Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/127857
RIDING IMPRESSION (Left) The KTM 250SX Is now equipped with WP suspension components, inc luding a new 50mm Extreme conventio nal f ork, whic h does a good lob 01 absorbing the big hits. (Right) We li ked th e KTM's narrow layou t but not the overly hard seat. Later model s will have softer foam . (Below) At S5698, the KTM co sts less than most of its Japanese rivals. By Kit Palmer· Photos by Cameron Coa tney ver since Gr eat Brita in ' s Kurt .I Nicoll debuted th e Prog ressive " Damping Sys te m (PDS) direct~ link rear-suspension system on his works KTM on the GP circuit last yea r, we've bee n in trigued by the new co n ce p t. Act ua ll y, the non-linkage rear- su spen sion concept isn' t e xac tly new: After all, ATK Ms been ut ilizin g a non -link-type design for years. Howeve r, KTM stro ngly d eni es th at it s n on -lin k sys te m is anyth ing like ATK's. The idea of a linkageless sus pension sys tem makes a lot of sense, really. By 16 going to suc h a des ign, yo u elimina te the ne ed for link ages, thus decreasi ng w ei ght a nd redu cin g main tenance. Doing awa y with lin kages also means that the shock can be mounted di rectly to the swi nga rm, making shock removal . and accessibility 10 times easier. It also means that you have more optio ns as to w here you can mo unt the shock - and KTM chose to mo unt the shock on the side of the bike, thu s allowi ng the use of a larger airbo x. A larger airbox means more air, w hich mea ns more power - at least in theory. . H o w ev e r, KTM cla im s that th e biggest adva ntage of the PDS system is being able to buil d a stro nger chas sis , thus red ucing flex and increasing torsional resistance. So w hy didn' t KTM, or many of the ot her manu facturers, go to this non-link - age- ty pe sy s te m a lo ng ti me ag o? Because sho ck technology just w asn't there, as it took a long time to bu ild a shoc k tha t co uld perform two jobs at once con tr ol da mping' and produce pro gressive sensitivity (or a rising rate), a ta sk normally taken ca re of by ' the linkages. The KTM's WP shock is ex tremely com plex, as there are now two pistons ins id e the body: One piston h andles damping du ties and the ot he r - which incorporat es a "p rop rie ta ry ," or p ro gres sively tapered, needl e va lve - provides a rising-ra te func tion. KTM refers to its shock as the first shock "with a brain" - it ac tually ad ju st s itself as it travels ove r rou gh terrai n . > On e would think tha t a big cha nge like complet ely redesigning a suspension system would be all tha t a manufacturer could handle in just one model year, bu t this wasn't the case with KTM, whic h mad e man y other major changes to the bike, as we ll. One of those chan ges inclu d es the fork, where KTM aba ndoned the SOmm Mar zocchi Mag num fork for the SO mm WP "E xtreme" fo rk, w h ic h h as less un de rhang than the previous "Zokes." The new rear-su spen si on d esi gn u nderst and ably resulted in an all-new chassis and frame, inclu d ing the subfram e, seat, airbox an d bodywork com- , po nents. Just sitting on the bike for the r first tim e, you can certa inly feel a slim- .I