Dr Engelbert Buxbaum wrote in message ...
Xelax wrote:



Dr Engelbert Buxbaum wrote:
Currently I use tires reinforced by a 5 mm neoprene layer (made by
Schwalbe), they too work very nicely.

I think I've seen them in bike shops, but I thought it was the tubes
which were reinforced or self-healing.

Yep, you can by some sort of thick liquid in bike shops which is put
into the tube to make them self-healing. If a puncture occurs, the stuff
plugs the hole before too much air is lost.

I have not tried this, so I can not comment on the effectiveness
(Anybody been there, done that?). My guess would be that this works only
for small punctures, not for a big gash.

Dear Xelax and Engelbert,

Skip to the bottom for flat-tire data comparing a thousand rides
on Slime tubes versus a thousand rides on the same route with
thick tubes and protector strips. I suspect that glass and
thorns present somewhat different threats.

Thicker inner tubes are usually marketed as "thorn-resistant"
in the U.S. I just measured a section from one and found that
its maximum outer thickness is 0.115", tapering to 0.060" along
its inside curve. This sounds about only half as thick as as the
5mm that you mention for Schwalbe inner tubes--which may have
a different kind of rubber, not just thicker rubber. (A normal
tube measures only 0.030" and thinner walls are available.)

These "thorn-resistant" tubes work in two ways. First, they add
enough thickness to the tire-tube combination that some of the
short puncture-vine thorns so common in the U.S. fail to penetrate
completely. Second, even when the tiny thorns do penetrate through
the extra rubber, the tremendous air pressure tends to seal the
pinholes forced through all that rubber instead of leaking out.

All this extra rubber, unfortunately, increases rolling resistance.
Some riders feel no difference, others claim to notice huge increases,
and most of us are left wondering what the actual losses are.

A similar approach is to insert tire liners of tough plastic or
kevlar (Mr. Tuffy is the popular plastic brand). Jobst Brandt
suggests that these plastic strips work on the thickness principle,
with the hard little thorns easily penetrating plastic or kevlar,
but being held at arm's length by the extra layer of material.

These separate protector strips might offer more protection from
larger chunks of debris, such as glass chips, than thicker tubes.
They certainly add even more to the rolling resistance, and a
number of posts have mentioned problems with the ends of the strips
wearing holes in the inner tubes.

Some modern tires feature an integrated kevlar belt that mimics
these protector strips. Again, Jobst Brandt and others have
pointed out that kevlar fibers offer no more resistance to
sharp thorn points than a steel-wool pad offers to a needle.
But the extra-thickness protection (and rolling-resistance
drawback) still apply.

Here on the Colorado prairie, I used a combination of thick
tubes and plastic strips for several years along my mindlessly
regular daily 15-mile ride in the countryside. When I switched
from 27" wheels to 700c, I also switched to the Slime tubes,
which are otherwise normal tubes filled at the factory with
a few ounces of a lurid green liquid, faintly tacky, and tiny
chopped-up white fibers. The slightly sticky liquid and the
fibers work on the principle of a clogged drain pipe, being
forced into any holes by the escaping air--hence, they work
better on high-pressure road tires than on low-pressure
mountain-bike tires.

The lurid green slime makes it hard to ignore slow leaks.
Even a drop shows up clearly on a tire. Often, a wisp of
tiny white fiber is forced out through the tube and tire.
A fair number of tiny leaks are sealed and later revealed
when larger punctures lead to replacing the tire. The
higher up the sidewall of the tire a thorn penetrates,
the less likely the slime is to seal the hole--the liquid
spins and concentrates against the outside of the tire.

Drawbacks include the potential for green slime to foul
and even ruin air gauges, green slime splattering on you
and your bike, cost, a few ounces of extra weight, and the
need to carry spare tubes because patches may not stick to
rubber covered with the chemical.

Jobst Brandt warns that a massive flat, a blowout, could
cover everything on the wheel with slippery stuff and lead
to a crash.

None of these anti-flat measures will stop nails, tacks,
sharp chunks of rock or glass, inch-long Russian olive
thorns, or jagged metal debris, although the Slime does
slow the immediate rate of air loss with a whoosh-whoosh
fountain-spray.

My yearly records for flats for my daily ride suggest that
I ought to wake up and switch back to thicker tubes and
protector strips. Below is part of an even more tedious
post from September, comparing the results from two 3-year
periods of 15-mile daily rides over the same puncture-vine
infested route:

In 1997, 1998, and 1999, I rode an old Schwinn touring bike with
thick-walled thorn-resistant tubes, Mr. Tuffy protector strips,
and 27-1/4" tires.

year rides miles rear front total
---- ----- ----- ---- ---- ---
1997 319 4785 2 1 3
1998 330 4950 8 0 8
1999 349 5235 11 1 12
--- ---- ---- --- --
998 14970 21 2 23

I averaged one flat every 650 miles and one front flat to 10 rear
flats.

In 2000, I bought a used 1998 Schwinn LeTour, partly because it
was a better bike and partly because most wheels and tires are
700c. I also switched from Mr. Tuffy protector strips and thorn-
resistant tubes to Slime tubes (with green sealant and white
clogging fibers), having read that that protector strips increase
rolling resistance noticeably.

My switch was arguably disastrous.

year rides miles rear front total
--- --- --- --- --- ---
2000 349 5235 18 15 33
2001 339 5085 16 13 29
2002 343 5145 36 17 53
--- ---- -- --- ---
1031 15465 70 45 115

I averaged one flat every 134 miles and suffered one front flat
for every two rear flats. The 700c tires and Slime tubes went
flat five times as often during a thousand rides in three years
on the same route.

It seems unlikely that the huge increase in flats was due to any
change in my riding skill or habits, so I reluctantly conclude
that the thorn-resistant tubes and plastic strips offer far more
protection than sealant and normal tubes where stickers and road
debris are a problem.

Carl Fogel