18 July, 2016

Born to Win – A Pure XC Full Suspension Race Bike


Born to Win – A Pure XC Full Suspension Race Bike

We say Oiz is “born to win” and it’s true. From the prototype Catharine Pendrel raced to her first World Championship in 2011, to the updated BWC version (also a final prototype) she piloted to victory in 2014, Oiz hasn’t spent much time away from the podium. It’s a massive vote of confidence that an elite athlete was willing to risk racing a days-old prototype, not once but twice, at the most important event on the calendar. We both had much to lose, but Oiz and Pendrel delivered. There was a little bit of luck to be sure, but the success ofOiz was not by accident. It’s the result of a clear mandate that Oiz is engineered for one purpose – Speed.

As early as 2003 we were exploring ways to combine a rear shock with a pure cross country frame that wouldn’t compromise efficiency but would in fact make the bike faster in every way. As we developed new iterations of the Oiz over the years, cross country racing evolved at a similar pace and today there are often as many racers taking the start on a full suspension bike as those who choose the venerable hardtail. The work we have put in has paid huge dividends. Oiz has won two World Championships under Luna racer Catharine Pendrel and is a rider favorite everywhere. The Oiz today is lighter and stiffer with better geometry than the competition, and is proving even more capable as World Cup tracks begin to showcase more aggressive terrain. Instead of a major revamp of Oiz to handle the needs of cross country riders, we are pleased to be in a position of being able to make subtle refinements to the genetics of an already -superb platform with the confidence we’re onto something special.

So what makes up the DNA of a bike Born to Win? It’s a combination of chassis, suspension and geometry that are adapted to aggressive riding at top speed and full exertion. None of these things by itself makes the best bike, it’s only by checking ALL these boxes that we are satisfied, and the only way you can fall in love with your bike when it helps you cross the line first, top a rooted climb ahead of your friends, saves you from a gruesome get-off, or garners a wolf whistle in the parking lot after a ride. Oiz does these things every day.

Seeking the holy grail of low weight and perfect stiffness

Monocoque construction is nearly ubiquitous these days as the best method for building performance carbon bikes. Oiz is no exception and a perfect example of the extreme amount of effort required to make a very simple frame. Oiz is molded in just three pieces – the front triangle and right/left sides of the swingarm. This means there is only one bonded point on Oiz, and it’s in the relatively low-stress area of the large cross brace near the BB. Molding as few pieces as possible reduces the numberer of bonded areas, which means a big increase in reliability and ride quality since glued intersections interfere with carbon’s natural strength and durability.

The “Full Carbon” philosophy exhibited in this frame eliminates even more weight. We have reduced aluminum inserts or frame pieces to the minimum. Headset, Bottom Bracket and through-axles insert directly into carbon and even the unique shock linkage is made from carbon. Far from reducing durability, these solutions increase strength in these critical areas, again by avoiding the use of glue. Oiz, just like all our frames, has a lifetime warranty and it’s analysis and testing with our desire for simple sophistication that have led us in this direction. Oiz uses technologically advanced carbon molding construction to make the best frame possible – A complex and painstaking process with results you will appreciate on the trail.

The acronym U-FLEXION by ORBEA started with the distinctive flattened “U” shape of the original chainstay design. As early as 2005 we were among the first manufacturers to realize eliminating pivot hardware from the swingarms of our XC frames would reduce weight and increase torsional stiffness. The first Oiz used a flexible chainstay to deliver 75mm of travel. While other manufacturers stayed with variations of this early design in spite of the undesirable main pivot location somewhere along the chainstay, we wanted a more sophisticated and efficient suspension feel. In 2010, as we began working on a newOiz, we married a traditional main pivot to a flexible “seat stay” UFO design and have never looked back. Today there are multiple competitors who have adopted this design, we are complimented by the validation and motivated by our experience keeping us ahead of the pack.

The UFO design of the Oiz does away with a pivot near the rear axle to make a lighter, simpler bike that requires less maintenance. UFO bikes are laterally stiffer for precision and acceleration like you’ve never felt in a full suspension bike. UFO saves about 110g in bearings and hardware on the Oiz frame and yeilds a weight of 1.7kg for a MD 29, making it possibly the lightest full suspension frame available. Oiz stays flex 7mm downward at maximum deflection. The amount of force required to flex the stays is negligible, amounting to about 2% of the force required to fully compress the suspension. This small effect is easily compensated for during shock tune selection and testing.

Tensegrity is part of our Full Carbon construction philosophy. We worked overtime to create this elegant full-carbon, one piece swing link of the Oiz. The deceptively-simple linkage took us a few months to perfect because of the unique forces at play on this crucial piece. Obviously, most of the movement in the linkage is in the plane of the shock. But there are small torsional spreading forces from the individual swing arm sides that caused the minimalist link to fail too early in testing. We revised the shape and added material, but it wasn’t enough. Finally, just before giving up and using Plan B, an 80g heavier alloy link, one of our engineers took inspiration from the numerous suspension bridges in the basque country and installed a shortened spoke through the linkage – Eureka. The linkage far exceeded our testing parameters and Tensegrity was born. The minimalist steel tension strut in the joint between the linkage and the seatstays balances lateral forces and provides optimal stiffness at an extremely low weight.

