flash_xx

I've been steadily improving the Mustangs handling but it has reached a point where I really need to do something about the panhard bar. My heart was set on a Watts Link but they are all so seriously expensive I can't really justify the cost right now. While looking I came across the Kenny Brown AGS 4.0 panhard bar relocation kit, which by the way is nearly as expensive as the fays2 watts link. He claims just by moving the panhard bar down you can fix the rear end.

I have access to a machine shop and can make relocation brackets for free if it truly is just a matter of changing the roll center by moving the bar down, but something tells me it's not that simple. Does the AGS 4.0 system really work or is it just marketing fluff?

Norm Peterson

What is it that you're noticing here that seems to be defining a limit?

Are you running the OE PHB or one of the available aftermarket replacement PHBs?


Norm

flash_xx

Hi, sorry for the late reply, I'm running a BMR adjustable panhard, so the rear is centered. What I meant by doing something about the panhard was actually getting a watts link so the car behaves the same turning both ways. It corners much better to the left than to the right, which I attribute to the way a panhard works.

Looking back I could have worded that post better. Right now the car understeers, which of course I blame partly on the staggered setup but it also behaves differently left to right.

Now to rephrase the question. Without any other changes, would changing the roll center benefit the handling like Kenny Brown claims? Seems to simple a solution.

Norm Peterson

Raising the rear RC *should* "loosen" the car up a bit (reduce understeer). If that's what your car needs (or can at least be tolerated without scaring you by being too loose), then it would be considered an improvement. Most times, it probably is.


On edit, the PHB raises the rear RC slightly when turning right and lowers it a little when turning left. That would be responsible for at least part of the Right vs Left "asymmetry".

There's a couple things going on here. One is lateral load transfer (LLT) through the roll centers, which affects handling balance pretty much from the get-go (because for this effect there is no waiting for the suspension to get around to rolling over to its final position). And when you increase LLT at the rear only, the handling loosens up a little (becomes less understeerish). There is also a small effect on axle roll steer caused by moving the rear RC up or down that's also a "loosening" effect when the RC goes up.

Be careful - overdoing "less understeerish" can and will result in oversteer, which requires a bit more skill to stay on top of and not let it get away from you.


Norm

flash_xx

Thanks, that helps a lot. I think before I start wasting money on mods I don't need I should probably get a dedicated set of wheels and tires. I'm leaning towards 18x9.5 and 275/35R18 all around. Does that sound ok?

Norm Peterson

For 275-wide tires - which have around 10" of tread width - and the activity shown in your sig pic, I think you'd be better off with 10" or even 10.5". If nothing else, you'd have more room to grow when you discover that 275/35 isn't enough tire any more. But even with the 275's the wider rims will offer slight advantages for turn-in and general steering precision.

My opinion - 18 x 9.5's is a good wheel size for 255-wide tires and probably 265's, but just a little narrow for 275's. So you won't think I'm trying to push you more extreme that I'd go myself, my track tires (285/35-18) that do see at least as many street miles as track miles are fitted to 18x11's.


Norm

flash_xx

Which rims are you using and at what offset for the 285's?

Norm Peterson

Forgestars, from Vorshlag. No offset data other than I have less than 1.5mm strut to wheel and strut to tire clearances up front (and I needed to make an 0.025" spacer for the right front to get that - that's not a typo, BTW).


It's not a combination for everybody, as they're stretched a little and the outer sidewalls and wheel flanges aren't quite under the fender (although all of the tread is as seen from directly above).








Norm

flash_xx

Nice, I'd been looking into those. One of these days I'm going to sell all the suspension parts, wheels and tires I currently have and just get the Vorshlag setup. Either that or the Cortex Racing, but that one runs quite a bit more $$. Now that I think about it, I honestly could just put the car up in jackstands and start selling everything locally, then get a decent, already sorted out setup.

I have a spare 2004 GTO to use in the meantime

Right now I'm running Steeda Sport springs, Koni STR.T,s adjustable panhard with heim joints, aftermarket rear lower control arms with urethane bushings and whiteline relocating brackets and whiteline adjustable upper with poly on the car side and the steeda heim bushing on the differential. Up front I have GT500 arms and camber plates. Stock roll bars front and rear. Tire setup is the same size as the 2007 GT 500, 255 front 285 rear. Nitto NT555

brakes are 2012 GT rotors up front and EBS yellowstuff pads with Motul RBF600 brake fluid. Haven't felt the need for Brembos as the brakes have never faded with this setup.

Running 3:73 rear diff with stock LSD.

audioAl

Not to interupt, but BMR has a new axle mounted watts link for $550.00 Norm is the Man with suspension advice!