Is Jeff Jones on crack?

ronaldo_jeremiah said:

Alright, I exaggerate a bit, but I'm interested in something JJ says in
his recently posted review of Conti tires:

"Rear tyres get more flats because the things that cause them - shards
of glass, usually - don't naturally stick up from the road presenting a
sharp edge to a passing bike tyre. Rather, they lie flat. But when a
front tyre hits a shard, it can flick up so that it does present a
sharp edge - just in time for the rear tyre to hit it."

I don't think there is any way that this can be true with any
significant frequency. If rear tires flat more, I have to believe this
is due to (1) increased pressure/wear on them from supporting more
weight than the front, and (2) the rider's decreased ability to place
the tire exactly where he wants it, relative to the front which is more
precisely seen and steered.

Does anyone agree with JJ's glass-flicking theory? Is it his or did he
get this elsewhere?

Side note: A punctured tire is much less of a problem than a punctured
blimp...

-RJ

Dear Renaldo Jeremiah,

I am curious about the use of the term "on crack". Do you mean when he
speculates about glass flicking causing flats that he is talking really
fast and is desperate for another "rock"? If not, perhaps it might be
better to say he is on acid, peyote or mushrooms and is therefore
seeing things that may not exist.

Thanks,

Ed

ronaldo_jeremiah said:

Does anyone agree with JJ's glass-flicking theory? Is it his or did he
get this elsewhere?

http://draco.acs.uci.edu/rbfaq/FAQ/8b.7.html

Bob Schwartz
[email hidden]

ronaldo_jeremiah said:

Does anyone agree with JJ's glass-flicking theory? Is it his or did he
get this elsewhere?

I've read it elsewhere and more than once. I can see where it might
happen on occasion, but I doubt it is the case most of the time or all
that often, unless you are one of those that has a flat on a daily
basis. I think someone with a case of beer bottles, a balpeen hammer a
lot of time and spare tires could check it out. I'm willing to supply
the beer bottles. If Chung will do a chart of the results, I'll even
give up a tire or two (but not the $ 47.95 kind...)

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

Ed Sullivan said:

ronaldo_jeremiah wrote:

Quoted message said:

Dear Renaldo Jeremiah,

I am curious about the use of the term "on crack". Do you mean when he
speculates about glass flicking causing flats that he is talking really
fast and is desperate for another "rock"? If not, perhaps it might be
better to say he is on acid, peyote or mushrooms and is therefore
seeing things that may not exist.

Thanks,

Ed

Mister Ed,

I address you like that, because I respect the elderly. I believe "on
Crack" is totally appropriate, and can be used to denote general crazy
behavior or talk.

RVD
PS Chicken head

I always assumed it was because of the extra weight. The placement
issue is not a factor with me. I can hardly ever remember seeing
something I could not avoid with both tires. When I get a flat it is
because I never saw it in the first place. Note that I must get 5 times
or more flats in the rear in spite of using much tougher tires. I
started to use lighter more supple tires in front many years ago. I
also normally use lighter wheels in the front (rarely a matched set
unless the set has a lighter front). I think I started doing this in
the 80s when I had a pair of 28 spoke GELs280 (obvioulsy race use on
certain courses only) and I blew out the rear on the first test ride. I
replaced the rim with a 400 gram rim. The next pair I built I used was
330s with 32 spokes in the rear and 28 in the front. I also had some
Wolber rims for the front and I never used a matched set. Now it seems
all of the decent prebuilt (boutique?) wheels are optimized. The only
pair of wheels I used that lasted any time at all were the GP4s which
lasted for a few years. I remember the tires I used back then were
Vittoria Corsa Cx and Cg which I was told were intended from front and
rear respectivly though lots of times people just ran one or the other
(mostly the Cx with a super fine tread) but even then I tried to run
silk Clements (when I could find them) in the front.

