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What's the benefits of carbon cranks over aluminum?

43K views 106 replies 43 participants last post by  Radical_53 
#1 · (Edited)
I'm shopping for some shorter cranks and figure I might as well look into an upgrade while I'm at it. My current cranks are the Truvativ Descendant Dub 6k set.

I'm either looking to go ahead and get a 7k series aluminum crank, or maybe even trying a carbon crank.

Is carbon even worth it? Will I feel a difference on the trail? Or are carbon cranks just for bling and weight savings?

EDIT: I should mention I am not the smoothest rider out there, so durability is an important factor.
 
#12 ·
I think your question should better be : What is the benefit of Aluminum over Carbon. The answer is : Aluminum cranks NEVER give you problems, and, are nearly just as light. Every single pair of carbon cranks I tried on my MTB failed in less than a single season. After the 3rd pair I went back to Aluminum and have never looked back. Aluminum cranks simply work, never fail, and never produce issues....and...are cheaper.
 
#16 ·
I think your question should better be : What is the benefit of Aluminum over Carbon. The answer is : Aluminum cranks NEVER give you problems,
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#20 ·
IMHO, a crank seems to be the most expensive and worst place to save weight unless your life depends on being on the podium. Low center of gravity. And when I look at my Al-cranks and see the battle scars, I'm glad it is not fragile. It looks like rocks don't move out of the way, no matter how often i hit them. Yes, carbon is strong for the design forces, but not for impacts.

Some people put protective sleeves over their Cf cranks. But they add weight.

This is just my personal opinion and thoughts. It is your money and you have to decide if the few gram are worth it. The above may not apply if you are a very good rider that coordinates crank position well to avoid rocks.

Crank is the one part I think I need to change at some point due to damage without actually crashing. So better not to put all my money in it.
 
#31 ·
A few thoughts...

SRAM GX Eagle cranks are $130 including a chainring. Weight is given with the ring. XO1 is sold w/o and weight is given w/o ring to make the difference seem larger. The difference is about 1/4 lb IRL vs carbon or eewings.

eewings look like the best solution but the price is wtf and carbon is unreliable, IME.

I think carbon cranks are more reliable when used with shorter clipless pedals. Flats or clips w/ big platforms will put far more torque on the pedal threads when the end of the pedal hits a rock.

Handlebars are the best use of carbon on a mtb because they damp vibration better than Al and don't fatigue. Same with the frame, but more tradeoffs.

For the vast majority of buyers, spending more than $130 on GX Al cranks seems like a waste of money. It's hard to argue carbon is as reliable and Ti is unreasonably priced.

I spent $135 on an AB PVD coated oval front chainring though, $5 more than the crankset, in hopes it'll last much longer than a std ring. I actually wanted to buy eewings, but just can't justify it. I don't think they are functionally better than GX Al.
 
#7 ·
I "feel" their stiffness. Maybe more so than any other part next to rims.
I'll second this sentiment. I find Al cranks to be overly flexy and harsh for my tastes. I'm a bigger guy who can put down decent power, so the flex is very noticeable. I also have a disdain for the trail feedback that comes through Al, preferring the ride feel of carbon.
 
#4 ·
Maybe you can feel the extra rigidity, but the weight savings is worth more than that. Weight savings isn't just a fashion choice or something and there is a solid 1/3# rotating to save there.
That said, CF cranks are a great choice for XC trail riding but I'd only consider Eewings for AM riding just because I've broken CF cranks.

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#34 ·
My Hollowgram SiSL2s are lighter than most carbon cranks, stiffer than most, and far more durable.
Longevity is suspect though, due to the nature of bonding of clam-shell style designs. They got to create a lot of surface area for the bond, especially in high-stress areas, without creating additional stress risers.

It's also difficult to insulate the bond from exposure to the environment and other real-world hazards that can weaken the bond (heat/cold, humidity, salt, solvents, oil).
 
#42 ·
I've only noticed cheap road cranks flex. Like really cheap old square tapers on lowest end bikes.

Even a $80 slx crank is crazy stiff. I bought my x01 mostly because I wanted an x01 crank. I can't feel a difference between it and any Shimano crank, but the price was right and I wanted a cool crankset.

High end cranks are a pretty colossal waste of money.
 
#69 ·
I've only noticed cheap road cranks flex. Like really cheap old square tapers on lowest end bikes.

Even a $80 slx crank is crazy stiff. I bought my x01 mostly because I wanted an x01 crank. I can't feel a difference between it and any Shimano crank, but the price was right and I wanted a cool crankset.

High end cranks are a pretty colossal waste of money.
I never felt a crank flex. Any frame flexes way before the cranks anyway.
 
#80 ·
Elastic deformation, sure.

