Safety: Clincher vs. Tubies in Hills

[Jobst Brandt]

Andrew Bradley writes:

>>> And I'm still not convinced that a tub with a latex inner tube won't pinch less.

>> Your double negative makes unclear what you do or do not believe. I can assure you that in the
>> days when we rode tubulars all the time, we had many dented rims without getting flats. It was at
>> that time, on weekly tire patch sessions that I introduced the term "snake bite" because riders
>> could often not find the second hole in latex tubes because they were so small. However, on close
>> inspection, a pinch flat can always be recognized by the embossed fabric pattern on the tube
>> (surrounding the hole).

> Reading this paragraph I'm not sure there isn't a fair amount of non-clarity as to whether you
> think racing clinchers might have represented a step in the wrong direction as regards pinch flat
> avoidance.

I'll accept that accolade. I think I should have said that among the regular tubular repairs that
were made, there were pinch flats, not that these were why we had tire patch sessions. There were no
MTB's and no fat clinchers, so we rode our tubular equipped road bicycles over the trails and rocky
roads (Last Chance Road for instance) of the Santa Cruz mountains, something I still do but with
clinchers.

I find odd that wherever I meet bicyclists out in the woods, they are sure that I could not have
gotten there with a road bicycle and slick road tires. Besides that, they believe that one cannot
ride trails with less than 11t-34t and a triple up front. Marketing has succeeded 100%.

So now back to you, Andrew. Please clarify the statement at the top of this note.

[not, won't, less] which modifies which and how are we to take this?

Jobst Brandt [email protected] Palo Alto CA

 

[Andrew Bradley]

jobst.brandt:
>
> >>> And I'm still not convinced that a tub with a latex inner tube won't pinch less.
>
> >> Your double negative makes unclear what you do or do not believe. I can assure you that in the
> >> days when we rode tubulars all the time, we had many dented rims without getting flats. It was
> >> at that time, on weekly tire patch sessions that I introduced the term "snake bite" because
> >> riders could often not find the second hole in latex tubes because they were so small. However,
> >> on close inspection, a pinch flat can always be recognized by the embossed fabric pattern on
> >> the tube (surrounding the hole).
>
> > Reading this paragraph I'm not sure there isn't a fair amount of non-clarity as to whether you
> > think racing clinchers might have represented a step in the wrong direction as regards pinch
> > flat avoidance.
>
> I'll accept that accolade. I think I should have said that among the regular tubular repairs that
> were made, there were pinch flats, not that these were why we had tire patch sessions. There were
> no MTB's and no fat clinchers, so we rode our tubular equipped road bicycles over the trails and
> rocky roads (Last Chance Road for instance) of the Santa Cruz mountains, something I still do but
> with clinchers.
>
> I find odd that wherever I meet bicyclists out in the woods, they are sure that I could not have
> gotten there with a road bicycle and slick road tires. Besides that, they believe that one cannot
> ride trails with less than 11t-34t and a triple up front. Marketing has succeeded 100%.
>
> So now back to you, Andrew. Please clarify the statement at the top of this note.
>
> [not, won't, less] which modifies which and how are we to take this?

The statement does it's job: it is logically consistent with my view but isn't categorical. I
am under the impression that tubulars pinch less than the equivalent section clincher at a
given pressure.

See this is one of two mechanical myths your rbt has yet to completely dispel for me. What with
latex vs butyl and the shapes of the pinching surfaces.

The other myth, BTW, is that a flimsy wheel can be squishy in corners.

It's personal experience (real or imagined) vs a lack of data/quantitative analysis to the contrary
that allows these myths to live on.

Andrew Bradley

 

[Tim McNamara]

In article <[email protected]>, [email protected] wrote:

> I find odd that wherever I meet bicyclists out in the woods, they are sure that I could not have
> gotten there with a road bicycle and slick road tires. Besides that, they believe that one cannot
> ride trails with less than 11t-34t and a triple up front. Marketing has succeeded 100%.

Tending to ride whatever bike I'm on where ever my fancy leads me, I often end up on trails with my
road bikes. None of the trails around here are extreme in difficulty. They're in fact quite easy to
ride on a road bike, except the really loose deep sandy spots. Regardless, I am routinely greeted
with "whoa, dude, a road bike" when out in the woods passing a group on their full-suspension 30 lb
"freeride" bikes. Once I was even told "dude, there's no way you belong out here on *that*" (I was
on my cyclo-cross bike at the time).

