Why is mechanical grip more important in the wet?

[raymondu999]

Hey all.

Just wondering. We've seen many times over the years that generally good mechanical grip helps in the wet, and aero grip, less so. Why is this? I mean, we've even heard reports in the past (pre-2009) that Ferrari sprayed water on their test tracks so that they can start testing how come the McLaren was so much more sure footed in the wet than Ferrari.

Thanks

[machin]

In short, because the wet conditions mean that there is less grip from a given car speed , that means the cars go around the corners slower (or they'd fall off the track). Slower speeds means less aerodynamic downforce, hence less grip... and that means the cars go even slower round the corners... etc etc... the result is that the effect from aero is less than it is in the dry...

[SoliRossi]

I would actually suggest that the opposite is actually the case. In wet weather aero grip is not effected (except by car speed) where as mechanical grip or mech traction is very limited.

Think back to the RB5 (even the rb4) that car had pretty terrible mechanical grip. Its strength was in the aero department. Hence it was great around Silverstone but rubbish around Monaco (williams tend to have good mechanical grip and hence go well at Monaco), but getting back to my point the rb5 was brilliant in the wet, even with its poor mechanical grip. On one of the Friday practice sessions last season Ant Davidson commented that the RBR boys 'lucked' into having a car that complemented the profile of the wet tyre. It was not done intentionally but when they bolted on the wet tyre it just clicked with the cars aero (proportionally more than the other teams).

A car going at 100kph on a wet or dry track will produce the same amount of downforce regardless of the track/air conditions. The only loss in downforce when on a wet track is the lower speed you will carry. The same can not be said for mechanical grip thought.

The available grip is always going to be a lot less than what your car can normally transmit to the tarmac. Sure teams will alter their set up to try to increase the amount traction they can get but all in all they are 'traction limited'. SO no matter how good your mechanical grip is the limit of adhesion is always going to be a lot less.

So to be good in the wet, simplistically, you need more aero down force. Mechanical grip will give out very early, and in turn will be a factor that will close cars performance gaps up. Its the car that can be pushed into the wet tarmac the best, use it tyres the best that will be fastest.

This is a pretty simplistic explanation but hopefully I managed to put it across clearly enough.

[raymondu999]

let's take for example the 2008 Ferrari vs the 2008 McLaren. McLaren had the better mechanical, and ferrari the better aero. But the McLaren was much more surefooted in the rain.

I think you're approaching it the wrong way too. A car that's good aerodynamically, will get its good downforce say at 150kp/h, and it gets that downforce less often in the wet.

A good mechanical setup however, that's amazing in the dry, will get decent traction in the wet. A car with decent traction in the dry will get horrendous traction in the wet.

[mike]

what happed in 2007 where mclaren had the best wet weather car and won in monaco?
or event in 2006 looking at tracks like monza and monaco the mclaren were pretty fast
if you reckon that RB5 had downforce with a single deck in china 2009..what about the brawns with their double decker??

my theory is completely different to yours. i reckon that mechanical grip is more about camber, toe, caster etc, they provide great grip but as the cost of running the tires too hot and hence wear, they generate grip from sliding rather than vertical loads around a corner so if you maxed out or take away all downforce they will be faster (monza and monaco and wet condistions) newey cars and mclarens (2007 & 2008 or even 2009)

it is true that in wet conditions that you still generate as much downforce, however if the tyres are too cold with is the case in the wet mostly you run the risk of it not working at all. but generating too much heat if its in normal conditions or drying....(2007 china, lewis hamilton)

what good mechanical grip really means is that for every Newton of down force they give off better grip but the tires have to work harder.

the Brawn/Ferrari is in reverse to the Newey/Mclaren theory. they run low camber and toe settings and rely on the vertical load to keep the car on the track they tires will have lower temps so they in theory live longer and the pace is more consistent.

i personally do not think that Newey adds 30% downforce to his cars, its just that they require 30% less downforce to get the same amount of grip so that their cars are highly efficient. the Brawn/Ferrari on the other hand will have to get that 10% more down force they may require a greater drag penalty.

