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#71
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Road tire life span
Tim McNamara writes:
That fits the description of a temporary loss of traction below the limit. It is similar to slipping across a slick spot or a spot of sand on the road. Once the lean angle exceeds the traction there is no return to stability. I've had slight slippages like that occur in races crossing the lane striping; slipping on these is much more pronounced when it is wet, of course. But the width of the excursion, if that's the correct term, is only a couple of inches and then once you're off the stripe you're back on pavement with a high coefficient of friction. Front wheel slippage seems to be less recoverable than rear wheel slippage. If one wishes to see lots of crashes due to such slippage, watch the 1993 men's road race championships in Oslo Norway- a nasty wet day with lots of crashes resulting from the wheels slipping out on lane stripes. Some of them looked quite painful. IIRC Ekimov actually went over a "Jersey wall" type barrier and landed on commuter railroad tracks. I am curious about the tires these riders used on that course. From what I have seen, many racers ride on colored tires, some of which make all sorts of claims to have more traction on the side than the middle depending on color stripes. This is so much BS because a rider needs maximum traction when braking before a curve while upright as well as needing it to get around the corner. There is no excuse except fashion to have any less traction than the best on the entire tread and that is presently still gotten only with carbon black tread. People who say otherwise are either lying or are as uneducated in the matter as the public on whom they pass this sort of hype is. The former is probably true, there not being an excess of tribological expertise in the bicycle business, judging from the faux pas we see regularly. I recall when Umma-Gumma, non black, tires were foisted on the 7-Eleven team for their lower RR but were so bad in the wet that crashes rapidly got them back to the supplier. Jobst Brandt |
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#73
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Road tire life span
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#74
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Road tire life span
wrote in message ... I have yet to see a cyclist crash or go down on DRY payment when leaning too far into a turn. I have and did so myself in years past. That's called low-siding when the bicycle goes out from under the rider. Low side because the distance to the ground is relatively small. High-siding is worse because the rider goes up and over the bicycle and hits harder. My friend did that on Mt. Hamilton recently on the day of the bicycle race... Collar bone + two ribs. I didn't think "High-siding" was possible on a bicycle until I saw Joseba Beloki do it in last years Tour de France. I believe that was due to melted tar at high speeds through a turn. I'm thinking he might have hit the rear brake. I'm don't worry much about my cornering ability , but more concerned about the road condition on high speed descents. My hardest fall was when someone put sand on the road during the winter to help melt the ice. The roads were dry, but I lost traction on the sand. I also slipped and almost lost it on the back side of Mt. Hamilton due to some gravel on the road. -tom |
#75
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Road tire life span
g.daniels wrote:
what happened to walnut shells? Like you, they're cracked. Bill "ty...tyvm" S. |
#76
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Road tire life span
Tim McNamara wrote:
... If one wishes to see lots of crashes due to such slippage, watch the 1993 men's road race championships in Oslo Norway.... Sorry, my time machine is out of commission. -- Tom Sherman – Quad City Area |
#77
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Road tire life span
Dave Lehnen writes:
I am curious about the tires these riders used on that course. From what I have seen, many racers ride on colored tires, some of which make all sorts of claims to have more traction on the side than the middle depending on color stripes. This is so much BS because a rider needs maximum traction when braking before a curve while upright as well as needing it to get around the corner. There is no excuse except fashion to have any less traction than the best on the entire tread and that is presently still gotten only with carbon black tread. Since maximum braking when upright is limited by the angle from the front contact patch to the center of gravity, as often discussed on this newsgroup, traction greater than required to raise the rear wheel does not provide better deceleration. Even the hardest- compound touring tires seem capable of lifting the rear wheel, at least in dry conditions. I think you'll find that braking in the wet can skid the front tire before the rear wheel lifts but that is less than the whole story. In poor traction, rear wheel braking is also needed and compromising that which carbon black tires offer has caused crashes even while braking. When cornering, acceleration is limited only by traction. It would make sense to trade off some tread life, or rolling resistance, or cut resistance, if it would help traction, on the side tread. That may be the thinking of those who have different center stripes from edge tread but they are inconsistent, some having the color on the sides and black in the center, others having the converse. I suspect that both colored and black are silica filled instead of carbon. Since bicycles can't brake at much more than about 0.6g, it would make sense to optimize the center tread for other desirable properties, as long as traction was more than could be used anyway. Not on my bicycle. I have ridden enough wet mountain passes and exceeded traction often enough to not mess with even poorer traction that I had on carbon tires. People who say otherwise are either lying or are as uneducated in the matter as the public on whom they pass this sort of hype is. The former is probably true, there not being an excess of tribological expertise in the bicycle business, judging from the faux pas we see regularly. I recall when Umma-Gumma, non black, tires were foisted on the 7-Eleven team for their lower RR but were so bad in the wet that crashes rapidly got them back to the supplier. Jobst Brandt |
#78
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Road tire life span
Tim McNamara writes:
If one wishes to see lots of crashes due to such slippage, watch the 1993 men's road race championships in Oslo Norway- a nasty wet day with lots of crashes resulting from the wheels slipping out on lane stripes. Some of them looked quite painful. IIRC Ekimov actually went over a "Jersey wall" type barrier and landed on commuter railroad tracks. I am curious about the tires these riders used on that course. Boy, I have no idea and I don't have a copy of the video. I do remember quite clearly seeing riders slip out in turns as they crossed the heavy white painted stripes, the wheels going out almost instantaneously. There were some very painful looking crashes. Well for slick material, all bets are off. Metal utility covers, solid paint stripes, and crack sealant are slick to any kind of rubber. It's the rider's business to not demand any side forces from such surfaces. Of course, in a dense pack of riders, that may not be visible until it is too late. I once watched a video of a Paris-Roubaix rider go down on a straight section of basalt cobbles just from the inter cobble rounded seams. I recall in the days of yore I would demonstrate this with my car at a low rolling speed and run it up through the gears on wet basalt without gaining more than 2-3mph while the tachometer registered 3000rpm in 3rd (of 4) gear. That makes a badly floating rear end if you aren't on a level street. Jobst Brandt |
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