Tyre blowout advice

[Ajax Bay]

I have not rolled P7s but note they have 60tpi. I can't find the max recommended pressure.
"Techbelt Road: 60 TPI nylon casing structure with an added layer of high cut resistant fabric underneath the tread to provide superior puncture protection in a wide variety of conditions."
https://www.pirelli.com/global/en-w...relli-p7-sport-a-new-road-cycling-tire-53397/

 

[silva]

The plus is that you can cut out new sunglasses before binning it.

 

[Tom B]

Just my tuppeneth worth but I usually try to install or fit tyres with the start of the branding or similar feature inline with the valve.

That way if I get a puncture I can find it in the inner tube and easily locate the corresponding spot on the tyre to check for sharp objects.

In this case you could check to see if it is the same place on each occasion or moving around.


The only time I've had a failure like that was riding over inflated old tyres. I'd pulled over under a viaduct to explore the curious bumping sensation when the tyre wall split the inner tube popped and left a chap at a bus stop under the bridge diving for cover

 

[Once a Wheeler]

Such things have happened to me. On tour, I would usually carry a 20cm section of outer cover. This can be fitted in under the torn cover and, inner tube repairs permitting, make a good-enough mend to get you to a bike shop. A lumpy ride but it gets around the problem for a few dozen kilometres.

 

[Ajax Bay]

Such things have happened to me. On tour, I would usually carry a 20cm section of outer cover. This can be fitted in under the torn cover and, inner tube repairs permitting, make a good-enough mend to get you to a bike shop. A lumpy ride but it gets around the problem for a few dozen kilometres.

Well the OP carried a spare tyre: a "good enough" solution, albeit 200g heavier and (more of an issue when touring) extra volume.

 

[roubaixtuesday]

More woe.

We have been running the randonneur slightly overpressure (85 psi vs 75 nominal rating, religiously checked every morning) and all seemed fine until another failure this morning, about 400 miles use only.

The bead has failed *inside* the casing which rubbed a puncture, happily, rather than a blowout.

The Conti GP5000 is now on, again just slightly overpressure (110 vs 100 nominal). Our hope is that the extra pressure over the Vittoria will help support the weight. This is also the advice of Swallows, who built the tandem and wheels. They're very surprised we've had these issues.

Intend to get another gp5000 spare, will probably need to order ahead somewhere.

Pic of inside (blue arrow pointing to protruding bead) attached. On the outside there's no damage from the rim, just a tiny split on the surface material. Have also attached a pic of that, though it's hard to see anything.

Thoughts?

 

[ExBrit]

More woe.

We have been running the randonneur slightly overpressure (85 psi vs 75 nominal rating, religiously checked every morning) and all seemed fine until another failure this morning, about 400 miles use only.

The bead has failed *inside* the casing which rubbed a puncture, happily, rather than a blowout.

The Conti GP5000 is now on, again just slightly overpressure (110 vs 100 nominal). Our hope is that the extra pressure over the Vittoria will help support the weight. This is also the advice of Swallows, who built the tandem and wheels. They're very surprised we've had these issues.

Intend to get another gp5000 spare, will probably need to order ahead somewhere.

Pic of inside (blue arrow pointing to protruding bead) attached. On the outside there's no damage from the rim, just a tiny split on the surface material. Have also attached a pic of that, though it's hard to see anything.

Thoughts?

View attachment 731205

View attachment 731206

That's exactly what happened to me during a 600km ride. It's a badly made tire.

 

[roubaixtuesday]

That's exactly what happened to me during a 600km ride. It's a badly made tire.

It's now happened to three tyres...

 

[Dogtrousers]

It's now happened to three tyres...

Have you considered that you might have been cursed?

 

[roubaixtuesday]

Have you considered that you might have been cursed?

Several times. Particularly on the *two* occasions when a brand new inner tube exploded on inflation (same brand, same batch, no problems with any others).

 

[Ming the Merciless]

Definitely nothing wrong on inside of rim?

 

[Tom B]

What (make and model) tyre was it this time? - I've lost track

 

[roubaixtuesday]

Definitely nothing wrong on inside of rim?

Certainly not as far as I can find.

And the damage here was inside the tyre, which I think must mean it can't be the rim?

I know exactly where this one was, so will know if there is another, whether it's a repeat location.

 

[roubaixtuesday]

What (make and model) tyre was it this time? - I've lost track

Vittoria randonneur 32

 

[Yellow Saddle]

Here's a Parthian shot on the issue. Overinflating a wide 32mm tyre by 10PSI is far more dangerous than overinflating a 23mm by 10PSI.

Overinflated tyres fail by hoop stress, in other words stress accross tye tyre, not along the tyre.

This may help you visualise it. Draw a 1 cm band across your tyre and count the number of of square cms (inches make this awkward for now) in there. Pretend your tyre doesn't have a rim and is a perfectly round tube. You'll count 10 x 1cm squares in that band because 2 Pie R etc.

Now do the same with a 23mm tyre. You'll count only 7 squares in there - three fewer than the wider tyre.

At the same pressure in both tyres, the hoop stress in the 32mm tyre is 42% more.

In other words, a similar increase in pressure creates a disporportionately large increase in stress.


Moral of the story: don't overinflate your tyres, boys and girls. And stay away from whatever crap tyre we're discussing here.