Wheel Alignment, Shelby GT350

So, wifey went out and bought a toy back in the Spring--2017 Shelby GT350 with 12k miles.  A consequence of my (too) slow progress on the '66 Chevy II.  Nice enough car.  Sweet shifting 6-speed manual.  Supernatural brakes.  Good noises.

Definitely looking near-term to retiring the OE tires (Pilot Super Sports).  The fronts are worn on the inside edges, due no doubt to the wonky alignment that came with the car.  We recently had it re-aligned at the local Ford place.  The before readings show -0.21 on the DS, +0.07 on the PS.  After numbers are -0.07 DS, -0.06 PS.  The acceptable range is shown as -0.15 to +0.05, and the current numbers are very near the middle of that range.

The car has always seemed a bit squirrelly to me.  Some roads cause it to tramline quite aggressively.  Because the car will likely never see a track, I'm interested in making it more pleasant to drive on the street.  I've played with the available driver settings and also increased inflation pressures on the tires.  This and the new alignment have made the tramlining  much improved from previous. 

There are two factory alignment specs for this car--street and track.  My wife specified street when she took the car in.  I understand the basics of toe settings and their effect on handling. 

Will I see an improvement in straight line stability and decreased tramlining if I have the car re-aligned so that the fronts are at zero toe to slightly positive (toed in)?

2005 GT Upgraded to GT350 Specs

1/16 Toe Out

YRMV

Good Luck

Anybody else?  I can't help but feel that some of you guys know a little about wheel alignment. 

Yes, if you dial in some toe in the car will have improved straightline stability.  I'd go straight to the Max factory setting for your usage.

I guess mt 15 years of NASCAB Engineering does not apply to street cars

HMMMMMMMMMMMMM

RacingComputers said:

I guess mt 15 years of NASCAB Engineering does not apply to street cars

 

HMMMMMMMMMMMMM

Well, to be fair, I didn't have a chance to review your résumé.    I don't doubt the validity of your response, since 1/16 out = -0.0625 which is right where the dealer set it.  I'm just wondering if I'll get better straightline stability (and more even tire wear) if I go with zero to very slightly toed-in.

The other thing I'm learning is that some of the issue may well be these old tires with some funky wear on them.

Your alignment "fix" is the same net alignment, just with the steering wheel centered. (-.14 total before, -.13 total after). If you want to calm the car down you want it in the zero to slightly positive range. Should help with tire wear too. I'm impressed that the OE specs actually call for toe out.

I just had my new to me '19 Bullitt re-aligned, I picked it up with just under 20k miles and the tires were trashed, 1/4" wide of cord showing on insides of both fronts. Wonky alignment and inability to rotate tires due to staggered set up is not a good combo. I have a similar alignment and my shop told me if I was lucky I might get 25-30k out of this set.

1988RedT2 said:

The other thing I'm learning is that some of the issue may well be these old tires with some funky wear on them.

Well jeez... start there. No alignment specs are going to fix funky tires. Adding caster would also increase straight line stability. 

In reply to imgon :

I don't see any mention of this being a 4 wheel alignment.  This car has independent rear suspension, has anyone looked at how that is set? If that is not also set to street settings it will add to instability and may even hurt front tire wear.  The front also needs to be adjusted "square" with the rear settings, just adjusting one end alone can end up with the car not symmetric.

I agree the front needs to be set to some toe in.

You also won't be able to know how it really is if the tires are the originals, the type of high performance tires it came with will age faster than a normal tire combined with already having poor wear = random tracking.