Carbon rims for touring
12-04-21, 09:31 AM
#51
Senior Member
stae, thats kind of how I look at it too.
my one concern is flying with carbon stuff, as a shifted item in a box could easily end up with a metallic bit being crunched into a carbon wheel or whatever during a very possible side crush type impact to a travelling bike box---a way more tricky situation to find yourself in when unboxing the bike in wherever you've flown to......
but ya, even I wouldnt be concerned with carbon wheels now, as I've written before, how they get the living crap beaten out of them by mountain bikers.
my one concern is flying with carbon stuff, as a shifted item in a box could easily end up with a metallic bit being crunched into a carbon wheel or whatever during a very possible side crush type impact to a travelling bike box---a way more tricky situation to find yourself in when unboxing the bike in wherever you've flown to......
but ya, even I wouldnt be concerned with carbon wheels now, as I've written before, how they get the living crap beaten out of them by mountain bikers.
12-04-21, 09:55 AM
#52
Senior Member
Carbon>>aluminum
Strength is not determined by the spokes.
Most spoke failures are due to insufficient tension. Obtaining sufficient tension is never a problem with carbon rims.
Aluminum will bent. Carbon will not. Truing wheels is a thing of the past with carbon rims.
https://www.bikeforums.net/20740244-post16.html
Here is a good visual
https://www.youtube.com/watch?v=VfjjiHGuHoc
2-5X stronger, sorry the exact number depends on the weave, epoxy, and amount of material used but if Danny's video is not convincing, nothing will....
https://smicomposites.com/carbon-fib...w-they-differ/
Strength is not determined by the spokes.
Most spoke failures are due to insufficient tension. Obtaining sufficient tension is never a problem with carbon rims.
Aluminum will bent. Carbon will not. Truing wheels is a thing of the past with carbon rims.
https://www.bikeforums.net/20740244-post16.html
Here is a good visual
https://www.youtube.com/watch?v=VfjjiHGuHoc
2-5X stronger, sorry the exact number depends on the weave, epoxy, and amount of material used but if Danny's video is not convincing, nothing will....
https://smicomposites.com/carbon-fib...w-they-differ/
Also that's not how wheels or carbon works.
The reasons why spokes break are complex. Insufficient tension is one, but too much loading can also cause breakages. You'll get a lot of loading with low spoke count wheels. Also while some carbon wheels can handle severely high tensions, it's inadvisable to crank the spokes up to 1500N or more. The nipple threads may not be able to handle it and it's just a general pain to do any maintenance afterwards.
What matters more than rim material is lateral geometry, spoke count and rim stiffness. Modern alu touring rims are stiff enough, that in terms of durability you'll get marginal gains from increased rim stiffness in carbon wheels. Which you'll only really get with higher profile rims.
Carbon also isn't 3-5x stronger in a finished product. Strong isn't a measure of anything. It has higher tensile strength per weight ratio and higher stiffness per weight. But both are directional, meaning it takes some care in layup and otherwise to achieve same stiffnesses as aluminum at the same weight. If you compare finished carbon frames or components against their metal equivalents, you'll notice that the carbon part is not in fact 3-5x stiffer or stronger. The differences are in fact surprisingly modest. Because of that directional aspect of carbon fiber we're talking about increases of only 20-30%. And that's if the layup is done well. With cheap carbon there's no telling.
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