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Bursting tyres with heavy loading



 
 
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  #1  
Old June 1st 11, 10:58 AM posted to aus.bicycle
Travis
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Posts: 231
Default Bursting tyres with heavy loading

I've been riding to uni on a clunker of an old mountain bike, using
that instead of my Trek roadie because I could mount a rack to it and
carry panniers.

I don't think I've really got all that heavy a load in there. A laptop
computer, change of clothes and my lunch. On some days, a lab coat too
and possibly a thin plastic rain jacket. That's it!

The bike is a somewhat heavy one and I weigh about 105kg.

Today my brand new rear tyre and/or tube burst. There was a loud
"pshht" and then my tyre had no air left in it. It had been inflated
to 100psi as per the sidewall markings and the tyres are supposedly
"thornproof", for what limited good that is.

This tyre is a 1.25" x 26" thin (ish) mountain bike tyre.

A few weeks ago I managed to burst a wider (1.75" I guess) rear tyre,
but I blamed that on it being a very old one which had been squashed
under its own weight uninflated in a shed for a couple of years at
least and therefore dodgy. That one had been inflated to 60psi.

First of all, is it more likely to be the tyre or the tube which is
responsible for a popping tyre? The tube I bought off eBay is a Kenda
which I understand is a fairly well known brand. The tyres were these
Innova ones: https://www.torpedo7.com.au/products/INTYMNNPPXX125

Should I blame the tyres, and possibly ask for a refund from Torpedo7,
or blame the tubes and maybe try for a refund from the eBay vendor, or
is a bursting rear tyre normal enough when one tries to load them up
with a 100kg+ rider, a 20kg bike and 15kg of luggage?

In the mean time, I have a 1.75" tyre and tube in good condition. For
the loads I'm carrying, would I be less likely to see another burst if
I just patch my 1.25" tube and put the 1.25" tyres back, or should I
switch to the wider tyre for the back?

100psi is the "Max PSI" according to Torpedo7. Should I inflate it
less than that? How much less?

Travis
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  #2  
Old June 1st 11, 12:08 PM posted to aus.bicycle
Dave Hughes
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Posts: 228
Default Bursting tyres with heavy loading

On Wed, 01 Jun 2011 02:58:41 -0700, Travis wrote:

Should I blame the tyres, and possibly ask for a refund from Torpedo7, or
blame the tubes and maybe try for a refund from the eBay vendor, or is a
bursting rear tyre normal enough when one tries to load them up with a
100kg+ rider, a 20kg bike and 15kg of luggage?


What let go? You should be able to see an obvious rip in a tube if it went
that loudly. If it's on a seam, it might have been a dodgy tube, but you'd
be doing well to get any kind of refund on a tube - there are too many
non-obvious ways to install them badly.

If the tyre has obvious damage, then I'd speak to T7, but that's still
going to be a case of showing you hadn't hit anything, etc.

Assuming it's the tube:

If the hole is near the valve then you've probably got a dodgy rim strip -
look for exposed metal and incomplete coverage.

You may have got part of the tube caught between the rim and the tyre,
which will work fine until you manage to flex the tyre enough that the
tube snaps back inside. This tends to make them go pop pretty quickly.
This is one of those gotchas I was mentioning earlier.

As far as what's best - I'd run a larger tyre on the back at slightly
lower pressure to give me a bit of comfort on a commuter, but my current
commuter is a 700c x 28mm tyre that's normally somewhere between 50 and
110 psi, depending on when I last checked it... Commuter bikes tend not to
get a lot of love!

Best option is to get a new tube, carry a spare and a pump, and try to
avoid sharp edges.

--
Dave Hughes -
"First things first, but not necessarily in that order." - The Doctor

  #3  
Old June 1st 11, 02:11 PM posted to aus.bicycle
terryc
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Posts: 134
Default Bursting tyres with heavy loading

Travis wrote:

The bike is a somewhat heavy one and I weigh about 105kg.

Today my brand new rear tyre and/or tube burst.
This tyre is a 1.25" x 26" thin (ish) mountain bike tyre.

First of all, is it more likely to be the tyre or the tube which is
responsible for a popping tyre?


Tyre doesn't match rim or you didn't align it evenly.
FWIW, i found thornproof tyres a complete waste of money. They all
eventually split along the rim. heavy loads and a very stiff tyre. OTOH,
thornproof tubes are fantastic.


100psi is the "Max PSI" according to Torpedo7. Should I inflate it
less than that? How much less?


If the tyre popped off, then it is a mismatch of tyre to rim. you need
to try different tyres and/or rims(worst case).

No recommendations as to brand as all I ever used were yumcha .
  #4  
Old June 1st 11, 02:18 PM posted to aus.bicycle
Travis
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Posts: 231
Default Bursting tyres with heavy loading

Well I just found the problem.

When I took the tube out I found a smallish hole, which I patched. I
then reinstalled the tube, pumped it up to 100psi, and it promptly
burst again.

Suspecting a dodgy patching, I took the tube out and did a bubble
test, only to find that the patch was intact and not leaking. Then I
found another hole, but interestingly enough it was located exactly
opposite the valve from the previous hole. Although inspection of the
tyre hadn't shown any issues, I now had an idea where to concentrate
my search. (I should add that I have the writing on the tyre lined up
with the valve, hence the relative position of the tyre to the valve
is constant, though evidently I'd turned the tube around when I
reinstalled it.

