F1technical.net

Wanted to talk a little bit about the actual mechanics here outside of the race thread. I think my opinion on the matter is clear based on comments there but having some time now to fiddle around with my DVR and get some close up shots, I went over the final few laps about a ten times.

I'm attaching some pictures for more analisys, but the last two pictures are very striking and it's got to be a very important aspect of why Vettel's tire blew.

Here is it at lap 41



Can't see it there but when you get up close it's far more obvious. Maybe it has something to do with it maybe it doesn't, but when you view in in moving, it's clear that whatever it was is going around with the tire.



There it it, close up, a couple of turns later.

Now on the top of Eau Rouge, just at thy get on the Kemmel straight. First Vettel, look at the compression of that tire, the angle and then look how much the rim overhangs.



Now, the very same spot, Grosjean following immediately behind. Stark contrast in the way the Vettel example is being supremely punished.



Regardless of what we think of the "safety" aspects, that tire was not going to survive lap after lap of that.

Not sure what you mean by compression. The rim overhangs are nearly the same for front and rear.

Tires for several other drivers did survive for the race distance, albeit a few cuts

http://www.motorsport.com/f1/news/pirel ... gp-weekend

Compression... The black is the lip of the rim, the red is the shoulder of the tire. Notice the difference. Then notice the fact that the lip of the rim is hanging out about 3 cm over the sidewall on the bottom while compressed and laterally stressed.

It looks like there's a bubble in the sidewall.



If so, it's a sign of sidewall separation, which can be caused by underinflation, among other factors.

Given what we saw on Saturday...

bhall II wrote:

...and what it could signify...

Physically explicit theory of standing waves in tyres at high vehicle speeds wrote:[all emphasis mine]

The phenomenon of standing waves in tyres occurs at high speeds, when a vehicle speed exceeds a certain
‘critical velocity’. Then quite intensive flexural waves travelling around the circumference of the tyre
emerge from the trailing edge of the contact patch. To the observer these waves in the tyre appear to be
stationary, but they are in fact travelling around the tyre at the same speed as the rotation of the tire. This
is why these waves are often referred to in the literature, not quite correctly, as ‘standing waves in tyres’.
Since this term is already well established, we will use it as well.

The large displacements of the tyre surface due to the generated standing waves introduce a large amount
of energy into the tyre material, which can lead to a quick tyre failure or at the very least can severely
affect the handling of the vehicle. Since the phenomenon of standing waves is usually observed at high
vehicle speeds, clearly aircraft tyres, race car tyres and to a lesser extent passenger car tyres are likely to
experience it. Note that manufactured tyres normally have a speed rating to indicate the experimentally
established maximum vehicle speeds below which they can be used safely. However, the real vehicle
speeds at which the standing waves occur can be substantially lower due to poor maintenance of the tyre
and/or due to its under-inflation as well as because of other conditions, such as the load on the tyre.

[...]

...I wonder if low inflation pressure has more to do with this than anything else.

Seriously, I'm faaaaaaaaaaaar from a Pirelli apologist. But, I have trouble accepting that their product is wholly at fault here. Two sets of tires over two days with signs pointing to a single factor that's more or less beyond their control.

(Speculative as hell? Absolutely.)

bhall II wrote:
Seriously, I'm faaaaaaaaaaaar from a Pirelli apologist. But, I have trouble accepting that their product is wholly at fault here. Two sets of tires over two days with signs pointing to a single factor that's more or less beyond their control.

(Speculative as hell? Absolutely.)

Pirelli has guidelines for tire pressure and camber, and they have been in place since the 2013 fiasco.

Perhaps Pirelli's guidelines are wrong, but I can't possibly see them owning up to that

As far as I know, the only hard rule to come out of that ordeal was a requirement to run the tires in the direction intended. Otherwise, the teams rejected usage restrictions - and rightly so.

Daily Fail wrote:'In November 2013, Pirelli requested that there should be rules to govern the maximum number of laps that can be driven on the same set of tyres - among other parameters to do with correct tyre usage,' Pirelli said in a statement.

