1965 Oldsmobile Cutlass - The Whole Suspen-Chilada - PHR Project Car
We Show You How To Install A Complete DSE Suspension, And Get The Most Out Of It By Fine-Tuning The Corner Weights And Alignment.
From the February, 2010 issue of Popular Hot Rodding
By Stephen Kim
Photography by Robert McGaffin
The art of engineering, unfortunately, is often a compromise dictated by the lowest common denominator. How else can you explain the existence of Macintosh computers, Jitterbug cell phones, and TiVo? The factory suspension design of a typical muscle car is no different. In retrospect, while it may seem like Detroit engineers of the '60s were absolutely clueless, they knew exactly what they were doing. With rippling big-blocks, squirmy bias-ply tires, and four-speed sticks shocking the driveline with each powershift, saving drivers from their own incompetence took precedence over trying to set new lap records at the Nürburgring. Spindles that pointed toward the wrong end of the car (forward) and front tires that gained positive camber as the suspension compressed were common tricks used to ensure loads of easy-to-manage understeer at the expense of sharp handling. Our '65 Olds Cutlass project car is no exception, and to fix what the factory intentionally messed up, we decided to install a complete Detroit Speed and Engineering front suspension system.
DSE's comprehensive Speed Kit 3 (PN 031326) includes tubular upper and lower control arms, forged drop spindles, coilovers, a splined sway bar, a quick-ratio steering box, and tie rods. When matched with the DSE four-link we installed last month, the result is a state-of-the-art suspension, designed and built to modern standards, that can fend off the most agile of autocross aggressors. Nevertheless, merely installing the parts is only half the battle. Maximizing the cornering potential of any chassis requires meticulously scaling, aligning, and corner-weighting the suspension. To help us get everything dialed in, stepping up to the plate once again is Brent Jarvis of Performance Restorations. Not only does Jarvis build Pro Touring muscle machines for a living, he's a diehard A-Body man who's been racing them since 1974. He's logged hundreds of miles on the road course and autocross behind the wheel of various A-Bodies over the decades, and drives to work every day in a big-block-powered '68 Chevelle-on R-compound tires! Here's a step-by-step outline of how to install a trick front suspension, and just as importantly, how to fine-tune the alignment and cornerweights in preparation for high-g combat.
"To properly align a car, you first need to determine the real usage of the vehicle. It should always be done with the simulated weight of the driver in the car. McGaffin intends on driving his car a lot on the street and taking it to the autocross, but doesn't want to have to switch his alignment back and forth. I've been carefully monitoring tire wear on all the street and race cars that we build, and have come up with some great all-around specs that work well on a dual-purpose car like this Olds. On a setup like this, I like to dial in 1.5 degrees of negative camber, 6.5 degrees of positive caster, and set the toe-in 1/8 inch. I like a lot of caster for a couple reasons. It gives great steering wheel feel. It prevents the car from climbing the sides of uneven roads. It counteracts negative camber on the inside tire when turning, and increases negative camber on the outside tire when turning.
"After assembling the suspension, the caster and camber were almost perfect, while the toe only needed some minor adjusting to get it close. I only needed to remove one shim to tweak the camber and set the toe, and we were done. I see lots of guys camber in the front ends over 3 degrees and run toe out at the autocross, and while it does help the cornering a bunch, it will just grind the rubber off the inside edges of the tires when driving around town. There is always some give and take when it comes to alignment, however, my '68 Chevelle tips the scales at 4,000 pounds with me in it, and I've run these same specs as in the Olds for over 6,000 miles this summer. I've road raced, autocrossed, and drag raced on a set of R-compound tires, and they still have plenty of tread left." -Brent Jarvis
"Road racing and autocrossing A-Bodies for years has revealed that you need a huge difference in front-to-rear tire pressure. A-Bodies are front-heavy and almost always have smaller tires on the front. Consequently, we preset the tire pressures at 37 psi up front and 32 psi in the rear. Autocross will always use a little less air pressure than when road racing because you don't have the same high-speed lateral g-forces on the tires. Tire pressure is one of the best adjusting points on the car when on the autocross. As a general rule of thumb, if the car is experiencing oversteer, either lower the rear pressure or raise the front pressure. If the car is experiencing understeer, either raise the rear pressure or lower the front pressure. This is assuming you have the car dialed in fairly close to ideal, and you're watching the tires closely for even wear and heat transfer across the tread." -Brent Jarvis
"After setting the alignment and tire pressure, the corner weights can be dialed in. If a car's corner weights are out of whack, you'll end up with a car that turns in one direction better than the other. That's because the tires and sway bars will be loaded unevenly. It makes a huge difference if you set up the corner weights right, and you will definitely turn faster lap times. That said, it is impossible to get any lefthand or righthand drive car perfect unless you build it from scratch with weight placement in mind. With the exception of a select few high-end sports cars, all cars are front heavy, with most of that weight biased toward the left side. The weight of the driver, steering wheel and column, steering box, brake master cylinder and booster, power steering pump, gauges, foot pedals, and sometimes the battery all add up to one big unbalanced mess. As a suspension tuner, it's our mission to get these weights as close as we can without making the car lean to one side or the other. The beauty of coilovers is that they allow you to fine-tune the corner weights, raising or lowering one corner of the car individually." -Brent Jarvis
|PROJECT OLDS THE COST SO FAR
|'65 Olds Cutlass
|DSE four-link suspension
|DSE front suspension
DSE's Speed Kits can be had...
