need help suspension steering problem!!

[67coupestang]

sorry its a little winded...

Ever since I slapped the disc brakes and 16's on my car there has been a problem with the way it steers. Let me try to explain what happens. Its only at higher speeds, handles straight as an arrow and doesnt pull what-so-ever. But if enter a corner at highway speed... Its fine the first few degrees I turn the steering wheel, after that it feels like the passenger grabbed the wheel and cranked it further in the same direction and the car darts. It seems like its related to weight transfer because i felt it do it during a quick lane change too. It sucks and i have to really 2 hand it going in to turns on the highway. I'm running 1.5" adapters to get the 16"s to work right, which i could have probably got away with a 1.25". I've had it aligned, no change, I checked the ackerman (thinking the 73 that i got the disc brakes from was a longer wheelbase and that the spindles may have been different). The only thing i am leaning towards is not enough caster, which like i said it drives straight as an arrow, or maybe bump steer?? the car is not "lowered" but the original springs are sagged plenty. I looked at the lower control arm and the steering arms and they appear to be parallel. Its driving me nuts so if anyone has any input... TIA!!!

 

[Hack]

Do you know what the suspension alignment settings are?

 

[67coupestang]

no i just had them do it to stock specs...

 

[WORTH]

well, a few things to look at are;
any loose parts, a little slack can make a big difference in steering.
caster, caster keeps the wheels straight, withour it they can turn either way on their own.
weak strut bushings, this can change the caster, and is very noticable when you hit a puddle with one wheel.

 

[Tim65GT]

Possibly rear spring bushings? The axle moving around back there could effect it. My car does the same thing when I get aggresive in corners at speed. I thought it felt like the rear axle moving. I plan on a full suspension rebuild in the future.

 

[67coupestang]

oh yea should have mentioned the suspension only has like 1500 or so miles on it, its all tight. bumps dont seem to effect it at all, it really handles nice when straight, smoother than my 98 explorer!

 

[WORTH]

if everything is tight I'd add some caster, moving the tire out with a spacer probubly didnt' help the geometry much.

 

[Ozsum2]

How are the tires wearing? I'd suspect an alignment issue like Worth.

 

[67coupestang]

i havent logged a lot of miles on the 16"s yet, 1) its scary to drive and 2) it keeps overheating, but so far nothing weird, no chirping around corners, pulling, etc... I though about just adding more caster too, maybe it trying to pull itself straight might help a little... I think honestly versuses the 14"s i had on before the center of the tire is only like 1" farther out though, my 14"s had some goofy offsets