more 29-er flat problems

Hi, Dave, I had similar problems on a tandem once, and also on my
MUni.

A pinch flat is caused by pinching the tube between the rim and
something else. So if you ride with low pressure, the tube and tyre
will distort all over the place and occasionally the tube will get
trapped. A higher pressure will usually prevent this, unles the tube
and tyre are too wide for the rim in which case you might not eliminate
it entirely.

The loud bang implies that the pressure caused or exacerbated a problem.
I've had threeloud bang deflations on a unicycle. On the first
occasion, the tube was too long for the wheel size, and the manufacturer
had folded it abit to make it fit! I pumped it up to hard (60 ish?) and
rode for a while, hit a bump, and BANG! This caused a long jagged tear
in the tube. The second occasion whas when the tube had slipped round a
bit and was dragging the valve into a diagonal position. The valve tore
out. The third was years ago when I inflated a cheap tube/tyre
combination with a track pump then parked the unicycle in the sun!

You should easily be able to get a pressure of 60 or more psi with a
decent hand pump. A track pump just makes it easier. I doubt that you
could get enough pressure to burst a tube encased in a tyre. When I
search for punctures and have no water supply, I remove the tube and
pump it to 3 times its working diameter (approx.) and this has never
split one yet. A tube properly positioned in a tyre won't stretch or
distort, so it shouldn't burst.

I wonder if you have a concealed sharp object either in the tread of the
tyre, or in the rim tape. Alternatively, do you have a spoke that's a
bit too long, or has a sharp end? is your rim tape seated properly?

I cured the tandem problem and the MUni problem (repeated unexplained
punctures) simply by replacing the tyre and tube. No doubt in each case
there was a tiny tip of a thorn embedded in the tyre casing or
something.

--
Mikefule - Roland Hope School of Unicycling

Everyone should be fatuous for 15 minutes.
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Hi, Dave, I had similar problems on a tandem once, and also on my
MUni.

A pinch flat is caused by pinching the tube between the rim and
something else. So if you ride with low pressure, the tube and tyre
will distort all over the place and occasionally the tube will get
trapped. A higher pressure will usually prevent this, unles the tube
and tyre are too wide for the rim in which case you might not eliminate
it entirely.

The loud bang implies that the pressure caused or exacerbated a problem.
I've had threeloud bang deflations on a unicycle. On the first
occasion, the tube was too long for the wheel size, and the manufacturer
had folded it abit to make it fit! I pumped it up to hard (60 ish?) and
rode for a while, hit a bump, and BANG! This caused a long jagged tear
in the tube. The second occasion whas when the tube had slipped round a
bit and was dragging the valve into a diagonal position. The valve tore
out. The third was years ago when I inflated a cheap tube/tyre
combination with a track pump then parked the unicycle in the sun!

You should easily be able to get a pressure of 60 or more psi with a
decent hand pump. A track pump just makes it easier. I doubt that you
could get enough pressure to burst a tube encased in a tyre. When I
search for punctures and have no water supply, I remove the tube and
pump it to 3 times its working diameter (approx.) and this has never
split one yet. A tube properly positioned in a tyre won't stretch or
distort, so it shouldn't burst.

I wonder if you have a concealed sharp object either in the tread of the
tyre, or in the rim tape. Alternatively, do you have a spoke that's a
bit too long, or has a sharp end? is your rim tape seated properly?

I cured the tandem problem and the MUni problem (repeated unexplained
punctures) simply by replacing the tyre and tube. No doubt in each case
there was a tiny tip of a thorn embedded in the tyre casing or
something.

--
Mikefule - Roland Hope School of Unicycling

Everyone should be fatuous for 15 minutes.
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I run my 29er at 65-70 each time I pump it up and then ride it till it
goes down to about 35-40. The big apple can take at least 70psi without
problems. There must be something odd happening with your uni.

If you can wait till mid/late september, there'll hopefully be a ride in
nottingham organised by me, bring it down then and we'll have a look at
it.

