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On Thu, 02 Sep 2004 18:12:35 GMT, wrote:
Terry Morse writes: The next time it rains around here, let's go for a ride and I'll show you a rear tire slipping on a climb. It happens to me often, without the benefit of tar snakes or metal grates. Maybe you can't make the rear tire slip with those monstrous big gears you like to use, but I certainly do with a 42" gear. How does the gear affect slip on a hill? If the wheel torque is sufficient to propel the bicycle, what does the contact patch care who supplies the torque? The gear affects slip on a hill because lower gears produce higher wheel torque at the peak of pedal force, when standing. Mountain bike riders know this phenomenon all too well, since traction is far less on the dirt than on pavement. If my rear wheel begins to slip when climbing, I click up a gear or two and try to move my hips farther over the back wheel. It works. Just for comparison, I have ridden up Filbert St in SF, the steepest street in the city (31.5%) in the rain. It is a smooth hand finished sheen concrete paved street with stairs for a sidewalk. It produced no wheel spin. But then you climb using comparatively high gears. Try the same stunt with a low gear, and you might be surprised at how easily the back wheel slips. These outings to Filbert street were with several riders and they all used the lowest gear on their good quality racing bicycles. There was no wheel spin. Not all of them made it to the top but that has no bearing on traction demands. Just the same, if you believe slip is gear dependent, then we don't need to go to a steep hill. This can be done accelerating on a flat road. If that doesn't offer enough resistance then a road overpass can be used for a simulated hill, many of these having as much as 10% grade. Jobst Brandt I think slip is more weight dependent than gear dependent. -- Bob in CT Remove ".x" to reply |
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On Thu, 02 Sep 2004 19:27:10 +0000, jobst.brandt wrote:
Bob Viggen writes: I think slip is more weight dependent than gear dependent. Could you expand on that theory. What effect does weight have on tire to road contact and how does this affect tire slip? F = N * Cf N = normal force Cf = coefficient of friction -- Chris BeHanna Software Engineer (Remove "allspammersmustdie" before responding.) I was raised by a pack of wild corn dogs. |
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On Thu, 02 Sep 2004 19:27:10 +0000, jobst.brandt wrote:
Bob Viggen writes: I think slip is more weight dependent than gear dependent. Could you expand on that theory. What effect does weight have on tire to road contact and how does this affect tire slip? F = N * Cf N = normal force Cf = coefficient of friction -- Chris BeHanna Software Engineer (Remove "allspammersmustdie" before responding.) I was raised by a pack of wild corn dogs. |
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-----BEGIN PGP SIGNED MESSAGE-----
In article xVZYc.1499$3l3.1435@attbi_s03, Peter Cole wrote: "Claire Petersky" wrote in message link.net... "dreaded" wrote in message ... Any opinions out there on road tires for commuting on steep hills in the rain? I had some continentals but they wore out pretty quick and the vittorias are a little slick on wet pavement. I ride with Avocet Cross II tires for commuting. These are very durable and in my experience, grip well. I can also get them over the rims, something that wasn't true with the Michelins I used to have. Biggest drawback: the bike shop sometimes has to order these for me because they don't always have them in stock. Really heavy, lots of rolling resistance -- these tires are made for unpaved surfaces. _ Not really, they are a pretty good compromise tire if you do both pavement and dirt. If you do just dirt there are better tires. They are a pretty good choice if you want a heavy duty tire that rolls fairly well on pavement. Due to the extra tread, they will also hold up to lots of miles and be potentially more flat resistant. They are the only "cross tire" that I would consider for everyday pavement use. You do pay a weight penalty, but in my experience they roll nearly as well as a slick tire of the same dimensions. _ Booker C. Bense -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBQVCJ02TWTAjn5N/lAQEJrgP/T8PcY9pJ4ZYk3AFgPL/isKR7QVR19Us7 vvOqmjvN7HdC/peNkHWlhzmuL4wd0Ot5S7Fe6Gc32ruUS7O+FHOAjbEG1eDTaoN Q 4ZM4jpfdoPTXTZZxCn9rNe8oxyiaPPdhY/so3cOLr6R8tlNziNiIvUwpTQqzk960 yovRAobCIcA= =19x6 -----END PGP SIGNATURE----- |
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Mike Anderson writes:
Road traction is a measure of how well the tire corners on wet pavement and this is interaction of the tread rubber with micro-roughness of the aggregate used in the pavement, concrete or asphalt. Does this mean that the only way an 'average buyer' could find out if a certain tire have good traction is to: 1. ride faster and faster until it slip out on you fall or: 2. take a decision after listening to marketing plays by makers? I do not know which of the two would hurt you most physically, but number two would probably dig the biggest hole in your wallet. How did you come to the conclusion about colored thread, I gather this is not something you just say? The colored tread was a try to match colors of mini cars in Europe to work as a sales gimmick. I read about the development in Automotive News and that the idea was scrapped for lack of durability and wet traction. This dawned on me immediately because in the days of Clement tubular tires that we all rode, red TT tires were available for low RR but caused crashes in the wet. Umma Gumma light colored tires from Specialized were furnished to the 7-11 team in Europe, where several riders promptly crashed in the rain. The road tires were promptly withdrawn from the market although with knobby tires that seemed to make no difference. The best track TT tires in the days of fine silk tubulars used latex treads that didn't last more than a few kilometers but were touted (logically so) as having low RR. Otherwise the same tires could be had with a carbon black tread strip. As I recall these were called Tipo-00. The inner tubes looked like condoms and held air long enough for a track session. http://www.bikepro.com/products/tires/spec_over.html Jobst Brandt |
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