The perfect suspension characteristics for our XC masterpiece

XC suspension is different from that of a trail bike. Racers want suspension that is virtually unnoticed until it is needed, and no energy should be wasted when the trail turns upward. But balancing efficiency with control is a difficult task. Riders will frequently inflate their rear shock until there is very little sag for excellent support under power, but they still need a design that soaks up rough terrain and allows full travel when needed. The Advanced Dynamics suspension of Oiz delivers on both fronts

Advanced Dynamics is a process, not an unchanging design. We’re not tied to one single configuration applied to every use from XC to Gravity. Instead, we let our Advanced Dynamics process determine what links and pivots look like, where they’re positioned and how they will work with the damper for ultimate performance.

Advanced Dynamics is at the heart of every Orbea suspension bike. It is a computer-based modeling process we developed in conjunction with CEIT (Centro de Estudios e Investigaciones Tecnológicas) that allows us to virtually test and fine-tune our suspension platforms. Using a vast database of shock tunes and component behaviors we can study a design under a simulated rider exerting forces on the pedals, saddle and handlebars. We can shape the tests to evaluate different variables – rider height, weight, riding style – on different tracks. Even tire pressures can be tested and recorded before a welding torch is lit.

When tires finally hit the dirt we can focus on fine-tuning damper characteristics and spring curves with our expert suspension partners. The advantage of starting at 90% means we get closer to perfection, this is the obsessive tinkering that turns a good bike into a great one. There is a general perception this is how other companies design their bikes – but it is not the case. Orbea’s Advanced Dynamics testing database, compiled with an unusual degree of cooperation with our suspension partners, is unique in the industry.

The leverage ratio curve of the Oiz is perfect for efficient XC riding. Sag can be set as low as 15% for a firm pedaling feel and the progressive/regressive leverage design still delivers a full 95mm of travel when needed. The leverage ratio increases for the first 3/4 of the shock stroke, then switches to a falling rate to overcome the progressive nature of the air shock to achieve full travel on large impacts. Custom tuning of the damper minimizes bottom-out forces and keeps the suspension riding high, maintaining geometry and efficiency.

The main pivot point on the new Oiz is located to work efficiently with both single and double chainring setups and customized shock dampers were developed with Fox to match the characteristics of the suspension design. Pivot location was further adjusted based on bottom bracket drop to provide the same 100% anti-squat characteristics when larger cassette cogs are used with larger wheels to maintain the same gear development.

Features Adapted to World Cup Racing

Oiz’s Racing Geometry is born from years of designing world-class XC bikes. The position is aggressive, comfortable and fast. Unlike trail geometry that sacrifices some precision for endurance, XC geometry is aimed at maximum power transfer. Angles and dimensions are considered carefully across a range of sizes, maximizing wattage by increasing efficiency.

Shorter chainstays, lower stack heights and longer cockpits are the primary characteristics of bikes designed to tackle the demands of rough XC courses. Head angles are tuned for wheel size (27.5 or 29) but are generally getting slacker and slacker as drops, rocks and rooted chutes become more and more common in race track design.

Increasing rear axle spacing to Boost 148mm over the 142mm standard moves the chainline outboard by 3mm, increasing the space available at the bottom bracket. This doesn’t sound like much, but it means tire clearance is increased and there is more room for larger chainrings and a front derailleur. The new Oiz can fit 2.4 tires with adequate clearance, which is a boon in sloppy conditions and gives an added level of flexibility. 1x drivetrains are gaining popularity, but 2x configurations are still king on steep courses and more room means lowering the risk of chain suck and more chainring size options. Additionally, the switch to Boost brings through-axles front and rear for the absolute best tracking and braking characteristics.

All of it adds up to more durability, nimble handling and better tracking through rough terrain.

Oiz is designed for pure speed. For racers who are counting grams, this likely means a super-light carbon seatpost. But Oiz is far from a dainty descender, there is time to be taken on the downhills as well. Internal dropper routing is a simple detail that will be appreciated by the riders who don’t mind a heavier dropper post when it allows them to leave the competition behind when gravity takes over. Just in the last few months of 2016 we have seen top WC competitors accepting the 250g penalty of a dropper to take full advantage of the ability to maximize speed on the entire track, not just the climbs.

What’s the Bottom Line?

Oiz is designed for fast, experienced riders who demand a superlight, efficient and reliable suspension bike. Oiz is a multiple World XC Championship winner and the full-suspension racing bicycle of Team Luna Chix.

We have deliberately avoided turning Oiz into a 100mm universal XC bike with plush suspension and “do it all” features because that’s simply not what wins races at the top level. We have spent years interviewing riders, designing and testing Advanced Dynamics virtual models and logging thousands of kilometers on every type of terrain imaginable. We labored over subtle refinements of carbon molds and layup schedules to bring to life the dream of every pure-XC rider – The lightest, stiffest and most efficient FS XC bike on the market.