Roulette wheels are mechanical. They have moving parts and are subject to wear and tear. It stands to reason that a Roulette wheel may begin spinning in perfect balance, but over time and after countless rotations, it will inevitably develop some slight inconsistencies of motion, which may translate in a “bias” for certain numbers on its face.

Of course, modern casinos monitor their Roulette wheels closely for any imperfections. Adjustments are made immediately if imbalance is detected. Nevertheless, many players believe that by “clocking a wheel” (studying its results for several hours), it is possible to discover certain numbers or sections of the wheel that are biased and more likely to produce winners than others. And there are certainly cases where Roulette clocking has paid off big for its practitioners.

A Clocker Breaks the Bank

Back in the 19^th century, the theory of wheel bias fascinated a British engineer named Joseph Jaggers (1830~1892), who coincidentally turned out to be a distant cousin of rock star Mick Jagger. In 1873, Jaggers gathered six clerks, trained them in discretely observing Roulette games, and took them to the Monte Carlo Casino in Monaco. For six straight days, he had them record the results of every spin on all of the casino’s Roulette wheels.

Based upon a careful study of all the outcomes, Jaggers identified one wheel that was definitely biased. Over the next several days, he then exploited that information, betting nine numbers (7, 8, 9, 17, 18, 19, 22, 28 and 29) and winning an estimated £80,000. At one point, the table’s “bank” (allotted funds for the day) was depleted and management had to stop play.

During the course of this winning streak, the casino owners noticed that Jaggers only played at one particular table. They suspected the wheel might be problem, so they moved it overnight to a different location. But Jaggers had noticed a blemish on its wooden surface, found where the wheel had been relocated, and began winning again. That’s when the casino took the errant wheel out of play for good, ending the clocker’s incredible run of “good luck.”

How to Clock a Wheel

Jaggers’ adventure was the first documented success of Roulette clocking, but there have been many others since—some of them quite spectacular. For example, after World War II, a syndicate of about 50 vanquished German sailors led by Herr Helmut Berlin used hidden cameras to clock wheels at the seaside Central Casino at Mar de Plata in Argentina. Over many months of play, they raked in about $425,000.

So there can be no doubt that clocking works and can be made to pay off. The only problem is that it is not easily accomplished. The minimum time required to clock a single Roulette wheel with any accuracy at all is 200 spins or about six hours. As many as 1,000 spins may be required for mathematical precision. If a casino has five wheels and one is biased, it could easily take from 30 to 150 man-hours of observation to discover which one it is.

Few casinos will allow a spectator to stand by watching a game for hours on end. An alternative is to pass by the table about once every 20~30 minutes and note the results posted on its electronic display, assuming one available. Otherwise, surreptitious filming of the wheel may be needed, which is illegal in most jurisdictions.

Once a bias has been detected and analyzed, the theory of which numbers to play must be tested. Small bets may be used initially, gradually increasing as proof of the bias becomes clear. But even if the wheel’s imperfections give the clocker a 5% advantage, which is about the most than can be hoped for before the casino notices the problem, winning a substantial amount can take many hours of play. For that reason, whether Roulette clocking is worth the time and money invested is still open to debate.