75.5mm Seismic Alpha Defcon Longboard Skateboard Wheels

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(2 reviews)
  • Durometer: 78a and 76a
  • Width: 62.5mm
  • Contact Patch: 62.5mm
  • Lip Profile: Square/Sharp
  • Core Placement: Offset 6%
  • Wheel Surface: Smooth
  • Diameter: 75.5
Choose Variation
$97.00 USD
1 Quantity = 4 Wheels, enough for a complete longboard.

The 75.5 Seismic Alpha Defcon was designed for maximum roll speed on smooth surfaces. Racers or riders that aim for speed will find what they are looking for in the new Alpha Defcon formula.

Defcon Formula and the Fushion Core explained in more detail by Seismic Team Riders:

76a Defcon: Vice-like grip and very snappy directional slide, with plenty of slowdown power. Ideal for aggressive racing.

78a Defcon: Very stiff edges that give loads of grip with a friendly slide and crisp hookup. Ideal for smooth roads and lighter riders.

The 75mm x 63mm Alpha Race Wheel
Stout S-shaped lip profile optimizes edge support, maximizes edge-hold under extreme G’s, and ensures predictable slide initiation & hookup
0.5mm concave running surface pre-loads lips, heightens rebound, and enhances in-slide feedback
6% offset for progressive lip engagement and more consistent wear

Debuting our proprietary Fusion Core!
Measures a whopping 46mm x 44mm – making it the largest & most supportive hub on the market for a wheel of this size!
Deep “saddle” profile minimizes lateral wheel flex and creates outstanding mechanical lock w/urethane
Unmatched edge support
Robust bearing lugs
Fiber-reinforced 85D – the strongest, toughest hub material in the industry

Guinness WR roll speed
Directional slide
Long-lasting grip
Slow, consistent wear

Seismic's Description

A perfect balance of optimal properties for modern competitive racing: size and momentum to carry you past the competition in straightaways; finely-tuned width and supremely supported edges for smooth, predictable handling through even the hardest corners; and the very fastest urethane that the skateboard industry has ever seen, bar none.

Available in two proprietary formulas –

Defcon™: Guinness WR speed • directional slide • long-lasting grip • slow, consistent wear

BlackOps™: ultimate balance of speed and grip • extreme traction fresh • buttery and smooth broken-in • comfortable and predictable

A giant step forward in race wheel engineering. The Alpha’s stout S-shaped edge profile optimizes lip support, maximizes traction under extreme G’s, and ensures predictable slide initiation and hookup. The running surface features a 0.5mm concave that pre-loads the edges, heightens rebound, and enhances in-slide feedback. The bearing seat is offset 6% for progressive lip engagement and more consistent wear.

The Alpha™ also marks the debut of Seismic’s proprietary Fusion™ core – at 46mm tall x 44mm wide, the largest and most supportive hub ever seen in a wheel this size. Features include a deep “saddle” profile, 8 perpendicular support beams (hollowed-out for lightness and aesthetics), and robust bearing lugs. The Fusion minimizes lateral wheel flex, supercharges edge support, and assures absolute mechanical lock with the urethane. Formed from 85D fiber-reinforced thermoplastic – the toughest hub material in the industry.

75.5mm tall x 62.5mm wide ALPHA Wheels
62.5mm running surface • Bearing seat offset 6% • Square outside edge, straight-cut inside edge
8.125 oz. each • Sold in sets of FOUR wheels


Fastest Wheels
on 2021-08-31 Verified Purchase
Rode these at my first ever race and placed 3rd in the finals. I rode green Cuei Killers for downhill before these and they are definitely faster. The grip is about the same but less contact patch and same grip mean faster speed because that's less friction (material) on the pavement than the Killers. Also, they accelerate super quickly and feel really nice through diving turns when you have to sink into that deep lean at 35+ mph. I would be buying another set if they were in stock
Fun for lighter riders
on 2019-12-29 Verified Purchase
Despite the Mango Alpha's reputation as a killer race wheel, I decided to try the Mint Alphas this time around. As a lighter rider, I figured the harder duro might feel better, especially during pre-drifts. I'm pleased to say that fresh Mint Alphas were exactly what I was looking for. They accelerate crazy fast and the roll speed is uncanny. Being a bit harder, the kick out on them is much easier and has none of the chatter I get as a lighter rider on many softer square lipped wheels. I feel confident sliding these even in the cold. The only downside is durability, I feel like I scrubbed these quicker than the Mangos would have lasted. But even scrubbed, they're a fun wheel and plenty grippy for most grip runs I do. Would 100% recommend, just be aware that the trade off for easier kickout and insane roll speed is a bit less durability.