OK, it's been a while now since the Mojo Carbon first came out. There was initially a lot of speculation about strength of the carbon frame, especially in sharp, rocky areas where laying it down hard would scratch through the first few carbon layers.
What have your real-world findings been? Has anyone had failures? I haven't heard of anything. Could anyone post photos of any damage? Is it mainly cosmetic? Any big crashes? etc...
I am not criticising the use of carbon, nor am I trying to start a carbon vs. alu/ti/steel debate. I'm just after genuine rider feedback, particularly from those living in rough, rocky areas.
Thanks in advance.
Here's a couple of thoughts.
But first, someone tell me if I'm posting too much. It's not like I need the attention or anything. I'm just trying to answer a few questions.
First of all, when I was in machinists school, there were guys working at the Leer aviation factory. They would come in with their stories about the material. It's really tough.
Having said that, I'm relieved to put my thin walled tubing bike away. And wherever one would encounter a problem with carbon fiber, one would most certainly have at least the same problem with tubing.
And sorry, no real world experience with rocks or axes. Just saying that it's almost academic. I'm glad to put my beer can bike away.
My Mojo has had a couple of body slams and ejects on rock trails lately. No problems. Clear coat scratches is all. Even my carbon crank arms (that are likely only a thin carbon weave over aluminum) show no damage and only surface scratches - and they hit rock hard fairly often. Surface scratches disappear with a bit of nail polish. Impacts seem to be less of a problem with quality carbon than with other materials (including my body!).
It would be very hard to scratch through "the first carbon layers" and even if you do I am not sure that it would be a problem. (I mean: I really don't know nor does anybody else besides IBIS). However note that it is a misconception that a carbon composite is compromised if you cut through some of the layers. Other things being equal compromising the integrity of the piece simply depends on the thickness of the material. The thicker the lesser of a problem is "superficial" damage ...
Originally Posted by TJT
Windsurfing people (myself included) use carbon needle masts for waves (and some speed trials). These are small diameter but 2-3 times as thick as a standard (large) diameter mast and are basically unbreakable, you can litterally bang the thing around with little consequence ... aluminum masts (and booms to a lesser extent) have disappeared from windsurfing (heavy, fragile, and prone to fatigue and snap) I think it is only a matter of time until carbon is fully accepted in MTB.
Last edited by Davide; 03-30-2007 at 11:51 AM.
Thanks. Obviously a thicker carbon build in high-stress areas, or those frequently hit by rocks, will make a big difference.
Purely out of interest, approximately what sort of thickness are we talking about for a Mojo frame? How does this compare to aluminium frames?
Thanks for your replies.
You beat me to it, TJT.
Not like I'm a bike designer or anything, but I know that bikes are designed to be as light as possible. I have done some stress analysis in my day. I want to say it's not like a plane. But it is in the respect that it's designed for weight. A plane has a factor of safety that must be maintained. So does a bike. I don't know how they worked that out. Certain areas are treated differently, is probably an extremely simplified way of putting it.
There is a thread floating around about the wall thicknesses of this frame. Or it might have been on the Ibis site. They are substantial, I know that. I would bet that Ibis is working on that part of the frame as we speak. Weight. But my guess is that a frame is built to a very low factor of safety. It's not airborne. But risk is minimized. (I'm actually pretty beat up from a long ride. I don't even know if I"m making nonsense. )
Also I don't know the number of laminations. Nor do I know how many laminations can be cut. Nor do I know how easy it is to cut them. I am guessing carbon fiber is not easy to sever. And unlike other materials, even when cut it doesn't necessarily create the same kind of stressor as ordinary engineering material.
So I've kind of said nothing. Semi trashed, and finishing a Sapporo. I think the down tube or chain stays are the most vulnerable and stressed, around the bottom bracket. And it's pretty hard to wreck them with the chainwheel there. Still, it seems that it would be way easier to kill a conventional metal tubed frame than this one.
Bla bla bla, I'm dissolving into a puddle of happy alcoholic murmuring nonsense. I like it .
I'll now go stare at my Mojo and be happy.
The wall thickness varies from under 2mm to over 6mm in some areas. I'll post some photos of a cut up frame at some point when I have a chance.
I need a new sawsall blade. Tom borrowed it and now there is only a smooth spot where the teeth used to be
Some of the areas are so solid and tough you can literally hit it at full force with a framing hammer and nothing happens, it just bounces off. I don't suggest you try this on your own bike though.... Occasionally we do put a hole in the frame. Thus far nothing that wasn't repairable or would cause you to walk home though...
We are going to make a video of this for your amusment as soon as we can....
I knew we could coax you guys out of your cubby hole. Yay!
Please do share that video with us. It'd be very interesting to see how this material looks and responds to being "tested".
I did have a good investigation before putting the forks on.
I'd also really like to see the manufacturing process. I know there are ways to set up the laying up process. Or whatever it's called. But it's a mystery. I can only suppose it's sacrificial and removable cores, and a vacuum bagging process.
All I know is you guys pulled off a great project.
I think from a marketing standpoint, the more info Ibis puts about about carbon fibre, the better.
All the info on their website certainly helps put potential customers' minds at rest, but a couple of videos would really help them allay some of the common fears people have about CF.
Its tuff stuff and Chuck Ibis knows whatZup
All materials can fail. Ti can fail. Steel can fail. Aluminun can fail.
Everything is breakable. There is no bike out there that is beyond breaking.
The truth is that its hard plunking down stoopid amounts of cash money for a frame that you can't honestly say will last forever, but thats life in the high end world of mountain bikes these days.
Carbon is tuff, particularly when used properly and designed with the application in mind. If you are considering a Mojo I would take heart in knowing that Scot has been riding and abusing mountain bikes longer then 99.99% of anyone riding MTBs. He knows whats up and he knows how and why materials fail. He isn't going to ship product that sucks ass and breaks without a damn good reason.
Its hard getting over the bias of all those old carbon fibre tennis raquets we all beat the hell out of as kids, but that was then and this is now. And its a crappy comparison anyways.
I say Buy With Confidence!
Similar subject here: my handlebar and grips
I just tried out Serfas Crux clamp-on grips. While tensioning the screw, a piece of the clamp broke (didn't know this at the time.) I managed to get the grip not to rotate (as per instructions). I rode it around my drive way and pulled the grip off, and low and behold, the little piece of clamp fell out. Fine, a shoddy product will be returned to my full-service REI store.
Problem: that little piece of metal clamp scratched a groove around my carbon Yeti Arc handlebar, as if someone had used a pipe cutter on it. ARGH!!! So is the bar still structurally sound? I don't crash much, so I'm not too concerned about a failure on impact; more afraid of it snapping off in my hand while riding (wouldn't be pretty..)
What makes CF strong, and does scratching a thinner piece of it mean toss it?
"i don't wanna smell your vinegary, old, pissy plastic jersey in the woods." - nativeson
Looks like most damage is to the clear coat. Look at the end of the bar and see how thick it is. put nail polish on the scratch and it will look good again.
Originally Posted by 105millimetersofpleasure
13 year old giant cadex
I have thirteen year old giant cadex hard tail that was my first mountain bike. I have stacked it many times. It has scrapes on the top tube from the brake levers hittinhg when the bars spin. More scrapes on the downtube from a presta valve that was glued in to replace the dodgy football valve in the old mag 21s(try getting replacement parts in Australia)
After I got my first duallie this bike became my commuter and now has over 100 000 Km on it. It now does duty as a single speed. It gets jumped over small rythm sections no bigger than about 4 foot high and 2 bike length gaps.
The longevity of my giant is the reason I bought a mojo. I have broken a couple of aluminium bikes.