, when I had the original front wheel ( no dynamo) I could get it to move, but put this down to the low (20 hole) spoke count.
I put another wheel on for a short time, with 32 holes and this was significantly better, but there was still some movement.1-2mm max.

So in order to get a complete fix, given that the fork has always ( probably) had some lateral flex, I should replace the fork?. I don't think it's on its way out.
I am going to get the SP hub changed to a Shimano N80 hub.

Can I use any road fork? I would almost certainly go for carbon again. Any suggestions?

Many thanks

Martin

martinn
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Re: front wheel flexes whilst climbing? cause

Postby martinn » 9 Sep 2019, 7:50pm

Ok quick update,

I had my wheel rebuilt with another SP hub, it was too complicated for anything else, this solved the problem, however, after the last long ride that I did, I noticed on a subsequent short outing that the wheel was again rubbing on the brake blocks when I was climbing.

The communication from the wheel builder regarding the actual problem with the last hub, was that I had just completely destroyed the bearings in the hub.

Now as the problem has reoccurred in the same type of hub, with every other variable remaining essentially the same, I am assuming that the bearings in this hub have also been destroyed.
The original purchase of the SP is now over two years, and I was assuming that the original guarantee would therefor no longer be valid.
I am left with the choice of either purchasing a brand new SP hub, and accepting that I will probably only get two years from it, using a Shimano hub, and accepting the increase in comparative resistance, or purchasing a Son Delux hub with a wide flange

Would the change in flange size make a difference?
What rim would you use? this is for a old style Audax bike for want of a better description max tyre width is 28mm with mudguards
I like the Archytpe H-plus son rims.

Interestingly, I have another dynamo hub on my commuter (Fixed wheel) that has a USE dynamo hub, which looks the same and I believe its either built by SP or built under license by USE, which gets a lot of abuse (I climb a "strava cat 4 hill" each day on my commute). the rim is a DT swiss 440, again using 28mm tyres, and there is minimal flex in this wheel. this is now two years old, and was secondhand when i purchased it.
The forks on this bike are steel (531 I think).
So is the USE hub of greater strength than the SP hub or could it be the rim/ hub combination or could the difference in fork material have any bearing (Carbon vs steel)?

( I like the fit and forget aspect to dynamo lighting, and regularly forget to charge USB lights and have limited luck with battery lights)

Many thanks

Martin