Joe

--
joemarshall - dumb blonde
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Cheers for the replies 🙂

Mike- I've had a few good inspections of the rim and tyre and found
nothing, but if it happens again I'll take everything apart at home and
give it a good going over.

I do wonder if there is a problem with the tyre- it is pretty old. I'm
tempted to go back to my old 45 mm before buying another 29-er tyre and
see if that results in no punctures.

Joe- my tyre is a Notos, not a Big apple, but you're right, I shouldn't
be getting this many punctures.

--------------

I found this on the web, it's got some of the usual ideas plus a couple
I've not heard before: -

http://tinyurl.com/55su4

(summary of the article is 'Wide rim + chalk in tyre + Duck tape rim
strip = happiness'😉

The chalk idea is interesting because I used to do a similar thing with
talcum power sprayed liberally in the tyre of my muni; for a different
reason- my valve kept going to a 45 degree angle after a bit of riding
and I was told that talc would stop it by providing lubrication for the
inner. Punctures on my muni are very rare and I wonder if this could be
due to the talc.

I have noticed on 29-er that the inner does actually stick to the tyre,
so maybe chalk dust, as the article suggests, would help.

One good thing about this is that I'm getting good at fixing punctures
🙂

--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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onewheeldave said:

*... just before getting to 65 there was a really loud bang as the
tube exploded!
*

Was the tube sticking out from between the rim an the tire? If so, I
did the same thing when I put a Big Apple on a 700c rim.

It's caused by two things - an improperly seated tire and too much
pressure. The bead of the tire has a wire in it to keep it from
stretching. If the bead is evenly seated under the hook of the rim all
the way around then the tire pressure pushes it evenly into the rim and
it's cool. If it's not hooked well at one spot then the tire pulls out
at that point and releases the rim to open air. Blamo!

The cure is to a) not overpressure the tire (usually 20-30 psi higher
than the number on the casing, which is why I got fooled. The Big Apple
went at 60 psi.), and b) seat the tire well. This is quite simple to do
- put 3-5 psi into the tire, just enough to firm it up, then slowly spin
the wheel and look at the bead. Is it even all the way around? If not,
then push/mush the bead around until it is. Then raise the pressure to
where you want it. If the bead isn't set right the tire will blow well
below it's max pressure.

onewheeldave said:

*Would it be true to say that, given pressure is not so low that pinch
flats are a problem, that going much higher makes normal punctures
more likely?

Also, as the tyre ratings are meant for a bike, couldn't it be the
case that they would not apply when used on a unicycle, as, being one
wheeled, there will be around twice the stress on it?
*

You're about right at 50 psi. Just get the bead to seat right. If it
just won't seat right then it's a bad combination of tire and rim.

onewheeldave said:

*Can anyone briefly explain what causes a pinch flat;
*

The sidewall of the tire bulges out when the tire is compressed, part of
the tube goes with it, and the rim pushes the part of the tire just
above the bead through both layers of tube. Hence the nickname
"snake-bite" flat. There are usually two holes or slots.

--
cyberbellum - Level 1.0 rider!

I was standing in the park wondering why frisbees get bigger as they get
closer. Then it hit me.
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cyberbellum said:

*
Was the tube sticking out from between the rim an the tire? If so, I
did the same thing when I put a Big Apple on a 700c rim.
*

I now suspect it was, for two reasons-

1. a page I found on my web search expressed the view that a explosion
would be impossible if the tube was properly in the tyre, as a contained
tube can only leak, not pop loudly.

2. tonight I decided to follow the advice mentioned above and put loads
of talc powder into my tyre and on the tube, this meant deflating the
tube, taking off the tyre etc. When I put everything back and started to
reinflate it i was extra observant and noticed that, near the valve, the
tyre wasn't seated properly and, had I not noticed it, I suspect that
the tube would have poked out as the pressure increased. This is
probably what happened previously.

-------------------

Concerning Big Apples- is anyone here using them successfully on a
Nimbus 700c (or similar) rim?

