The Heavy Hitter Stainless Top Headset Bearing Shim is a precision-machined one-piece stainless steel shim that replaces the standard split aluminum compression ring on MTB-style e-moto fork stems, made by Heavy Hitter and sold here at GritShift. It gives 100% bearing race contact on 28.40 mm stems to eliminate steering play, and weighs 0.01 lb.
Specs verified September 2026 against the live GritShift product page.
Specifications
| Material | Stainless steel, precision-machined one-piece |
|---|---|
| Weight | 0.01 lb |
| Replaces | Standard aluminum split compression ring |
| Bearing race contact | 100% across the entire interface, versus 2 to 3 mm on most split aluminum shims |
| Stem size | Standard MTB fork stems, 28.40 mm +0.20 mm |
| Fit tolerance | Machined with an air-gap tolerance for an exact fit on properly sized stems |
| Designed for | OEM tapered roller bearing, part 32906 (bearing not included) |
| Fork platforms named | Fox 40, DNM, FastAce, KKE, Rfloxa, EXT, Sirris CMX fork and similar MTB-style setups |
What bikes does the Heavy Hitter headset bearing shim fit?
- Universal: most e-motos using standard MTB fork stems (28.40 mm +0.20 mm)
Heavy Hitter names e-moto platforms running MTB-style fork setups such as the Fox 40, DNM, FastAce, KKE, Rfloxa, EXT and Sirris CMX fork. Measure your stem before ordering.
Why replace the split aluminum compression ring?
Most split aluminum shims rely on only 2 to 3 mm of contact area, which leaves room for unwanted movement and uneven load distribution. The Heavy Hitter shim is one piece and gives 100% bearing race contact, so force is distributed evenly through the whole interface. Heavy Hitter states the result as smoother steering feedback, longer bearing life and zero wiggle or slop, even after repeated high-impact riding.
Why is the shim tight to install?
Each shim is precision-machined with an air-gap tolerance for an exact fit on a properly sized 28.40 mm stem. That makes it slightly tighter to install than a split ring, but once seated it holds perfect alignment with zero flex. It is designed around the OEM tapered roller bearing, part 32906, which Heavy Hitter says outperforms ball-bearing upgrades that often reduce durability under load. The bearing is not included and is shown for reference only.
What else tightens an e-moto front end?
The shim addresses play at the top bearing race. For the steering stem itself, Heavy Hitter also makes the Heavy Hitter E-Moto Stem Lock, a universal bolt-on that locks the stem to prevent flex under jumps and hard landings.
Where can I buy the Heavy Hitter Stainless Top Headset Bearing Shim?
Right here. We sell the Heavy Hitter Stainless Top Headset Bearing Shim at GritShift. Browse every Heavy Hitter part we carry in our Heavy Hitter collection.
