# Seismic - 80.5mm ALPHA [DH]

**Spec:**  
Diameter: 80.5mm  
Width: 61mm  
Durometer: 74a, 76a, 78a  
Contact Patch: 60mm  
Lip Profile: Square/Sharp  
Core Placement: Offset  
Wheel Surface: Smooth

 80.5mm tall x 61mm wide DH Race: Superior top-end roll speed, traction, and braking power… with surprising quickness and agility for a wheel of this heft!_  
60mm running surface • Bearing seat offset 3.5% • Square outside edge, straight-cut inside edge • 9.125 oz. each_

**_A highly-optimized balance of properties for modern racing  
_**• Size and momentum to carry you past the competition in straightaways – yet agile enough for quick acceleration, fast edge-to-edge adjustments, and snappy technical pre-drifts. Welcome to a whole new realm of _FAST!_  
• Finely-calibrated width and supremely supported edges for smooth, predictable handling through even the hardest corners.  
• The very fastest urethane that the skateboard industry has ever seen, bar none.  
• Named after the Greek letter “alpha” (α), used in science to represent rotational acceleration.

**_A giant step forward in race wheel engineering  
_**• Stout S-shaped edge profile optimizes lip support, maximizes traction under extreme G’s, and ensures predictable slide initiation and hookup.  
• Running surface features a 0.5mm concave that pre-loads edges, heightens rebound, and enhances in-slide feedback.  
• Bearing seat offset 3.5% – 6.5% for progressive lip engagement and more consistent wear.

_**The Fusion™ core – integrating 15 years of advanced hub R&D**_  
• 46mm tall x 44mm wide – the largest and most supportive hub ever seen in a wheel this size.  
• Deep, wide “saddle” profile regulates lateral wheel flex, supercharges edge support, and ensures absolute mechanical lock with the urethane.  
• 8 lateral support beams (hollowed-out for lightness and aesthetics) form wide ridges that create _unprecedented circumferential lock and rebound_.  
• Robust bearing lugs.  
• Formed from 85D fiber-reinforced thermoplastic – the toughest hub material in the industry.

_**Available in DEFCON™ ultra-high-rebound formula, in two finely-tuned durometer choices**  
_Thoroughbred race ‘thane • Guinness WR speed • directional slide • long-lasting grip • slow, consistent wear  
_• 74A Plum (Aaron Hampshire pro signature wheel): Plush, velvety roll with extra edge hold, even on rough roads._  
_• 76A Mango: Vice-like grip and very snappy directional slide, with plenty of slowdown power. Ideal for aggressive racing._  
_• 78A Mint: Very stiff edges that give loads of grip with a friendly slide and crisp hookup. Ideal for smooth roads and lighter riders._

## Details

- **Price:** 908.0 HKD
- **Vendor:** Seismic
- **Type:** Wheels
- **Tags:** 74a, 76a, 78a, 80.5mm, Downhill Wheels, Seismic, Sharp&Square, Ungrounded, Wheels

## Variants

| Variant | Price | Available |
|---------|-------|-----------|
| 74a (Purple) | 908.00 HKD | In stock |
| 76a (Mango) | 908.00 HKD | In stock |
| 78a (Mint) | 908.00 HKD | In stock |

## Images

- Seismic - 80.5mm ALPHA [DH]
- Seismic - 80.5mm ALPHA [DH]
- Seismic - 80.5mm ALPHA [DH]
- Seismic - 80.5mm ALPHA [DH]
- Seismic - 80.5mm ALPHA [DH]

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> Source: [SBDW Longboards Hong Kong](https://sbdwlongboards.com/products/seismic-80-5mm-alpha-76a-78a-dh)
> Updated: 2026-05-17