Tires and flats
jobst....@stanfordalumni.org
posted here on wreck.bike, as I rode the Paicines-New Idria-Paicines
spring tour last Sunday. Those are the roughest roads I have seen of
which I have ridden many here and in the Alps (old WWI & WWII military
trails). The ride report is in wreck.bike.rides and I guess after
reading it again, I probably didn't make much hay over the New Idria
section. It's a blast if you like descending steep corkscrew
whoop-de-doos in striking landscape. In any case, I rode on a rear
tire that was into the cords and had no flat nor did I have any the
other times I rode that loop.
The belief that thin tires cause flats on rough chipped granite roads
(flints as one writer called them) doesn't hold true in my experience.
If that weren't so, I would not have been able to ride many of the
great alpine passes in the late 1950's when the Simplon, Stelvio,
Great St. Bernard and many in the Dolomites were unpaved and to be
ridden on racing tubulars as the ancients like Jean Robic, Coppi,
Bartali and others did before I got there.
It's still spring and the Paicines-New Idria-Panoche valley-Paicines
route is still cool and beautiful. Do it and don't try this in
reverse either. The road from New Idria has 25% sections.
Jobst Brandt
Andrew F Martin
down. What I think does matter in the case of "cord bare" tires is the
degredation of cornering performance. My rear tubular tire has a
rather worn "flat" section on it and the threads poke through in two
small spots, and I'm pretty sure my cornering comfort is paying the
price. Running at ~115psi I definitely don't feel as secure to the
road when doing higher-speed sweeping corners. I'm looking forward to
new rubber with the uniform, round tire surface.
Matt O'Toole
> I had to think of the many flat tire reports and their various causes
> posted here on wreck.bike, as I rode the Paicines-New Idria-Paicines
> spring tour last Sunday. Those are the roughest roads I have seen of
> which I have ridden many here and in the Alps (old WWI & WWII military
> trails). The ride report is in wreck.bike.rides and I guess after
> reading it again, I probably didn't make much hay over the New Idria
> section. It's a blast if you like descending steep corkscrew
> whoop-de-doos in striking landscape. In any case, I rode on a rear tire
> that was into the cords and had no flat nor did I have any the other
> times I rode that loop.
>
> The belief that thin tires cause flats on rough chipped granite roads
> (flints as one writer called them) doesn't hold true in my experience.
> If that weren't so, I would not have been able to ride many of the great
> alpine passes in the late 1950's when the Simplon, Stelvio, Great St.
> Bernard and many in the Dolomites were unpaved and to be ridden on
> racing tubulars as the ancients like Jean Robic, Coppi, Bartali and
> others did before I got there.
If you mean rocks and gravel don't cause flats then I agree. Roadies
often won't ride in winter when there's gravel spread on the roads, nor
will they ride even short sections of unpaved road on their road bikes. I
think almost all flats that aren't pinch flats are caused by glass, metal
shards, tire cord wires, etc. These collect where the gravel does, giving
the appearance that the gravel causes the flats. But even with thin tires
I rarely got flats mountain biking. I got plenty on the roads to/from
the trails though.
> It's still spring and the Paicines-New Idria-Panoche valley-Paicines
> route is still cool and beautiful. Do it and don't try this in reverse
> either. The road from New Idria has 25% sections.
Sounds like great MTB country!
Matt O.
jobst....@stanfordalumni.org
> I buy the flats issue. The rubber isn't doing a ton to keep the
> flats down. What I think does matter in the case of "cord bare"
> tires is the degradation of cornering performance. My rear tubular
> tire has a rather worn "flat" section on it and the threads poke
> through in two small spots, and I'm pretty sure my cornering comfort
> is paying the price. Running at ~115psi I definitely don't feel as
> secure to the road when doing higher-speed sweeping corners. I'm
> looking forward to new rubber with the uniform, round tire surface.
I doubt that a well worn rear tire has any effect on cornering because
that is done on the sides where the tread is not worn away, and unless
that tread is separating from the casing, it is riding on plenty of
rubber in hard cornering. I often wear tires through to the cords and
have no problem descending as hard as ever.
Jobst Brandt
jobst....@stanfordalumni.org
I think you'll do better on a road bicycle, as my group does, because
the main effort, other than the steepest climbs, is mileage and that
isn't so effective on a suspension knobby tired bicycle. Take food.
There are no services for 80 miles. New Idria is a ghost town!
Jobst Brandt
Andrew F Martin
how to sharpen rock up there. Prior to investing in Tuffy's there, I
got all sorts of flats from small shards of "flint" as the locals call
it. I guess they make the roads similar to our chip-seal, but with
this funny red rock that cracks into sharp pieces.
I was running relatively new Vittoria Rubino Pros at 110psi. I was
probably averaging a flat an hour from that stuff. Then I got Tuffy's
and the problem more or less went away. The locals told me to run
85psi instead and that just about fixed it.
Andrew F Martin
the point where the wear isn't touching the contact point...I'm pretty
sure I'd fall over.
Mike Jacoubowsky
> the main effort, other than the steepest climbs, is mileage and that
> isn't so effective on a suspension knobby tired bicycle. Take food.
