Depending on how long you owned your fixed gear and/or singlespeed bicycle you probably already had countless sleepless night which gear ratio is the best for the streets you ride. We can promise you that we had a lot of discussions before we went with the 46x17 on our bicycles.
For you that might be new to this world it basically comes down to choosing the right gear ratio, if you live in a city with lots of hills you might go for a slightly lighter gearing, and if you like me live in a city ( Shanghai ) that is flat like a pancake and always enjoy a tail wind where ever you are going you can go for a bigger ratio. But it does not only stop there, in order to not break the bank and order new tires every month you also need to consider the skid patches, this is basically where the tire stops every time stop peddling. A gear ratio of 46x17 gives you 17 skid patches which will save your rubber. If you ride your bicycle in singlespeed mode you do not need to worry about this at all, your break pads will take all the heat.
A friend who rides in Paris put up a great fixed gear calculator on their site Surplace.fr It will help you do all the calculations you need so go check it out here