BULLS Wild Core Prototype - Hafjell World Cup

Hafjell, Norway

BULLS
Wild Core Prototype

WORDS Mike Levy
PHOTOS Vanja Kodermac

Designing a downhill race bike from scratch is a daunting task, especially when that bike will see its initial testing take place throughout a full season of World Cup racing... talk about being in the spotlight. That is exactly how it is often done, though, and is also how Hendrik Gehring, the engineer behind the 200mm travel BULLS prototype shown here, took to the challenge of designing a competitive machine. The German BULLS brand is well known for their range of affordable bikes, from city cruisers to cross-country rigs, but this entry into the downhill realm is part of a three year development plan that will eventually see them offer a production version of the downhill bike pictured above, with it presumably being priced as competitively as the rest of their lineup. Tasked with developing the bike is 'Team BULLS powered by Mountainbike Rider Magazine', a four man squad that includes New Zealander Wyn Masters, German racers Christian Textor and Tommy Herrmann, as well as team mechanic Mikey McCallum and slope rider Teo Gustavson from Sweden.



The complete team bike sits at a claimed 37.9lb with a solid looking build kit that includes Shimano's Saint cranks and an FSA cockpit, and the team uses Mavic's Deemax wheels shod with special tires from Schwalbe that are part of the 'First Ride' development program. This gives Wyn and the boys access to some trick rubber that most racers won't be able to touch for quite some time, as well as putting them on equal footing with some of the larger teams when it comes to tire options. Suspension is an all RockShox affair, with a custom tuned Vivid R2C out back that has been shimmed to work well the Wild Core's suspension layout. An XTR derailleur from Shimano has been chosen due its longer cage, something required due to the chain growth caused by the bike's high main pivot, and Saint brakes slow the team down.




It comes down to tradeoffs, with there needing to be a balance between all performance aspects in order for the bike to perform well, and such a high pivot is usually associated with two drawbacks: chain growth as the axle moves up and away from the cranks, and the suspension stiffening due to pedalling loads when a rider is putting down the power. The latter issue was addressed by placing an idler pulley that routs the chain up from the Shimano chain ring and nearly inline with the bike's main pivot. The negates the chain's action on the suspension by eliminating its tendency to pull down, thereby allowing the suspension to work to its full potential when the drivetrain is under pedalling loads. The pulley itself features an integrated chain guide, complete with rub blocks, that should prevent any derailments, and its nicely finished aluminum construction looks to be ready for production. BULLS is far from the first brand to use an idler pulley (Canfield and others have done it for many years), nor are they the first to employ such a high main pivot, but they look to have pushed the concept to its extremes.



While Wyn and the rest of the team are loving the bike on fast, rough tracks, its high main pivot does make for a bike whose wheelbase grows quite a bit as the rear suspension nears bottom out. This can help by adding stability when the rider is landing in rugged terrain, but the downside can be geometry that changes drastically as its suspension compresses when thrown into a hard corner. ''We can only see from testing what is good and doesn't impede the performance of the bike's high pivot,'' team manager Jorn Hessen told us when questioned about it. ''We're trying to search for the best compromise.'' And word is that testing will likely result in the final prototype, the fourth iteration of the design before production, making use of a slightly lower pivot location that will sit a few millimeters down from the current placement. There could also be a final change to the linkage setup as well that will alter the progression slightly so that the bike ramps up a bit later in its stroke, another change that comes from Team BULLS powered by Mountainbike Rider Magazine racers putting the bike through its paces during the 2013 season.

One thing is for sure: we aren't often privy to such knowledge from team riders, with the public only hearing about how great the bike is, no matter what, from those who are paid to race it. Don't be fooled by the straightforward admissions written above, though, because all of the world's top bikes have gone through, or are still going through, similar processes before becoming the usually polished production bikes that you see in the catalog. We're looking forward to seeing and riding the production version that is born from the team's development work.



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