Mechanics of Mercedes problems

[Des]

Mercedes tyre management problems may be the consequence of lack of front end grip during initial turn-in to fast corners.

Consider the FRIC suspension system. It relies on hydraulic fluid being violently flung from one part of the system to another due to the car's change of speed and/or direction. This change of fluid pressure is used to inform the suspension geometry which is then able to stabilise the car during the manoeuvre.

The Fric System's regulator would be calibrated to give a certain reaction for a give acceleration (where acceleration is a change of speed and/or direction - velocity is a vector).

The car is tuned such that it can stay on the racing line and provides a neutral balance (front end gripping with the rear end) .

However, When the front end slips on initial turn-in (understeer), the regulators (especially those in the nose section) will experience less acceleration (rate of change of direction) than was envisaged - because the car runs wide of the racing line. The FRIC system will 'feel' as though the car is negotiating a wider curve than in actuality and its reaction will be insufficent to stabilise the car as the driver endeavours to make the corner.

To compound the problem, the FRIC system will act to provide a neutral balance but, since the front end is sliding then; the rear will tend to slide in these circumstances. Since the rear tyres are both driving the car and sliding, they suffer most.

Both Mercedes drivers have reported sliding on front and rear axles while the car is heavy with fuel. This brings us to another culprit - vehicle mass.

The W04 works very well in qualifying but tend to fade in the race where of course, the car may intially be 150 kgs heavier. Putting this mass on the mid-rear section of the car surely shifts the weight balance rearwards - making it harder for the front tyres to grip sufficiently when changing direction.

A solution may be found by biasing the cars set up to provide more front end grip (by running more front wing and tuning of the suspension). This would compromise the car's balance in qualifying and perhaps cost grid positions for the bargain of much better tyre management and pace during the first race stint.

At each pit-stop, the excess front wing could be dialled down in proportion to the reduction of fuel mass carried.

[tok-tokkie]

My understanding is that any form of active suspension is illegal. Electronic accelerometers can not control the FRIC. FRIC has to be passive. If my understanding is correct then it is hard to see how your explanation can be correct. Is there some way of responding to slip in a FRIC system which complies with the rules?

[Des]

Nowhere do I mention 'Electronic accelerometers' - by 'regulators' I am referring to hydraulic system components such as valves. These are widely reputed to be the means by which the purely passive FRIC system's behaviour is tuned and regulated.

[tok-tokkie]

The Fric System's regulator would be calibrated to give a certain reaction for a give acceleration (where acceleration is

a change of speed and/or direction - velocity is a vector).

Explain that.

[Des]

Err...the statement is in plain English - read the post carefully and do a little research. I am unable to help you to understand elementary ideas!

[monsi]

MGP laments over tyre but in reality their problem is fuel consumption?

But if this is the case then why would McLaren not also be affected ? We all know their problems this year, but they hardly looked a team with a hungry engine and heavy fuel load last year. If Mercedes is burning much more fuel than McLaren with the same engine, there must be some extraordinarily divergent design in the use of the engine - unless the Merc is very draggy which I would find hard to square with its qualifying speed.

If the Mercedes really is carrying much more fuel at the start, then I guess in theory the tyre contact patch of a new tyre under static conditions should reflect this. Whether this can realistically be measured by a sharp eyed observer with the right camera gear I don't know.

[olefud]

Mercedes tyre management problems may be the consequence of lack of front end grip during initial turn-in to fast corners.

Consider the FRIC suspension system. It relies on hydraulic fluid being violently flung from one part of the system to another due to the car's change of speed and/or direction. This change of fluid pressure is used to inform the suspension geometry which is then able to stabilise the car during the manoeuvre.

The Fric System's regulator would be calibrated to give a certain reaction for a give acceleration (where acceleration is a change of speed and/or direction - velocity is a vector).

The car is tuned such that it can stay on the racing line and provides a neutral balance (front end gripping with the rear end) .

However, When the front end slips on initial turn-in (understeer), the regulators (especially those in the nose section) will experience less acceleration (rate of change of direction) than was envisaged - because the car runs wide of the racing line. The FRIC system will 'feel' as though the car is negotiating a wider curve than in actuality and its reaction will be insufficent to stabilise the car as the driver endeavours to make the corner.

To compound the problem, the FRIC system will act to provide a neutral balance but, since the front end is sliding then; the rear will tend to slide in these circumstances. Since the rear tyres are both driving the car and sliding, they suffer most.

Both Mercedes drivers have reported sliding on front and rear axles while the car is heavy with fuel. This brings us to another culprit - vehicle mass.

The W04 works very well in qualifying but tend to fade in the race where of course, the car may intially be 150 kgs heavier. Putting this mass on the mid-rear section of the car surely shifts the weight balance rearwards - making it harder for the front tyres to grip sufficiently when changing direction.

I wouldn’t think under steer doesn’t necessarily follow with the addition of rear-biased mass –particularly with aero downforce as a major factor. To accomplish turn in the front tires only have to accelerate the mass acting on the front end. As a rule, tire turning thrust increases somewhat less than proportional to the total downforce on the tire. Thus the addition of the rear mass would seemingly promote over steer.

Cars with marked rear mass bias have big hunker rear tires and rather wimpy front tires.