DSE's Speed Kits can be had for both '64-67 and '68-72 GM A-Bodies. Speed Kit 1 (PN 031312; $2,315) includes upper and lower control arms, drop spindles, Koni shocks, and performance springs. Speed Kit 2 (PN 031319; $2,590) adds a mandrel-bent sway bar, and DSE coilovers. We opted for Speed Kit 3 (PN 031326; $3,982), which includes everything in Speed Kit 2, plus a quick-ratio steering box, a splined sway bar, and tie rods.
A suspension is only as good...
A suspension is only as good as its tires, so it doesn't make much sense to invest in a top-notch suspension unless the wheels and tires are upgraded as well. As purchased, Project Olds wears wimpy 235/60 radials on factory 14-inch wheels. Once the car was secured on jackstands, the 14s were dumped in favor of a set of sticky 18-inch Nitto NT01 rubber.
When battling 40-plus years...
When battling 40-plus years worth of rust, penetrating lube and an air ratchet or a big breaker bar are your friends. Since the DSE kit literally replaces every suspension component inside the wheelwell, it's easiest to remove both control arms, the spindles, and brakes as a single assembly. Jarvis says that it's imperative to use a quality spring compressor before removing tension from the springs to prevent them from flying out. After unbolting the control arms, tie rods, sway bar endlinks, shocks and brake lines, all the stock hardware drops right out.
Even those endowed with impressive...
Even those endowed with impressive biceps should seek the help of a friend to remove the control arm and spindle assembly out of the car. The stock arms are massive pieces of stamped steel that add unnecessary unsprung weight. The same applies to the factory drum brakes, which will be replaced with Baer discs in a future issue.
Once the suspension is out...
Once the suspension is out of the way, it's a great time to degrease the exposed framerails and hit it with a coat of paint. Any portion of the framerail that may have gotten scuffed up during the parts removal process will rust out very quickly, so this procedure isn't strictly for aesthetics.
DSE's upper control arms feature...
DSE's upper control arms feature two sets of offset bushings that can be flipped end-over-end to orient the bolthole in multiple directions. This changes how much the top of the spindle points rearward, resulting in a total of four different caster settings to choose from. Jarvis elected to position the upper control arms as far rearward as possible to maximize positive caster at 6.5 degrees.
The upper control arms attach...
The upper control arms attach to the frame rails using the stock 7/16-inch bolts, and a set of nyloc nuts and washers provided with the kit. Jarvis says 1.5 degrees of negative camber is ideal for street-driven A-Bodies that will also see time on the autocross. To accomplish this, he installed two adjustment shims on the front bolt and four on the rear bolt. Afterward, everything was cinched down to 50 lb-ft.
Over time, the lower control...
Over time, the lower control arm can wear grooves and burrs into their mounting brackets. Although it's not mandatory, grinding the pivot areas flat will help minimize the potential for binding once the new arms are installed. If you don't have access to an air grinder, a hand file will work just as well.
The lower control arms attach...
The lower control arms attach to the framerail using factory bolts torqued to 80 lb-ft. Unlike squeak-prone urethane, the Delrin bushings used in the DSE setup don't require any grease. Moving the arm through its range of travel confirmed that the integrated bump stops lined up to the framerail properly.
The forged 4140 steel DSE...
The forged 4140 steel DSE drop spindles are 1.5 inches taller than stock, which increases negative camber gain and lowers ride height by 2 inches. Before installing the coilovers and with the left and right sides of the suspension in place, Jarvis mocked the spindles into position to get the ideal ride height. This is when the center of the ball joints and the center of the lower control arm bushings are parallel. By placing a straightedge on top of the jackstands on each side of the car, it will be used as a reference point for the initial ride height setting in a future step once the suspension is all buttoned up.
With the spindles mocked up,...
With the spindles mocked up, Jarvis slid the coilovers into position, which feature 650 lb/in springs. The bottom crossbars attach to the lower control arms using supplied 3/8-inch bolts and nyloc nuts that torque to 35 lb-ft. Next, the shock shafts were bolted to the framerails with 5/16-inch nyloc nuts. Using a 1/2-inch box-end wrench to hold the shaft still, the nut should be tightened one turn beyond the point at which the rubber bumper on the shaft starts to compress.
Using the supplied DSE hardware,...
Using the supplied DSE hardware, the upper and lower ball joint castellated nuts were tightened to 50 and 80 lb-ft, respectively, before installing the cotter pins. The tie rods were torqued to 55 lb-ft on the spindles. While it's difficult to notice in pictures, DSE relocates the tie-rod mounting points to minimize bumpsteer.
In addition to vastly improved...
In addition to vastly improved geometry and lower mass, DSE's tubular control arms free up precious real estate inside the wheelwells. When stuffing as much contact patch underneath a car is the goal, that extra space is always a good thing.
