The OEM FOX 2.5 Internal Bypass is a great product and allows the f-150 to do things no other truck on the market will do. The valving and spring package was developed in conjunction with FOX and Ford to deliver great on and offroad performance. Compromises in valving, spring selection, and ride height had to be implemented to meet roll and vehicle dynamics testing standards for new production vehicles
The FOX Factory Series 3.0 front and rear upgrades are basically full blown bolt-on offroad racing shocks. They will deliver superior offroad performance by utilizing FOX's race department developed tuning specs, springs, and patented technologies. Being that they are a product of our offroad race department we've utilized materials and components that may require more frequent service then the OEM equipped product.
The patented FOX Factory Series 3.0 Coilover is the only position sensitive internal bypass shock on the market. Here are the differences between a position sensitive internal bypass shock and a velocity sensitive shock with a reservoir compression adjuster.
A compression adjuster that is located on the reservoir of a velocity sensitive shock adjusts the stiffness of compression by restricting the rate of oil flow into the reservoir. When the shock shaft moves into the body of the shock it takes up volume, the added volume requires that the excess oil to be transferred into the reservoir. By restricting the flow rate in which this oil is transferred you can make the shock stiffer. The drawback to this technology and to velocity sensitive shocks in general is that you cannot control where in the shock travel the added stiffness or compression comes into play. In order to keep the truck from bottoming out at high shaft speeds you need to increase valving and restrict the flow to the reservoir via the adjuster. The huge compromise is that at slow shaft speeds this will give the truck an extremely harsh or stiff feeling, making the truck skate on graded roads and bounce going down the highway.
A position sensitive internal bypass shock has multiple compression and rebound shock travel stages that are tuned independently of each other. When the truck is near normal ride height the shock piston is traveling within a zone that delivers a plush comfortable bottomless feel, allowing the transfer of weight for traction and that planted confident steering wheel feel in corners. When the truck takes a large ditch or lands from a jump, the shock piston travels into progressively stiffer zones to catch and slow the suspension before bottoming. Along with the increased compression control in the zone near bottom out, the internal bypass has an increased rebound control zone, which prevents the truck from bucking or bouncing after a hard hit. On the reverse end of the shock, when the truck becomes airborne the shock piston will travel down into a near top out zone to catch the suspension from having a hard stop, which prevents joint failure, and increases suspension component longevity.