> There are no services for 80 miles. New Idria is a ghost town!
>
> Jobst Brandt
You mention food, but not water. The news reports make it look like there's
quite a bit of water up there, but I prefer to get my mercury levels topped
off by eating Tuna.
--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com
<jobst....@stanfordalumni.org> wrote in message
news:445aa966$0$65438$742e...@news.sonic.net...
Matt O'Toole
I agree. All the bike's handling "feel" comes from the front tire anyway
-- how it turns into corners, etc. Different tires do handle differently
because of their profile/shape, but one quickly gets used to it, whatever
it is.
One should never have a worn tire on the front anyway. Put the new one on
the front and move it to the rear when the rear wears out.
Matt O.
jobst....@stanfordalumni.org
>> I think you'll do better on a road bicycle, as my group does, because
>> the main effort, other than the steepest climbs, is mileage and that
>> isn't so effective on a suspension knobby tired bicycle. Take food.
>> There are no services for 80 miles. New Idria is a ghost town!
> You mention food, but not water. The news reports make it look like
> there's quite a bit of water up there, but I prefer to get my
> mercury levels topped off by eating Tuna.
The water we drank was not from the clear creek recreation area but on
the ridge before that, besides, mercury and cinnabar is on the other
side of the mountain from Clear Creek.
Jobst Brandt
Mark Hickey
>I doubt that a well worn rear tire has any effect on cornering because
>that is done on the sides where the tread is not worn away,
<snip>
But it does make for an odd feeling in the transition to a lean
starting a turn. I don't notice so much on a road bike as I do on my
MTB (with its 1.75" slicks), but MUCH more so on my BMW. Obviously
this is because the "pivot point" (edge of the square patch) is
further from the centerline for the MTB and motorcycle.
Essentially, on a very "square" tire, you're actually "lifting" the
rear wheel slightly when you start to turn, and moving the point of
balance toward the inside of the turn (both bad things, IMHO).
But I agree entirely that ultimately this doesn't affect the bike's
ability to actually take the corner (since the square patch should be
entirely off the road by the time you're well into the turn).
Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame
Jan Lindstrom
> Generally I agree, except when riding in Denmark. Holy cow they know
> how to sharpen rock up there. Prior to investing in Tuffy's there, I
> got all sorts of flats from small shards of "flint" as the locals call
> it. I guess they make the roads similar to our chip-seal, but with
> this funny red rock that cracks into sharp pieces.
I switch to thicker tires when they start spreading crushed rock to
combat slipperiness in the fall here in Finland. I don't think I've seen
the flints penetrate the tires per ce, but they seem to go through
existing glass cuts.
I just had a mm long flint cause two punctures on my tour of Corsica.
The flint had stuck to an existing cut in the tire presumably at home
since I don't recall riding over any such roads uptil then on Corsica
and it worked through the cords in 600kms. When inspecting the tires you
could not see or feel the flint protrude to the inside, but sure enough
I had another puncture (very small pinhole both times) at the same spot
and found the small flint and removed it and that stopped the punctures.
Still, these types of punctures are rare. I've had maybe 3 punctures in
the last 30000kms caused by crushed rock.
Jan Lindström
jobst....@stanfordalumni.org
>> I doubt that a well worn rear tire has any effect on cornering
>> because that is done on the sides where the tread is not worn away,
> But it does make for an odd feeling in the transition to a lean
> starting a turn. I don't notice so much on a road bike as I do on
> my MTB (with its 1.75" slicks), but MUCH more so on my BMW.
> Obviously this is because the "pivot point" (edge of the square
> patch) is further from the centerline for the MTB and motorcycle.
I have not been able to feel any of that. In the days of Specialized
Touring II tires with the raised center ridge i could feel no
difference and because I didn't care to go to the limit of traction on
a raised center ridge, I changed rear to front when the ridge was
worn flat. I could feel none of that but I believe there was more
margin before washout in curves if the ridge was gone.
> Essentially, on a very "square" tire, you're actually "lifting" the
> rear wheel slightly when you start to turn, and moving the point of
> balance toward the inside of the turn (both bad things, IMHO).
Don't believe that. The compliance of the tire makes up for that if
you don't inflate over 140psi.
> But I agree entirely that ultimately this doesn't affect the bike's
> ability to actually take the corner (since the square patch should be
> entirely off the road by the time you're well into the turn).
It would be deformed to expose a broad contact patch. The flat area
isn't sharp edged and the tire isn't rigid.
Jobst Brandt
carl...@comcast.net
wrote:
Dear Jobst,
If you mean big chips fixed to a chip-seal road, then I
expect that you're right. They're probably too big and too
dull to pierce a tire at one blow, and they won't stay stuck
in the tire and keep working their way in.
But when loose, sharp-edged chips resembling tiny bits of
shattered glass work into holes in tires, they can and do
cause flats.
(I don't know if they make the holes themselves or just get
picked up by existing holes--which begs the question of what
makes the holes, which are bigger than goathead holes.)
I occasionally go around my tires and pry the little devils
out. Things have improved since the gravel pit shut down on
the highway on my daily ride, but come to think of it . . .
