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PostPosted: Sat Feb 19, 2011 8:24 am 
Dirt Disciple

Joined: Tue Sep 22, 2009 3:20 pm
Posts: 68
I've bought some new wheels (Kooka Carba) described as full carbon.

The wheels have red decals and my bike is blue so decided to take them off using a hair dryer and credit card. The carbon rim has warped under the heat and I didn't think it would do this!

Does this mean the wheels are only carbon wrap? Would poper carbon do this?

The braking rim is alloy and the inside of the wheel where the spokes connect is alos alloy so it makes me think the whole wheels is with just some wrap around the outside.

Cheers


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PostPosted: Sat Feb 19, 2011 9:53 am 
Retro Guru
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Joined: Tue Mar 30, 2010 4:04 pm
Posts: 686
Location: Way Up In The Norfolk Mountains
Sounds like they are similar to the old HED wheels. The carbon is just an aerodynamic fairing, not structural in any way. If it flexes slightly as you squeeze it near the rim apex, that means the spokes just go straight through it.


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PostPosted: Sat Feb 19, 2011 10:49 am 
Retro Guru

Joined: Mon Feb 01, 2010 8:57 pm
Posts: 774
Structural carbon uses a thermo-set resin so would be unaffected by heat - sounds as though your rims are alloy with an aero fairing which is quite common and using a thermo-plastic resin which has obviously distorted. If the spoke nipple is secured in the alloy rim, then you've probably little to worry about structurally, just a wonky rim. I'm not sure whether you'd be able to restore its shape though.


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PostPosted: Sat Feb 19, 2011 2:10 pm 
Retro Guru

Joined: Mon Jan 15, 2007 12:12 am
Posts: 1513
Location: Gold Coast Australia
Thermoset resins like epoxy will distort with a lot of heat (less than Thermoplastics need actually) but the thermoset resin matrix will not be able to be re-shaped like thermoplastics should (in theory anyway)

Hard to tell from your post but Is the carbon part of the structure ?

These wheels ? http://grahamweighcycles.co.uk/gwcshop/ ... roduct=401


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PostPosted: Sat Feb 19, 2011 8:57 pm 
Dirt Disciple

Joined: Tue Sep 22, 2009 3:20 pm
Posts: 68
Hi, Cheers for the posts. There the wheels. It's the carbon part that distorted. i.e. where the stickers are.

I've found that nail varnish remover gets rid if the stickers/paint. Just a bit anoyed that I bought carbon wheels only to find out that they appear to be alloy with a carbon rap.


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PostPosted: Sun Feb 20, 2011 5:29 am 
Retro Guru

Joined: Mon Jan 15, 2007 12:12 am
Posts: 1513
Location: Gold Coast Australia
It has only been recently that a high pressures hook bead was able to get moulded into a full carbon clincher so alloy under carbon became the de facto standard for those rims , they also have to consider pressures from the spokes tension and the friction on the braking surface as well as how heat created by the brake pads affect everything (like softening/distortion of the epoxy and increased pressure in the inner tube)


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PostPosted: Sun Feb 27, 2011 2:20 am 
Newbie

Joined: Sat Feb 26, 2011 10:13 pm
Posts: 5
carbon fibre


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