Rik Van Diesel said:

Ed Sullivan said:

ronaldo_jeremiah wrote:

Quoted message said:

Dear Renaldo Jeremiah,

I am curious about the use of the term "on crack". Do you mean when he
speculates about glass flicking causing flats that he is talking really
fast and is desperate for another "rock"? If not, perhaps it might be
better to say he is on acid, peyote or mushrooms and is therefore
seeing things that may not exist.

Thanks,

Ed

Mister Ed,

I address you like that, because I respect the elderly. I believe "on
Crack" is totally appropriate, and can be used to denote general crazy
behavior or talk.

RVD
PS Chicken head

Dear Rik Van Diesel,

Thanks for the update on what the kids are saying nowadays. I really
enjoy such totally now and groovy talk.

Thanks,

Ed

Bob Schwartz said:

ronaldo_jeremiah said:

Does anyone agree with JJ's glass-flicking theory? Is it his or did
he get this elsewhere?

http://draco.acs.uci.edu/rbfaq/FAQ/8b.7.html

Indeed (and I guess this should go in tech, but I can't be bothered
following more than one newsgroup).

I confess that when I wrote the review, I thought the increased frequency of
rear punctures was mainly due to the extra weight on the tyre, but after
consulting with my superior (John Stevenson), I'm coming around to the
glass-flicking idea. Apparently, the weight distribution on the rear is not
that much greater than the front (like 60/40), which also surprised me. You
get far more rear flats than front flats - well out of proportion to the
weight distribution.

My other argument was going to be that the rear tyre wore out faster because
of the extra weight, but again, this is apparently not the case. It's
because the rear wheel is the one where all the driving forces are = more
wear.

Then I thought, if the rear tyre was more worn out, wouldn't it be
susceptible to more punctures? In some cases, yes, if glass lodges itself in
there and works through. But mostly not. See glass flicking theory again.

I'm still a bit skeptical, and I still reckon extra weight contributes
*something* to getting more flats, but I'm willing to accept John's far, far
greater tech knowledge on this point.

The one thing I have no doubt about is that riding in the wet is the
quickest way to shred your tyres, because water is such a good lubricant.

Jeff (I didn't answer the question about being on crack. That should be
obvious by now.)

"Jeff Jones" <jeff@cyclingnews-punt-com> wrote in message
news:[email hidden]...

Quoted message said:

Bob Schwartz said:

ronaldo_jeremiah said:

Does anyone agree with JJ's glass-flicking theory? Is it his or did
he get this elsewhere?

http://draco.acs.uci.edu/rbfaq/FAQ/8b.7.html

Indeed (and I guess this should go in tech, but I can't be bothered
following more than one newsgroup).

I confess that when I wrote the review, I thought the increased frequency

of

Quoted message said:

rear punctures was mainly due to the extra weight on the tyre, but after
consulting with my superior (John Stevenson), I'm coming around to the
glass-flicking idea. Apparently, the weight distribution on the rear is

not

Quoted message said:

that much greater than the front (like 60/40), which also surprised me.

You

Quoted message said:

get far more rear flats than front flats - well out of proportion to the
weight distribution.

20% difference is a big difference. If one rider had 20% more power than
another would you say it's "not that much greater" with regard to their
power output?

Quoted message said:

My other argument was going to be that the rear tyre wore out faster

because

Quoted message said:

of the extra weight, but again, this is apparently not the case. It's
because the rear wheel is the one where all the driving forces are = more
wear.

Then I thought, if the rear tyre was more worn out, wouldn't it be
susceptible to more punctures? In some cases, yes, if glass lodges itself

in

Quoted message said:

there and works through. But mostly not. See glass flicking theory again.

Jobst theories get around. I don't buy this one.

J.V. said:

Quoted message said:

I confess that when I wrote the review, I thought the increased frequency

of

Quoted message said:

rear punctures was mainly due to the extra weight on the tyre, but after
consulting with my superior (John Stevenson), I'm coming around to the
glass-flicking idea. Apparently, the weight distribution on the rear is

not

Quoted message said:

that much greater than the front (like 60/40), which also surprised me.

