Sonic Boom

iTrader: (11)

Does anyone know at what speed the rear wing on a 3 Door starts to become effective at producing useable downforce?
Cheers Rich

MrC

90mph

Harris.

I heard that too. i also heard that if it fell of at that speed the car car would spin .

MrC

Spoilers are designed to work at high speed, the only reason ford added it was because the car was capable of 150+mph so needed something to keep the arse down on the sierra at such high speed.

Sonic Boom

iTrader: (11)

I just wanted to see if I could whole my foot flat through a certain corner because the rear spoiler would give me the extra down force required.
Looks like it would be touch and whether I reached 90mph before the bend.
Rich

lacey

I have some paper work some where and it said something like 500 Newton metres of down force at 126 mph , and 100+ of up lift without it

Sonic Boom

iTrader: (11)

Be nice if someone had the figures of downforce at different speeds.
Rich

MrC

if you were going round a track, and taking a bend at 90mph your car will stick tarmac as it should. if you didn't have the spoiler the car would over steer considerably.

cossie891

iTrader: (1)

How come you can hammer a normal sierra at 100 and it won't spin out and kill everyone?

Mr C

iTrader: (2)

You can't just say that a 3dr WILL stick through corners at 'XX' speed, it depends what traction is available, turning forces are involved etc etc
The 3dr may well produce downforce at 90MPH with the tail on but it will only just be -ve lift, you'll have to find out what KG of downward pressure is added at what speeds and find out how much extra traction you gain from that depending on your tyre grip/speed/testicle size when you try to go faster for the first time.
Try a set corner that you can manage 90+ with no tail on and note the maximum speed you could get through it before the car slides at the rear, then repeat it with the tail on- you should feel it more planted at the rear/have more front push at the same speed that you noted earlier. Then have a go at finding the limit of grip WITH the rear tail.
because the above posts seem to point towards a bit of downforce as being a 'grip switch' or something lol

Mr C

iTrader: (2)

Spot on.
Sounds like you now know what you get at 126 MPH

MrC

Try the 160mph sierra with no whale tail, you'd notice the difference, also don't forget the front spoiler aswell to keep the nose down

james kiely

iTrader: (5)

rich i have read that
the 3dr produces 45lbs at what i assumed was 90 to 100mph [as it didnt say]

but the rs500 rear spoiler combo produced 200lbs of downforce at 100 mph

which is quite impressive over the standard setup

the_frozen_one

iTrader: (1)

Makes sense, there's not much angle on a standard whale tail compared to the rs500 additions

matthewpickup

I thought aero dynamics started around 70mph upwards but I guess it depends on the car , the above info is quite interesting

Sonic Boom

iTrader: (11)

I've got a rear lower spoiler to go on (2.0 Sport one not a genuine 500 item) I might look into getting one of those GRP RS500 upper lip add ons too.
Rich

opposite lock

iTrader: (3)

I thought it was 80kg of downforce at 100mph .

YOREVOL

the shear weight of the thing must hold the back end down at low speed!

dojj

iTrader: (3)

the 3 doors didn't have the larger rubber flaps on the rear windows that the later sierras got to aid with cross wind stability

let me find some pics to show you what i mean and you will understand the sierra aera a bit better in the case of the 3 door vs the 5 door

dojj

iTrader: (3)

this has it



this doesn't



see what i mean?

dojj

iTrader: (3)

also, have a look at any 3 door sierra and just check the paint behind the rear side windows where the air has been streaming across the top off

Sonic Boom

iTrader: (11)

Is that the 3 Door of RS500 figure?
200lb is 90kg
Rich

Sonic Boom

iTrader: (11)

Is rear quarter window on the 5 door the same profile as the 3 Doors rear quarter glass?
Wonder if you could fit them to a 3 Door?
Rich

dojj

iTrader: (3)

The profile is the same but trying to get the moulding to be made to fit the 3 door would be the issue

MrC

I'd bum the bird In that top pic lol

boy-racer-1

the pieces on the rear windows of that mk2 were a revised item and a call back for mk1's as it was due to swaying/stability problem with the mk1's at a certain speed, also id imagine the weight of cosworth bumpers and spoilers arches etc is enough to keep it down as if you compare them to standard mk1 sierra items they feel as though they weigh more then twice as much

Mike1

The 'rabbit ears' were just to provide a better 'departure point' for the airflow off the rear of the car than from the original design. As said, there were lots of complaints about high speed stability in crosswinds, highlighted by accidents such as the Kinnock crash.

RS500 rear wings produced 100kg downforce at 100mph.

On the 3-door Cosworth the rear wing produced about 20kg downforce at 70mph. If Lothar Pinske, Motorsport boss, had had his way it would have been more but the designs were 'softened' somewhat for the road, especially at the front .

Having said that, the normal road cars would produce quite a lot of 'lift' at those speeds, so those figures for the RS cars have to be taken in context. There was an interesting article in "Motor" mag years back when John Miles, who did some aero work on a 3-door XR4i shell in readiness for the RS cars' aerodynamic addenda examined the differences in lift, yaw and Cd in the wind tunnel.

Sonic Boom

iTrader: (11)

20kg downforce doesn't sound like alot.
Rich

Mike1

You have to weigh it against how much lift a normal 3-door 1.6 had at that speed