A couple of years ago I chanced upon an entire family riding along one of the better MTB trails in
the area- Mom and Dad on their department store 3 speeds and the kids on kiddie bikes. They were
having a great time and had no idea they "didn't belong" out there. More power to 'em!

 

[Tim McNamara]

In article <[email protected]>, [email protected] (Andrew
Bradley) wrote:

> The statement does it's job: it is logically consistent with my view but isn't categorical. I am
> under the impression that tubulars pinch less than the equivalent section clincher at a given
> pressure.

This statement is clear; your previous statement was rather an incomprehensible semantic mess.

> See this is one of two mechanical myths your rbt has yet to completely dispel for me. What with
> latex vs butyl and the shapes of the pinching surfaces.

The lore is that tubulars are less likely to pinch flat. The lore is also that latex tubes are less
likely to pinch flat. I don't personally know what's true in this regard.

> The other myth, BTW, is that a flimsy wheel can be squishy in corners.
>
> It's personal experience (real or imagined) vs a lack of data/quantitative analysis to the
> contrary that allows these myths to live on.

The quantitative data for the wheels exists.

 

[Jay Beattie]

<[email protected]> wrote in message news:[email protected]...
> Tim McNamara writes:
>
> >> Besides that, here in the Santa Cruz mountains we have enough steep roads that tubulars often
> >> melted their glue and pulled off the stem as the tube went around the rim. It wasn't for
> >> nothing that I put insulator strips on my rims between tubular and aluminum to prevent this.
>
> > Andrew Bradley mentioned this too. I've never seen these- what were they? Just an extra layer of
> > fabric?
>
> Since this was a serious problem, both in the local hills and the Alps, I devised an insulating
> strip made of cotton webbing (cotton belt material) soaked in epoxy and secured to the rim with
> conventional rim glue. Such strips are available in 5/8 inch width. The strip was butt-sewn into a
> loop with a valve stem hole opposite this seam. The rim was coated with rim cement as though for a
> tire. This was important because the prototype failed suddenly when the epoxy cracked and
> separated from the rim together with the tire on a descent.
>
> The epoxy soaked strip was carefully mounted on the rim, a plastic sheet placed between it and a
> used tubular tire that is mounted on the strip and inflated hard. This makes a cotton-filled epoxy
> insulator, securely attached and engaged in the spoke recesses, shaped like a tubular tire to be
> mounted on it. A little dressing of the strip before the epoxy was fully hard was done to round
> the edges.
>
> I have four sets of these wheels with Mavic and Fiamme rims collecting dust. Forty spoke rear
> wheels on Campagnolo Record hubs, no less. I don't need no steenkin heat shields no more!

Why not just glue the tire with something like base-tape cement that does not react so poorly to
heat? Isn't there a suitable high temperature cement? It seems to me that there must be something
out there in industry land. What do they use on the space-shuttle tiles (maybe not a good example)
or boiler gaskets. Hell, if sew-ups ride so well when they are flat, just glue them once with super
heat resistant glue and never take them off even if they flat. -- Jay Beattie.

 

[Jobst Brandt]

Jay Beattie writes:

>>>> Besides that, here in the Santa Cruz mountains we have enough steep roads that tubulars often
>>>> melted their glue and pulled off the stem as the tube went around the rim. It wasn't for
>>>> nothing that I put insulator strips on my rims between tubular and aluminum to prevent this.

>>> Andrew Bradley mentioned this too. I've never seen these- what were they? Just an extra layer of
>>> fabric?

>> Since this was a serious problem, both in the local hills and the Alps, I devised an insulating
>> strip made of cotton webbing (cotton belt material) soaked in epoxy and secured to the rim with
>> conventional rim glue. Such strips are available in 5/8 inch width. The strip was butt-sewn into
>> a loop with a valve stem hole opposite this seam. The rim was coated with rim cement as though
>> for a tire. This was important because the prototype failed suddenly when the epoxy cracked and
>> separated from the rim together with the tire on a descent.

>> The epoxy soaked strip was carefully mounted on the rim, a plastic sheet placed between it and a
>> used tubular tire that is mounted on the strip and inflated hard. This makes a cotton-filled
>> epoxy insulator, securely attached and engaged in the spoke recesses, shaped like a tubular tire
>> to be mounted on it. A little dressing of the strip before the epoxy was fully hard was done to
>> round the edges.

>> I have four sets of these wheels with Mavic and Fiamme rims collecting dust. Forty spoke rear
>> wheels on Campagnolo Record hubs, no less. I don't need no steenkin heat shields no more!