One of my possible future upgrades was going to be getting the new 29-er
Nimbus frame and putting a Big Apple in, but I wonder if it will work
without a wider rim.

--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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I had a similar problem with my new 28" uni. The original tube popped
loudly when I increased the pressure from 50lbs to 65lbs.

Inspecting the tire, I found shavings of metal (brass looking)inside the
tire. I suspect the shavings came from the spoke nuts rubbing the rib
while the spokes were being tuned.

What I did was wipe the inside of the tire clean, replace the rubber
tube protector with that cloth 'tube protector' tape from the bike
shop. Replaced the tube. When filling, fill ~30lbs, deflate, then fill
again.

I'm no expert but I now have 70lbs in the tire now. Good luck.

--
Chrashing

Regards,
Chrashing
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Oh yeah, Those tires are loud when they pop. My ears were ringing for a
few minutes.

--
Chrashing

Regards,
Chrashing
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Chrashing said:

*Inspecting the tire, I found shavings of metal (brass looking)inside
the tire. I suspect the shavings came from the spoke nuts rubbing the
rib while the spokes were being tuned. *

Metal shavings can be left in the rim after manufacture. The drilling
of the spoke holes can leave shavings either floating around between the
walls of the rim or still attached to the spoke hole.

When the wheel is built it should have been checked to make sure there
were no metal shavings in it. All of the spoke holes should have been
checked to make sure they were clean and then compressed air blown
through (carefully) to make sure no shavings were floating around in the
walls of the rim.

A metal shaving from the rim is no match for most rim strips. A shaving
can easily poke through a cloth or rubber rim strip. I got a flat on my
freestyle unicycle back when it was new due to a metal shaving hiding
under the rim tape.

--
john_childs - Guinness Mojo

john_childs (at) hotmail (dot) com
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I once had chronic flats on a road bike due to a tire with a bad bead.
The tire passed a visual inspection, but replacing it fixed my problem.
It had the "loud bang" problem due to the tube poking out the side of
the tire as I approached a moderate tire pressure using a floor pump.

--
mscalisi - Not such a newbie anymore
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onewheeldave said:

Concerning Big Apples- is anyone here using them successfully on a
Nimbus 700c (or similar) rim?

One of my possible future upgrades was going to be getting the new 29-er
Nimbus frame and putting a Big Apple in, but I wonder if it will work
without a wider rim.

I bought my Nimbus with a 35 mm tyre. Later I retrofitted the Big
Apple 2.35" with no problem. The rim's inside width is only 22 mm and
the rimstrip states 26x1.75/2.125. It is a 700c wheel so the 26
puzzles me. The Big Apple is wider than 2.125 but it runs very fine. I
keep it at about 3 - 4 bar which is around 50 psi. I use it almost
exclusively for road rides for which it is excellent - no folding over
at that pressure.

Note that the Nimbus II frame (square crown) is OK for clearance, but
the round Nimbus I (28"😉doesn't accept the 28 x 2.35 Big Apple.

Klaas Bil - Newsgroup Addict
--
I like the idea of not having to balance when out on a ride - joe

[quote="onewheeldave"]Having established on a different thread that my recent, very frequuent,
29-er punctures were probably pinch flats caused by too low tyre
pressure, I bought a track pump with built in guage.

A few puncture free rides at around 50 psi seemed to have resolved the
problem.

The only down point was a few days ago when I removed the tyre to do
some wheel truing. I decided to inflate it to 65 psi, the max on the
tyres range; just before getting to 65 there was a really loud bang as
the tube exploded!

New tube and back down to 50-55 psi.

Then today I got another puncture. Though I'd just bought yet another
spare 700x45c tube I decided to do a repair on the damaged one, partly
to save the hassle of having to take the wheel off.

It went OK, then I inflated the tube, no track pump available here so I
did my best with the hand pump, knowing that I wouldn't get it up to 50
psi.

I decided to get the tyre as hard as possible- as soon as I'd finished
there was a nasty sound of air escaping, and it deflated in seconds.

Annoyed now I took the tube out again to find another hole had appeared
in a different place! How could this happen without even riding the
thing?

