Rotobox Wheels Cracked

Hello everyone! Guys, I have a problem has anyone encountered such a problem with Rotobox Bullet wheels, almost every spoke has cracks at the junction of the forged carbon fiber. Is this dangerous? I suspect that the varnish or resin is cracking.

That’s part of the problem with “forged” carbon fiber. It isn’t laid up with the fibers aligned for their strengths, it just smashed into the shape a done. I would say it’s “normal” for forged carbon fiber, but certainly not in my view of a good bond.

I dont like them, I think there are better carbon wheel designs. I am not sure that the delamination is a significant problem but it is a problem. I would contact the manufacturer/supplier and make a warranty claim

If you run your finger nail over it, is the resin on top cracked or is it just cracking underneath?

BullandBear1 said:

If you run your finger nail over it, is the resin on top cracked or is it just cracking underneath?

Click to expand...

bro you can barely feel it with your fingernail, in the photo it looks much worse than in real life

I’d email rotobox and see what they say then. That’s very strange. On the set I have, I haven’t noticed that.

One way to tell you’re having issues is if you’re losing air. Have you lost any air in your tires? Also, is it front and rear? Or just the rear?

Maga1201 said:

bro you can barely feel it with your fingernail, in the photo it looks much worse than in real

Click to expand...

... are you willing to gamble with your life riding on those wheels, that's the question you should be asking yourself.
What others think about cracks is irrelevant!

Bo13R said:

... are you willing to gamble with your life riding on those wheels, that's the question you should be asking yourself.
What others think about cracks is irrelevant!

Click to expand...

This...

It's PROBABLY cosmetic and nothing. But I'd personally be terrified to take those over 75MPH for fear of a freak failure of some sort.

But then again equipment failure is my single biggest riding fear. Not traffic. Not the speed itself. But way in the back on my mind I'm always wondering about what would happen if a tire blew out, a carbon wheel shattered, a chain snapped and rolled itself up into the rear wheel and locked it up somehow, my engine lets go and coats my rear tire and the road in oil...all very unlikely events... but I do all I can to make sure none of them happen to be best of my ability.

Eh.

You're much more likely to get smoked by a smooth brain sending a hyper urgent nonsense text message in a mini-van making a left while while hitting a vape than a mechanical failure.

I've had a few members purchase BST wheels from me to replace their cracking rotobox wheels. No catastrophic failures but don't think people feel comfortable riding with them after a few cracks form, so who knows what would happen.

Maga1201 said:

Hello everyone! Guys, I have a problem has anyone encountered such a problem with Rotobox Bullet wheels, almost every spoke has cracks at the junction of the forged carbon fiber. Is this dangerous? I suspect that the varnish or resin is cracking.

Click to expand...

Have you reached out to Rotobox for input?

A surface crack on each spoke? That's bad news I'd bin them or take them out of service immediately. Not because they are necessarily going to fail next ride but the risk is unacceptable.

I work with CF as an aerospace engineer every day. Don't use that anymore! Delams and cracks severly reduce the strength of CF you have no idea if they grow under the surface and get bigger and bigger.

X15b said:

I work with CF as an aerospace engineer every day. Don't use that anymore! Delams and cracks severly reduce the strength of CF you have no idea if they grow under the surface and get bigger and bigger.

Click to expand...

Yeah there was this thing called titan a while back. Didn’t go well for them…

SBK-SP said:

Yeah there was this thing called titan a while back. Didn’t go well for them…

Click to expand...

That was an exercise in hubris and monumental stupidity, and what happens when rich idiots believe their own ......... James Cameron's interviews about Rush's antics are scathing. Back to carbon, it is an amazing material but it still has to be designed and built well. Given the failures reported here with both wheel designs I would be very hesitant to use Rotobox carbon wheels. A couple of points, the rims are made from cloth and directional fibres which is standard but the spokes are forged carbon. Forged is a marketing term for what glassfibre guys call chopped strand. CS matt is held together with a binder and "melts" into the shape you want when resin is applied. Its cheap and relatively weak compared to unidirectional or multidirectional woven cloth. When most people think of fibreglass, they think of chopped strand. Forged carbon is the same but much stronger however because the fibres are short its nowhere near as strong as directional fibres full length on the load paths, the key here on these wheels is how the forged carbon spokes connect to the rim. If the connection is via the short fibres to the surface of the rim then ANY delam is a major issue because the fillet where the loads transition from spoke to rim is meant to reduce any stress risers. The other point to note is that most of the loads are taken by the outside layers which is why surface delam is a big deal.

Here in Australia BMW were replacing OE CF S1000RR wheels on the regular back in 2019-20 for very small surface cracks in the same area where the spokes met the rim.

The design of those wheels always looked sketchy to me, and I had three separate tire installers tell me about those wheels breaking or cracking during tire changes no matter how careful you are.

Looks to me like that design allows too much flex, wheels need to be stiff…and those cracks may well be from the wheel flexing too much.

Maga1201 said:

bro you can barely feel it with your fingernail, in the photo it looks much worse than in real life

Click to expand...

Probably totally fine then

I have had some issues lately and have been searching all over and found this thread.

Sorry to bring up the old thread. Did this ever get resolved?

Also saw this video today too!

Bo13R said:

... are you willing to gamble with your life riding on those wheels, that's the question you should be asking yourself.
What others think about cracks is irrelevant!

Click to expand...

Yeah man, those cracks will buff right out.