ZRace RX crankset - broken

[Linsook]

After ~3000km, they've decided to die.  I've not been particularly gentle or rough on them, used them like I would any crankset - rain or shine, road or gravel.  I was on my trainer with them just starting my session and it gave way at 350 watts, something like that. 

[hagerd]

Yikes, first failure I've seen of this crank. Its a shame because its one of the only 29mm spindle cranksets on aliexpress that's reasonably lightweight.

edit: looks like a similar failure linked here: https://www.reddit.com/r/bicycling/comments/16p795v/dont_buy_zrace_rx_cranks_i_guess/

[Linsook]

Yikes, first failure I've seen of this crank. Its a shame because its one of the only 29mm spindle cranksets on aliexpress that's reasonably lightweight.

edit: looks like a similar failure linked here: https://www.reddit.com/r/bicycling/comments/16p795v/dont_buy_zrace_rx_cranks_i_guess/

Thanks for the link.  Ya looks and sounds exactly the same, I was out of my saddle as well.

Just bought some sencix FM2's.  Hoping they do better.

[electrolux]

Well I guess its as good as Shimano then 

[jonathanf2]

Yikes that looks scary. Glad it didn't happen on an actual ride!

[Wet Noodle]

Looks nasty, like it could have really hurt. Now I'm kind of worried for my Rotors with their anorexic pedal eyelets and spindle interface and all the crazy drilling ("Stress risers? There is no such thing, silly!").

[00Garza]

That could've caused a major wipeout on the road/trail.
Is this more likely to be a design flaw, or low quality alloy issue?

[Linsook]

That could've caused a major wipeout on the road/trail.
Is this more likely to be a design flaw, or low quality alloy issue?

Need an expert to chime in.

Some closeups.

[raisinberry777]

Thanks for the report - I had looked at buying some recently because the price of buying one with a Magene P505 was cheaper than the Magene PM by itself - dodged that one!

[AzureEssence]

Any chance the pedal extenders increased the leverage on the crank arm, contributing to the break?

[BalticSea]

Yikes, first failure I've seen of this crank. Its a shame because its one of the only 29mm spindle cranksets on aliexpress that's reasonably lightweight.

edit: looks like a similar failure linked here: https://www.reddit.com/r/bicycling/comments/16p795v/dont_buy_zrace_rx_cranks_i_guess/

Fovno Aurora Pro is even lighter, but also more expensive at around 120 euros. Should be receiving mine soon.

[Sebastian]

Bought one of these slightly used for almost nothing. Now I’m hesitant to put it on my bike. And I put another one of these on a friends bike. He bought it together with his LTWOO RX12 groupset. It’s holding up fine so far. We’re both not exactly world tour sprinters. So maybe that helps.

[hagerd]

Any chance the pedal extenders increased the leverage on the crank arm, contributing to the break?

I would say yes, a larger moment is being exerted on the connection point because of this.

[St0mpB0x]

Need an expert to chime in.

Some closeups.

I wouldn't go as far as expert but I have a little bit of knowledge of this kind of things. If you could get some good close up photos of the two faces if you can get them apart that might be helpful. Make sure to indicate which side is the pedal side.

[St0mpB0x]

Also, Driveside or Non-Driveside?

From what I can make out from the pictures the failure surfaces look quite interesting. The third picture looks like it shows some microvoid coalesence which is indicative of ductile failure so was likely to be the final section to fail. The first picture looks like there are some beach marks visible which typically point to fatigue. The holes through the centre of the crankset are interesting though as they seem to show a different fracture surface again. No idea whether thats because its actually a different material or whether the drilling process effectively heat treated or modified the material around the holes.