As the hole was near the seam I decided to switch in the spare, and
managed to ride home on it without incident.

-------------

Can anyone offer useful insights into this problem, because I'm deeply
confused and on the verge of giving up 29-ing, if only because I've
bought four tubes (and a track pump) this month alone and can't justify
the expense.

My thoughts are that I do need to keep the pressure up with the track
pump to avoid pinch flats, but also that maybe I need to stay away from
the max of 65 psi.

So I'm currently going to stay at 40-45 psi and see what happens.

Would it be true to say that, given pressure is not so low that pinch
flats are a problem, that going much higher makes normal punctures more
likely?

Also, as the tyre ratings are meant for a bike, couldn't it be the case
that they would not apply when used on a unicycle, as, being one
wheeled, there will be around twice the stress on it?

Can anyone briefly explain what causes a pinch flat; I know the normal
explanation is that it's when the tube gets trapped between rim and
tyre, but, assuming that the tube is installed properly, how can this
occur. Certainly my flats seem to be happening on normal riding i.e. not
when dropping off curbs etc.

Has anyone else had problems with excessive 29 flats? One of my theories
is that maybe the tubes are faulty, possibly sat in the shop too long;
although this is no help as tubes don't come with a sell by date.

Another possibility is that, because my rim isn't designed for 29-ing
(it's the old style nimbus 700c and consequently quite narrow) that this
is causing the punctures. Although this wouldn't explain why it was OK
during my last big 29-er phase at the beginning of this year, when I was
riding every day for around a month and don't recall any flats.


--
onewheeldave - Semi Skilled Unicyclist

Dave your one wheel or shall I say tyre probably has a thorn or similer in it.Run your hand slowly around the inside of the tyre to try to locate it.

I had some flat problems with the Big Apple, but that's becuase I was
going urban off road (no drops). I switched to the Nanorapter, with
good results so far.

Billy

--
BillyTheMountain
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When Peter Bier, Steve Pavarno and I did 'The 42nd Traverse'
(http://tinyurl.com/4d7gw) on 29ers Peter got 2 punctures. (As well as
that I broke a cotterpin and had to walk out, but that's another story.)
Both punctures were pinch flats. The cure I'd recommend is to get a
thicker walled 29" specific inner tube. A standard 28"/700Cx45 will be
stretched to the point of being very thin inside a 29 inch tyre. This
makes it very easy to get pinchflats, especially during offroad riding.
There are at least three different 29" specific inner tubes available,
'one of which is made by WTB' (http://tinyurl.com/65j9y).

+0}\[y

--
TonyMelton - www.unicycle.co.nz

See some photos of the first 'NZ MUni Weekend'
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Another day, another puncture 🙂

Felt this one go- an audible pop while riding up a hill.

Not a pinch flat this time, but a single hole facing the rim and right
over a spoke.

I'm guessing that it was caused by the top of the spoke nipple which is
one of the ones that got a bit shredded during an attempt to tighten it
with a screwdriver last week.

I think my priority has to be to get a decent rim strip, the present one
is thin rubber and doesn't look as though it could be much use.

Being Sunday there was nowhere open to buy one so I've improvised my own
with some wrapped newspaper.

Tony, I checked your link- those tubes look a bit expensive, and they
only seem to come with presta valves with I try to avoid.

I think I'd be more inclined to get one when I've got a better
understanding of why I'm getting so many punctures, especially as the
punctures seem to be of different types- I'm suspecting that there's
more than one thing wrong here.

It'd be a shame to get a pricey tube to stop the pinch flats, and have
it ruined by the normal punctures I'm also getting.

On the positive side I've learnt some useful stuff from this problem, an
internet search turned up a method of getting tyres of the rim without
using levers and on todays puncture Igot the tyre off easily with only
my hands and also got it back on again without levers🙂

--
onewheeldave - Semi Skilled Unicyclist

"He's also been known to indulge in a spot of flame juggling - but it's
the Muni that really fires him up."

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