F1Fan

Fiction.

F1Fan

Save your money and do it right with a Watt's link. The guy is just trying to scare people to sell product.

F1Fan

Of course you do.

F1Fan

You need to have the rear axle centered. You can do it on an alignment rack using monofiliment and a tape measure or use a laser rack to get your front and rear axles on the same centerline, look at thrust angle.

F1Fan

If you lowered the ride height 1" and set your adjustable panhard bar to the same length as the stock panhard bar it is not set correctly and the axle is probably too far to the left or driver side of the car.

The entire point of an adjustable panhard bar is so you can set the length of the PB to allow you to center the rear axle after reducing ride height. Some basic 8th grade geometry will prove you need to shorten your fancy new adjustable panhard bar with your lowered ride height. This is due to the axle following the arc described by the panhard bar. The advantages of a Watt's linkage is that the lateral axle loads are introduced to equally to both side of the chassis whether turning right or left and the axle move up and down in an almost perfectly vertical line. If you have a good Watt's link you also can optimize the linkage geometry and roll center height to minimize the size of the rear anti-roll bar which improves ride, handling and noise.

UPRSharad

Interesting responses! Normally the open track guys are all worked up about bushing bind. Meanwhile you don't care what happens to the suspension if a person's rear end is an inch or so off center? That's different!

F1Fan

LOL! The obvious answer is I'm not normal. I actually know the how and why a suspension works and unlike the last gen SN95 Mustang chassis, on a stock S197 bushing bind is the least of the chassis rear axle problems. The stock 3-link was designed with virtually no mechanical bind and uses low compliance rubber bushings. Yes O.E. style bonded rubber bushings have some internal friction, this is how and why these bushings work so well in O.E. applications. In practical terms this means there is no artificial spring rate or bind being introduced. This is why when an S197 chassis gets firmer bushings and better damping having a stiff adjustable panhard bar and a stiff brace can make a noticeable improvement in handling.

As to the rear axle being "an inch or so off center," on an S197 chassis that has not been in a crash you are either exaggerating or ignorant about the way the panhard bar works in the S197 chassis. What you describe cannot happen on a stock S197 chassis, it is impossible. Do the math or if you don't know how you can simply go measure it on the car.

Let me help you with that; assuming a stock length panhard bar (approx. 41.75" CTC) moved 4" in compression (that means up) there would be less than 1/2" of movement toward the driver's side of the chassis at which point the axle would start to move back to the passenger side of the chassis as the end of the panhard bar reaches the height of the arc. This is the real handling problem with a panhard bar, first left then right.

The insecure handling feel is not so much the shifting of chassis drive thrust angle (though it is an unsettling feeling under power), so much as the fact that the lateral loads change directions as the axle moves up and down and the way theses loads are introduced into the chassis when turning left vs right. Those differences in force are what makes a panhard bar chassis behave differently left vs. right and feel unsettled over bumpy surfaces. But the changing load is not very noticeable in S197 chassis handling due to all the high compliance bushings Ford used which filter out these movements and changes in load direction.

All this changes when you install lower compliance bushings and wheels and tires that can generate more grip, it makes the car interesting to drive but not in a good way. These issues are why I installed a Watt's link so long ago.

Yes, I'm different from the average guy here in that I'm not looking for help, I'm here to give help and unlike you I'm not trying to sell them anything. Not that there is anything wrong with it.

Norm Peterson

I honestly wish I knew how various people manage to come up with that much lateral axle shift. Geometrically it simply isn't there.

I suspect that the PHB bushings might possibly introduce a little axle shift if they aren't re-clocked (like you're supposed to do, though I suspect most folks don't bother with this step). But I'd be surprised if there's even a quarter inch here.

That leaves the idea that measurements may not have been made under the same conditions. Measuring the 'before' condition at full droop or any other slightly raised condition, and the 'after' condition with full weight on the rear tires is certainly going to make it look like the axle shifted (from where? was only the left side observed?). I'd guess there would be a few inches difference in ride height and greater axle shift would show up that way, but since math based on guesses is still a guess I won't bother.



Near as I can tell from my car, the PHB ends go from about a 1.5" difference in height down to about 1.2" when I get in it (the car is still on its OE springs). Any more than about 1.25" lowering would then drop the PHB down lower on the chassis side as driven, which starts pulling the axle back toward the passenger side . . . which makes me wonder why people obsess over this.

Because the LCAs are not quite parallel in plan view, there theoretically is a tiny shift in thrust angle as the axle shift laterally. Nothing you'd notice, though, and probably not even reliably measurable.


OP - just lower your car, re-clock the PHB bushings, roll it back and forth to settle the suspension, check tire clearances, and drive it. Then see whether any axle recentering is necessary.


Norm

tigercrazy718

still stock springs? do you run in the stock class then? sorry that just caught my eye lol

/hijack

Norm Peterson

Can't.

My wheels are an inch too wide and the rear LCAs aren't legal there either. When I do get springs, the car won't even be legal where it is now (not because of the springs themselves but a related reason).

[/hijack reply]


Norm