[Elist] Where the rubber meets the road
John Del Santo
mcbwaycool at yahoo.com
Sat Aug 27 06:04:46 PET 2011
WHERE THE RUBBER MEETS THE ROAD
by John Del Santo
An ideal riding situation calls for our tires to be nestled firmly against the roadway, responding as we ask them to. We should start with a good tread pattern on properly inflated tires. Improper inflation will cause our tires to cup or crown, and less tire will be touching the road. Balding tires and canoes go sideways in the water. But, you don’t always get what ya’ want….There are the common items that cause us some concern, like rain on the road…Dry road will exhibit a coefficient in excess of 0.7, (3/4 of a measuring unit), while the same pavement when wet may exhibit friction values down to 0.25 (1/4 of a measuring unit). When you are on a ride up in the mountains and the water starts to ice up, the available friction may be as low as 0.05…Slip Slidin’ away !
We are also aware of the danger of those steel construction plates…When we get on one of those, we don’t even think of touching our brakes ! The ability to stay off our brakes when necessary, is one of the reasons that we always keep a good following distance. Some of the other hazards that sneak up on us are sand, gravel and steel sewer covers. When you come around a corner and find your front wheel on either gravel, sand, or steel, if you gas or brake at that moment, the front end and back end of your bike will want to react differently and move off in different directions.
Then there is that substance that the highway crews put down to help us out…but very often does just the opposite…..Pavement Paint. Paint markings are put on the pavement to guide drivers, but the degree of skid resistance that they provide is of increasing concern with the growing use of plastic materials. Painted markings generally lower the skid resistance of a pavement and when applied over large sections, will increase the distance it will take you to come to a stop. There is a multitude of different paints that can be used; Fast drying white paint with beads are ok; Hot plastic with beads are not as safe; and the worst…Smooth cold plastic with no beads. Non-beaded plastic has the friction level of Hydroplaning or melting ice. Unfortunately, as we are approaching a painted pavement marking, we have no way of guessing which paint was used !
When one of your tires is on pavement and your other tire is still on a painted marking there will be differences in Friction Coefficients and will create difficulties in controlling your bike when braking or accelerating. There is even a difference in Co-efficiency of Friction between Blacktop and Concrete. Marking materials generally lower the skid resistance of a pavement, and differential friction caused by marking materials may also give rise to hazardous situations, such as excessive vehicle yaw during locked wheel skids. ( I looked up “yaw”, it means “side-to-side movement”…That’s different than “Y’all” ).
To sum it up, when we are approaching any painted surface we should probably assume that it’s the more dangerous type, and do most of our braking before we actually get our tire on the paint….Or to avoid doing any big-time acceleration until our back tire is off the paint. . Smooth….Even….and Easy does it !
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