Cycle News - Archive Issues - 1970's

~at Richt er helped develop the Fox dual-rate Airshox. ~ '"To set th e shock up rig ht a fellow has to hav e a nitrogen air tank system , :Yhich is somewhat expensive, " ~xplains Bob. "It's a shock that has to be maintained week ly - certainly not a non-maintenance shock for the trail rider. J " Because of the rubber bladder design in the AirShox , and because no rubber is perfect, gas will permeate through the bladder and air pressures \:.oill change over a period of weeks. Air pressure needs to be reset every ,weekend , and oil in the shock should be changed every one or two months. "Actually, air can be used in suspension systems instead of nitrogen . In theory the oxygen in air will somewhat oxidize oil , but it takes a long time to happen." Brad Lackey and Pat Richter ran a set of Fox Shox with single air settings and external coil steel springs at the last few Trans-AMA races. Are these ' pro totype units , and what changes have you made to the Fox Shox since they were first introduced ? "The first AirShox had single-rate air settings and featured adjustable damping which · could b e set extl;rnally," says Bob . " Present shocks Fox Shox are hand assembled and dyno tested. now have dual -rate air settings '- one for initial soft rate travel and the other for firmer full travel use as the shock nears bottoming out. It 'definitely ' works better than any dual -rate exter na l spring system. When we went to the dual -rate air system , though , we had to do awa y with the external damp ing adju stm ent feature . Damping now is changed internally by the replacement of Holly automotive carburetor jets. Right now we're working on an improved damping system which will give less damping at high operating speeds, and ' more damping at low shaft speeds. "Regarding the air/spring shock experiment seen during the TransAMA Series, Kent, Brad, Pat Richter and Gary Chaplin all seemed to like the regular dual air pressure setup better. It was interesting to note , that in some situations they thought the spring/air setup did work better. I should make not e that anytime modifications are made to th e Air Shox . bolt -on kits will always be made available to update older shocks so they never be come obsolete. The improved damping changes we're working on will be available in a kit for about SIO. "T he Fox Shox may seem like a lot of money to invest in a shoc k absorber initiall y wh en comp ar ed to a co nventi ona l sho ck , but for th e serious particular was a dual air spring system for front forks , similar in principle to the dual air sp rin g system for the Fox AirShox . The dual rate air fork system allowed p recise dialing-in of air sp ru ng forks for small and large bumps, some thi ng th at really can't be done with single stage air forks . Brad Lackey used su ch a pair of dual rate air forks on his factory Husky for almost a n entire year. Unfortunately, marketing suc h a kit in large enough volume to be profitable would be difficult, because it would have to cost arou nd $80 -100 and require that forks be sent t o Moro -X Fox for , modification , A more practical and less expensive solu tion is to use soft springs in conjunction with single stage air forks , similar to th e prototype Kayaba forks on the Japanese works bikes. Moto-X Fox is presently marketing such kit s for all major brands of dirt bikes. Stev e Simmons is presently working on a leading a xle front fork assembly spec ifica lly for front wheel travel over th e l Ovinc h lim it. The forks will hav e super thick tubes to do away with flex , 'a nd lots of slider overlap for safety and no seal leaking. It wouldn't be too difficult to offer such forks with a dual rate air spring option , the advantages of which would be total tuning-in of the forks for track conditions and less unsprung weight. Steve's 'new forks should be available through Moto-X Fox early in 1977 . Because they seem to know more about suspensions than anyone in America , we asked Bob and Jeff where they felt suspension technology was heading. " I think suspension travel will reach its limits up around 12 inches ," says Bob, "T he new smaller-diameter rear tires like the 4.50 x 17 which Brad used during the Trans-AMA could help suspension operation as far as giving better, traction , but it has to be r emembered that a tire is an un d am ped spring and -it will affect shock damping." "We feel that Kent Howerton's rear suspension, which Er1c Crippa modified to allow the use of a longer shock mounted on the swingarm near the rear axle, is the ideal setup ," says Jeff. " T h er e's less stress on the ' swingarm that way . The setups which are on the Suzukis and the Maicos aren't very good because they allow the swingarrns . , particularly on the production bikes, to flex too much , whi ch also puts a lot of stress into the fram es, Suzukis have alw ays had flex 'pro blems with the RM swingarms , and while the aluminum-box swingarms which are , available from accessory companies correct some of the problems, they don't solve all of them . Fox is now offering swingarm kit s with 17;-2-inch shocks mounted near the rear axle for Suzuki RM 250 /370 , Husky GPs , and Honda CR-125s (I5 l-2 -inch shocks). "R id ers think they can get more rear wheel travel by bolting on longer shocks, but it isn't a good idea. Jim Pomeroy wanted to use our shocks on his Bultaco, but we couldn't offer him our shock in the same length as the Koni s he was using without causing him to lose an inch of travel. Our shocks have beefier bearings and internal parts which take up more .sh aft travel than normal sho cks . For b ikes to get more rear wheel travel , the frames , or swingarms need to be modified. That's where we feel our new swingarm /shock kits will De a good idea, Just ask Kent Howerton or Steve Wise how well they work. " Bob and Jeff Fox are deep ly involved in th e improvement of suspension components for off road comp etition . Their engineering background g-ives th em the knowledge to design and build some of the best suspension systems' available, rivaling the top Japanese and European companies, Amazing what a little ingenuity can do. • Experi m ental air /spring shock s on Kent How erton' s Hus k y, race r - over an en tire sea son or two of racing - he will end up spe nd ing less becau se he won 't be repla cing shocks every co uple of m onths, And he'II ha ve the best shocks avail able . I've been worki ng on th ese shoc ks for two years a nd have yet to make a dime on th em beca use I'm consta nt ly inc orporating new d esigns into them and cha ngi ng toolin g , I guess I'm too mu ch of a good engi neer a nd not eno ugh of a business m an ." So me of th e ideas whi ch Bob and J eff have developed , with th e help of assoc ia te Steve Simmons, have proved to be pr etty sp ectacula r. One in 13

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