> Why not just glue the tire with something like base-tape cement that does not react so poorly to
> heat? Isn't there a suitable high temperature cement?

If its not heat sensitive, it isn't sticky (pressure sensitive). Track glue, (Mastice Gutta, Tipo
Pista) a hardening non sticky glue, basically shellac, is not heat sensitive, but you can't change a
tire on the road with it.

> It seems to me that there must be something out there in industry land. What do they use on the
> space-shuttle tiles (maybe not a good example) or boiler gaskets. Hell, if sew-ups ride so well
> when they are flat, just glue them once with super heat resistant glue and never take them off
> even if they flat.

I think you've got it. However, why use them at all. Just use rim tape. There's no need for a
pump that way.

Jobst Brandt [email protected] Palo Alto CA

 

[Jobst Brandt]

Andrew Bradley writes:

> I am under the impression that tubulars pinch less than the equivalent section clincher at a given
> pressure.

Yes, I agree but I have reasons for believing so.

> See this is one of two mechanical myths your rbt has yet to completely dispel for me. What with
> latex vs butyl and the shapes of the pinching surfaces.

A pinch perforation occurs when compressing a sheet of rubber makes it displace laterally far enough
to make it fail in tension. Rubber is essentially incompressible, and under pressure expands
laterally when compressed vertically. Latex rubber can stretch several times as far as butyl rubber
before failure, something we can test with latex rubber bands and a similar band sliced from the
cross section of an inner tube.

Butyl rubber is designed to hold air and is not primarily intended for elasticity. Latex in
contrast, has a high elasticity but greater air permeability. Those who ride in latex tubes are
aware of the daily inflation they require. A butyl tube can keep a bicycle tire in the useful range
for more than a month.

> The other myth, BTW, is that a flimsy wheel can be squishy in corners.

I've never heard the definition for the "flimsy" wheel. The only condition I can imagine for being
"squishy" in corners is a nearly flat tire and that isn't the wheel.

> It's personal experience (real or imagined) vs a lack of data/quantitative analysis to the
> contrary that allows these myths to live on.

Pleas, list more of these myths. They make good targets.

Jobst Brandt [email protected] Palo Alto CA

 

[Jobst Brandt]

Andrew Bradley writes:

> I am under the impression that tubulars pinch less than the equivalent section clincher at a given
> pressure.

Yes, I agree but I have reasons for believing so.

> See this is one of two mechanical myths your rbt has yet to completely dispel for me. What with
> latex vs butyl and the shapes of the pinching surfaces.

A pinch perforation occurs when compressing a sheet of rubber makes it displace laterally far enough
to make it fail in tension. Rubber is essentially incompressible, and under pressure expands
laterally when compressed vertically. Latex rubber can stretch several times as far as butyl rubber
before failure, something we can test with latex rubber bands and a similar band sliced from the
cross section of an inner tube.

Butyl rubber is designed to hold air and is not primarily intended for elasticity. Latex in
contrast, has a high elasticity but greater air permeability. Those who use latex tubes must inflate
them daily. A butyl tube can keep a bicycle tire in the useful pressure range for more than a month.

> The other myth, BTW, is that a flimsy wheel can be squishy in corners.

I've never heard the definition for the "flimsy" wheel. The only condition I can imagine for being
"squishy" in corners is a nearly flat tire and that isn't the wheel.

> It's personal experience (real or imagined) vs a lack of data/quantitative analysis to the
> contrary that allows these myths to live on.

Please, list more of these myths. They make good targets.

Jobst Brandt [email protected] Palo Alto CA

 

[Anonymous]

>> More people object to wearing fur than leather because it is safer to harass rich white women
>> than motorcycle gangs.
>
>Well that's a big misrepresentation. Motorcyclist's pants and jackets are made from slaughterhouse
>hides, fur coats are made from endangered species.

That's a misrepresentation. Fur coats are made from any number of species that are far from
endangered, such as rabbit and fox. Animal activists are more concerned with the pain and treatment
of animals than impact on their numbers. On the contrary, a legitimate trade in a species would
guarantee its survival.

Doug

 

[David Damerell]

Jay Beattie <[email protected]> wrote:
>"Bluto" <[email protected]> wrote in message
>>But leather saddles were a proven technology long before bikes came along, and I imagine they'll
>>be with us until cows get to vote.
>A BROOKS IS MURDER! Wait, I guess I have a leather cover over my plastic saddle. Never mind. --
>Jay Beattie.

Yeah, but murder tastes - er, feels _good_.
--
David Damerell <[email protected]> Distortion Field!