2001 Pontiac Trans Am Suspension Upgrade - Suspension Intervention

The new 21mm solid antiroll bar is assembled using the provided poly mounting bushings and new brackets (gold), and bolted to the rear-but not fully tightened yet. We found that with the car in the air, the antiroll bar ends were at a severe angle compared to the brackets on the car, so to get the end links in, we had to put the car on the ground and crawl underneath (larger and/or claustrophobic individuals can use jackstands, of course). BMR advises it is best to tighten these bolts while on the ground anyway, to prevent suspension binding when the car is lowered down. Even with the car on the ground, we found the supplied bolts weren't quite long enough to get the nuts started on the end, so we bought new 6 1/2-inch long, 3/8-inch bolts (about 1/2 inch longer than those supplied), to give us more thread to start on.

After final tightening of the antiroll-bar end links on the ground, the mounting clamps get 18 lb-ft. Note that you must make sure these clamps are on their seating tabs on the axletubes (finger pointing). The geometry of BMR's antiroll bar dictates the need to push these clamps and bushings as far outward as possible to stay on the tabs. Ours ended up right on the edge, and were good to go.

On to the lower control arms, which are removed via two 18mm bolts aside. The rear bolt can be tricky to get out, thanks to the parking-brake cable in the way, so disengage the e-brake to allow yourself more clearance. Look at the flimsy, stamped construction of the stock LCAs and their stock rubbery bushings.

The BMR LCAs are much beefier, yet they incur no weight penalty because they are chrome-moly (the stockers are 4.5 lbs each, versus 3.4 lbs for the BMRs). In addition, they are available with boxed construction, as well as in an adjustable version (with or without rod ends), for more race-oriented applications. Also note that we chose the optional bushing upgrade, which replaces one of the polyurethane bushings on each LCA with a neoprene one (black). This highly elastic synthetic rubber is much stiffer and more durable than that used by the factory. According to BMR, having Neoprene on one end of the LCA results in nearly as good a performance gain with less road noise than if using poly at both ends.

The LCAs slide into place, helped by the provided lube on the outside of the bushings, but the bolts cannot be fully tightened until the rear suspension is loaded. Since we are also installing subframe connectors, they need to be set loosely in place before the front LCA bolts are inserted (look closely and you can see how the front LCA bolt helps position the subframe connector end plate, near my right hand). Caution: The factory LCA bolts are not the same length. The longer ones (12mmx1.75x105mm) normally go at the rear axle connection, and the short ones (95mm) go at the frame connection up front; however, we found that with the added thickness of the BMR subframe-connector end plate, the factory front LCA bolts did not fully engage the nut threads to our satisfaction. As a grade 10.9 bolt of this size is virtually impossible to find at any hardware store, we ordered a duplicate set of rear LCA bolts at our local GM dealer (PN 22657681, about $4 each), and as you can see here, they're plenty long enough to work up front.

With the subframe connectors held loosely in place at the rear, we use a screw jack to hold the fronts up securely. A wire wheel is used to get to bare metal at all weld points, here at the front of the driver side. As with all components we are installing, the BMR subframe connectors are finished in a gorgeous and durable wrinkle black powdercoat the company calls Black Hammertone (aka Silver Vein). This finish has excellent UV protection, as well as high resistance to heat. It's a shame that some of it has to be removed!

Because all four wheels must be loaded during the subframe connector install (to replicate chassis flex as it sits on the ground), it is impossible to weld them in using our style two-post lift. We need to drop the car on the ground and, with the front wheels resting on the floor, use jackstands under the rear axle (not the frame--the red stands you see are only there as a safety precaution). The subframes are then heavily tacked into place before lifting back up to complete the welding. Made from 1 5/8-inch, 0.120 wall, DOM seamless tubing, these subframe connectors are intended to enhance chassis stiffness without compromising ground clearance.

After painting the welds and tightening the LCA bolts (not nuts!) fully to 87 lb-ft with the car on the ground, the install of all BMR components is complete. We then pumped a little grease into all appropriate fittings, and sat back to admire our newly improved undercar looks. Will in-car handling improve, too?

Pushed to the limits at an SCCA autocross at Raceway Park in late May 2007, our WS-6 performed admirably. It had been a while since this author's college experience with Formula SAE purpose-built race cars, so remembering how to read the series of cones took some trial and error. After a ride-along instructor got me on the right track (no pun intended), I enjoyed the reduced body roll and increased suspension composure provided by our new BMR parts. Despite a less-than-optimal track surface, at no point was I able to upset the car and send myself out of control--a feat that normally could be pretty easy with around 430 ft-lb turning the tires!