so Brawn/Ferrari once they get a downforce advantage usually runs away from the championship, while Newey/Mclaren can develop their cars throughout the season to have better performance.
looking at 2008 2009 situation where the Mclaren improved by 1.5 to 2 seconds throughout the season.

i think the Brawn/Ferrari theory were better with grooved tyres as side loads damages the tyres more, but that being said, if Brawn/Ferrari gets an aero or engine advantage they will be very fast (2009). In conclusion Brawn/Ferrari uses the aero to make the tires live long, Newey/Mclaren uses the tires to take load of the aero and increase aero efficiency

[marcush.]

The aero setup of the car is optimised for the dry conditions so in wet weather you will not see the same downforce simply because of the lower speeds.
You would run ALOT more wing in the rain if you could ...in effect totally different profiles with much more camber if that was a possibility.
So in effect the mechanical side of the car is getting upper hand in the equation because of the lower speeds -which place more emphasis on mechancal grip anyways and the aero working outside their window.
Don´t forget the rain tyres have more diameter so you will instantly move your front wing and undefloor say 5mm higher than optimum according to your aeromap.

come to this you will not be able to brake as hard because the grip is simply not there so you will not get the weight transfer so the car will not assume the rake under braking so potentially more downforce loss compared to dry conditions..

[speedsense]

The aero setup of the car is optimised for the dry conditions so in wet weather you will not see the same downforce simply because of the lower speeds.
You would run ALOT more wing in the rain if you could ...in effect totally different profiles with much more camber if that was a possibility.
So in effect the mechanical side of the car is getting upper hand in the equation because of the lower speeds -which place more emphasis on mechancal grip anyways and the aero working outside their window.
Don´t forget the rain tyres have more diameter so you will instantly move your front wing and undefloor say 5mm higher than optimum according to your aeromap.

come to this you will not be able to brake as hard because the grip is simply not there so you will not get the weight transfer so the car will not assume the rake under braking so potentially more downforce loss compared to dry conditions..

Actually, the braking G is the least effected of the "G" circle in the rain. With a good set of rain tires, the braking is very close to the dry braking G. As you increase the downforce, due to rain, it is relative to the drag produced when off throttle (even at a lower top speed). Just means the braking is a shorter distance but the G's produced are relatively close to dry braking G's.
The lateral G is the greatest reduction of G force in the rain and has the most direct effect on weight transfer. Hence the reason for removing ARB's, softening spring rates and rising the ride height (mostly for hydroplaning of the bottom of the car in puddles) and enable a "greater amount of weight transfer" to make up for the lack of G.

[747heavy]

The lateral G is the greatest reduction of G force in the rain and has the most direct effect on weight transfer. Hence the reason for removing ARB's, softening spring rates and rising the ride height (mostly for hydroplaning of the bottom of the car in puddles) in enable a "quicker weight transfer" to make up for the lack of G.

Could you explain the last part a bit better please?
I´m not sure about the "softer car = quicker weight transfer" bit of the statement
Thanks

[speedsense]

The lateral G is the greatest reduction of G force in the rain and has the most direct effect on weight transfer. Hence the reason for removing ARB's, softening spring rates and rising the ride height (mostly for hydroplaning of the bottom of the car in puddles) in enable a "quicker weight transfer" to make up for the lack of G.

Could you explain the last part a bit better please?
I´m not sure about the "softer car = quicker weight transfer" bit of the statement
Thanks

Fixed it, ..rented fingers while typing...

[747heavy]

The lateral G is the greatest reduction of G force in the rain and has the most direct effect on weight transfer. Hence the reason for removing ARB's, softening spring rates and rising the ride height (mostly for hydroplaning of the bottom of the car in puddles) in enable a "quicker weight transfer" to make up for the lack of G.

Could you explain the last part a bit better please?
I´m not sure about the "softer car = quicker weight transfer" bit of the statement
Thanks

Fixed it, ..rented fingers while typing...

Thanks!!