B-body Suspension Mods

As us B-body enthusiasts know, the stock suspension of most B-bodies is terribly overwhelmed with the weight of our vehicles.  While the stock Impala SS and 9C1 suspension setups aren't bad, they can be improved with relatively little work and minimal cost.

In choosing components for my Impala's suspension, I established a few goals.  First and foremost was to improve the roll resistance (increase the roll rate) of the stock suspension.  In doing so, I wished to establish "neutral" handling.  The stock setup is heavily biased towards understeer.  Second, I wanted in increase the damping, as the stock suspension can get just a bit "floaty" under certain conditions, such as cresting a hill in the middle of a turn.  Third, I wanted to improve upon the cargo-hauling capability of the stock suspension.  The stock rear springs on the SS are rather weak, and even a full tank of gas and a couple passengers in the back seat can cause quite a bit of sagging.  Finally, I didn't want to compromise the suspension travel.  The Impala SS already sits much lower than the B-body chassis engineers ever intended back in 1977, and lowering it past the stock ride height reduces the available suspension problems and causes even greater camber- and toe-control problems.

So, with those goals in mind, here's what I did.
 

Swaybars

The first step was to replace the swaybars.  Based on Scott Mueller's recommendations on the IGBA site (www.b-body.net - the swaybar info is in Technical Articles - Suspension), I decided that I'd choose the Herb Adams 38 mm rear bar and compliment it with the GM F-body 32 mm front bar (GM part # 356534 - discontinued).  Considering that the stock rear bar is only 26 mm in diameter, and the stock front bar is 30 mm in diameter, this results in a drastic increase in roll resistance (the rear is 450% stiffer than stock, while the front is 35% stiffer than stock). 

I used the recommended F-body 1LE 32 mm bushings (GM part #  10288551) and end-link kit (GM part # 10221779).  You could try to reuse your stock end-link hardware, but I have yet to remove it without breaking the bolt.  I've also used Perfect Circle bushings and the high-performance urethane end-link kit from Pep Boys when I retrofitted the stock SS bar onto my Roadmaster wagon, but I still think the 1LE parts are of higher quality and actually cost a bit less!  Don't forget to replace the stock bushing-clamp bolts with 4 new bolts (GM part # 15959689, or you can use 10x1.5x30 mm socket-head bolts from a hardware store).  If you try to reuse the stock bolts, there's a chance that you'll strip out the threads in the frame.  This would not be good, so spend the time and the money to get the new bolts.

Out back, the hardware requirements are bit more simple.  To mount the bar to the old-style trailing arms (which uses a bolt that threads into the trailing arm), use (4) 7/16x2" bolts.  The stock bolts are too short to attach the new (and thicker) HA swaybar.  Re-use the stock "thick" washers.  If you have the new-style trailing arms, where the bolt goes all the way through the trailing arm and has a nut on the top, you'll need 4 new 10x1.5x120 mm bolts (GM part # 11504610) and 4 new nuts (GM part # 11502812).

With this swaybar combination, the car goes from a heavily-understeering pig to a light, nimble, and neutral sports sedan.  OK, so the difference isn't quite that drastic, but the car does turn-in much better, and has very neutral handling characteristics.  At the limit, you can correct the car's line with just a bit of throttle modulation (letting up off the gas rotates the back end around and tightens the line; adding gas will push the car up towards the outside of the turn if you don't spin up the rear wheels).  This setup is not for someone who doesn't understand vehicle dynamics, since doing something boneheaded like jumping off the throttle mid-corner might just result in a little sidetrip into a ditch.

For more swaybar info, I highly suggest that you check out the IGBA page.  It's a real treasure-chest of knowledge!

Shocks and Springs

I went with the Konis and ordered them from Summit Racing using part #'s 8040-1087 and 8040-1088 (you'll need two of each).

The disadvantage of the adjustable feature is that the shock body must be fully-compressed and then twisted to adjust them.  This pretty much means that they need to be removed in order to be adjusted.  There's a total of five positions (you can barely feel the detents, so twist the shock slowly as you adjust them).   I just went with the maximum adjustment (full clockwise)!

For springs, it was clear that I wanted something stiffer than stock, but I also wanted the stock ride height.  Here's the options that I investigated:

I've included the Eibach springs for comparision.  The Eibach Caprice springs should provide the same ride height as the stock Impala springs, but with the same spring rate as the Eibach Impala springs.

Note that the stock and Eibach springs are wound as a progressive-rate spring, with a very soft initial spring rate.  This is the problem with the stock Impala springs - if you start loading-up the car, you're just compressing the soft portion of the spring, and so the back of the car can easily sink down a few inches before the stiffer portion of the spring "kicks in".  The Caprice wagon springs have a linear rate, so they won't suffer from this problem.  They're about 40% stiffer than the "weak" portion of the stock springs, so the roll resistance is much-improved, also.

Up front, the Global West springs provide a spring rate that's about 75% stiffer than stock, and a ride height that's essentially unchanged from stock (they did drop the front of my car about 0.5" or so).

If you combine the wagon/GW spring package with my swaybars, and then toss in the Koni shocks, you get a very firm suspension package that exhibits virtually no roll during hard cornering.  The downside to this is that you've got a very firm suspension package that exhibits virtually no bump-absorbing capabilities.  To be perfectly honest, it's not that bad.  A friend observed that the suspension firmness is somewhere between the extremes of the suspension settings on his father's 1996 Corvette.

The spring selection seems to have retained the same front/rear balance as my swaybar modifications, but with improved control at the limit.  At MISSL's track day at Waterford Hills, I was coming off Turn 8 in a very controlled tail-out drift at speeds of 85 MPH, and the car was just, well... settled.  It feels like a performance sedan should.
 

Next steps

When it's time for the suspension bushings to be replaced, I'll use Global West's Del-A-Lum parts.  Supposedly, they provide the firmness of poly bushings, but without all the squeaks, creep, and excessive wear.

At some point, I'd like to experiment with altering the front suspension geometry to provide proper toe and camber control.  If you've ever looked at your car while the front's up on jacks, you've hopefully noticed that the wheels have a lot of negative camber and toe-in while in the full-droop state.  Unfortunately, that means that the front wheels go towards positive camber and toe-out when compressed beyond their static position.  This is why our cars tend to exhibit some spooky handling when hitting mid-corner bumps.  I feel that some work on the center-link height and link, combined with repositioning of the upper control-arm pivot points, could result in huge improvements in the handling of the B-body.  Honda's been using good suspension geometry for the last 20 years to create cars that handle well without excessive suspension stiffness, and I think that creates a great street setup for the real world.

Questions or comments?  Email me at eric@bryantperformance.com!

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