Yes, indeed! A front tire still new enough to show delicate
tread cross-hatching has three holes, each plugged with a
tiny piece of rock, picked up somewhere on flat asphalt
pavement.
Not all holes have rocks, not all rocks are sharp, and only
a few rocks work in deep enough, but every now and then I
find a tiny slit in a flat tube that's opposite a tiny chip
that's worked all the way through the tread and casing and
is sticking out on the inside of the tire.
Here's one rock chip hiding deep in a hole in my front tire:
http://home.comcast.net/~carlfogel/download/rockchip1.jpg
Here's the same chip pried out a bit:
http://home.comcast.net/~carlfogel/download/rockchip2.jpg
The black 700c tire section is about 12mm wide. The little
cross-hatch diamonds are about 1mm.
Extracted, it turned out to be a white, flat, somewhat sharp
chip instead of a rounded pebble. I'm glad that I pried it
and its two friends out of my tire. Usually I throw a tire
away long before the tread is worn off because these holes
grow too large and too numerous.
This might be an example of regional variation.
Cheers,
Carl Fogel
Zog The Undeniable
> The belief that thin tires cause flats on rough chipped granite roads
> (flints as one writer called them) doesn't hold true in my experience.
Flints are not granite. They're little flakes of hard silica that cut
like a knife. We get a lot of them round here, because the predominant
bedrock is chalk. Continental Grands Prix seem especially vulnerable to
flints, but it's the sidewalls that are cut through, not the tread; this
is to be expected since flints lie flat and are unlikely to cut into a
tread if directly run over. Typically they hide in gravel swept to the
side of the road, where they are the correct height to slash a sidewall,
and all the flint cuts I've seen have occurred on minor roads with
gravel accumulations at junctions and at the verges.
This is naturally worse than a normal puncture because you need to find
a boot to stop the inner tube bulging out. From experience I can state
that using cardboard from a discarded cigarette packet lasts less than 5
miles, and I think something about the shredding effect of the tube/tyre
interface is already in the FAQ.
The moral is, of course, to ride on clean asphalt and avoid the areas
unswept by cars.
Dave Larrington
> Generally I agree, except when riding in Denmark. Holy cow they know
> how to sharpen rock up there. Prior to investing in Tuffy's there, I
> got all sorts of flats from small shards of "flint" as the locals call
> it. I guess they make the roads similar to our chip-seal, but with
> this funny red rock that cracks into sharp pieces.
We do flint here too, especially in:
o the downlands of southern England, and
o wherever Dave Kahn happens to be riding on any given weekend
I think it's either washed out of the soil or falls off the tyres of
farm vehicles.
--
Dave Larrington - <http://www.legslarry.beerdrinkers.co.uk/>
Never play leapfrog with a unicorn.
Sandy
> Mark Hickey writes:
>
>
>>> I doubt that a well worn rear tire has any effect on cornering
>>> because that is done on the sides where the tread is not worn away,
>>>
>
>
>> But it does make for an odd feeling in the transition to a lean
>> starting a turn. I don't notice so much on a road bike as I do on
>> my MTB (with its 1.75" slicks), but MUCH more so on my BMW.
>> Obviously this is because the "pivot point" (edge of the square
>> patch) is further from the centerline for the MTB and motorcycle.
>>
>
> I have not been able to feel any of that. In the days of Specialized
> Touring II tires with the raised center ridge i could feel no
> difference and because I didn't care to go to the limit of traction on
> a raised center ridge, I changed rear to front when the ridge was
> worn flat. I could feel none of that but I believe there was more
> margin before washout in curves if the ridge was gone.
Actually, I have had the (opinion follows) misfortune of riding
Hutchinson Fusion tires the last few thousand km, and I find the
multiple stripes (meaning, perhaps different compounds) is problematic
as the tire wears. The transition from simple vertical to leaning is
abrupt, the more it is used, and it engenders lower confidence,
--
Bonne route !
Sandy
Tom
from flints. One in the #$#$ pouring rain up in Santa Rosa in February
and another I believe on Foothill near Sunol.
Granted that I generally only get one of these a year compared to a ton
from glass or thorns but let's not pretend that they don't exist.
Jasper Janssen
<hroth...@yahoo.com> wrote:
>Flints are not granite. They're little flakes of hard silica that cut
>like a knife.
Not surprising, since both Flint and Obsidian are esseentially forms of
glass, and will be much sharper than even a razor edge on steel when newly
chipped. Those stone age men knew what they were doing,l using that
material for their blades and arrowheads.
Jasper
Michael Press
Jasper Janssen <jas...@jjanssen.org> wrote:
Flint is not glass. Obsidian is glass. Glass is amorphous.
Flint is crystalline.
Chert and flint are finely crystallized varieties of gray
to black quartz that occur as nodules or bands in
sedimentary rocks.
A cryptocrystal is a rock whose texture is so finely
crystalline逆hat is, made up of such minute crystals逆hat
its crystalline nature is only vaguely revealed even in a
thin section by transmitted polarized light. Among the
sedimentary rocks, chert and flint are cryptocrystalline.
--
Michael Press