Sure enough, there is a small hole in the sidewall right near the bead
of the tyre.

At the time of the burst today I was riding on smooth and relatively
clean bitumen.

So I can't blame the tube, it looks like I might have a dodgy tyre
after all. I'll see if Torpedo7 is willing to send me a new one or a
refund but in the mean time will install a different (and
coincidentally wider, since that's all I have) tyre on the back.

Travis
  #5  
Old June 1st 11, 02:23 PM posted to aus.bicycle
Travis
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Posts: 231
Default Bursting tyres with heavy loading

On Jun 1, 9:11*pm, terryc wrote:
Travis wrote:
The bike is a somewhat heavy one and I weigh about 105kg.


Today my brand new rear tyre and/or tube burst.
This tyre is a 1.25" x 26" thin (ish) mountain bike tyre.


First of all, is it more likely to be the tyre or the tube which is
responsible for a popping tyre?


Tyre doesn't match rim or you didn't align it evenly.
FWIW, i found thornproof tyres a complete waste of money. They all
eventually split along the rim. heavy loads and a very stiff tyre. OTOH,
thornproof tubes are fantastic.

100psi is the "Max PSI" according to Torpedo7. Should I inflate it
less than that? How much less?


If the tyre popped off, then it is a mismatch of tyre to rim. you need
to try different tyres and/or rims(worst case).

No recommendations as to brand as all I ever used were yumcha .


It didn't pop off the rim, it just instantaneously deflated with a
bang, but remained in place. I've since found a hole in the sidewall
which corresponds to the place where it burst and then burst again
after I patched it and pumped it up again!

Travis
  #6  
Old June 1st 11, 02:54 PM posted to aus.bicycle
terryc
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Posts: 134
Default Bursting tyres with heavy loading

Travis wrote:

It didn't pop off the rim, it just instantaneously deflated with a
bang, but remained in place. I've since found a hole in the sidewall
which corresponds to the place where it burst and then burst again
after I patched it and pumped it up again!


If it isn't where the rim would contact and really in the sidewall, then
it sounds like a defective tyre(never had one) or you hit a metal spike
that punctured through the sidewall.

if you want to keep using it, then you will need to sleeve it with
something very stiff oitherwise the tube will continue to burst. i've
used car vulcanisng patches in the past(on thirnprrof tubes and on tyres).

  #7  
Old June 1st 11, 08:32 PM posted to aus.bicycle
Geoff Lock[_2_]
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Posts: 475
Default Bursting tyres with heavy loading

On 1/06/2011 7:58 PM, Travis wrote:
I've been riding to uni on a clunker of an old mountain bike, using
that instead of my Trek roadie because I could mount a rack to it and
carry panniers.


Clunkers are good for building strength

100psi is the "Max PSI" according to Torpedo7. Should I inflate it
less than that? How much less?


I have a little el cheapo hand held plastic pressure gauge (Michelin
branded if you must know) which I use to verify that the pressures put
out by the foot pump I use is thereabouts to what it should be. It's a
bit finicky to have to work out two sets of readings using two different
measuring devices (the gauge on the foot pump and the gauge on my el
cheapo hand held gauge) AND then deciding which measurement is in fact
correct but after 2 or 3 exploding tyres in, like, 1 hour, I am grateful
for another opinion

Heheheheh, one of them tyres exploded when I bounced it to test its
integrity after inflation I think it was inflated to about 100 psi
when the tyre was rated at 65psi but 65psi was what the gauge on the
foot pump said This was what prompted me to get the hand held gauge
becos I realised I could not verify the reading on the gauge on the foot
pump. Probably problems with understanding Hooke's Law on the gauge in
the foot pump

The ACTUAL pressures you would use is something else. I, myself, have
softer pressures on the front and max pressure on the rear. I find it
more comfortable on my upper body to have a soft wheel on the front - so
I have 70psi on the front and 120 psi on the rear. Someone here posted a
link to some crazy guy (at least I think he is nuts but he sure wrote an
excellent paper on it) who did a study on tyre pressure. I'll try to dig
up the link and repost it if "somebody else" doesn't do it before me
I hope "somebody else" does it before me

On a last note, I suspect that ALL inner tubes show some micro leaks
during a bubble test but I have no real proof as yet becos my sample
size is small due to my personal experience. For me, a bubble test is
good only for indicating BIG leaks and I pretend that micro leaks are
merely a figment of my imagination.
  #8  
Old June 10th 11, 01:27 PM posted to aus.bicycle
Travis
external usenet poster
 
Posts: 231
Default Bursting tyres with heavy loading

On Jun 1, 5:58*pm, Travis wrote:

Should I blame the tyres, and possibly ask for a refund from Torpedo7,
or blame the tubes and maybe try for a refund from the eBay vendor, or
is a bursting rear tyre normal enough when one tries to load them up
with a 100kg+ rider, a 20kg bike and 15kg of luggage?



As a follow-up to this, Torpedo7 agreed to a warranty claim on the
tyre and have mailed me another one. They didn't have any more tyres
of my type in stock on the website, but some tech apparently found one
last one in the workshop or something and they're sending me that one.

Since Torpedo7 did the right thing by me, I thought they deserved a
little public acknowledgement that their customer service in this case
was pretty good!

Travis
 




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