Fox 2.5 Factory Series vs 2.5 Performance Series Coilovers

*Updated 4-20-16 to reflect newest version of Fox 2.5 Factory Series Shocks.

In 2014, Fox launched the 2.5 Performance Series coilovers for their off-road division to better compete with the more affordable King and Sway-A-Way shocks. The Fox 2.5 Performance Series coilovers feature industry-standard components, allowing them to offer a more budget-friendly option compared to the Fox 2.5 Factory Race Series coilovers. This article also includes a review of the latest upgrades to the Fox Factory Series coilovers.

Performance

Friction

Friction plays a crucial role in shock performance, as it contributes to harshness and limits damping control. Its impact is especially noticeable on lightly sprung vehicles, where friction makes up a larger proportion of the damping.

In 2016, both the Performance Series and Factory Series Fox 2.5 Coilovers were updated to reduce friction and improve damping consistency. These shocks now report 18 lbs (+/- 3 lbs) of friction, which is impressive for a large-bore off-road shock. Additionally, the friction remains stable across a variety of gas pressures (tested up to 300 psi), leading to more reliable performance.

Piston & Damping

In 2015, both the Fox Performance Series and Factory Series 2.5 coilovers were equipped with new pistons. The Fox 2.5 Factory Series piston features a high-flow race design with 3D CNC porting to optimize ride quality, while the Performance Series uses a standard, low-flow piston designed for ease of manufacturing. For an additional $50, the 2.5 Performance Series shocks can be upgraded to the 2.5 Factory Race Series piston. Both pistons come with two 0.098″ bleed holes from the factory, though we can customize the setup by adding either one or three bleed pistons as needed.

Compression

The new Fox 2.5 Performance Series coilovers feature much smaller compression ports, significantly reducing flow and increasing load. This change in compression damping is quite pronounced and may require specialized valving techniques on lighter vehicles with a 1:1 motion ratio to prevent harshness during compression. Fortunately, we have all the expertise and tricks needed to optimize their performance for you.

The new Fox 2.5 Factory Series coilover pistons feature a high-flow design with 3D CNC-ported inlets, which help reduce harshness and enhance the ability to fine-tune the shock for improved performance.

Rebound

The Fox 2.5 Performance Series coilover piston features small round rebound ports, which may require tuning adjustments on lightly sprung vehicles. In contrast, the new 2.5 Fox Factory Race Series coilover pistons have larger round rebound ports, offering enhanced tuning capabilities for lighter vehicles. Both pistons, however, should perform excellently on heavily sprung applications.

Wear Band

Both the Performance Series and Factory Race Series Fox 2.5 Coilover Shocks now feature an upgraded wear band with an o-ring preloader. The new wear band is made from a lower-friction, less abrasive, and more durable material, paired with an o-ring to enhance damping consistency. Over time, traditional wear bands can lose material, which contaminates the oil and reduces damping performance while increasing wear. The improved wear band addresses these issues, offering better durability and consistency. Additionally, the pre-load o-ring helps reduce oil blow-by around the piston, further improving performance. This upgrade is a significant improvement for both shock series.

Durability

There are some substantial durability differences between the Performance Series and Factory Race Series Fox 2.5 Coilovers.

Piston Rod

Piston rods are crucial for the durability of a shock, as they are highly susceptible to damage from flying debris, which is the leading cause of shock leaks. Using a harder, stronger piston rod significantly reduces the likelihood of a leaky shock. Factory Series shocks feature a 17-4 H900 stainless steel piston rod, known for its exceptional strength, resistance to flying debris, and corrosion resistance. The Fox 2.5 Factory Series piston rod is regarded as the best in the off-road industry. On the other hand, the Fox 2.5 Performance Series coilover shocks use a high-carbon steel piston rod, likely made of 1040-1060 case-hardened steel. High-carbon steel rods are industry standard and are similar to those found in King Performance Series shocks. As shown below, the Factory Series piston rod offers twice the resistance to flying debris (HRc) and nearly twice the strength.

Seals

The Fox Performance Series coilovers retained a urethane wiper and Buna main seal from the original blue Fox 2.5 coilovers. However, the main seal in the Fox Factory Series shocks has been upgraded to Viton, a material renowned for its superior durability and heat resistance. Over time, Buna seals can harden from high temperatures, making them more prone to leaks. While it’s difficult to pinpoint the exact temperature range for Fox seals, standard Buna is typically rated for 225°F, while Viton is rated for up to 350°F, offering significantly better heat tolerance.

Oil & Valving

Fox 2.5 Factory Series & Performance Series shocks both use the same JM92 oil and the same valve disks on compression and rebound.

External Parts

Bearings & Hardware

Both the Factory Series and Performance Series 2.5 Fox coilovers use COM-10T (5/8″ ID) bearings and come with spacers designed to fit a 1/2″ bolt with a 1.50″ width. The spacers in the Fox 2.5 Factory Series are made from 304 stainless steel, while the Performance Series spacers are made from zinc-plated steel. Both spacers feature o-rings to control rotation, but you can easily remove the o-rings to allow for full misalignment.

Dual Rate Stop Nuts

Fox Factory Series dual-rate coilover nuts are made from steel, while the Fox Performance Series dual-rate coilover nuts are crafted from aluminum. Both use the same dual-rate slider, and no functional differences have been observed between the two materials.

Remote Reservoir & Hose

In 2016, the Factory Series shocks were upgraded to feature new aluminum reservoirs. These reservoirs are lighter and include redesigned internal components that enhance damping consistency. The Factory Series shocks also use a high-quality -10 braided hose with reusable aerospace-style fittings, while the Performance Series shocks are equipped with industry-standard -8 crimp fittings and rubber hose.

Rod Ends & Lower Spring Perches

Fox 2.5 Factory Series coilovers feature a long rod end that fits well into trailing arms, keeping the spring perch protected. In contrast, Fox 2.5 Performance Series coilovers have a shorter rod end, which may require careful fitment inside deep trailing arms. The longer rod end on the Factory Series also accounts for some of the length difference between the two shock models. Additionally, the Factory Series 2.5 Fox coilovers use a clam shell design to hold the spring force, while the Performance Series 2.5 Fox coilovers rely on a snap ring. The snap ring is heavy and can be prone to scratching the rod end. For those seeking a similar shock length, the Factory Series 2.5 coilovers are available with a 1″ shorter rod end, making them nearly identical in length to the Performance Series.

Summary

Fox 2.5 Performance Series coilovers use industry-standard parts and a lower-performance piston, offering exceptional value for recreational users. However, for extreme off-roaders, racers, or those operating in corrosive environments, the Fox 2.5 Factory Series coilovers are the better choice due to their enhanced durability and performance.

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