1971 Chevy Chevelle BMR Fabrication's Level 4 Brake And Suspension Package Upgrade - Turn & Run
Creating a Corner-Carving Chevelle With BMR's Level 4 Suspension Package
From the January, 2009 issue of Chevy High Performance
By John Nelson
Photography by John Nelson
We all like a good dose of utility. The more uses we can put something to, the better. A street car is nice, and a strip car is cool, but a real street/strip machine, a muscle car that can both cruise the boulevard and throw down at the track, now that's really something to get excited about. That kind of dual-purpose utility is what BMR had in mind when it developed its Level 4 handling package for A-bodies, only with a twist. This setup is aimed at those who place a premium on handling, whether called Pro Touring or g-machine or some other turn-loving label. This is a serious setup, featuring strategically located spherical bearings as well as extensive tunability thanks to its Afco double-adjustable shocks. Can it be all things to all people? In this first installment we'll answer that question as it pertains to the street. In Part 2 we'll upgrade our subject '71 Chevelle's steering to match its enhanced suspension and put it to the test at the track.
First of all, this comprehensive package comes in two varieties: one for '64-67 A-bodies and another for '68-72s. In both cases the vehicle is lowered 2 inches at all four corners, thereby lowering the car's center of gravity. One of the most important features of this package is the use of tall spindles to improve the Chevelle's front camber curve, further increasing traction by allowing the front tires to remain squarer to the road as the suspension moves. BMR uses forged aluminum AFX spindles, which are light, very trick, and a direct bolt-in with BMR's upper and lower control arms. They also come with an extra benefit: the ability to bolt on a set of C5 Corvette front brake calipers for vastly improved braking.
The first big difference in this setup as opposed to BMR's other variations are the spherical bearings at the frame mount points on the upper and lower rear control arms. "It's a compromise between an all-out race setup and a street setup," says BMR's Allan Miller. "The bearings at the body locations articulate through their full range without binding." On the other hand, there's still some damping effect from the polyurethane bushings at the suspension-mount end of each rear control arm, though binding is greatly reduced here as well. While spherical bearings do tend to create a noisier, harsher ride, "This is less apparent in a full-frame car," according to Miller, assuring us that this setup is aggressive while remaining streetable.
The other big difference in the new Level 4 package is a set of four Afco double-adjustable shocks. In short, both compression and rebound damping are independently changeable, and with 40 settings at each location, their adaptability to various road and track conditions is extensive. Better yet, these adjustments can be made on the car in a matter of minutes. This versatility allows for soft settings to maintain comfort during a trip to the track, followed by harder settings for autocross, open track action, and even drag racing (though the straightline is not the strength of this kit). The shocks are performance-valved to match the higher spring rates found here.
So, what did all this reworking get us? Right off the bat the car's handling improved over a stock Chevelle's manners, at least as we've experienced these cars. Body roll was greatly reduced and turning ability considerably enhanced. On the other hand, when put to the test at the track, the car's steering took on a sluggish quality and didn't respond very quickly. This may or may not have been an issue with a less-aggressive package; even with this one, it probably wouldn't make a huge difference on the street. But in a setup aimed at autocross or open-track warriors, it's absolutely critical. So, before we lay all our cards on the table and tell you how this A-body performed, we're going to upgrade the stock steering box to something more performance-oriented, then head back to the track for more numbers. Until then, we bring you the highlights of this very comprehensive Chevelle suspension kit. Enjoy.
What we did:
Outfit a '71 Chevelle with a hardcore, multiadjustable suspension and brake setup
We got good results-but there's more to be had
$5,400 for the complete package with C5 front brakes
BMR Fabrication's new Level...
BMR Fabrication's new Level 4 handling package for A-bodies is formulated as an all-inclusive, high-end package. The kit is matched to work with the high-performance, almost-infinitely-tunable Afco double-adjustable shocks. According to BMR's Allan Miller, this setup is "more geared for autocross; it's set up for driving to the track or road course." Once there, the shocks can be reset for taking care of business, then softened up for a nice ride home.
One of the keys to this setup...
One of the keys to this setup is the incorporation of ATS forged aluminum spindles. Besides lowering the car 1 inch (another inch came via the springs), these pieces are tall spindles, meaning they endow the Chevelle with badly needed negative camber. In short, that means the upper part of the tire tucks in during bump (aka upward suspension travel), enabling more of the front tires to contact the ground.
BMR's front upper and lower...
