Tyre blowout advice

[presta]

I'm sure you can use a search engine as well as I can. There are papers around on coefficients of friction in bicycle tyres and there are papers comparing tubed and tubeless tyres in respect to their efficiency, rolling resistance and friction. You can find these yourself. I'm not doing that for you.

Some ability to understand what you read is a prerequisite too, not just an ability to type.

The evidence I've perused suggests that there is more friction generated in a tubed setup. I thus hypothesized, in a marginal situation, the very modest increase in pressure could be significant and push the tyrewall beyond it's safe limits.

Descending a steep hill at speed generates several kilowatts, much of which can end up being dissipated in the brakes, whereas if the rolling resistance you're referring to were more than a few tens of watts the rider would be unable to pedal the bike. If tyres were as near to failing as you're trying to make out they'd be failing all the time from overinflation and brake heating, but they don't. (My own personal experience of overinflating a tyre is that it doesn't cause tyre failure anyway, it just forces the tyre off the rim.)

Of course, I've not tested that hypothesis. I'm not a professor in thermodynamics with a penchant for bicycle tyres.

No sh!t?

 

[Ajax Bay]

My amateur suggestion would be to sacrifice the mudguards in favour of a wider tyre.

As for being on the move, one option may be to look on Amazon with a view to a purchase being delivered further on down the road either to a campground/hotel or one of the Amazon pick-up points. Just make sure that you pay attention to the delivery time/date.

Ditching the rear guard was a reaction I had to allow a sensible tyre width/height.
This is exactly what i had to do when (towards end of Day 4 of an end-to-end) I had to replace and chose an M+, not thinking that its height might foul the guard. Guard ditched (rack and bag provided some detritus intercept). Ride on.
PlanetX have stuff:
Here a Panaracer Tour in 32mm for a ridiculous <£10 (even in France - get one sent out to stop after next)
https://www.planetx.co.uk/products/panaracer-tour-700c-wire-bead-tyre?variant=43837901308134
No idea what the max pressure spec is.

 

[Ajax Bay]

I wasn't refering to your 'Natural enthusiasm for understanding'. I was referring to the attitude you present. I note I'm not the only person who has had the misfortune of contending with it and irrespective of whether you think someone is correct or incorrect, it is possible to be considerably more constructive than you appear to be.

I've left this a day.
Great to have you here on CycleChat since March: you have actively contributed.
But throwing shade around after a mere two months of membership probably means some introspection is merited.
Feel free to tag the other chatters whom you think have "had the misfortune of contending" so I have an idea what your stalking has turned up. With luck they can chime in and I can check with what they've had to "contend".
When I see suggestions which seem BS (such as tubes causing tyre temperatures to increase), I'll say so (though not in so many words), and ask for the basis. The difference between the rolling resistance of a tyre with butyl tube and the makers similar TL or TLR offering is max a few (<3) watts.
I have respect for Cycle Chat and consider it, among other things, as a useful knowledge resource. I'm keen to keep the standard up and not be diluted by BS which is not called out.
If, in the future or indeed trawling back), you think I have suggested something which is BS, please alert me to that. Occasionally I get things factually wrong, but I try not to.
@presta has addressed the other elements, along scientific lines.

 

[PedallingNowhereSlowly]

There's nothing wrong with challenging other peoples points of view - this is a forum after all.

You ignored the first part of my response, which is the context in which the second part was given:

I wonder if the tyre is too narrow and consequently you are running pressures too high for tandem load / speed?

The fact is, you then went on to infer that I'd stated something I had not with 'Blowout cause? I suggest not.' I simply said that a tubed setup will cause a further increase in air pressure - without any quantification. I did not infer or imply I thought that was the cause - it was stated casually as a possible a contributory factor in a situation where a tyre is run at high pressure, well loaded and used at speed.

Your choice of language - could be described and patronising, condescending or a mixture of both. The statement I made is not untrue. We might only be talking very small numbers, but it absolutely does not qualify as "bullshit".

And FTR, I've not been stalking you. That is another fabrication. I've come across many of your posts as I've been reading the forum and getting the lay of the land. I'm not the only person whom you've communicated in this totally unecessary way.

Factual correctness is one standard.
Being civil is another.

These are not mutually exclusive.

 

[roubaixtuesday]

I would very much appreciate it if the personal debate could be taken elsewhere? Maybe DMs?

The help in the specifics is very much appreciated and the debate ongoing now tends to put off contributors, which I would very much like to avoid as it might be critically important to us!

On the specific point raised on ambient temperature, which Ib think started this, it's been very cold here until today; the second blowout occurred at single figure ambient temperatures.

 

[roubaixtuesday]

Update

No problems today, and have acquired a hopefully never to be used second spare folding tyre, GP5000 32mm at extortionate expense in Nice. Marathon or M+ 32mm not available, will get one ordered in case of further difficulty.

Thanks all.

 

[fossyant]

Popcorn time. If someone's suggestion isn't right, it often get's pointed out. Heat isn't an issue here, or tyre size. There is either a problem with the rim (sharp), unlucky with tyre quality, or the OP has hit or caught something.

 

[ExBrit]

Just suffered the second of these on tour, both rear wheel. Sudden BANG with no apparent immediate cause, tyre still on rim but bead detached from tyre.

First was on the old gatorskins the bike came with, second on a new (~500 miles) vittoria randonneur.

Photo of the second attached.

Never experienced anything like it before, the second suggests more than mere bad luck.

Ask advice and suggestions welcome.

It's a laden tandem.


View attachment 729290

It probably doesn't help much but I had exactly the same problem with the same model tire. I had it on a few hundred miles and it blew during a 600km brevet so I had to DNF. It turned out the weld/braze/solder on the bead had failed and the sharp ends had worn through the tire. I don't see a problem with your bead though. I just think they are bad tires.

