Carbon vs Aluminum Frames - Which is Stronger?

5 years ago we had the go-ahead to visit their test lab, a room that, until now, had always been off limits to photo and video cameras. Joe Graney, head engineer at Santa Cruz Bikes, not only opened the doors for us, but also fired up their custom test machines for some bad-ass destructive 'research'.

Putting frames through their paces until they fail is not unusual, every manufacturer goes through this process. Allowing the likes of us in to film however is far from common. This is especially true when it comes to carbon. Fortunately for us, Santa Cruz was feeling a bit more open minded during our visit, pitting an aluminum Nomad frame against their carbon version in a battle to the death.

The goal: destroy both, discovering which one took more force to break in the process.

#mtb #moutainbiking

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[aslief]

2:14 *frame destroyed*
*some people : "woohh nice"
*me : "wohhh thats hurts"

[MrChangCJ]

Aluminium fails slowly, allowing one to detect problems before anything too serious happens. But carbon fails catastrophically (sudden snapping), which is way more dangerous to the rider.

[gedons]

The "smash the frame against concrete"-test at the end is majorly misleading.

A carbon frame that suffered from these impacts might feel safe in the hand and not show visible damage but internally those impacts lead to delamination which will result in cracks. As those delaminations are not visible it is a high risk for a rider to use a frame that suffered from such an impact yet from the outside you will not be able to tell if the frame is damaged. This is a reason why more and more companies offer carbon-bike inspection by using x-ray, ultrasound etc. to detect internal damage. This however was costly if performed after each (even minor) crash.

For that reason aluminium-frames are much safer in that way, that you can easily detect damage from the outside.
Furthermore quality-control is a major issue in the production of carbon frames. As carbon frames are assembled by hand even the tiniest imperfections (air bubbles, wrinkles, missalignment) can lead to major structural deficits.

Lastly the first tests shown in this video are also not quite fair in that regard, that major damage to the carbon frame happens before the sudden cracking. If you listen to it carefully you can here the fibres bursting much sooner (at forces similarly to the aluminium frame). Those cracking sounds indicated damage to the bike that would already render it unsafe.

In conclusion this video can lead to a quite wrong impression about carbon fiber strength. Ultimately carbon is more vulnerable to sharp impacts and are much more costly to inspect. Fatigue cant be assesed that easily either.

[pedrogoncalves]

On the first test the carbon frame was delaminating way before it snapped.
Once it starts to delaminate its over...
Carbon and aluminium have diferent properties. Simply saying carbon is stronger is VERY misleading.

[stevenleslie]

I would love to see a modern steel frame go through these tests

[DanRC]

I'm SO glad i watched this.
I know carbon fibre frames are significantly stiffer, but i presumed they'd fail catastrophically under a similar impact compared to aluminium.
I've seen so many competition level frames and wheels fail in a unnerving way, that it'd put most people off wanting to use carbon.
This clearly shows a good strong carbon frame with the correct weight and build for its purpose is HIGHLY durable.

[MTBIKEXC]

Casing a jump a lot of times goes the other way, like if you land on the flat, that causes the forces to try to spread the wheels apart rather than together. Hope those frames are strong in both directions.

[jdub]

Not wearing safety glasses is not very smart when testing to failure.

[JonathanFisherS]

For the weight drop test, AL frame failed with roughly ~170 joule impact, the C frame failed with ~440 joule impact, which is over 2x. Pretty cool

[RideBikes_Walkplaces]

The carbon one sounded like it had strands cracking before the aluminium one actually failed. Surly lots of smaller impacts at that load could cause significant unseen weakness?

[mithrandirtheistari]

This is an old video, no idea why they reposted it. Tests on this video were on the old Nomad2 platform while Nomad4 is around the corner. This would be interesting to redo to see how/if stiffness has improved on the new N4 platform.

[cup_and_cone]

in the first test, the carbon sounded like it was delaminating/cracking way earlier than the aluminum failed. you tested to total failure rather than stopping and assessing, but I bet the carbon gained defects way before the aluminum failed.

[Ripstop_pilot]

youll still be riding home on a bent ally frame. broken carbon is a walk home with a bike in 2 pieces.

[theoutsmarter]

At the end of the day, regardless of Alu or Carb, both frames are f-ing strong, and you prob will never break e'm. Ever.

[zachaxel]

They should have tested direct frame strikes for dents, cracks, stone strikes etc and lets see how the frame really holds as its the most common scenarios that happen when you crash in the trail..

[Mickofalltrades]

The first crackle at like 750lbs that CF frame lost strength.

[electricdeckhead]

carbon hides internal delamination well, which for me is just as dangerous as a bent or cracked alloy frame, aluminium has the win for me, if I was a sponsored rider carbon all day please.

[robbieroscoe]

I love the way you start with a very formal scientific controlled area and end smashing it against a corner

[curtmastor]

Was a Santa Cruz fanboy until I saw this. These guys mke sick looking bikes though.  I hope they played coy, and the SC engineers aren't this clueless.  Carbon microcraks and delaminates instead of bending or warping. Yes it exploded at a much higher pressure point than the aluminum but if you stopped the test for carbon at the failure point for aluminum and testing it with ultrasound you would see just how misleading this video is.  MTB pros use carbon not simply for the weight savings but for torsional stiffness, and its ability to do just intact at a further point in its structural failure.  When your racing a 3 min downhill and you hit a big jump wrong, youll be able to finish on carbon where as alloy will probably warp or bend.   Doesn't mean the frame is any less broken though, just more rideable enough to finish.  Works for the pros who will just swap a questionable frame out anyway, not so much for the dentist being a warrior on the weekends.

[getsomemtb]

But the carbon started popping around 500lbs and we know how one fracture can lead to catastrophe. I stick with aluminum.