A Cycling & bikes forum. CycleBanter.com

Go Back   Home » CycleBanter.com forum » rec.bicycles » Unicycling
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

more 29-er flat problems



 
 
Thread Tools Display Modes
  #1  
Old August 14th 04, 07:27 PM
onewheeldave
external usenet poster
 
Posts: n/a
Default more 29-er flat problems


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

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

------------------------------------------------------------------------
onewheeldave's Profile: http://www.unicyclist.com/profile/874
View this thread: http://www.unicyclist.com/thread/34547

Ads
  #2  
Old August 14th 04, 09:44 PM
Mikefule
external usenet poster
 
Posts: n/a
Default


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.
------------------------------------------------------------------------
Mikefule's Profile: http://www.unicyclist.com/profile/879
View this thread: http://www.unicyclist.com/thread/34547

  #3  
Old August 14th 04, 09:44 PM
Mikefule
external usenet poster
 
Posts: n/a
Default


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.
------------------------------------------------------------------------
Mikefule's Profile: http://www.unicyclist.com/profile/879
View this thread: http://www.unicyclist.com/thread/34547

  #4  
Old August 14th 04, 09:44 PM
Mikefule
external usenet poster
 
Posts: n/a
Default


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.
------------------------------------------------------------------------
Mikefule's Profile: http://www.unicyclist.com/profile/879
View this thread: http://www.unicyclist.com/thread/34547

  #5  
Old August 14th 04, 09:49 PM
joemarshall
external usenet poster
 
Posts: n/a
Default


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
------------------------------------------------------------------------
joemarshall's Profile: http://www.unicyclist.com/profile/1545
View this thread: http://www.unicyclist.com/thread/34547

  #6  
Old August 14th 04, 09:49 PM
joemarshall
external usenet poster
 
Posts: n/a
Default


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
------------------------------------------------------------------------
joemarshall's Profile: http://www.unicyclist.com/profile/1545
View this thread: http://www.unicyclist.com/thread/34547

  #7  
Old August 14th 04, 09:49 PM
joemarshall
external usenet poster
 
Posts: n/a
Default


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
------------------------------------------------------------------------
joemarshall's Profile: http://www.unicyclist.com/profile/1545
View this thread: http://www.unicyclist.com/thread/34547

  #8  
Old August 15th 04, 01:14 AM
onewheeldave
external usenet poster
 
Posts: n/a
Default


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 befo -

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."

------------------------------------------------------------------------
onewheeldave's Profile: http://www.unicyclist.com/profile/874
View this thread: http://www.unicyclist.com/thread/34547

  #9  
Old August 15th 04, 03:14 AM
cyberbellum
external usenet poster
 
Posts: n/a
Default


onewheeldave wrote:
*... 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 wrote:
*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 wrote:
*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.
------------------------------------------------------------------------
cyberbellum's Profile: http://www.unicyclist.com/profile/4550
View this thread: http://www.unicyclist.com/thread/34547

  #10  
Old August 15th 04, 03:47 AM
onewheeldave
external usenet poster
 
Posts: n/a
Default


cyberbellum wrote:
*
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."

------------------------------------------------------------------------
onewheeldave's Profile: http://www.unicyclist.com/profile/874
View this thread: http://www.unicyclist.com/thread/34547

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Principia gear selection problems sparky.g Marketplace 2 June 4th 04 01:42 PM
Noob: 'Bents and Lumbar Problems xkred27 Recumbent Biking 17 May 1st 04 06:57 AM
Outlaw Bicycles - problems anyone? docernie Marketplace 3 March 13th 04 05:41 PM
Knee problems, advice anyone Gus Recumbent Biking 13 February 7th 04 11:12 PM


All times are GMT +1. The time now is 10:04 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 CycleBanter.com.
The comments are property of their posters.