To set the baseline ride height,...
To set the baseline ride height, Jarvis used the reference point established in an earlier step (after mocking up the spindles) to help adjust the coilovers. This required moving the springs upward approximately an inch from the bottom of the threads. Fortunately, the DSE coilovers feature a Torrington bearingwedged between the bottom of the spring and the shock collar, which makes adjustment far easier.
One of the slickest components...
One of the slickest components in DSE's kit is the heat-treated, 1.5-inch-diameter, 4130 splined front sway bar. In a conventional mandrel-bent bar, the torsional loads are distributed to the primary and swing arm sections of the sway bar. With a splined unit, torsional loads are absorbed entirely by the bar itself. This yields reduced deflection and free play for enhanced responsiveness.
Jarvis says advanced racers...
Jarvis says advanced racers can drill multiple holes into the swing arms of a splined sway bar to fine-tune the stiffness. The shorter the length of the swing arm, the stiffer the sway bar will become. For our needs, we decided to leave well enough alone.
The sway bar attaches to the...
The sway bar attaches to the frame in the stock location with a pair of billet aluminum pillow blocks that ride on Delrin bushings. Before raising the sway bar into position, the swing arms were slid onto the bar and tightened to 25 lb-ft using the supplied 3/8-inch bolts and nyloc nuts.
As was the case with Project...
As was the case with Project Olds, earlier '64-67 A-Bodies require the stock sway bar mounting holes to be enlarged and tapped to accommodate 3/8-16 bolts. DSE says that this step is not necessary on '68-72 model A-Bodies.
The DSE setup fit beautifully...
The DSE setup fit beautifully in one afternoon without any unforeseen hiccups. Despite the sway bar's substantial girth, its trim swing arm design actually increases tire clearance compared to the stock bar. Although the DSE steering box was installed at the same time as the front suspension, we plan on dedicating a separate story to it in a future issue.
After cinching down the pillow...
After cinching down the pillow blocks to 20 lb-ft using the supplied bolts and high-strength Loctite, the sway bar must be centered. To accomplish this, the distance from the end of the pillow block to the end of the sway bar should measure approximately 2.875 inches. Next, the aluminum lock collars must be tightened to 10 lb-ft using medium-strength Loctite to prevent the sway bar from moving from side to side. Finally, Jarvis attached the endlinks to the lower control arms using the supplied 1/2-inch bolts, and torqued them to 70 lb-ft.
With the suspension installation...
With the suspension installation complete, Project Olds got a big-time rolling stock upgrade with a set of 18-inch Booster wheels from Rocket Racing. They're wrapped in Nitto NT01 DOT-legal R-compound meats that measure 245/40 up front and 275/40 out back. Accurately scaling a car requires a perfectly flat surface, and Jarvis' lift was carefully installed to ensure that it's level. As long as this lift locks into position after raising or lowering a car, the scales read the same every time.
To assist in accurate corner...
To assist in accurate corner weighting, Jarvis uses digital scales from Longacre Automotive Products. After lifting the car off the rack at the suspension points using air jacks, the scales were centered under each tire and zeroed.
Before taking the initial...
Before taking the initial reading, Jarvis lowered the car down onto the scales, and jounced the suspension several times to help it settle in. Each scale is connected to a central control unit that displays the weight of each corner of the car.
Much to our surprise, the...
Much to our surprise, the heavy A-Body wasn't so heavy after all, tipping the scales at just 3,408 pounds. That's 500 pounds lighter than a new Camaro! The readings were as follows. Left-front: 1,023. Right-front: 970. Left-rear: 712. Right-rear: 703.
Adding 240 pounds of driver...
Adding 240 pounds of driver weight (McGaffin's a pretty big guy) really threw off the weight balance in the wrong direction. This changed the left-front, right-front, left-rear, and right-rear corner weights to 1,139-, 985-, 782-, and 742 pounds, respectively. Simply relocating the battery from the left-front to right-rear of the car changed those figures rather dramatically to 1,084-, 977-, 803-, and 784 pounds, respectively.
After some trial and error,...
After some trial and error, Jarvis ended up putting two additional rounds (one complete revolution of the shock adjustment collar) of tension in the right-front and left-rear. This effectively removed weight from the left-front and right-rear of the car. The final corner weights were as follows. Left-front: 1,069. Right-front: 991. Left-rear: 815. Right-rear: 773. As this example illustrates, adding tension to one corner of a car (right-front) and its diagonal opposite (left-rear) increases the weight over those corners, while reducing weight over the other ends of the car (left-front, right-rear). Overall, these collective changes shifted front/rear weight distribution percentages from 58/42 to 56/44, and left-to-right bias from 53/47 to 52/48.
To check the sway bars for...
To check the sway bars for potential binding, Jarvis disconnected and reconnected the endlinks to make sure they slid back on without any tension. Although it wasn't necessary on Project Olds, Jarvis says that there are occasions where the endlinks must be lengthened to remove preload off of the sway bar. Failure to do so will result in a sway bar that adds tension to the springs, and alters weight bias ever so slightly.