Mechanics of Mercedes problems

[gixxer_drew]

This tire thing is bringing up many very interesting questions. Its like a big magnifying glass on tire and suspension interaction. I have a feeling we wont figure it out on this message-board since there are people all over Europe right now with access to the data and teams of bright engineers pouring over the same problem. Even so, I have started collecting what I can and trying to break the problem down to understand it more. Unfortunately I cant get much for context... only what I can infer from looking at how various cars are reacting over bumps/braking/etc.

Of course basic spring stiffness is in question but I reckon theres much more depth to it. Looking at logs from cars I have worked on I think theres a lot to be had in setup. I do think there is going to be a big limit as far as what the drivers can do. They also face a nasty curve of how nice to the car they can be and how much it really saves the tires. The last race must surely be evidence of this, the driving was the first weapon and yet the field was still very different in terms of tire use. The teams are going to have to rethink their setup priorities and this is a learning experience for anyone around the sport. To be honest, I am fairly confident aerodynamic loading is a second or third order effect to tire heat compared to basic setup parameters. I might even go so far as to say that aerodynamics biggest effect would be that of airflow cooling the tire.

[pocketmoon]

Here's an idea. With tyres it's going to be about how much 'work' the are being asked to do and how this changes over the course of a lap and the race. And stresses are going to be very different for straight line work (traction in accelerating and braking) vs getting a car around a corner or through a chicane.

Do the current tyres work better for teams with higher straight line speed vs teams who rely more on carrying speed 'through the corners ?

[tathan]

The Mercedes times look rather unstable. Alonso's look fairly predictable. I would speculate that Mercedes spent much of the time right on the edge, or just falling out, of a tyre operating window. Anyone know if their problem is insufficient or excessive heating of the tyre, and if so which ? Given that Jenson complained that a very slow formation lap caused his tyres to drop out of the window, I would guess that Mercedes are happier at lower temperatures, but it is a guess.

It's only a few laps but the beginning of the 2nd stint looks very much like somebody homing in on a specified delta and would explain how they are able to drive to required times so comfortably and just turn it on at end of stints - they are well, well below what the car can do to try and keep the tyres cool, more so than anyone else. I know everybody is having to do this, but Fred looks like he's just consistently driving at a given level of 'push' (albeit a low one given the tyre situation) whereas the Merc is actively aiming at a lap time target miles below their ultimate speed.

I agree with the posters questioning 3 stops - if the car had so much pace in hand that it couldn't use because of tyres, maybe 4 or even 5 stops with a much lower target laptime would've been faster. Drive flatout at 3s a lap quicker than everyone else and pit every 10 laps, job done!

[kilcoo316]

There are a whole bucket-load of things that all contribute to how a car heats (and wears) the tyres. Some of which are:

- Amount of downforce in high speed corners contributing to vertical load through the tyre sidewall.
--- Which impacts the friction of the tyre, from which comes lateral load - through cornering speed - through the tyre sidewall.
--- Which impacts the slip angle of the tyre, in terms of contact patch slip to sidewall deformation.
--- Which reduces slide of the contact patch.

- Sensitivity of aeromap to car pitch, roll and yaw.
--- Allows softer springs/dampers, reducing peak loading through the tyre sidewall in the more transient phases of cornering.
--- Allows softer anti-roll bars, reducing contact patch slide in slower speed corners.

- Differential settings.
--- Obviously, influences distribution of load on each tyre throughout a corner.

- Suspension camber
--- Wear across the contact patch and also heating variation between inside/outside sidewall.

- Suspension roll centre
--- The above throughout suspension deflection range.

- Tyre pressures
--- Obvious.

- Engine mapping (on over-run and acceleration)
--- Bias of tyre load front-rear on the car under braking and the usability of the brakes.
--- Compliant mapping leads to less wheelspin in acceleration.

- KERS mapping
--- See above for under braking.

- Toe-in/Toe-out angles
--- Obvious.

- Chassis torsional rigidity
--- Dictates how effective the suspension controls deflection/load distribution and also peak load amount.

- Suspension 'friction'; i.e. the forces/torques "lost" in the loadpath between tyre and spring/damper/roll-bar.
--- More lost = less control from suspension = worse for tyre.

- Car c.of.g
--- Obvious.

- Car rotational moment of inertia
--- Obvious.

