How big is a 650B mountain bike wheel

A 650B or 27.5" wheel with a tire measures 27.4803" inches. Now, all of the 650B tires are not the same. For example, Nino Schurter rides a 650B wheel with 50mm Dugast Tubular tires measuring 685mm which translate into 26.9685  inches. Following aveage size tires though the measure is approximately  27.4803".

While most of you would agree that number is just one inch different.the picture to the right tells us a different story. The picture says that the supposed 26" wheel is actually larger. The exact measure of a 26" wheel with tire is 26.4961 inches. That's actually .4724 of an inch different from a 26" wheel with tire in diameter. If you were to look at how it would affect the actual height o the wheel then it would be .2362 of an inch or 5.99948 mm.