Fox Suspension Makes Your Harley Better

Fox offers full suspension kits for H-D touring models.

2018 Harley-Davidson Street Glide
Upgrading the suspension on this 2018 Harley-Davidson Street Glide improves rider confidence when heading into steep turns like this one.Fox Factory

Harley owners love to customize their motorcycles. Thousands of dollars are poured into parts while still-new pieces are thrown in the take-off bin. But while seats, handlebars, and exhaust pipes fly off the shelf, components critical to the way the bike rides are often neglected in lieu of their more visibly noticeable alternatives. A motorcycle's suspension affects almost every aspect of the ride, from acceleration and braking to cruising straight or twisty roads, and while onlookers may not notice an upgrade in your fork or shocks, you as the rider definitely will. Leading a new charge into American motorcycling and committed to proselytizing the value of good suspension is Fox Suspension, known for years in the dirt segment but now making a push into V-twin motorcycling with its fork cartridge kits and line of shocks.

Suspension isn't cheap, and demonstrating its value is difficult without being able to actually put riders on an upgraded bike to try out, but no other upgrade has a bigger impact for the price. The goal is to eliminate any large, jarring hits, smooth out the small bumps, maintain contact with the road, reduce fork dive on braking, all improving stability throughout straight roads and turns. To do this, we would be using the Grip Street Performance Cartridge Kit ($549) inside the fork, as well as the IFP-R Shocks ($799) set up in the back.

The Fox IFP-R shock
The Fox IFP-R shock ($799) that was installed on the tested H-D touring model.Fox Factory

The 2018 Harley-Davidson Street Glide I was testing came stock with emulsion shocks with adjustable preload on one of the two units. Stock shocks have the spring on the outside that is tightened or loosened by hand through an external preload knob, and a cartridge containing a mixture of oil and gas inside that is forced through two small internal holes (known as valving) to control damping and compression. Rebound and damping aren’t adjustable on this shock, and as the rider spends more time on the bike, the oil and air mix, emulsifying and lowering the hydraulic efficiency, leading to cavitation and the loss of damping.

Fox’s IFP-R shocks use an Internal Floating Piston (IFP) to separate the oil from the pressurized nitrogen compartment. As the shock compresses, the oil displaced by the shaft presses against the IFP, and the nitrogen charge behind it keeps the oil under pressure to avoid cavitation. While compression is not adjustable, a small knob at the bottom of the shock unit adjusts rebound by controlling oil flow around the main piston valve. When the needle is closed, all the oil flows through the main piston valving, creating the maximum damping forces for this particular tune. When the needle backs away, the jet port is open, and oil is allowed to flow through the shaft, bypassing the valving, and thus creating less damping. Preload and sag are easily adjusted at the top of the shock, and numbered markers make these adjustments quick and precise.

We tuned the shocks for our weight in the morning and made a couple of small adjustments throughout the day. Once we found a balance on the rebound adjustment, control on large bumps was greatly increased and small ones were practically inconsequential. Contact to the road felt constant and stable, and the rear end that had been wavering through the turns in stock trim had lost all of its wobble.

Grip Street Performance Cartridge Kit
A Grip Street Performance Cartridge Kit for Harley-Davidson models is available in 41mm or 49mm for $549.Fox Factory

Front suspension on stock 2017 and later H-D touring models is Showa Dual Bending Valve suspension, which uses two valves to generate both compression and rebound damping force, paired with progressive-rate springs. Progressive-rate springs have multiple tensions and are designed to fit a wide range of rider weights, still feeling responsive at the top for lighter riders, but stiff enough to avoid bottoming out with heavier riders. The crossover points from one spring rate to another can feel harsh, especially if the difference in rates is large. Manually adjusting preload on progressive springs can move the crossover points and create inconsistencies, as well. While stock suspension works decently well up front, the springs lead to inconsistencies that have you guessing where on the spring you’ll find yourself as you enter a turn.

Fox installed the 49mm Grip Street Performance Cartridge kit in the fork, which are rebuildable and tunable before they easily drop in. Just like the shocks, the cartridges keep oil and gas totally separate using an IFP, to keep the riding experience consistent no matter the amount of use. Dive on breaking is greatly reduced, contact with the road is improved, and any unsteady feeling through the turns has been all-but eliminated.

The real gain with this upgraded suspension is confidence. Heading into turns at speeds quick enough to upset the stock suspension, we found the Fox units smooth and predictable. Getting consistent responses in braking and cornering from the start to finish of the ride made me much more comfortable with the bike I was on, which led to a much more fun and spirited ride. For less than $1,400, Harley riders can vastly improve both performance and comfort, and the more riders who are able to test that out and see it for themselves, the more Harleys we’ll see with upgraded suspension.