tyrion

https://www.redbull.com/gb-en/red-hook-crit

WhyFi

Yeah, but which half?!

MoAlpha

Thanks. Interesting. Completely out of it.

aclinjury

carbon rims can be stronger than alu rims, provided the carbon rims are not made light, which unfortunately is what many carbon road rims go for, lightweight. Lightweight carbon rims definitely are more fragile than your typical alu rims.
But there are also heavy duty carbon rims made for mtb use that are stronger than alu rims, but in the roadie world, a heavy carbon rim just ain't gonna sell

colnago62

Carbon Wheels have been around a long time. Remember Spinnergys, the Specialized Tri spokes?

cycledogg

I have a set of Mavic Open Pro CD and Mavic MA2 wheels, both laced to Shimano Ultegra hubs, both doing well. Hand built in the late 90's. As just mentioned, Spinergy Rev-X wheels were the cutting edge (no pun intended) back in the 90's. IIRC Now, if you want to bump up the years some, again, which would you rather buy, a used set of 10 year old carbon wheels or a used set of 10 year old alloy wheels. I would still get the alloy. JMHO

downhillmaster

What makes that different than any other BF thread?
A&S is 88% made up.

Seattle Forrest

Are you saying that if you want to buy a wheel that someone else has been using for decades, the cheaper option is what you might go with?

cycledogg

What I'm saying is alloy wheels in my opinion last longer than carbon wheels. And if I were given a choice of the two, considering age, I would spend my money on the alloy set.

WhyFi

If I were given the choice between a 10-year-old set of alloy wheels and a 10-year-old set of carbon wheels, I'd slap myself upside the head for even considering a 10-year-old set of wheels.

SuperPershing

Uhhhh this escalated quick. Guess some good infos and insights. But "Half of it is made up" so... oof. I just fear that i will waste my money cause i cant true my carbon wheels back like a alloy rim would. And btw, im planning to buy that quarter minim carbon clinchers in 38mm.

Seattle Forrest

You can true carbon wheels.

The rim won't bend (permanently). If you hit something, like a pothole or whatever, here's what might happen, in order of how much force is involved:

1. Nothing. The wheel will stay true. This is what usually happens.
2. A spoke can unwind, it'll pull the wheel out of true until you fix the tension. The wheel will come back into perfect true.
3. Your wheel will break.

Alloy and carbon rims are both breakable, if you hit then hard enough. A metal rim can be bent to the point where it can't be pulled back into perfect true, but that doesn't happen with carbon. Either it'll break, or it'll come back to shape.

BluFalconActual

I know these are mountain bike wheels, but it shows that carbon wheels can be built really tough if the manufacturer decides to.
For the record, my carbon Vision Metrons have been absolute tanks.

peterraymond

Carbon material has a higher strength to weight, so if you replaced aluminum with the same weight of carbon, the wheels would be stronger. That is, the carbon could take a larger load before the material limits were reached. However, carbon also has higher stiffness, so the same amount of deflection produces higher loads.

But, at one level, there's no competition. You can adjust the design for the same weight and higher strength for every scenario, the same strength and lighter weight, or some combination of the two.

This of course doesn't tell you how well the wheel was designed, or built.

The only simple answer is "it depends". I did see a fatigue test of carbon, aluminum and steel frames. The heaviest frame was steel and it had the shortest life. The lightest frame was carbon and it lasted the longest. The reality is that if you want to get the lightest possible part in any material, the strength will then be compromised, but a higher performance material will set the trade-off at a higher point.

I can't really speak to life, but carbon can certainly be strong. That's what Formula 1 race car crash protection is made out of and F1 probably has the best safety technology in the world.

Duragrouch

There are several criteria for rim design materials:

- Yield Strength: How much the rim can deflect before yielding, but not fracturing.
- Ultimate Tensile Strength: How much the rim can deflect before fracturing.
*Note*: For "graceful degradation" failure mode, you want some "spread" between Yield and Ultimate strength, as that absorbs energy, and the rim may flat-spot, ruining it, but not completely falling apart, thus possibly avoiding a crash.

- Fatigue Strength: Resistance to cracking from cyclic (fluctuating) loading below the yield strength of the material.
- Stiffness (within the elastic range below the yield strength limit: Completely separate from strength.
- Heat resistance: Temperature at which the material begins to weaken.
- Heat transfer: Ability to dissipate braking heat (does not apply if disc brakes instead of rim brakes).
- Hardness and abrasion resistance to brake pads: (also does not apply if disc brakes instead of rim brakes).

OK now. Let's sort this out.

