SCS, HIC and IHC Compression Systems: Differences and Compatibility

⚡ In short: the type of compression is determined by the forks. The handlebars and clamp are selected for it.

Compression tightens the headset so the handlebars have no play while still turning smoothly. Today, three systems are used: SCS (the strongest and heaviest, with handlebars without a slit), HIC (oversized 35/32 steel handlebars with a slit), and IHC (the lightest, most common on complete scooters, with handlebars with an inner diameter of 28 mm). The fourth, ICS (a bolt underneath the fork), is a thing of the past and is found only on old scooters.

If you’re not sure what you have, see the section How to tell which compression I have. It is always tightened in the order compression → sleeve.

🔩 What is compression and what is it used for on a scooter?

A freestyle scooter does not have a folding joint. The handlebars, fork, and deck are held together by three components that must work together:

• Headset (headset assembly) consists of two bearings in the deck’s head tube. They allow the fork and handlebars to turn.
• Compression is a bolt (and a washer, cap, or clamp that goes with it) that pulls the fork toward the deck so there is no play in the headset, while still allowing the handlebars to turn smoothly. Without compression, the handlebars would rattle, and the play would increase with every impact.
• Clamp is a ring with 2–4 bolts that tightens the handlebars around the fork steerer to prevent them from rotating. The number of screws is not important.

There are three common compression systems: SCS, HIC, and IHC (and the historical ICS, which is no longer used today). They differ in the route of the compression bolt and in which fork and handlebars they fit. They all do the same thing, but they are not interchangeable. The type of compression is always determined by the fork; the handlebars (inner and outer diameter, with or without a slit) and clamp are then selected to match.

The same sequence applies to all systems: tighten the compression fitting first, then the sleeve. The clamp fixes the handlebars to the fork, so the compression bolt would have nothing left to tighten. In detail in the How to tighten the compression correctly section.

🅰️ SCS (Standard Compression System): the strongest, but heaviest

How it works: SCS is a large clamp with two diameters: the lower part clamps around the fork steerer, while the upper part holds the handlebars.

The compression system is hidden inside the stem: the compression bolt with the top cap screws down into the threads in the fork and presses against the stem’s inner edge, tightening the headset. The clamp then secures the handlebars with four (three on lightweight models) side bolts. The compression fitting and the sleeve are therefore one piece.

Who it’s for: for riders who want maximum strength: heavier or taller riders, street riding, hard impacts. It is the most robust system and also the most difficult, so it is used less with the youngest children.

• Fork: SCS or HIC fork (they are identical; the steerer tube has a built-in thread for the compression bolt). The fork must not extend beyond the inner edge of the clamp, otherwise the compression will not tighten fully. It is fixed by adding a spacer under the stem or shortening the fork.
• Handlebars: ideally without a cutout. The SCS clamp tightens around the entire circumference of the handlebars, so it would pinch the slit and the handlebars would crack. Handlebars with a notch can only be used with a bar adapter (a metal insert that fills the notch). All three diameters fit: standard steel 32/28, oversized 35/32, and aluminum 35/28.
• Socket: SCS itself. The inner diameter of its upper part must match the outer diameter of the handlebars: 32 mm (standard) or 35 mm (oversized). Standard 32 mm handlebars work with oversized SCS only with a shim.
• How to tighten: place the clamp on the fork, screw in the compression bolt from above, and tighten it until the headset has no play and the handlebars still turn freely. Tighten the lower clamp bolts (the ones that clamp the fork). Then install the handlebars, align them with the front wheel, and tighten the upper clamp bolts.

🅱️ HIC (Hidden Internal Compression): rigid, for oversized steel handlebars

How it works: An HIC shim is placed on the fork steerer tube (the same as with SCS), increasing its diameter so that it fits inside oversized handlebars. The compression bolt with a cap screws down into the built-in thread in the fork and presses the washer against the deck’s head tube, tightening the headset. The handlebars are then fitted over the spacer and secured with a standard clamp. The entire compression mechanism is hidden inside the handlebars, hence “hidden.”

For whom: for riders who want a solid system, but one that’s lighter than SCS.

Typically mid-range and high-end, street and park. Disadvantage compared to SCS: the handlebars must have a slit, which is always a weaker point than a solid tube.

• Fork: HIC or SCS fork (same steerer tube with an integrated thread). Older forks used a press-fit “star nut” (starnut) instead of a thread; you won’t find it on modern forks.
• Handlebars: only oversized steel or titanium handlebars, 35/32 (35 mm outer diameter, 32 mm inner diameter) with a slit. Neither a standard 32/28 nor an aluminum 35/28 will work with HIC, because they have a narrower inner diameter and the HIC shim won’t fit inside them.
• Clamp: standard (non-SCS) with an inner diameter of 35 mm, most commonly with two or three bolts. It should cover the notch.
• How to tighten: install the HIC spacer, screw in the compression bolt, and tighten to the sweet spot (no play, smooth rotation). Then install the handlebars, align them with the wheel, and tighten the clamp in a cross pattern. If you want to tighten the compression later, you need to loosen the sleeve, remove the handlebars, and tighten the bolt from above.

🅲 IHC (Internal Hidden Compression): the lightest and most common on complete scooters

How it works: the same principle as HIC, but the IHC fork has a thinner steerer tube. As a result, it fits handlebars with an internal diameter of 28 mm, including standard steel and aluminum handlebars. An IHC compression ring (the smaller C-ring) is inserted into the upper headset bearing to fill the gap between the narrower steerer tube and the bearing. Fit the IHC shim onto the bar, then place the cap on top and thread the compression bolt into the built-in thread in the fork.