You

Quoted message said:

get far more rear flats than front flats - well out of proportion to the
weight distribution.

Quoted message said:

20% difference is a big difference. If one rider had 20% more power than
another would you say it's "not that much greater" with regard to their
power output?

First, your math is off. There is a 50% difference. The
difference in the weight distribution between the front
and rear wheels is 50% of the weight on the front wheel
if it is a 60/40 split.

What this is saying is that the orientation of the glass
shard is much more important than the amount of weight
pressing on the tire. This is absolutely true for
Michelin wires. If this were not the mechanism then you
would never pull a Michelin wire out of a tire. It has
to be standing on end in order to be embedded. It works
the same way for glass. The sharp end has to be pointed
up.

Quoted message said:

Jobst theories get around. I don't buy this one.

Find a sharp object and throw it on the ground so that
it lays flat. Press a wheel on top of it. Press hard. Have
your friends help.

Then fix it so that it is pointing up. Now press a wheel
on it.

Bob Schwartz
[email hidden]

J.V. said:

"Jeff Jones" <jeff@cyclingnews-punt-com> wrote in message

Quoted message said:

I confess that when I wrote the review, I thought the increased
frequency of rear punctures was mainly due to the extra weight on
the tyre, but after consulting with my superior (John Stevenson),
I'm coming around to the glass-flicking idea. Apparently, the weight
distribution on the rear is not that much greater than the front
(like 60/40), which also surprised me. You get far more rear flats
than front flats - well out of proportion to the weight distribution.

20% difference is a big difference. If one rider had 20% more power
than another would you say it's "not that much greater" with regard
to their power output?

It depends on the absolute numbers a bit (20 to 24 watts or 400 to 480
watts?), but that wasn't what I was talking about anyway. If punctures were
directly proportional to weight distribution, then you'd expect to get 4
punctures on the front for every 6 on the rear. I get far more flats on the
rear than on the front - like 5:1, so weight distribution can't be a big
factor.

Jeff

If I recall correctly the ubiquitous Jobst Brandt quoted at least one
study that took slow motion photography of flat causing particles and
the result was that you could visibly see the front tire rotating the
components or breaking off the small shards of glass from larger pieces
and flicking it at the rear tire.

I think I agree -- I've more than one experienced road racer also agree
with the more frequent rear flat theory of "front tire transfer of
sharp debris to the rear."

-Ken

Really going from 40% to 60% is a 50% increase.

"J.V." <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"Jeff Jones" <jeff@cyclingnews-punt-com> wrote in message
news:[email hidden]...

Quoted message said:

Bob Schwartz said:

ronaldo_jeremiah <[email hidden]> wrote:
> Does anyone agree with JJ's glass-flicking theory? Is it his or did
> he get this elsewhere?

http://draco.acs.uci.edu/rbfaq/FAQ/8b.7.html

Indeed (and I guess this should go in tech, but I can't be bothered
following more than one newsgroup).

I confess that when I wrote the review, I thought the increased

frequency

Quoted message said:

of

Quoted message said:

rear punctures was mainly due to the extra weight on the tyre, but after
consulting with my superior (John Stevenson), I'm coming around to the
glass-flicking idea. Apparently, the weight distribution on the rear is

not

Quoted message said:

that much greater than the front (like 60/40), which also surprised me.

You

Quoted message said:

get far more rear flats than front flats - well out of proportion to the
weight distribution.

20% difference is a big difference. If one rider had 20% more power than
another would you say it's "not that much greater" with regard to their
power output?

Quoted message said:

My other argument was going to be that the rear tyre wore out faster

because

Quoted message said:

of the extra weight, but again, this is apparently not the case. It's
because the rear wheel is the one where all the driving forces are =

more

Quoted message said:

Quoted message said:

wear.

Then I thought, if the rear tyre was more worn out, wouldn't it be
susceptible to more punctures? In some cases, yes, if glass lodges

itself

Quoted message said:

in

Quoted message said:

there and works through. But mostly not. See glass flicking theory

again.

