Convince me on carbon fibre rims

Discuss light weight issues concerning mountain bikes & parts.

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whyamihere
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Joined: Tue Aug 05, 2008 7:18 pm

by whyamihere

I'm looking to build up a new XC wheelset, most likely using Hope Pro 4 hubs and DT Revolution spokes. I just need to choose the rims. I'm far from a small chap (currently a little under 90kg), so super light alloy rims like Crests are out. I've been looking at the DT Swiss rims, mostly the XR361, but I'm also tempted by carbon rims, such as these from Nextie or these (standard) from Light Bicycle.

The carbon options will be about twice the price of the alloy DTs, but will trim a (tiny) bit of weight, allow higher spoke tensions and presumably be stiffer and stronger. I imagine this would allow me to get away with fewer, lighter spokes. However, will this make enough of a difference to be worth doing? The price difference could get me some other nice upgrades.

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wheelsONfire
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by wheelsONfire

It's easier to have to the alu rims bent and even crack them if you use tubeless tires. This, if you use a bit over-pressure when you seat tires on the rims.
Carbon rims are more prone to handle much higher pressure than it's alu dito.
Otherwise, carbon rims should be stiffer, talking stiffness to weight.
With that out, if you're 90kg´s, you shouldn't buy the most light weight rims.
They should handle your weight fully dressed + the bike weight and possible extras you carry along.
Let's say bike is 10Kg, you 93kg dressed. Then rims should handle 103kg´s minimum.
The rest is your call!
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LeDuke
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by LeDuke

whyamihere wrote:I'm looking to build up a new XC wheelset, most likely using Hope Pro 4 hubs and DT Revolution spokes. I just need to choose the rims. I'm far from a small chap (currently a little under 90kg), so super light alloy rims like Crests are out. I've been looking at the DT Swiss rims, mostly the XR361, but I'm also tempted by carbon rims, such as these from Nextie or these (standard) from Light Bicycle.

The carbon options will be about twice the price of the alloy DTs, but will trim a (tiny) bit of weight, allow higher spoke tensions and presumably be stiffer and stronger. I imagine this would allow me to get away with fewer, lighter spokes. However, will this make enough of a difference to be worth doing? The price difference could get me some other nice upgrades.


I'd just like to point out that higher spoke tensions will NOT make a wheel stiffer.

Hub geometry, spoke thickness, and the rim? Yes. Those will impact wheel stiffness.

FWIW, I have several sets of LB rims. Good stuff. No complaints at all.

bikewithnoname
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by bikewithnoname

I've some Light Bicycle rims on one of my road bikes, very nice quality product, my wheel builder was very impressed with thier straightness and finishing and I've no complaints with how they ride.

WRT carbon MTB rims, I've ridden enves in the past and genuinely didn't notice any real benefit vs Alu other than looking awesome
"We live in an age when unnecessary things are our only necessities." Oscar Wilde

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MikeD
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by MikeD

wheelsONfire wrote:It's easier to have to the alu rims bent and even crack them if you use tubeless tires. This, if you use a bit over-pressure when you seat tires on the rims.


What?



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whyamihere
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by whyamihere

LeDuke wrote:I'd just like to point out that higher spoke tensions will NOT make a wheel stiffer.

I'd just like to point out that I didn't say it would. :wink:

To be honest, I think I was already convinced, just wanted to validate my own thinking. I think I'll be going for the Nexties, just because of the slightly higher weight limit. I'm not planning to be this weight for long, but no point in having wheels I can't ride if my weight loss isn't as good as I want it to be.

Jaker
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by Jaker

I definitely noticed a huge difference in the ability to hold my riding line A LOT better with my carbon front rim over the aluminum rim that it replaced. That is entirely due to the significant increase in stiffness of the wheel build-up with the carbon rim.

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wheelsONfire
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by wheelsONfire

MikeD wrote:
wheelsONfire wrote:It's easier to have to the alu rims bent and even crack them if you use tubeless tires. This, if you use a bit over-pressure when you seat tires on the rims.


What?



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Do you want to me to express myself a bit clearer?

It's more easy for an aluminium rim to become bent or untrue.
It's also easier to crack an aluminium rim if you inflate it to much, while seating a tubeless tire (most likely using compressor)
For instance, if maxiumum pressure is 3 bar and you go over this, the rim can crack.

Does this make it easier?
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MikeD
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by MikeD

wheelsONfire wrote:
MikeD wrote:
wheelsONfire wrote:It's easier to have to the alu rims bent and even crack them if you use tubeless tires. This, if you use a bit over-pressure when you seat tires on the rims.


What?



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Do you want to me to express myself a bit clearer?

