Bulging Tube?

[Joel Crawley]

I was out last weekend and somewhere on the trail I must've picked up a thorn. I wasn't even aware
of it until I was on my way home and noticed that it seemed hard to pedal. I stopped and noticed my
front tire going down. It wasn't too flat and I continued to ride until I got to the point that it
wasn't going to support me and walked it the rest of the way.

I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
"high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did it.
Better but still noticable. Seems like there's a weak spot in the tube or something that allows the
tube to expand there more than the rest of it. The tire is seated on the bead fine and the rim is
true. Is it just a cheap tube or is there something I'm doing/not doing that's causing it to inflate
improperly? I'm airing up with a hand pump and tried doing it as slow as possible.

Thanks

 

[Jon Isaacs]

>I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
>"high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did
>it. Better but still noticable. Seems like there's a weak spot in the tube or something that
>allows the tube to expand there more than the rest of it. The tire is seated on the bead fine and
>the rim is true. Is it just a cheap tube or is there something I'm doing/not doing that's causing
>it to inflate
improperly? I'm airing up with a hand pump and tried doing it as slow as
>possible.

Not exactly sure what you mean by a "high spot."

If the bead is properly seated, ie the mold mark at the rim is identically positioned around the
tire, then it is possible that you have damaged tire.

It is the tire itself rather than the tube that determines the shape of the tire, the tube just
expands to fit the tire.

jon isaacs

 

[Jobst Brandt]

Joel Crawley writes:

> I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
> "high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did
> it. Better but still noticeable. Seems like there's a weak spot in the tube or something that
> allows the tube to expand there more than the rest of it. The tire is seated on the bead fine and
> the rim is true. Is it just a cheap tube or is there something I'm doing/not doing that's causing
> it to inflate improperly? I'm airing up with a hand pump and tried doing it as slow as possible.

Most tubes have a non-uniform wall thickness and will have thicker and thinner cross sections when
inflated beyond natural size. If your tire has high and low sections, they are caused by the tire
being improperly seated in the rim. Check for this by looking at the side of the tire while
rotating the wheel. The sidewall will dip in and out from under the rim. It should be uniformly
positioned. With light inflation, these areas can manually be made to seat before inflating hard.
Of course if they are only low spots, they will usually come up when the tire is inflated hard,
harder than normal.

You should consider carrying a spare tube and pump (or CO2 inflater) because you could get a flat
uncomfortably far from civilization. A patch kit is also a good thing to have.

Jobst Brandt [email protected] Palo Alto CA

 

[Joel Mayes]

In article <[email protected]>, Joel Crawley wrote:
> I was out last weekend and somewhere on the trail I must've picked up a thorn. I wasn't even aware
> of it until I was on my way home and noticed that it seemed hard to pedal. I stopped and noticed
> my front tire going down. It wasn't too flat and I continued to ride until I got to the point that
> it wasn't going to support me and walked it the rest of the way.
>
> I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
> "high-spot."

<snip>

my LBS recommends once you have the tire on, push the valve all the way in before pulling out into
place, can't remeber the reason why, but what it is ment to prevent is exactly what you described.

--
| Joel Mayes | Linux and OpenBSD | /"\ ASCII ribbon | Accordionist | | \ / campaign against |
| Musician | My PC, My Rules | X HTML mail and | Music Teacher | | / \ postings |

 

[Fredzep]

"Joel Crawley" <[email protected]> wrote in message
news:[email protected]...
> I was out last weekend and somewhere on the trail I must've picked up a thorn. I wasn't even aware
> of it until I was on my way home and noticed that it seemed hard to pedal. I stopped and noticed
> my front tire going down. It wasn't too flat and I continued to ride until I got to the point that
> it wasn't going to support me and walked it the rest of the way.
>
> I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
> "high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did
> it. Better but still noticable. Seems like there's a weak spot in the tube or something that
> allows the tube to expand there more than the rest of it. The tire is seated on the bead fine and
> the rim is true. Is it just a cheap tube or is there something I'm doing/not doing that's causing
> it to inflate improperly? I'm airing up with a hand pump and tried doing it as slow as possible.
>
> Thanks

I would inspect the casing on inside of the tire. You might have torn it enough with the thorn to
produce a small bulge. That is assuming the tire is seated properly. As mentioned earlier it is the
tire that determines the shape not the tube. If it's not too large you might try to patch the inside
of the tire.

Fredzep

 

[Dion Dock]

The tire's casing has a cut, allowing it to bulge when inflated. Junk the tire, keep the tube.

-Dion

"Joel Crawley" <[email protected]> wrote in message
news:[email protected]...
> I was out last weekend and somewhere on the trail I must've picked up a thorn. I wasn't even aware
> of it until I was on my way home and noticed that it seemed hard to pedal. I stopped and noticed
> my front tire going down. It wasn't too flat and I continued to ride until I got to the point that
> it wasn't going to support me and walked it the rest of the way.
>
> I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
> "high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did
> it. Better but still noticable. Seems like there's a weak spot in the tube or something that
> allows the tube to expand there more than the rest of it. The tire is seated on the bead fine and
> the rim is true. Is it just a cheap tube or is there something I'm doing/not doing that's causing
> it to inflate improperly? I'm airing up with a hand pump and tried doing it as slow as possible.
>
> Thanks

 

[Joel Crawley]

Well I hate to sound snobbish but it must've been the tube. I unmounted the tire, inspected it,
inspected the tube again and remounted it. Still had the "high spot." Went to the bike shop and
bought a new tube. All is well.

The idea that the tube will only conform to whatever is encasing it sounds valid and I assumed that
I did have some type of tire problem but for whatever reason the cheapy tube was the cause.

Thanks for all the replies,

Joel


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

> I was out last weekend and somewhere on the trail I must've picked up a thorn. I wasn't even aware
> of it until I was on my way home and noticed that it seemed hard to pedal. I stopped and noticed
> my front tire going down. It wasn't too flat and I continued to ride until I got to the point that
> it wasn't going to support me and walked it the rest of the way.
>
> I happened to be going by a Wal-Mart so I picked up a tube. When I put it on I noticed I had a
> "high-spot." I figured the tube wasn't in just right so when I got home I took it off and re-did
> it. Better but still noticable. Seems like there's a weak spot in the tube or something that
> allows the tube to expand there more than the rest of it. The tire is seated on the bead fine and
> the rim is true. Is it just a cheap tube or is there something I'm doing/not doing that's causing
> it to inflate improperly? I'm airing up with a hand pump and tried doing it as slow as possible.
>
> Thanks

 

[Jobst Brandt]

Joel Crawley writes:

> Well I hate to sound snobbish but it must've been the tube. I unmounted the tire, inspected it,
> inspected the tube again and re-mounted it. Still had the "high spot." Went to the bike shop and
> bought a new tube. All is well.

> The idea that the tube will only conform to whatever is encasing it sounds valid and I assumed
> that I did have some type of tire problem but for whatever reason the cheapy tube was the cause.

With each tube inspection or change, the tire in question was re-mounted, most likely in a different
engagement with the rim. As I said, almost any tube will have at least one bulge when inflated
outside a tire. Not having any strength of its own to contain pressure, the tube shape has no
bearing on the inflated tire shape when. The tire contains the inflation pressure, the tube strength
against anything more then 2-3psi is ineffective in shaping the tire.

The tube that gave you trouble was probably stuck under the bead and prevented it from seating
properly. This can be caused by a tube that is too small in major circumference or one that is too
large to fit the tire without getting under the bead.

Jobst Brandt [email protected] Palo Alto CA