Quoted message said:

Jobst theories get around. I don't buy this one.

In article <[email hidden]>,

Bob Schwartz said:

If this were not the mechanism then you would never pull
a Michelin wire out of a tire. It has to be standing on
end in order to be embedded.

I've never had one of those in a front tire. And they're always worse
for me when it's wet out.

--
tanx,
Howard

Butter is love.

remove YOUR SHOES to reply, ok?

Jeff Jones said:

Jeff (I didn't answer the question about being on crack. That should be
obvious by now.)

Any word on the teaspoon issue?

Jeff Jones said:

It depends on the absolute numbers a bit (20 to 24 watts or 400 to 480
watts?), but that wasn't what I was talking about anyway. If punctures were
directly proportional to weight distribution, then you'd expect to get 4
punctures on the front for every 6 on the rear. I get far more flats on the
rear than on the front - like 5:1, so weight distribution can't be a big
factor.

Over the last two years (as far back as I can remember, I have had equal
opportunity to replace front or rear flats. Just two days ago I replaced
my front tub because I found it flat when I grabbed the bike for a ride.

Like you, I thought that the rear would be more prone to flats, so I run
a clincher on the back and a tubular on the front. First, because I like
the handling of a front tubular much more than a clincher and second,
it's cheaper and less of a pain in the ass to fix a clincher on the
road. The tubular is also easier to handle when it flats suddenly on a
twisty descent.

However, since I have made this accomodation, my observations have not
backed up the reasoning.

Jeff Jones said:

Jeff (I didn't answer the question about being on crack. That should be
obvious by now.)

No crack required for the blimp orgies, however viagra and various
endurance enhancing banned substances are de rigeur. Any stomach or vision
complaints yet ?

On Tue, 07 Jun 2005 21:41:38 -0000, Bob Schwartz <[email hidden]>

Quoted message said:

Find a sharp object and throw it on the ground so that
it lays flat. Press a wheel on top of it. Press hard. Have
your friends help.

Then fix it so that it is pointing up. Now press a wheel
on it.

Except that I haven't had a single flat in 40 plus years from a
Michelin wire. OTOH, glass shards can cut from any angle - there is no
flat side - and many thorns have more than one entry point in a
literal sense.

The majority of my flats - not that I get that many - are IMO from
small splits that pick up gravel. The splits seem to be as much a
function of wear and bad roads and the gravel is from the miserable
patches. No telling how long the gravel goes for a ride before the
blow-out, but for some reason it amuses me to remove the pieces from
the tire later. Usually it is the penalty for me not replacing the
tire when I knew I should, and the one puncture usually has a couple
of embedded gravel companions well on their way to popping the tube.

(I did once put a tube and tire on forgetting the rim strip. The tube
got well out into the countryside before all hell broke loose. Not
sure how that counts.)

The only punctures on a good tire I can remember are from glass, and
any side of it would have penetrated. Mostly on wet days, but that's
life. Making the wrong decision about whether or not it was going to
rain at the last turn around point, fixing your flat in the rain 30
miles from home and casually wondering if whether or not a car
actually stopped, you'd take a ride home...

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...

On Wed, 8 Jun 2005 07:43:54 +1000, "Jeff Jones"

jeff@cyclingnews-punt-com said:

It depends on the absolute numbers a bit (20 to 24 watts or 400 to 480
watts?), but that wasn't what I was talking about anyway. If punctures were
directly proportional to weight distribution, then you'd expect to get 4
punctures on the front for every 6 on the rear. I get far more flats on the
rear than on the front - like 5:1, so weight distribution can't be a big
factor.

Doubt it works that simply. There would be issues of how well sprung
the weight in the rear is compared to the front - some people have no
vision, anticpation or handling skills and their front flats a lot.
There are bound to be some items that puncture at the margin that make
the difference more important than the simple percentage.

Curtis L. Russell
Odenton, MD (USA)
Just someone on two wheels...