For whom: for most children and beginners. It is the lightest system, and you will find it on most complete sets in the intermediate and beginner classes. The thinner bar is also its limitation: for the hardest street riding and heavier riders, advanced riders tend to choose HIC or SCS.

• Fork: IHC forks only. Cannot be combined with another system.
• Handlebars: any handlebars with an inner diameter of 28 mm and a slot: standard 32/28 steel and 35/28 aluminum. Oversized 35/32 doesn’t fit on IHC, even with an adapter.
• Clamp: standard (not SCS). Inner diameter according to handlebar outer diameter: 32 mm for standard steel handlebars, 35 mm for aluminum handlebars. An oversized 35 mm clamp can also be used on 32 mm handlebars with a reducer (shim), if one is included.
• How to tighten: insert the IHC ring into the bearing, fit the washer and cap, tighten the compression bolt until it reaches the sweet spot, install the handlebars, align them, and tighten the clamp. As with HIC, the handlebars must be removed to tighten the compression.

🕰️ ICS (Inverted Compression System): a historical system with a bolt at the bottom of the fork

ICS is an older system that is no longer used today and is only found on old scooters. A long compression bolt passes through the fork from below (from the front wheel) and threads into the star nut inside the handlebars; the handlebars have an internal diameter of 28 mm and a slot. The front wheel must be removed for tightening. If a scooter like this knocks and the headset slips, converting it to IHC or HIC (new fork + handlebars) is usually a more sensible option than repairing it.

🔩 Threaded system: what you’ll find on the cheapest scooters

Before SCS/HIC/IHC came along, scooters were held together like an old bicycle: a threaded fork, a threaded (non-integrated) headset, and two nuts tightened against each other. The lower matrix pulls the headset down, while the upper one counteracts it. The handlebars are held in place by a clamp.

It is very cheap, which is why it is unfortunately still used in the cheapest sets. Disadvantages: threaded forks crack sooner, cheap headsets wear out quickly, and the nuts are difficult to tighten enough to stop the handlebars from rattling. If the scooter is only used for riding, you can live with that. For jumps and tricks, we recommend a scooter with an integrated headset and one of the three modern compression systems (SCS, HIC, IHC). Parts for the threaded system are hardly sold anymore these days.

📋 What fits with what: compatibility table

Handlebar diameters are given as outer / inner in mm. Standard steel = 32/28, oversized steel or titanium = 35/32, aluminum = 35/28. More in the article How to Choose Handlebars for a Freestyle Scooter.

A shim is a thin reducing insert that decreases the clamp’s inner diameter from 35 to 32 mm. Many oversized sleeves include it in the package. You can find compression parts in the HIC, IHC, ICS, shims and star nuts category, regular clamps in the clamps category, and SCS clamps in the SCS category.

🔍 How can I tell which compression I have?

You don’t have to take anything apart. Just take a look at the connection between the handlebars and the fork:

If you're not sure, take a photo of the handlebar and fork connection from the side and above and send it to us, or bring your scooter to our store in Pardubice. It’s especially useful before buying new handlebars.

🔧 How to properly tighten the compression and what to do if the handlebars rattle?

Properly tightened compression has a sweet spot: there is no play in the headset, but the handlebars still turn smoothly and easily. Over-tightening the compression “to the max” won’t improve anything; on the contrary, it makes turning harder (which gets in the way of barspins and whips) and prematurely wears out the headset bearings. Insufficiently compressed snow clumps together and keeps coming loose with every impact.

1. Loosen the clamp (on SCS, the lower bolts that clamp the fork). As long as the clamp holds, the compression screw has nothing to tighten.
2. Tighten the compression screw in small increments. After each step, grip the front wheel between your feet, hold the handlebars, and try rocking them back and forth. Once the will disappears, stop.
3. Check the rotation: the handlebars must turn freely without rubbing. If they rub, loosen them a little.
4. Align the handlebars with the front wheel and tighten the clamp: tighten the bolts gradually, evenly, and in a crisscross pattern (for four bolts, use the sequence 1-3-2-4).

Tools: an Allen key is all you need for the compression bolt and clamp, most commonly 6 mm (the size varies by manufacturer). The full inspection procedure for a new scooter is covered in our guide How to assemble a new freestyle scooter and what to check before your first ride.

⚠️ Common mistakes

• Notched handlebars in an SCS without an adapter. The notch clamp presses in, and the handlebars crack at the bottom. Either handlebars without a notch or a bar adapter.
• Oversized 35/32 handlebars on an IHC fork. It doesn’t fit, and no adapter will fix it. Only the inner diameter of 28 mm fits the IHC.
• Aluminum or standard handlebars for HIC. The HIC shim does not fit inside a 28 mm inner diameter. HIC = only 35/32.
• Tightened sleeve, then compression. Then there is nothing for the compression to pull down, and the handlebars keep knocking. The order is always compression → sleeve.
• Compression tightened to the max. The handlebars rub, and the headset bearings wear out. Look for the sweet spot.
• Clamp above the notch. The notch should ideally be completely beneath the clamp. If the clamp fits only over the end of it, the handlebars break at the notch.
• Mixing parts from different systems. IHC fork with an HIC shim, an HIC shim on an IHC fork, and so on. Each system has its own components; they are not interchangeable.

❓ FAQ