Speed Wobble Risk Calculator
Assess skateboard speed wobble risk from truck tightness, bushing durometer, and wheelbase.
Returns risk rating and recommendations to prevent wobble.
What causes speed wobbles:
Speed wobbles (also called death wobbles or shimmy) occur when small steering oscillations amplify through positive feedback at high speed. The trucks pivot, the deck tilts, and each correction overshoots the last, building into violent oscillations. Understanding the physics helps you set up your board to avoid them.
Key factors in wobble onset:
The critical speed at which wobbles begin depends on several mechanical factors:
Wobble onset speed ∝ √( Bushing stiffness × Wheelbase ÷ (Rider height × Truck angle) )
Mind the brackets. Both the rider’s centre of gravity and the truck angle sit on the bottom, so raising either one lowers the speed at which wobbles start.
Higher bushing stiffness → higher onset speed (more stable) Longer wheelbase → higher onset speed (more stable) Lower truck angle → higher onset speed (more stable) Higher center of gravity → lower onset speed (less stable)
Stability scoring by factor:
| Factor | Stable (0 pts) | Moderate (1 pt) | Unstable (2 pts) |
|---|---|---|---|
| Bushings | Hard (96A+) | Medium (90–95A) | Soft (< 90A) |
| Wheelbase | 30"+ (longboard) | 22–30" | < 22" (standard) |
| Truck angle | < 42° (downhill and split-angle baseplates) | 43–48° | 50°+ (standard TKP) |
| Speed | < 25 mph | 25–35 mph | 35+ mph |
| Rider weight | Light (< 68 kg) | Medium (68–90 kg) | Heavy (> 90 kg) |
Bushing durometer guide by rider weight:
| Rider Weight | Soft Carve | All-Around | Downhill |
|---|---|---|---|
| < 55 kg | 78A | 85A | 90A |
| 55–70 kg | 82A | 87A | 93A |
| 70–85 kg | 85A | 90A | 95A |
| 85–100 kg | 88A | 93A | 97A |
| > 100 kg | 90A | 95A | 98A |
Example assessment:
A rider (80 kg) bombing a hill at 30 mph:
- Bushings: 87A, which is under 90 and therefore soft → 2 points
- Wheelbase: 36" (longboard) → 0 points
- Truck angle: 50° → 2 points
- Speed: 30 mph → 1 point
- Weight: 80 kg → 1 point
- Total: 6 points = High risk
- Fix: the two 2-point entries are the ones to attack. A 43° rear baseplate and 95A barrels take both down to 1 each, and the score falls to 4, which is Moderate.
To reach Low you would have to zero them outright: 96A or harder, and a baseplate under 42°. That leaves the two points you cannot do anything about, your weight and the speed you want to go, and that is exactly the point. Setup buys you back the risk that equipment controls, and nothing else.
Note the bushing line. 87A sounds like a middling number and it is not: the scoring table above puts anything under 90A in the soft column, and soft bushings on a 30 mph run are the single most common cause of a wobble.
How to prevent speed wobbles:
- Tighten the rear truck slightly more than the front
- Use harder bushings (especially rear)
- Lower your center of gravity by bending your knees
- Use split-angle trucks (lower angle rear, higher angle front)
- Shift weight to the front foot, because wobbles always start at the rear
Emergency recovery:
If wobbles start, do NOT grab the board or stand up straight. Instead, carve wide to bleed speed, crouch low, and shift weight aggressively to your front foot. Tightening your muscles makes wobbles worse. Staying loose and weighting the front is what rides them out.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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