Front End Drift

[BMK]

Peter

Sorry I was Posting and typing when you replied, so missed your Post.

I have been thinking about the height and I can remember George V from Python cars talking about height at the track at LeMans in Adelaide. He had Christian Agostin driving the #98 car and there was feedback that the car was floating on the main straight. Christian had previously been in a Porsche race car.

George then experimented with from spoilers etc. BUT his Cobras were a further 50mm+ - 2 inches lower than street height.

Now I know I am not driving fast enough to cause any lift. I feel the suspension set up is the problem. I don't think the body shape is contributing to the problem. Then again..

I will try the adjusment and see what happens. The shockers sound logical to me.

I just checked it and I am on position four (4) so there are another eight (8) positions to try up.

As I said I will keep you Posted. I will get some good feedback tomorrow from McDonald Bros. Racing and will Post the results/findings.



And all the time I thought it was my driving ability.

Cheers

Bernie

Bernie Knight
Mt. Gambier South Australia

Visit our City site at www.mountgambier.gov.org

[maxrpm]

Am I correct in saying we are not talking about a race situation. I was having the described situation at speeds as low as 40-50mph. After playing with the shocks, alignment & ride height, I finally fixed my problem with a pair of softer front coils. I can't say this is the cure-all, but what I can say is this: I wish I checked that first! It could of saved me 4 trips to the alignment shop. I tried raising/lowering the front/rear to shift weight to the front- lowering the front- all the shock settings etc...etc...then it came to me while watching a NASCAR Happyhour session that I was possibly overlooking the simplest thing. There they were, tossing coils in & out of this car & I thought what did I have to lose? There must be an easy formula for figuring the baseline lb spring rate needed for a cars front /rear axle weight but I never bothered asking. With an aluminum headed Windsor and narrow lightweight frontwheels, anyone care to guess the front axle weight of my car? Does anyone know the front axle weight of their own?
Ok, I gotta go sit by the fire now.....SEND HEAT!!

[maxrpm]

Peter, I just looked at pics of your car.....WOW is it slammed! Don't go buying/changing anything until you pick it up outta the weeds! She looks sweet when she's parked but sure must be harsh to go down the road in. New meaning to the term 'snake in the grass'!
Ed

[PCC]

Ed,

The back end's out of the weeds, now just in the long grass.

The front end is still sniffing the soil, but hopes to one day find out what its supposed to be looking at.

Hey - to some-one who just thinks V8 / convertible its awesome.

Its not until you see it against other Cobras you think may be not.

An inch higher all round and no handling problems I'll be happy.

Thanks mate.

[BMK]

Hi Peter,



I checked my Cobra last night and it is four inches all around off the ground at floor height. About 110mm.

I have flat plate right through from the firewall to the rear below the tank.

The option of playing with shocker adjustment is the cheapest and easier option right now. Then I will try the springs as this suggestion makes sense.

I do not experience this problem of floating or drift until I am at about 140 - 160 ( 85 - 100mph ). Then it does get a little bit hard to hang onto if road surface is un even.



Mike Moore has organised some track time at Calder Park so I may get out there. The other option is to get someone else to drive it and this seems the way to go.

May be a day or two before I get to take the Cobra to McDonald's Racing as it pouring here. Will Post once I have some feedback.

Thanks again everyone for the feedback. Pete thanks for placing this Thread. As I said I thought it was me (Perhaps it is)



Cheers

Bernie

Bernie Knight
Mt. Gambier South Australia.

Visit our City site www.mountgambier.gov.org

[PCC]

No worries Bernie.

My rad sits exactly 4 inches above floor level.

Chassis, just in front of rear wheel 5 inches and fuel tank 6.5 inches.

Based on the above the front end needs lifting approx 1 inch to level the car out.

I find the floating at any speed, but only under firm acceleration on undulating surfaces.

Before the back end was lifted, had no problems as any grunt seemed to force the whole car down into the tarmac.

Pretty sure that when the front end is lifted equilibrium will be restored and it will be a case of simply playing around with the shocks for fine tuning.

Strange you said getting someone else to drive it as I was thinking on the same lines this morning.

Currently back on to the wire issue tidying up here and there.

Remember guys - spend your dosh on top rate wiring as when a problem arises it takes time and effort to resolve - personal experience.

