S
S o r n i
Guest
g.daniels wrote:
> what happened to walnut shells?
Like you, they're cracked.
Bill "ty...tyvm" S.
> what happened to walnut shells?
Like you, they're cracked.
Bill "ty...tyvm" S.
T
Tom Sherman
Guest
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
> ...
> 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
J
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
[email protected]
>> 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
[email protected]
J
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
[email protected]
>>> 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
[email protected]
