Casinos have known about the vulnerabilities of roulette games for years and in fact for more than 130 years to be exact. When attacked with betting systems then the long term invulnerability of roulette is pretty well documented. Paying odds of 35-1 on single zero wheels when there are 37 numbers in the wheel is not going to produce long term profits and this is the case however convincing the betting system happens to be. But yet it is these same odds of 35-1 that makes casinos nervous because that is a big pay off at the end of the day.

It is the same with cheating moves, it doesn’t matter if the house has an edge on roulette when you cheat and you do not need to cheat and get away with it very often when the odds are 35-1. Another factor what makes casinos somewhat nervous is in the operational characteristics of their own wheels. At the end of the day these instruments are made from metal and wood and these can and do suffer from flaws that are often brought about by natural wear and tear. No casino that I ever worked in (and I worked in six) inspected their own wheels as thoroughly and as precisely as what they should have done. They would often be left for long periods of time unsupervised and it would definitely be possible for staff or punters to rig them. Biased wheels are roulette wheels where certain numbers are appearing more than what they mathematically should do.

Let us look at this from an aspect of statistics. If a certain number comes at the rate that it should which is once in every thirty seven spins then the casino doesn’t have a problem as it has a house edge of 2.7%. However if you discovered that a certain number was arriving once in very thirty six spins then you would be playing level with the house. But this bias is not enough to overcome the house edge and many biases are even smaller than that. Once in every 36 spins is the same as two in every 72 spins or three in every 108. But a very slight bias of say three in every 105 would not be enough to overcome the 2.7% house edge.

So finding a bias is one thing but finding one that is strong enough is something else. It is not always possible to identify why wheels have biases and even the experts who have known that a bias existed inside a certain roulette wheel have often been unable to identify the real cause of it. Sometimes it is loose frets or canoes and other times it can be impossible to quantify like it is with atmospherics for example. But one thing is clear and this is that bias does exist although not in every single wheel but if you are a regular roulette player then it may be well within your interests to look if you are taking numbers down anyway.