 

[Ajax Bay]

No problems today, and have acquired a hopefully never to be used second spare folding tyre, GP5000 32mm at extortionate expense in Nice. Marathon or M+ 32mm not available, will get one ordered in case of further difficulty.

The 5000s are not cheap - sorry - but so many of the 'road' tyres don't come in 32 and I knew I had a pair in the 'box'. They measure up accurately btw @75psi on a 15mm internal width rim.
An M+ would not have been a good choice as the extra height they have (drawing pin length) 3mm more than their height means it would surely have fouled your guard. Schwalbe Marathon not as bad.

 

[Yellow Saddle]

Does it take you a great deal of practice, or does it come naturally to you?

We've had some cold mornings and warm afternoons. So we could be talking about a significant difference in ambient temperature, plus the the addition of heat generated from friction. As we are talking about a tandem, we have larger forces at play acting on the tyre and potentially higher speeds.

The maximum recommended tyre pressures printed on the side of the tyre are the inflation pressures that assume normal use. I would expect there's plenty of safety margin manufactured into the tyre - but my experiences of riding around on a fully loaded tandem and being able to maintain 30 mph for long stints on flat or being able to accelerate quickly up a climb in order to go from being on the tail end of large group to the front of a large group on club rides suggest to me it is a possible corner case, if the tyre was inflated to the max indicated pressure on a cold day. Especially given that the rim width/tyre/width/nominal pressure/load have not yet been disclosed.

The amount of friction generated by properly inflated bicycle tyres is so small that it cannot even raise the temperature of the tyre. You can raise the temperature of a tyre by pedalling on one of those trainers with a very small roller and a soft tyre. That generates a reasonable amount of heat - say an increase in 20 or 30 degrees. But, you'll know if you have done it, it destroyes the tyre (from unnatural flexion, not overheating) and, it is very, very hard work. Further, a bike that travels real distance has cooling air circulating around the tyre whereas a static bike doesn't.
Therefore it is safe to assume that tyre friction on a loaded tandem is not going to heat up the tyre.

Now lets have a look at what artificially heating a tyre does to pressure. Since tyre diameter does not change with inflation, the volume of a hot or cold tyre is constant and we can use Gay-Liussac's law to calculate the rise in pressure with the rise in temperature. It turns out that if you heat a wheel with tyre inflated at 100PSI from 0 Degrees C to 100 degrees C the pressure goes up by 34PSI. I.e. you end up with 134 PSI.

Let's talk about cold mornings and warm afternoons, let's say 0 degrees start and 20 degrees warmer later on.

Then your 100PSI tyre would go up to 107 PSI.

It is plausible that if your tyre is rated at 100PSI Max and you heat it by 100 degrees, you'll have a blow-out. But is this a realistic scenario? No.

It is not plausible that a good tyre rated at 100PSI will blow off at 107 PSI.

One calculation kills a lot of speculation.

 

[Yellow Saddle]

Just suffered the second of these on tour, both rear wheel. Sudden BANG with no apparent immediate cause, tyre still on rim but bead detached from tyre.

First was on the old gatorskins the bike came with, second on a new (~500 miles) vittoria randonneur.

Photo of the second attached.

Never experienced anything like it before, the second suggests more than mere bad luck.

Ask advice and suggestions welcome.

It's a laden tandem.


View attachment 729290

That is a rubbish tyre. It is crude and unsuited for tandem use. According to the Vittoria website, it is a 20TPI tyre. TPI stands for threads per inch and is an indication of how closely wowen the casing cords are. 20 is very, very low. A good road bike tyre will be between 130 and 150 TPI. More threads per inch requires thinner threads (simply to fit more in per running inch of tyre) but the decrease in thread thickness is compensated for the increase in threads and the use of stronger, better quality material like rayon or kevlar. In the days of tubular tyres the treads were sometimes made of silk.

Thick, 20TPI threads could be cotton or soe other cheaper material. Thick cords have a high rolling resistance and poor maximum pressure.

A blow-out on a tandem is no joke, so just buy better tyres.

 

[Ajax Bay]

That is a rubbish tyre. It is crude and unsuited for tandem use. According to the Vittoria website, it is a 20TPI tyre. TPI stands for threads per inch and is an indication of how closely woven the casing cords are. 20 is very, very low. A good road bike tyre will be between 130 and 150 TPI. . . . In the days of tubular tyres the treads were sometimes made of silk.

The Vittoria Randonneur has a max pressure spec of 70psi and OP was running at 87psi, as pumped at breakfast. Tyre blew in cool conditions.
But they can't fit any wider than 32mm and are carrying a 200kg load (so need the pressure up there).

OP has shared that they have bought, as a spare(?, I would fit immediately) a GP5000 (I know you're not a fan of Contis, but whatever).
They have TPI shown as 3/330 so should meet your 'good road tyre' threshold.
"Treads sometimes made of silk" eh? In Ireland that'll be.

 

[Smokin Joe]

In the days of tubular tyres the treads were sometimes made of silk.

I'm sure that was the carcass of the tyre, with a rubber thread stuck on the business end.

 

[roubaixtuesday]

A blow-out on a tandem is no joke, so just buy better tyres

Thanks for the advice.

In my naieveté, and having worn out several marathon/ marathon+ tyres in the past without problems, I assumed a touring style tyre was "better" ie stronger and bought accordingly.

It seems not.

The other spare tyre we have is a pirelli p7 sport 32.

Would be interested in your and @Ajax Bay opinion on that too.

Cheers.

 

[Yellow Saddle]

I'm sure that was the carcass of the tyre, with a rubber thread stuck on the business end.

Should read threads, obviously.