[marcush.]

a car can be perfectly balanced but cooking the rears and cooling out the fronts..at least for a short period of time...a lap or two...
a perfect car would never stress a single tyre or part of the tyre at any given moment but distribute the loads according to the available grip on each corner /or under longitudinal accelerations .
so load transfer is your enemy as it will by definition transfer load from one side or end to the other ,reducing the available grip on the unloaded tyre and at the same time overstressing the loaded tyre .

[thisisatest]

i think their poor full load pace and tire consumption is inherent in their FRIC system. it has too much static friction, too much inertia, or high pumping hysteresis. whatever it is, it's causing the tires to load up on every steering input or bump encountered, it doesnt react quickly enough, and so it is overworking the tires.
i also think Lotus specifically dont have this problem, while still benefitting from a crosslinked suspension system, because their suspension package is largely conventional, with the crosslinking being a "tuning aid'. the FRIC part is smaller, handles less of the energy dissipation, runs lower internal pressures, etc.
later in the race, the car just starts edging into the tires' now-wider operating window.

[autogyro]

Surely the Merc simply gets more grip from the tyres because the FRIC suspension works far better than other types.
Because they get more grip they get more wear.
It is the same trade off as more downforce equals more drag.

It is yet another area of FIA regulation that prevents logical technical development.

In this case making Pirreli produce tyres with such low wear rates to meet the artificial need for entertainment.
In the real world where things progress, Merc would work with a tyre company to secure tyres that matched the operating needs of their cars suspension.
They would not be compromising everything including the drivers ability to finish a race that they have no chance of winning because of outside forces.
I think we will see regulations in the future that tend even more to favouring the bigger promotional players, i,e Ferrari.
At the moment it will be interesting to see how Merc handles the politics behind their present position.

[kilcoo316]

Surely the Merc simply gets more grip from the tyres because the FRIC suspension works far better than other types.
Because they get more grip they get more wear.
It is the same trade off as more downforce equals more drag.

No its not.

It is completely different.

[autogyro]

Surely the Merc simply gets more grip from the tyres because the FRIC suspension works far better than other types.
Because they get more grip they get more wear.
It is the same trade off as more downforce equals more drag.

No its not.

It is completely different.

Of course the science is different but the analogy is correct.

[DaveW]

No its not.

It is completely different.

I'm inclined to agree with you, but do you have evidence....?

[Mika1]

The Mercedes times look rather unstable. Alonso's look fairly predictable. I would speculate that Mercedes spent much of the time right on the edge, or just falling out, of a tyre operating window. Anyone know if their problem is insufficient or excessive heating of the tyre, and if so which ? Given that Jenson complained that a very slow formation lap caused his tyres to drop out of the window, I would guess that Mercedes are happier at lower temperatures, but it is a guess.

Excessive heating of the rear tyres, the rear tyres are the main problem.

[kilcoo316]

Of course the science is different but the analogy is correct.

No its not.

If you are going slower around the track (without sliding all over the place), you are asking for the tyre to provide less grip from the contact patch and less longitudinal/lateral force from the sidewall. Therefore heating through the contact patch and through longitudinal/lateral loads on the sidewall is lessened.

[kilcoo316]

I'm inclined to agree with you, but do you have evidence....?

This train of thought of "more grip = more wear" is, quite frankly, ridiculous.

But to humour it... if it was as simple as saying they had more "grip" than the rest; then to keep the tyres in good condition all they have to do is slow down to the pace of the rest - since their car will slide less than the rest (due to being run well within itself with respect to the competition), tyre wear would be less (with respect to the competition).

[pocketmoon]

I'm inclined to agree with you, but do you have evidence....?

This train of thought of "more grip = more wear" is, quite frankly, ridiculous.

More grip (through better planting of the car through corners, more downforce, etc) = a faster car through the corners = more work being done by the tyre = more heat. If you're outside the operating window I suppose you get more wear ? But as you say, the solution would be to drive slower through the corners, which sucks for Mercedes.

[Richard]

Surely more grip is a corollary of less slipping? So less energy in the tyre for the same laptime? Or to put it another way - If there are 2 cars at the same laptime,the one with less effective suspension is going to be harder on its tyres?

Of course there is a trade off between tuning for mechanical versus aero benefits. One could imagine that a system that allows greater control/manipulation of suspension in order to achieve aero benefits might end up placing greater demands on the tyres than a more passive system.

So perhaps Merc could de-tune FRIC to be easier on the tyres with the penalty of loss of laptime. They'd be able to start low down the grid but have as stronger race.

....

If only was that simple!