BMR's front upper and lower control arms are created from DOM steel tubing. They come outfitted with low-deflection polyurethane bushings, ball joints, and bumpstops, and the uppers have new billet steel cross-shafts. A&E Motorsports' Brandon Matarese installed the new Afco shocks to the lower control arms, bolted the upper and lower arms into place, and installed the new springs with a bit of grease to guard against squealing.
The BMR control arms are designed...
The BMR control arms are designed to work with the ATS front spindles, making this upgrade a direct bolt-in. Forged from lightweight and strong 6061 T6 aluminum, they also use Corvette sealed-bearing hubs, which have a higher load capacity than stock, and incorporate C5 wheel speed sensors, if you want to run ABS. This is accomplished without changing the Chevelle's wheel fitment or track width.
The arms are then equipped...
The arms are then equipped with bolt-on anodized aluminum steering arms in the same manner as the originals, though of course much more advanced. The tie-rod mounting point is relocated to reduce bumpsteer, while their greater strength makes for more responsive steering.
As we mentioned, the ATS spindles...
As we mentioned, the ATS spindles come with a Corvette hub assembly, making installation of matching C5 calipers a snap. The kit includes the Vette dual-piston calipers, of course, as well as 13-inch slotted and vented GM discs and high-performance pads. All mounting hardware is included, sans brake lines.
The nearly complete front...
The nearly complete front end setup looks good. Installing upper and lower BMR front control arms cuts 10 pounds off the front of the car, with less flex than the originals. The front springs have a 520 lb-in rate and lower the car 1 inch in addition to the 1-inch drop of the spindles. The stainless steel brake lines shown aren't part of the brake kit, but are recommended, so we installed a set.
To finish up the front end...
To finish up the front end of our subject '71, Matarese bolted on the package's front swaybar, which is cold-formed from 11/4-inch solid steel bar. BMR says this piece is four times stronger than a stock 7/8-inch bar. It bolts right on using Energy Suspension mounting bushings and endlinks.
Out back, Matarese first stripped...
Out back, Matarese first stripped off the Chevelle's stock suspension pieces, then went after the car's differential bushings. It takes a bit of extra work to drive out the old pieces and install the new polyurethane bushings, but this step is important for reducing bind in the upper control arms and making the most of the Level 4 handling package.
The frame-mount sides of the...
The frame-mount sides of the upper and lower control arms utilize spherical bearings to eliminate any binding and allow both arms to fully articulate during hard line driving. This is an aggressive setup, aimed right at track action, while the poly bushings at the other end retain some damping and street civility.
Matarese continued the suspension...
Matarese continued the suspension conversion by inserting the BMR lower control arms, which are created from 1 1/2x3-inch rectangular steel tubing, greatly minimizing the torsional flex found in the factory stamped pieces.
With both control arms and...
With both control arms and the adjustable BMR reinforcement braces in place, all those bright red pieces clearly illustrated the configuration of the Chevelle suspension. Also note that our test car's owner had installed C5 rear disc brakes to match the binders we installed, so we'll be able to bring you the scoop on this full brake conversion pieces as well.
The back end provides for...
The back end provides for a good look at the Afco double-adjustable shocks used in this kit. Both compression and rebound damping can be independently adjusted, by hand and on the car. With 40 settings at each adjuster, the flexibility is enormous. These cool aluminum dampers are also designed with a large-diameter shaft for the higher forces seen in extreme driving and road racing. The rear springs lower the car 2 inches and have a spring rate of 200 lb/in.
BMR upper rear control arms...
BMR upper rear control arms allow for the car's rear tires to be centered, as well as for on-car pinion angle adjustment. Once the tires were correctly set in the middle of the car's rearend, we measured the arms and used those figures as our starting points for setting the rear pinion angle, which was adjusted to -1 degree.
These pieces are fabbed from...
These pieces are fabbed from 1 5/8x0.120-inch steel tubing. The adjuster is a beefy 1 1/8 inches in diameter. To guarantee alignment, the upper control arms are created as one piece. The tubing section is then cut in half and the tube adjusters welded in.
The rear setup is very attractive...
The rear setup is very attractive and trick to boot. The 1-inch solid rear sway bar is clearly visible, as are the Nitto NT01 gumballs we bolted up to make the most of this setup. We employed 275/35ZR18s up front and 315/30ZR18s out back. These tires are DOT-approved competition radials, created to provide sharp steering response and accurate feedback for the weekend racer. Once we've outfitted this Chevelle with a steering setup that matches the rest of this aggressive package, we'll return to the track and get the real story of this performance-handling package.
Santa Fe Springs, CA
|Nitto Tire USA|