twitchy at speed

[pcoghlan]

I noticed yesterday thatthe car is pretty twitchy at speed, especially when accelerating. This makes it hard to drive comfrotably above 65-70 as you are having to constantly adjust the steering to keep it in a straight line!

Driving over a change in road surface at 70 is interesting to say the least. It hops around a little although adjustments at the steering wheel do keep it on line.

Anyone had anything similar? Am I being unreasonable expecting it to be a solid, smooth ride?

I am taking it to get aligned this morning with settings from the Lonestar forum.

Toe total (1/8)" on both sides, + or - (3/32)
Camber - 1 (1/2), + or - (1/2) deg on both sides
Caster + 4 (1/2), + or - 1 deg

Paul

[strictlypersonl]

What tires are you using?

Frankly, it sounds like a bump-steer issue to me.

[Tommy]

Alignment can make a lot of difference. Do you know your current alignment settings, or is this going to be the first alignment for this car? ... Caster is particularly important for steering stability. Greater caster increases steering effort while increasing steering stability.

[BMK]

I agree with Tommy. If you find the Cobra is easy to handle at low speeds and feels light at the wheel, then the Caster is the focus.

At higher speeds the floating or stepping out effect is a result of caster or zero adjustment made.

Just watch over correcting until you correct this problem, as this will have a direct affect at high speed as it's exagerated.

[Excaliber]

Double check that toe in. Zero toe, and that COULD happen at speed despite the initial settings, will really make a car wander.

[TampaFla]

Depends on your definition of "twitchy" also. Any slight movement of the steering wheel at 80+ will be "more noticeable/responsive" than an equal movement at 25mph. At least that's the explanation offered by many rollover participants.

[pcoghlan]

OK, tyres are:

BF Goodwrich Radial T/A's
FRONT: 245/50 R16 96s
REAR: 295/50 R16 107s

Went to the local Pepboys (bad move?) who explained their computer MUST have the correct vehicle to start with or they cant do it?! Finally got them to find the AC Cobra MK III which has different settings (castor is 3 versus recomneded 4.5 from Lonetsar). They then confirmed they can override computer recommendations. So, why they couldnt simply pick ANY car and override the settings is beyond me.

Anyway, they gave me an appointment for 1pm so I should know more then. They did suggest such wide tyres on the front may cause the high speed issues?

Paul

[clayfoushee]

The tires in the front aren't too wide. Rear alignment is very important too.

[pcoghlan]

clay

I just had the car in a shop for the last week where they stripped the rear end and rebuilt it "with correct geometry" as many of the bolts on the original installation (not by me!) were loose and some of the components were installed the wrong way around!

I would HOPE this means the rear alignment is OK.

I will see what news the front end alignment brings. I will ask them to let me know what was out and by how much.

Paul

[jwoodard]

as a previous Lone Star owner and builder I offer the following suggestions:

Do a 4 wheel alignment

Pinion angle is critical for good handling with this car

Replace the standard heim joints on the four links and panard bar that Lone Star provides with some good quality teflon lined ones. QA1 sells great quality heim joints. You won't believe the difference this change makes in the handling and ride.

[JayBar]

Paul,
Call Doug at MasterAuto Car in Jupiter
561 741 1650. He has done a number of the local Cobra guys
cars. Know what he is doing, and can tweek it a bit if you are racing.
One cheep and easy thing to check is to re-center your wheels.
Jack up the car loosen the lug nuts. Then go around 1/2 turn each till the wheel is seated frimly then tighten all the way.
This cured my wheel shimmey at 65mph.