4.2 Side Spin · what it actually does
Three effects, two of them work against you
Why English makes you miss
Side spin (a.k.a. English) is the most over-used and misunderstood tool in pool. Beginners reach for it to "get there" when their position fails, and they miss more.
Reason: when you put right English on the cue ball, three different things happen at once. Two of them work against your aim.
This lesson teaches what those three effects are. Lesson 4.3 teaches when (and when not) to use them.
All physics here is from Dr. Dave Alciatore's series on squirt, swerve, and throw at billiards.colostate.edu.
Effect 1 · Squirt (deflection)
The instant the cue tip strikes off-center, the cue ball squirts in the OPPOSITE direction of the spin you tried to apply.
Right English → CB squirts left. Left English → CB squirts right.
Cause: the cue's shaft has end-mass; striking off-center pushes the ball sideways before the spin develops.
Magnitude: 0.5° to 2.3° depending on the cue (low-deflection shafts squirt less). Speed-independent — squirt is a constant fixed by your cue's properties, not your stroke.
Result: at standard maximum English, your aim is off by ~1-2° before the ball even crosses the table. This is why English-heavy shots miss.
- CB jumps OPPOSITE the spin direction at impact
- Caused by cue shaft end-mass
- Magnitude 0.5°-2.3° depending on cue, independent of speed
Effect 2 · Swerve (post-launch curve)
After the cue ball is in flight, cloth friction on the spinning ball gradually curves the path toward the spin direction.
Right English → CB curves right (the opposite of squirt's initial deflection).
Magnitude depends on:
- Cue elevation — more elevated stroke = more swerve
- Distance — more travel time = more swerve
- Speed — slower shots have more swerve (more time for friction)
Net effect: at slow speeds and long distance, swerve overpowers squirt and the CB ends up past the squirt direction. At fast speeds, squirt dominates.
- CB curves TOWARD the spin direction (opposite of squirt)
- Grows with elevation, distance, and time-of-flight (slower shots)
- Swerve and squirt are different effects pulling opposite ways
Effect 3 · "Squerve" — the combined deviation
"Squerve" = squirt + swerve combined. Same English, same aim, can miss in opposite directions at different speeds:
- Fast shot, short distance → squirt dominates → CB misses opposite the spin
- Slow shot, long distance → swerve dominates → CB misses past the spin
- Medium speed and distance → roughly cancel → CB goes nearly where you aim
This is why using English on long thin cuts is so unreliable: small speed errors produce different miss directions. Pros use English at moderate speeds in known positions.
Throw is the third effect, separate from squerve, occurring at the OB collision.
- Squirt + swerve = "squerve"
- Direction of net miss depends on shot speed and length
- Long thin cuts with English are the highest-error shots in pool
Effect 4 · Throw (object ball deflection)
At impact with the OB, spinning contact friction pushes the OB sideways (off the line through the contact normal).
Two kinds:
- CIT (cut-induced throw): even with no English, a cut at moderate angle (~30°) creates ~3-5° of OB deflection due to the squeeze of the contact patch.
- SIT (spin-induced throw): with English, the CB's surface speed at contact pushes the OB additionally. Right English on a thick cut throws the OB left.
Max throw ≈ 5° at moderate cut angles. Throw is largest near the 30° cut and falls off at thinner cuts.
"Gearing" outside English (~40% spin at 30° cut, ~70% at 60° cut) cancels CIT exactly — used by pros to remove the throw effect.
- CIT: cut-induced, present without English at medium cuts
- SIT: spin adds to throw, direction depends on side of spin
- Gearing English cancels CIT — pro-level adjustment
Recap: 3 effects of English
| Effect | What | When |
|---|---|---|
| Squirt | CB jumps opposite spin direction | At cue impact (instant) |
| Swerve | CB curves toward spin direction | During cue ball travel |
| Throw | OB deflects sideways at impact | At OB collision |
The mental model: before English, you had one source of miss (your aim). With English, you have three additional sources, two of which fight each other.
Lesson 4.3 covers when to use English anyway — and how.