If you follow us on our social channels, you know that on Friday we let you guys ask UNNO any question, and Cesar Rojo himself will be answering the most interesting question every Monday. The first question is from Facebook user Johann Grognux: “During TP 2011 you stated that carbon was a bad material for MTB (argument was: it’s like a spring blade). You also said that when you started thinking of making your own bike in 2013 (or 14?) going carbon was a no brainer. What made you change your mind?”
Here is Cesar’s answer: “The reason behind that statement was based on the bikes I had tested back then [in 2011]. Due to lack of development in the carbon fiber segment all were really “heavy” frames utilising lots of material, which at that time translated into high stiffness. High stiffness is the opposite of what you want on a good mountain bike. You need a certain amount of flex to control the grip when the bump does not hit in the same direction of the suspension travel.
Let’s take an example, exaggerating things a bit. If you are cornering and while you have a 45 degrees lean angle you hit a bump, only a certain amount of energy from the bump will be absorbed by the suspension as it will not be aligned with the direction of the suspension travel. The rest of the energy is going to go into the tires, wheels and of course in the frame. If the frame is super stiff (let’s exaggerate, as I said before) and does not flex, all the energy is going to be absorbed by the tire deforming and loosing grip, and also by the wheel, even though you won’t be able to absorb the same energy as if your frame flex was helping to reduce the stiffness of the whole package of tire, wheel and frame. This will lead into a bike with a more on and off feeling, where you actually loose grip without notice.
So this is why controlled flex is super important, and this was one of the things we took huge effort in developing our own carbon layups and a big reason to be doing our bikes in-house. We measured the stiffness in one of our favorite aluminum bikes and tried to mimic that same ratio between torsional and lateral stiffness in our carbon frames. Still carbon does not absorb the energy the same way aluminum does and aluminum might have some edge there, but a good development for sure can overcome that. Carbon also has other advantages as it allows for a much more stronger frame construction and lighter weight.
The reason why we picked carbon is because as a material it gives you way more freedom than aluminum to play around with stiffness, you can make also lighter and stronger constructions and to top it off the design of the frame can be much nicer – you have much more freedom to play with shapes than with aluminum.”