Doubt a human pedaling can cause permanent deformation.

I figure that anyone in the MTB crank-making business should consider designing them to withstand getting caught on a rock with a ton of inertia (the kind of high-speed pedal strike that causes a crash). Not sure what other kind of abuse compares from normal riding.
 
#107 ·
I've been using a set of carbon cranks for years now, no issues yet. Benefits mainly? Stiffness. I'm tall, heavy, so a 30mm carbon axle & stiff crank arms really help. Q-factor is much nicer than regular Shimano was.
I'd always go for carbon again. Next builds are most likely featuring RF Next cranks, still deciding which type.
 
#3 ·
I'm not afraid of carbon, have tons of it on my bike. Cranks is the one place it's not worth it to me.
You can get AL cranks that as light as carbon. My Hollowgram SiSl2 are 460g with Wolftooth Camo spider and 32t oval.
I have a set of Rotor Kapic coming from Germany. Not as light but a good balance between price, weight and it's not carbon.
 
#5 ·
My 2018 carbon stumpy came with one of those truvativ descendant (non boost) cranksets. after splurging on axs eagle and all the xx1 bits, i came across a deal on a set of x01 cranks, so I figured why not...

i honestly have not once noticed any difference between the old alloy cranks and the shiny x01 carbons. I know they're lighter, supposedly stiffer, etc. but in real world use that was the most intangible upgrade I've ever made. I'd still do it again just because I like shiny things and even if I can't feel it, weight savings make the flabby parts of me happy. It also forced me to switch out the original pf30 BB for a dub compatible model, which in turn came in handy when i changed bikes last year.

I've known more than a few others who have upgraded to carbon cranks and feel the same way (most of them far more expereienced riders than me.)

No regrets regarding durability though. I slapped on the typical crank end boots on day 1 and despite running my Enduro flip chip in the low setting, and being a fairly crapy rider, the chunky az trails have yet to even destroy the cranks, or even scratch them.
 
#11 ·
I have mixed luck with carbon cranks. Have a pair of 7 year old X0 cranks which I love, and a pair of Raceface carbon cranks that gave out, got warranteed, then failed again.

I'm not sure I'm sold on it, definitely not when the focus is primarily on dropping weight. I've never noticed flex in AL, but never really thought about it either. I'll have to think on that.
 
#99 ·
Funny you say that, I had the exact opposite experience ... X01 came with my bike so didn't have much to compare to. Broke at the pedal insert after 2 months. I'm 155lbs but ride mostly park, so I abuse em quite a bit. Replaced with alloy RF Atlas cranks cause this was at Killington Bike Park and that's all they had in their shop.

Didn't notice a difference at all, and concluded that carbon cranks aren't worth the premium if your riding downhill, enduro, etc. Might make more sense for XC riders.

Also cracked my carbon handlebar and replaced with alloy Fatbars which have been great. In both components, I haven't noticed a difference in stiffness, feedback or weight.

The most noticeable difference was the X01 cranks cost $350 and RF Atlas are $185.!
 
#25 ·
What do people think about the Truvativ Descendant Carbon Eagle Dub crankset for $260? I know the weight savings aren't there. Any tangible differences for the minor price increase over the Dub 7k's? Is carbon that cheap is even worth it?
 
#28 ·
We swapped the aluminum SRAM NX cranks on my wife's bike to CF Truvativ Stylos (which I also have on my bike). I would estimate that shaved almost 1/4 lb off of her bike. Is it "worth it"? That's a matter of opinion with no right answer.

I snapped an aluminum Shimano LX crank arm in half on my commuter while sprinting away from a stoplight a few years back. It was an old crank and probably had a stress riser (nick) in the metal from years of use. But, everything can break.
 
#32 ·
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Shimano XT far stiffer than SRAM XO carbon. 102 N of force for each mm of flex/deflection vs 78 N.

Stiffness-to-weight is another story though. Between cranks of similar weight, cranks with large hollow sections were stiffer. Lightning/SWorks has some of the best stiffness-to-weight. Heavier cranks are generally stiffer.

Upgrade worthiness here more dependent on riding style. If you prefer to plow and cruise with stability, comfort, smoothness, steady-turtle-like pacing, etc. over being active with agility, playfulness, thrills, rapid-accelerating-rabbit-like pacing, etc. then it's generally a waste to spend money on lightweight cranks. Carbon is generally a compromise people make for the sake of lowering weight.
 
#33 ·
Shimano XT far stiffer than SRAM XO carbon. 102 N of force for each mm of flex/deflection vs 78 N.
I have to wonder here, is that the 30mm SRAM spindle? By the picture, it doesn't look like it. It looks like the 24mm.
 
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