Keywords: 27.5, 650b, super light,full suspension

The full suspension frame

Gerard Vroomen - 24-Sep-2014
Thanks for all your comments and emails about the full suspension frame. So here I have some more info for you and some extra photos.
  • Our goal with this frame was to create a cross country/marathon frame with 120mm of travel. So very solid when climbing, yet tons of travel on the descent combined with a relatively short wheelbase and agile handling.
  • The kinematics, as we mentioned before, is based on Liteville's system as used on their 301. We like their kinematics a lot, they graciously allowed us to use it, and we then made some adjustments to fit our exact needs. The big advantage of their system is that it is very passive while climbing and very active when you need it, so ideal for being "energy-efficient" with those precious Watts you're squeezing out of your legs.
  • Some have asked if a cross country fully shouldn't have just 100mm of travel to make it even racier, but given how efficient the kinematics are 120mm is the perfect solution and it really makes a difference on the descents. With regards to weight, there is actually hardly any difference because parts like shocks and forks often use many of the same parts for both travel sizes and for the frame itself, the bits are virtually identical. So 120mm gives you a lot of upside with hardly any downside.
  • Andy and I went back and forth on wheelsize and built prototypes to figure out where to go. In the end, the decision was that in the rear, in order to keep the agile handling and short wheelbase that OPEN is known for, we needed a 27.5" wheel. It allows us to keep the rear end tight and keep the overall balance.
  • We experimented with 27.5" and 29" front wheels as well as different headtube angles; in fact that is probably where we had the most heated debates. In the end there were two set-ups we liked: (1) a 27.5" front wheel with 130mm of travel and (2) a 29" front wheel with 120mm of travel.
  • With the 130mm travel and the 27.5" front wheel, you can ride the bike on almost any terrain. The bike turns on a dime, can take big hits and just feels very alive.
  • Side note: For those set in the school of thought that front and rear travel should be identical, it might be nice to remember that the rear travel is (more or less) vertical while the front fork travels at an angle. If you take the vertical component of that 130mm travel, you get (drumroll please) .... 120mm.
  • The 29" front wheel really makes the bike want to roll, ideal for longer stretches. It gives you the advantage of the bigger front wheel to roll over obstacles more smoothly and the short rear-end to still get great handling (and the 27.5" wheel in the back doesn't affect roll-over very much since it is pulled over objects by the momentum of the bike rather than being pushed up against it the way the front wheel in combination with a suspension fork is. 
  • It's not that Andy was in favor of one and I was championing the other solution, we actually both like both options because they reflect the different ways we and plenty other people ride.
  • In the end, the decision was actually a non-decision because once we started optimizing the headtube angle for each of these two options, it turned out that we can offer both with the same frame. So you can get this frame, build it up with either of these two fork/wheel options and in both cases the geometry will work beautifully. Of course if you so choose, you can switch back and forth between the two set-ups.
  • Side note: In some official UCI races, you have to use the same size wheels front and rear, an archaic rule but one that may be enforced at some races you participate in so it's always good to check. Of course, between the OPEN 29" hardtail and the 27.5" full suspension, you always have something good to use no matter what the race. 
  • Some astute observers may think that the gap between a hardtail and a 120mm travel bike is quite big. But our hardtail has so many details to make it vertically compliant, meaning you can ride it in tougher terrain very well. On the other end of the spectrum, as we explained there is virtually no drawback to increasing the travel from 100mm to 120mm. So why not take that extra 20mm? That combined means that the "gap" between the two frames is actually not as big as one might think.
If you want to stay up-to-date on the progress of the full-suspension frame (or the pathfinder frame, just tick the boxes on top right. Of course if you've read the previous blog, you'll know I won't give you an availability date for this frame yet! And here are the photos I promised (again, remember this is the first frame out of the mold so far from perfect):

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