Bowling Ball & Oil Pattern Guide
The rule of 31 applied to any pattern, with a lane diagram and a coverstock, surface and line recommendation for what you are facing.
What to throw
Reading the numbers on your ball
Both numbers are printed on every modern ball. USBC caps them at 2.46–2.80 RG and 0.060 differential, so anything outside those ranges is either a typo or not legal for sanctioned play.
Coverstocks
| Type | Hook | Best for | Notes |
|---|---|---|---|
| Polyester (plastic) | ●●●●● | Spares and very dry lanes | Effectively no hook. Almost every serious bowler carries one purely for shooting corner pins straight. |
| Urethane | ●●●●● | Short and burnt-up patterns | Smooth, predictable and low-flare. It saves oil rather than eating it, which is why it dominates on short patterns. |
| Reactive hybrid | ●●●●● | Medium patterns and unknown conditions | Splits the difference between solid and pearl. The safest single ball if you only carry one reactive. |
| Reactive solid | ●●●●● | Heavy oil and fresh patterns | Reads the lane earliest and handles the most volume. On dry lanes it burns up before the breakpoint. |
| Reactive pearl | ●●●●● | Broken-down lanes and long patterns | Cleanest through the front with the strongest backend reaction. Needs friction down lane to work. |
Breakpoint board by pattern
| Pattern | Length | Breakpoint |
|---|---|---|
| Typical house shot Heavy oil in the middle, dry outside. The wall of friction at the edge is what makes house scoring so much easier than sport patterns. | 40 ft | board 9 |
| PBA Wolf The shortest of the animal patterns. Balls hook early and hard; playing deep inside is usually a mistake. | 32 ft | board 1 |
| PBA Cheetah Short and edge-friendly. Traditionally played out near the gutter where the oil ends. | 35 ft | board 4 |
| PBA Viper Short-to-medium. Rewards a straighter angle than its length suggests. | 37 ft | board 6 |
| PBA Chameleon The classic transition pattern — it moves around during a block, hence the name. | 39 ft | board 8 |
| PBA Bear Flat, with almost no side-to-side ratio. Brutally unforgiving: there is no wall to hold a miss. | 40 ft | board 9 |
| PBA Scorpion Medium-long. Plays up the middle with a controlled shape rather than a big backend. | 42 ft | board 11 |
| PBA Shark Long. Straighter angles, later read, and very little room to swing the ball. | 45 ft | board 14 |
| PBA Badger The longest of the animals. Almost point-and-shoot — big hooks simply run out of lane. | 52 ft | board 21 |
The rule of 31: subtract 31 from the pattern length and you get the board your ball should be on when it reaches the breakpoint down lane. A 39-foot Chameleon breaks around board 8; a 45-foot Shark around board 14. It is a starting point rather than a law — your speed, rev rate and ball surface all move it — but on an unfamiliar pattern it puts you in the right neighbourhood instead of guessing, which is worth a lot in the first frame or two.
How to use
- Find the pattern length in feet.
- Subtract 31 to get the approximate breakpoint board.
- Adjust your line and ball choice from there.
- Watch how the pattern breaks down through the session.
Frequently asked questions
What is the rule of 31?
Subtract 31 from the pattern length in feet to get an approximate breakpoint board — the board your ball should be near at the end of the oil. A 40-foot pattern suggests around board 9. It is a starting point that gets you close, not a solution.
Why does oil pattern length matter so much?
Because oil determines where the ball can hook. On a short pattern the ball encounters dry lane early and hooks sooner, demanding a straighter line closer to the pocket. Long patterns delay the hook and generally require playing more directly up the boards.
Why do my shots change through a session?
Because the oil moves. Every ball carries oil down the lane and pushes it around, so the pattern breaks down and shifts as games go on. The line that worked in the first game frequently does not in the third, and adjusting rather than repeating is the skill.
What is the difference between house and sport patterns?
House patterns have far more oil in the middle and much less outside, which steers errant shots back toward the pocket and flatters the bowler. Sport patterns are much flatter across the lane, so accuracy is genuinely required and averages drop substantially.
Does ball surface matter more than the ball itself?
Often, yes. Surface texture determines when the ball starts to read the lane, and a sanded or polished finish on the same ball behaves very differently. Adjusting surface is cheaper and frequently more effective than buying another ball.
Can I see the oil on the lane?
Barely, and not reliably. Oil is nearly invisible under lane lighting, which is why patterns are published as diagrams and why reading ball reaction is the practical method. Watching where the ball transitions tells you more than looking at the lane does.
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