Death Of The Top Tube

Spanish brand "UNNO" just announced the Dash. (Image courtesy of UNNO)

I've been keenly interested in mountain bikes since the late 1980's. Since that time, there have been several permutations of mountain bikes and much evolution in thought within the mountain bike design community. 

This is perhaps most evident in some of the newer designs I have seen in the last several years. Things are at such a state that, if it were possible to time-travel backward and show these bikes to designers from 20 years ago, they might just cause quite the stir. I'm positive that would be the case. Take this bike I am featuring today from the Spanish brand UNNO. Their Dash model is a 150mm/140mm travel dual suspension, "all-mountain" bike.

Something like 25 years ago now, in the seminal mountain bike magazine known as "Dirt Rag" (R.I.P.), there was an article I recall which gathered together a symposium of then current movers and shakers in the mountain bike design and manufacturing communities. There were questions about where MTB design might be going in the future. 

Of course, suspension design was a hot topic then, and "all-mountain", "free-ride" bikes like Cannondale's  Super V were blowing the doors off of conventional design theories. Those Super V bikes were polarizing- You either loved them or thought that they were the ugliest thing ever designed, but they were a portent of things to come. 

Catalog snip of a Cannondale Super V 3000.

But however they affected people, those bicycles and others were challenging the conventional design thought of the day. How much suspension travel was too much? How would longer travel forks integrate with the rider and the ergonomics of the bicycle?

I recall that one of the so-called "limiting factors" for design was front end height. Keep in mind that all throughout the 1990's the 'pinnacle' of mountain bike design was thought to have been achieved by the then ubiquitous "NORBA geometry hard tail". It might be hard to understand this now, because examples of such bikes are rare anymore.

But imagine a steep head angle- 71°- and a what would be considered laughably slack now 73° seat tube angle. Consider that 29" wheels did not exist- Everyone was on 26"ers, and that was the ONLY choice. Then throw in the "long travel" forks which were 80mm, with 38mm fork offsets, and you can begin to see that these bikes were radically different than what we have today. My favorite feature of bikes from that era are the stem lengths. Think about this factoid; A 135mm long stem was considered as "short" in those days! 

And all of that hampered the Cannondale Super V's and other designs of their time. So when the designers were asked what the limits were, these conventions were where they were coming from. You simply could not imagine a fork with longer than 100mm travel because it would jack the front end up so high, mostly due to that steep head angle, that the bike would be laughable. Top tubes would become so sloped, to accommodate stand over, that these bikes would look like- excuse me here, but this was the term back then- "girl's bikes". 

Boy! Have we come a long way in many areas, but I wanted to paint a picture here of where we've come from in terms of design. Top tubes? What top tubes? If ever there was a bike that could claim the name "full-suspension mixte'", it would be the UNNO above, and I think this is a design which features currently held design maxims which- in my opinion- will be gone in the future as well. We've rid ourselves of those pesky top tubes, the seat tube will be next!

GAS GAS trials moto (Image courtesy of Motocross Action)

I think about motorcycle trials bikes here. These bikes typically have no saddles or any provision for one. Of course, they have a motor to propel them, so pedaling is not a concern. How would one eliminate the seat tube to gain maximum clearance for the rider on a bicycle? How about eliminating the seat post/seat tube idea and making a telescoping seat tube instead? 

The unit could be so compact that it would take that bike in the first image and make it look a heck of a lot more like the motorcycle to the left. (Or a parallelogram linkage saddle which could be raised and lowered.) Imagine it with an integrated electric motor/transmission, such as what we are seeing proposed now for HPC/ebikes, and you could easily see something that looks a heck of a lot like the trials bike here. 

Just like the elimination of conventional top tubes seemed unthinkable to that panel of experts in the late 90's, this idea may seem out-to-lunch to you now. However; I think it has legs, especially when you see how goofy that provision for a seat post is on the Dash above. The top tube is dead! Seat tubes? We're coming for you next!