+ Carbon is light and very strong for its weight. There is virtually no spread between yield and fatigue strength limit, its only failure mode is complete fracture. But the strength is high enough that at that load level, an aluminum rim would probably crumple as well.
+ Carbon is stiff *IF* the fibers are oriented in the correct direction. In fact, for some applications where you want stiff in one direction but softer in another direction (frames, for a good ride), carbon is spectacular compared to "isotropic" materials that have all the strength equal in all directions.
+ Carbon has fantastic fatigue resistance, especially compared to aluminum (which has no "fatigue limit", no stress level below which the rim will never fatigue. Aluminum will always fatigue eventually, it's just a question whether you get radial cracks at the spoke holes in 3 years or 100 years of riding*.)
- Carbon has terrible heat transfer and heat resistance (of the resin holding the carbon fibers together, not the fibers themselves) and abrasion resistance. If you have rim brakes and use them hard, like on a tandem touring over mountains, or a mountain or cross bike braking often in mud, you don't want carbon rims. In those respects, carbon rims are strictly for race/performance road bikes with meticulous brake pad cleaning to keep them clean from grit. Aluminum doesn't have tons of heat resistance either, it can begin to weaken below 300 degrees F, but it has superb heat transfer so you really have to abuse it to get it hot enough to hurt it, but it can be done. Even if not the whole rim, you can get local heating on the rim walls enough to weaken and cause problems like galling, but both are helped by hard anodizing for a harder surface and a grippier texture for the brake pads so more effective, less pressure needed.

* Each 10% reduction in stress roughly doubles the fatigue life. Using double-socketed rims that tie the spoke nipple into both inner and outer walls of the rim cuts stress in half, and even more because the sockets are wide and spread the load. But just cutting in half results in 2^^5 = 32X increase in fatigue strength (50%/10% = 5). The rims last practically forever. But they weigh a lot more due to all the steel sockets, and at the rim where it also increases rotating inertia.

SO... MY VIEW: Carbon rims can be great for a road race bike with frequent brake pad maintenance, or a road bike with disc brakes. In those cases, you will get the performance advantages of carbon (less weight), and the rims may be more durable over time. Otherwise, I would not use carbon rims due to the issues noted above.

cycledogg

Which will last longer? Carbon or alloy wheels? That's my concern.

woodcraft

Carbon rims will stay more true and be easier to get back to true than alloy ones.

On that score there's no contest.

cycledogg

Disagree. All my carbon rims are not accurate smooth. With in tolerance, yes, but true as my alloy rims, no. I can true up an alloy rim within .05mm. Carbon not so much. The brake surface on a carbon rim has too much variance to get within a .50mm all the way round. Plus, my alloy rims stay true much longer than the carbon rims. YMMV

Seattle Forrest

Yep. Absolutely.

woodcraft

Huh.

IME, alloy rims deform & then take lots of variation in spoke tension to true, which tends not to last,

where carbon rims pretty much stay whatever shape they were made so they will go back to that shape with less input.

fietsbob

What kind if thrashing to you plan on subjecting the wheels to?

Psimet2001 

Yeesh....lots of half info in here. Now I understand how scientists and medical professionals feel when people talk about science or medical issues.
^-- This.

Carbon is just a material. We use carbon fiber layups (a composite of carbon fiber weaves and resins) to make carbon components. Taken on it's own carbon is a lot "stronger" than aluminum. This allows us in the industry to build more complex shapes in wider and deeper depths at lower weight for the same or improved strength.

Nothing will fix a bad design though. You can have that with any material.

Psimet2001 

Ooooooo this one makes me sweat a little.

1. This has been discussed in many ways on lots of different threads. The better threads are on the actual racing forum.
2. There are some who will continue to say aero/deep over weight in crits. Those are usually the people who get to experience a crit off the front a lot. Those who don't will appreciate something lighter at the rim that will accelerate a bit snappier.
3. "Better sustain speed for crits" - is achieved by better positioning and better/smoother/lighter braking - not through wheel depth. You would know that if you raced crits though.
4. I'm just gonna yell troll on this one BUT there are some out there that I can feasibly see asking this as a question. Your answers are in this thread. Beware the tons of misinformation though. You came to a collection of random people on the internet with a science question. you get what you get.

Psimet2001 

This one causes me to break out in hives.

Carbon rims, on average, are orders of magnitude straighter and more consistent out of the box than aluminum rims are.
The fact that you say you can "I can true up an alloy rim within .05mm." demonstrates that this is something you seemingly have to do often and I assure you that if you true all of your aluminum rims to under 0.05mm that your tension variance is so high that you're rims are going out of true often when being ridden or you're paying an immense ton of money on your rims. Quite simply the extrusion process for creating an aluminum rim is highly prone to small issues that the vast majority of extruders just can not control. These small variances in something as little extrusion pressure can greatly affect wall thickness variance. That variance can be in spec but will require a large tension variance in the spokes in order to maintain true. All looks good on the stand then you ride it...womp womp.

To top this off the process for forming the extrusions into a round rim and then connecting the two ends (pinning, sleeving, welding, etc) is by it's nature another natural point in which small variances are introduced into the rim's shape. Back long ago all the Kinlin XR300 rims of which we sold 1,000+ all had the same slight low spot about an inch from the rim joint. Turns out that's where they had a clamp holding it while joining. It was consistent, repeatable and introduced a tension variance that you had to handle a certain way.

Carbon rims deviate from this immensely. While they do have variances - like all manufactured items - the number of them that you can simply bring up to tension and have be almost at finish spec initially is astonishing. The rims are way more consistent. They don't change through use like aluminum rims do as well.

I have piles of aluminum rims that have been rejected due to variances being bad enough to prevent me from being able to build with them. Not so with carbon. Lucky for me I get to stretch tubulars on them.

Psimet2001 

This.