Tribute to the strength of Lightweight wheels

Discuss light weight issues concerning road bikes & parts.
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rico
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Joined: Thu Jan 01, 2004 3:49 am
Location: Kingston, the heart of UK weenie-ism

by rico

I crashed in a race this morning. It was a violent crash, mid-sprint, only about 100m from the finish, involving eight or nine riders. My first thought when I sat up in the middle of the road was 'jeez I hope my bike's OK.'

The Lightweights remain perfectly true and there is not a scratch on them apart from a very slight section of the rim where the CF has delaminated slightly. This could not be said of some of the other wheels involved....

rico

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mrowkoob
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Joined: Thu Feb 26, 2004 7:35 pm
Location: Middle of nowhere, EU

by mrowkoob

So what´s the best price you have found in the Eu for a set of lightweights? I´ve noticed carbonsports are starting an online direct sale but no prices yet. Around 2000 Euros no?

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asphaltdude
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by asphaltdude

rico wrote:apart from a very slight section of the rim where the CF has delaminated slightly.


So you're gonna have to buy new wheels anyway :cry:
Damn...
Whow! That's a pretty damn nice garage door!

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martin
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by martin

asphaltdude wrote:
rico wrote:apart from a very slight section of the rim where the CF has delaminated slightly.


So you're gonna have to buy new wheels anyway :cry:
Damn...

Of course a specialist will have to have a look at them, but even carbon fibre parts can be repaired (ask any boat builder), if the damage's not structural.

Martin
Snowman and Strong Walker
Scott Sc
my old stuff
my new stuff

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rico
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Location: Kingston, the heart of UK weenie-ism

by rico

I don't think so - it looks cosmetic and it's certainly not structural. Either the LBS who sold me them will deal with it or (if the worst comes to it) I can get them sent back to the factory for a rebake.

PS Martin - what sort of spoke magnet is that on your LWs. Is it one of the Sigma ones that slides on?

rico

rom
Posts: 29
Joined: Thu Apr 15, 2004 12:00 am

by rom

I can't imagine any part of a lightweight wheel is not structural. If there is a nonstructural part, remove it and have lighterweight wheels. Also, you can not see underlying damage in composite structures. If it was a structural aircraft part it would be C scanned to find the hidden damage and then repaired or removed from service. In my opinion you should be very conservative when your health is at risk. Maybe you can get the wheels replaced for a nominal amount.

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Cyco
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Joined: Sat Nov 30, 2002 4:49 am

by Cyco

The quick and dirty check for delamonation:

1. Find a coin/spanner/screwdriver with a nice ring when tapped.

2. Hold area of composite part to be tested horizontal (this wont be to hard with a wheel, but frames are more difficult).

3. From a hight of approx 10mm (It is more important to keep the hight consistant then finding an exact hight) drop coin/object on surface.

4. It should ring on the good and thud on the delamonated parts.

5. As a rough check tap about every 30-50mm and when you hear thuding close the tap spacing to mark out the exact area of delamination.

Boeing uses a more expensive version of this technique to test their wings and flaps (theirs involves water jets and ultrasonic taps in the water stream).
Success is how far you you bounce back up after being knocked down

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martin
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by martin

rico wrote:I don't think so - it looks cosmetic and it's certainly not structural. Either the LBS who sold me them will deal with it or (if the worst comes to it) I can get them sent back to the factory for a rebake.

PS Martin - what sort of spoke magnet is that on your LWs. Is it one of the Sigma ones that slides on?

rico

Yes its the sigma, i had wrapped around a strap of scotch tape to secure it. But it is off the wheel now, i'm going to replace it with a Tune.
Martin
Snowman and Strong Walker
Scott Sc
my old stuff
my new stuff

veldt01
Posts: 58
Joined: Tue Mar 02, 2004 5:50 pm

by veldt01

How strange this may sound: most carbon parts should be exchanged after a (severe) crash.
Stem, fork and front wheel are the first thing you have to think of.
I had my Leightweight frontwheel crashed last year and the wheel looked perfectly fine afterwards, X rays however showed several internal cracks so ordering a new one was the only safe (read expensive) solution. Leightweights should be treated as any other cheaper carbon wheel and I guess this is the risk of racing (if you can't afford replacing just don't buy them). The other solution is to sell the parts after a crash through e-bay as I seen done by others several times.

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asphaltdude
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by asphaltdude

veldt01 wrote:The other solution is to sell the parts after a crash through e-bay as I seen done by others several times.


:shock: :lol:
Whow! That's a pretty damn nice garage door!

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divve
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by divve

I've heard of the technique before. I have a CF seat post that has a clearly visible indentation in a small section where it has been clamped by a frame for a year. It rings the same as any other part of the post and there no thud whatsoever. Does this mean the damage isn't structural? BTW, I'm not currently using the seat post anymore.

Cyco wrote:The quick and dirty check for delamonation:

1. Find a coin/spanner/screwdriver with a nice ring when tapped.

2. Hold area of composite part to be tested horizontal (this wont be to hard with a wheel, but frames are more difficult).

3. From a hight of approx 10mm (It is more important to keep the hight consistant then finding an exact hight) drop coin/object on surface.

4. It should ring on the good and thud on the delamonated parts.

5. As a rough check tap about every 30-50mm and when you hear thuding close the tap spacing to mark out the exact area of delamination.

Boeing uses a more expensive version of this technique to test their wings and flaps (theirs involves water jets and ultrasonic taps in the water stream).

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Cyco
Posts: 1903
Joined: Sat Nov 30, 2002 4:49 am

by Cyco

A part can undergo plastic defomation (creep) in a loaded situation.

With the slow onset of the deformation both metal and composite parts can oftern survive this. In some ways composite parts can survive the seat post clamp deformation better. The metal post can be more affected by the stress riser, and the reinforcing fibers in the composite post can redirect the load.
Success is how far you you bounce back up after being knocked down

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