Once you have dressed for the rain, you have only two issues to confront: traction and vision. Traction seems to be the primary concern for most riders, usually because they aren't sure how much grip they have available. While some surfaces—metal fixtures such as manhole covers and bridge gratings, painted areas, and places where built-up oil and grease have not washed off—become much slipperier when wet, you can actually call on a surprising amount of traction on clean asphalt or concrete. How much? The easiest way to test traction is to feel for it with your rear brake. Assuming you know how much deceleration you can develop on dry pavement before the rear tire breaks loose, you have a gauge of what's available if you repeat the test when the road is wet. This also assumes that you have a reasonable amount (say 3⁄16 of an inch) of tread depth. If you do this at moderate speeds on a flat, straight road, it won't become a thrill ride. Avoid locking up the rear wheel on a steeply crowned road, where it will tend to slide downhill and out of line.