[wilf leek]

Bernie - if your "float" symptoms are coming in at those kind of speeds, then I would suspect aerodynamic front end lift. Try setting the car up so it is higher at the rear tha the front, often helps, and is recommended by many as the "proper" way to set ride height.

Could you get someone to run alongside you at those speeds (safely) and feed back to you about the front end height at speed?

HTH

[maxrpm]

Bernie,you got balls that clank! 100mph in an ill handling car
I think at those speeds we are talking professional suspension tuning and alignment settings. There are so many other variables involved at those speeds. Aerodynamics will be a big factor, & I don't think a street setup will ever feel comfortable in these type of cars at those speeds- thats where the 'drivers' are separated from the 'DRIVERS'. I am one of those drivers(small letters) I learned I don't have what it takes to drive MY cobra beyond the lethal side of 100mph unless it's on a flat STRAIGHT surface and then for only a short distance(1/4mile) I'm in awe when watching archived footage of the way the drivers threw those Cobras in & out of turns at speed! If you study the footage you realize the Cobras didnt really have much grip, the drivers sort of threw the cars into a turn and just maintained a controlled out-of-control skid.
Mine don't clank, they sorta just slide up along side my adams apple when I try to do that.
Ed

[wilf leek]

Ed - I can't really see why a street car set-up should be unpleasant at high speeds. My car is essentially set up for street/touring comfort - fairly soft, certainly softer than a lot of cobras I've driven. Yet it sits straight and true at speeds up to, and occasionally over, 150mph. (GPS checked). Top I ever managed was 165, and that took several miles to wind up to.

On an autobahn, of course, officer.

No front end vagueness, no drifting, just lots of wind noise. The only thing that bothers me is those 6 little screws holding the windscreen to the pillars. Wonder what kind of wind pressure there is on the screen at those speeds?

[maxrpm]

Wilf, what I meant was I think taking a car at high speeds thru a racing course, braking cornering then accelerating would probably need a different suspension setup for optimum control. Probably different spring rates also. But I'm just babbling- I've never thrown my car into a corner at 90mph, so don't really know what it takes...aside from maybe first downing a pint of JD old #7.
I believe your statement about using softer springs than typical is the answer this thread was looking for. Most street cars are set up with higher spring rates that aren't suitable (or necessary) for public roads with all the dips, bumps and road kill we have to drive over. I think in one of my first responses to PCC I recommended softer springs. The softer the springs, the less chance of the bumps in the road upsetting the car at high speed. Now take that same soft front spring to a track, drive deep into a turn, brake hard and the car will probably nose over from all the weight transfer onto the front springs, causing a light condition in the rear- so when you accelerate out of the turn- the back end wants to come around. The heavy front springs don't let that happen.
About that windshield, my speedo quits at 160 & so did my shield-it cracked right down the center. I installed another but kept thinking about it. So I ordered a polycarbonate from Cobra Restorers and now the nightmares of eating my shield at speed have stopped. over-n-out.
Ed

[wilf leek]

Ed - you are 100% correct. My car is most definitely NOT set up for the track, although we have been there several times. Needs sway bars and an LSD for the track.

Mind you - I have managed a 100mph 4 wheel drift in it - once. And full opposite lock cornering a couple of times without spinning.
I hold the record for spinning most times in one lap at our local track - I claimed I was "getting to know the car". The Lotus 7 clones learnt to keep well away from me.

[BMK]

Hi all,



Well here is a little feedback on what I have done to remedy my drift or floating problem.



After reading all suggestions and talking it over with the guys at McDonald Bros. Racing we decided not to alter the front end alignment but to play with the shockers.

I have the QA1 shockers and they are mainly a drag racing type of shocker, but I am told they are more than suitable - see my photo shoot of the shocker.

I had them set at 4 the higher end. I adjusted the front down to 10 ( They have settings from 0 - 12 with 12 being tight/down).

I lifted the rear end by about an inche moving the four bars. There are three settings on the rear. I left the rear shockers set on 4.

Had someone standing on the side of the road to give me feedback on the front lifting etc.

Three or four passes at 170 and it appears the car sits dead level at that speed. So there is still slight lifting of the front still as the car was level prior to lifting it an inche.

I then ran down at 190 - 200 and there does not appear to be any floating or lift. So adjusting the shockers really has made a difference. I will consider lowering the rear end back and trying all of the above again.

At this stage there has been a real change.

Cheers

Bernie

Bernie Knight
Mt. Gambier South Australia

Driving in the sun