HST 4.0 Flow Kit — Full Truck Rebuild

Ten years in the making

Riders asked for more connected carving through the full lean range. Space inside the HST baseplate made traditional bushing solutions impossible. The Flow Kit solves it with a cast polyurethane compression bushing positioned inside our strongest spring. Here's a full blog on the Flow Kit and how it evolved.

Progressive Compression Technology (Patent Pending)

As you lean deeper, the wave cams and hanger compress the bushing against the baseplate, producing a non-linear force curve that gets progressively stiffer with lean angle. No hard stop at maximum. Full-range carving with a cushioned transition at the extremes.

Now with the Wave Cam 4.0

Our fourth-generation wave cam — single-axis geometry, two-piece all-nylon construction, with the cam key molded integrally into the lower. FEA shows peak slot stress reduced 2.77× vs. the 2.0, and off-axis rotation is eliminated at the source. Read more about the Wave Cam 4.0 →

Every component engineered

• Wave Cam 4.0 — single-axis, two-piece fiber-reinforced nylon

• 85 mm precision kingpins — threaded to prevent over-tightening

• Molybdenum-impregnated nylon washers — self-lubricating, virtually silent

• Cast polyurethane compression cone bushing — the patent-pending progressive element

• Optimized dimensions throughout for maximum carve

Spring options

Silver (2,700 lbf/in) — shorter and narrower decks (under 45"), traditional longboards. Responsive carving.

Gold (3,000 lbf/in) — longer or wider decks (45"+). Our strongest compression springs, for aggressive riding.

No Springs — if you already have springs you love, or want to source them separately.

If your HST Trucks are more than five years old, new springs are strongly recommended.

What's included (services two trucks)

• 1 × Wave Cam 4.0 Set (both pairs — enough for two trucks)

• 2 × 85 mm precision kingpins

• 2 × Molybdenum-impregnated nylon washers

• 2 × Cast polyurethane compression bushings

• 1 × Kingpin hex tool

• 1 × Wave cam lubricant packet (3 cc)

• 2 × Springs (Silver or Gold configuration only)

100% backwards compatible with all HST Trucks and Original Skateboards S8 trucks. 
(Note Photos will be updated asap).

How to Install & Adjust Your Wave Cams 📹 How-To Video

⚠️ Important: Do not over-tighten the kingpin. Especially on Original and first-generation HST Trucks with the Flow Kit, tightening the kingpin all the way down — especially with the bushing installed — can crack the wave cams, particularly in cold weather. A couple of threads showing through the locknut is enough — watch the video below for the correct technique. You may prefer to ride without the bushing entirely if you like a looser, more traditional feel.