It's more easy for an aluminium rim to become bent or untrue.
It's also easier to crack an aluminium rim if you inflate it to much, while seating a tubeless tire (most likely using compressor)
For instance, if maxiumum pressure is 3 bar and you go over this, the rim can crack.

Does this make it easier?


No, I never heard of a rim cracking by inflating a tire unless the sidewalls were seriously worn down (doesn't happen with disc brakes anyway) or the rim was otherwise damaged in some way, so I'm calling BS on this one.

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wheelsONfire
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by wheelsONfire

Oki Mike, I wish i could agree with you. But, you are dead wrong on this one.
I know for a fact that they can crack cause i have had one do exactly that.
Not even using a compressor.
That was a new rim, only had 3 short routes on it.
I also know for a fact that others have had it happen to.
Not only do i know persons which it has happened to, i know if from a wheelbuilder building wheels even for pro team riders.
I know it from talking to No tubes and Ryde. So you can call it BS all you want, but in this case you are sadly wrong.

EDIT: Yes yes yes, in these cases i can also say, these were disc brake wheels.
MTB wheels and wheels built for gravel/ road
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bikewithnoname
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by bikewithnoname

Just to chime in, in my 27 years of mountain biking the only time I've seen an Alu rim crack is through the application of extreme prejudice in the form of a tree, rock, car or wall. Sure I've seen ripped spokes ruin both Alu and carbon rims, and I've seen rock strikes ruin both types of rim but WTF are you doing to your wheels to crack a rim with a compressor?? 150psi or something??
Last edited by bikewithnoname on Tue Jul 04, 2017 5:11 pm, edited 1 time in total.
"We live in an age when unnecessary things are our only necessities." Oscar Wilde

Pegoretti Responsorium, Parlee Z5i, Donhou Commuter, 1946 MacLeans Featherweight L'Eroica!, 2x MTB 'dales

TheRookie
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by TheRookie

MTB rims tend to be thicker than road rims which regularly are inflated to 120psi and probably hit peaks of 200psi on bumps, I call BS. I suspect your rim was defective and going to fail for some reason or other in no time at all.

I have Stans Alpine rims on my bike with a silly low weight limit (75Kg as I recall), no issues despite being my first ever wheel build and weighing in at circa 90Kg ready to ride. Been using them for 3 years on local rides with steps and at trail centres.

That said my next wheel build will be carbon.
Impoverished weight weenie wanna-be!
Budget 26" HT build viewtopic.php?f=10&t=110956

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wheelsONfire
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by wheelsONfire

The tire in my case, didn't seat at low pressure, no compressor used.
About 75psi i think, then rim cracked. Yes, i have heard before, that it has happened pending on what width of tire and what pressure.
Spoke to both wheelbuilder and No tubes and Ryde. They say it has happened, but not usual.
Also know people who have have alu rims bent while cycling. Probably doing jumps hitting something.
Any case, it has just happened once to me. So i was estranged, i admit that is why i checked it up.
I would guess No tubes, Ryde and wheelbuilder have lots of more contact with people than any private person.
I also realize it's not very common, never the less, it has happened and it can happen.
A carbon rim, in these cases, will hold better.
If it's strange and / or if any of you not have it happen, i'm glad for you.
But to say it's BS, that is BS.

It's not like i'm trying to sell anyone carbon rims with a made up story.
So why would i write it down if not true?
To tell a a story for fun or?
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Ax Lightness Vial EVO D
Paduano Racing Fidia
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MikeD
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by MikeD

wheelsONfire wrote:The tire in my case, didn't seat at low pressure, no compressor used.
About 75psi i think, then rim cracked. Yes, i have heard before, that it has happened pending on what width of tire and what pressure.
Spoke to both wheelbuilder and No tubes and Ryde. They say it has happened, but not usual.
Also know people who have have alu rims bent while cycling. Probably doing jumps hitting something.
Any case, it has just happened once to me. So i was estranged, i admit that is why i checked it up.
I would guess No tubes, Ryde and wheelbuilder have lots of more contact with people than any private person.
I also realize it's not very common, never the less, it has happened and it can happen.
A carbon rim, in these cases, will hold better.
If it's strange and / or if any of you not have it happen, i'm glad for you.
But to say it's BS, that is BS.


That's the most bogus reason ever to choose a carbon rim over aluminum. Come on man. Maybe if you didn't use that crowbar to mount your tire...


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wheelsONfire
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by wheelsONfire

It has absolutelly nothing to do with the mounting or the tools.
Which was fingers and profile designs tire levers.
http://www.profile-design.com/product/a ... re-levers/

Actually, my first thought was, going light weight, i should have stuck to carbon.
Did it also slip you totally that i actually asked both No tubes, Ryde, and wheelbuilder.
Bikes:

Ax Lightness Vial EVO D
Paduano Racing Fidia
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