'This request was not accepted. The proposal put forward a maximum distance equivalent to 50 per cent of the grand prix distance for the prime tyre and 30 per cent for the option. These conditions, if applied today at Spa, would have limited the maximum number of laps on the medium compound to 22.'

Thanks TAG, I get it now

Perhaps Eau Rouge on that lap was the last straw.

When Pirelli's grant was not accepted nearly 2 years ago, its their responsibility to ensure that tires last the whole race distance on any circuit (total laps -1), any weather.

I think it's incumbent upon the sport to realize that highly restricted rules will result in teams pushing limits that maybe shouldn't be pushed. It's also probably not a good idea to ask anyone to push anything in an environment that doesn't allow a whole lot of real-world practice.

Competitive balance only changes with (often stupid) mistakes, Force India's b-spec car fell apart the first two weekends it was run, mysterious tire failures have become a fixture of the sport, and yet no one really mentions the role of these counterproductive rules.

EDIT: amped up the ranting a bit.

Thanks TAG and bhall II. Posts like yours are why I visit F1tech.

If low tyre pressure is implicated one assumes that it would be at the low end of Pirelli's specification, given that they are monitored by Pirelli. Or so I'm led to believe.

TAG, which lap did these images come from? Are there likely to have been several laps with that much rim to sidewall distortion?

The lump in the sidewall doesn't look good.

Many years ago I had a failure form just such a blister on my road car. Turned out a tiny piece of carcase thread was lying across the sidewall plies and provided a site to fatigue the sidewall. Admittedly the tyre did several thousand miles but I wasn't punishing it through eau rouge, pouhon and blanchimont every 2 minutes. Fortunately I noticed the blister and it went bang on the tyre fitters inflation rig.

Let's hope that Pirelli, the FIA and the teams are trying to find the cause rather than who to blame.

.

Started on lap 41, the "debris" I noticed and circled around the rear tire, The actual closeup of the compression is perhaps two seconds before it blows.

bhall II wrote:As far as I know, the only hard rule to come out of that ordeal was a requirement to run the tires in the direction intended. Otherwise, the teams rejected usage restrictions - and rightly so.

Daily Fail wrote:'In November 2013, Pirelli requested that there should be rules to govern the maximum number of laps that can be driven on the same set of tyres - among other parameters to do with correct tyre usage,' Pirelli said in a statement.

'This request was not accepted. The proposal put forward a maximum distance equivalent to 50 per cent of the grand prix distance for the prime tyre and 30 per cent for the option. These conditions, if applied today at Spa, would have limited the maximum number of laps on the medium compound to 22.'

They only dumped the lap limit, while the others (min air pressure, chamber etc.) were pushed through.

http://www.f1fanatic.co.uk/2013/07/05/f ... punctures/

http://www.f1fanatic.co.uk/2013/07/05/f ... punctures/

The FIA has imposed minimum starting front and rear tyre pressures of 16psi and minimum running pressures of 20psi for front tyres and 19psi for rears.

Pardon my noob-ness, but can someone help me understand the above statement. What are Minimum starting tire pressures? Are they fresh tires fitted to cars at pitstops?

Thanks

n_anirudh wrote:http://www.f1fanatic.co.uk/2013/07/05/f ... punctures/

The FIA has imposed minimum starting front and rear tyre pressures of 16psi and minimum running pressures of 20psi for front tyres and 19psi for rears.

Pardon my noob-ness, but can someone help me understand the above statement. What are Minimum starting tire pressures? Are they fresh tires fitted to cars at pitstops?

Thanks

Yes. A tire's pressure will naturally rise with heat. So that's why the minimum pressure is being specified for cold and hot tires.

... and at what speed/temp are running pressures maintained/monitored. After a few laps when the tire carcass is fully warmed up?

But how may the tire not be pressurized adequately anymore?

Two things come to my mind:
a) a slow puncture, caused by whatever reason.
b) reduced tire performance due to less rubber on the carcass

Is there a third plausible cause?

If (b), wouldn't this then actually support Pirelli's statement that Ferrari/Vettel overextended the tire wear?
Thus being their own fault?