I was almost rear-ended this morning. I was stopped in rush hour traffic on the interstate with wet roads and a bus broken down in the car pool lane. Look in rear view mirror. Car coming way too fast. Panicked look on driver's face. He swerves right. I give it gas and pull left into the carpool lane. Just missed me.
I know it wouldn't have mattered in this situation, but this made me wonder if manually deploying the spoiler in wet conditions would improve handling in slippery highway conditions (i.e. driving 60 mph).

 

My recollection is that the spoiler on a 911 Turbo when fully deployed adds about 450 lbs of downforce @ 100 mph. I suspect that downforce varies logarithmically with speed, ie, it would be less than 270 lbs @ 60 mph (450 - 40%) and I don't know what the design difference is between a Carerra spoiler and the Turbo - sorry.

A much more important consideration to wet weather traction is how capable your tires are of siphoning water away from the contact patches. If they can't do that, no amount of downforce is going to help very much as you'll basically just be hydroplaning to varying degrees. That's why you see a lot of guys at the track with big, adjustable wings and running on slicks and r-compounds just park it when it starts to rain.

But to directly answer you question, it wouldn't hurt to deploy your spoiler; just don't expect miracles. Best,

 

Another variable out of one's control is the amt of oil on the surface of a road during a cloudburst. Well into the rain season would suggest far less than a "first rain in weeks" scenario.

 

I think what you did was the best advice for inclement weather...watch out for the other guy and be prepared to take evasive action. Good moves.

 

The short answer is no, it won't help.

On simply wet pavement, your tires have decent traction.

Hydroplaning is when the treads become flooded and the tire rides up on the water like a boat--losing comtact with the pavement. Although the exact formula is more than what most people can reasonably do in their heads, take your tire pressure, double it, then subtract about 10% (a little less, really). That's the speed at which your tires will hydoplane IF there's enough water on the road to flood the tread. This applies to sports cars and semi-trucks. So, even if your spoiler added a little weight to the rear, it wouldn't affect hydroplaning....but adding a few extra pounds of air pressure would help (as well as keeping your speeds within the envelope determined by your tire pressures).

Note that this is not a dichotomy of contact with the pavement and suddenly no contact. With the tread flooded a tire increasingly loses contact as it apporoaches the speed identified in the equation.

So, a car or truck running 30lbs of pressure will lift off at about 56 miles an hour. It will start losing traction within 5-7 mph of that speed.

Slower speeds, higher tire pressures help increase the target speed. Narrower tires, deeper tread, tread design, grooves in the roadway, water depth, etc., will affect the speed at which the tread on your tires become flooded.

 

hell, that's a mantra for EVERYDAY, given some of the drivers out there.

 

A good reminder on why it's never good to pull up on the bumper in front of you - ever. Always have a plan to move.. and give yourself room to move.

 

I don't think the spoiler would have made much difference here either... the best move you made IMHO was that you gave it gas and swerved to the left.

The rear-ward shift in weight as you accelerated offered a way bigger traction advantage than the spoiler would have

Kudos to you for the quick reaction times!

 

This is why we're taught a few things in the UK like "tires and tarmac" and the "2 or 4 second rule" oh and how can I forget two words that don't even feature in the US driving eduction vocab, "lane discipline"!

You should never stop behind a car so close that you can't see the tires touching the road, leaves you an exit plan or at the very least reduces the chance of a pileup chain in the even someone does ram you.

You should always leave at least a 2s gap behind the car in front of you when driving, 4s at least in the wet. It's rough but hey, it gives you enough distance to deal with just about any surprising situation. Personally, I tend to leave a little more than 2s.

Well, lets not even get started on lane discipline in the USA, there is none. I've lost track of how many times I've been stuck on a 2 lane road where both lanes are doing *exactly* the same speed and no-one moves over but that one's for another day.

 

why would manual deployment make any difference? there is no downfoce at slow speeds which is why wing does not go up.

 

would be you are more visible to the traffic coming up on you. I don't think the C2S spoiler adds much down force, I think it is more about cooling, but I could be wrong

 

Hm,.. that depends on what you have. Spoiler... spoils the airflow over the top.. which doesn't technically 'add' downforce, it just destroys the wing effect which can end up creating 'lift' on the car.

A wing produces downforce.

For a non-turbo, we have spoilers... and at speeds below 70mph, it probably isn't necessary as the wing effect hasn't taken place yet.. so there isn't anything to do for a spoiler. If you have a wing (not which I'm guessing the turbo wing is) would potentially provide more downforce.

How much additional braking distance that produces I'm not sure about.

 

the spoiler reduces lift on the carrera models.. when really wet i extend mine manually to aid in downforce(lack of lift) on the rear.. yes it goes up automatically at a certain speed but i do notice the downforce at high speed and feel its not "unnecessary" in the rain.