John Jamison via CarCraft.com: I own a '66 Pontiac Tempest with a 389 and a four-speed, and I want to improve the handling on my car. I've heard some talk about something called negative roll, but I don't know anything about it. I've heard it may have something to do with the frontend alignment. These cars are not the best-handling cars on the road (especially compared with a fourth-gen Firebird), but I think it could be better. Can you help me?
Doug Norrdin, owner Global West Suspension Systems: We get this question all the time, John. The term negative roll refers to improving the suspension geometry on most '60s and '70s cars' front suspensions to produce a better front-tire contact patch under high-cornering loads. Most factory cars from the musclecar era when pushed hard through a corner tend to understeer. This is a condition where the front wants to continue to go straight through a corner, even though the steering wheel is turned. In many cases, when the body rolls as the car turns the corner, the top of the outside loaded tire (such as the right front in a hard lefthand turn) will tend to tip outward, producing excessive positive camber. This situation lifts much of the tire tread off the pavement, reducing traction and creating that understeer or "push" condition.
It's a bit complicated to get into the specific geometry changes that Global West creates in building a negative-roll system, but in the case of your '66 Tempest, it is generated by combining a taller front spindle with a custom-designed tubular upper control arm. With these components in place, along with a higher-rate front coil spring, a good shock absorber, and a larger front antiroll bar, we can create a situation where we minimize the amount of body roll. Combined with the front geometry changes, the top of the outside loaded tire tends to tip inward slightly, creating a small amount of negative camber, which maximizes the tire contact patch to the pavement, increasing traction and improving the speed at which the car can now safely take the corner under complete control.
This negative-roll idea can be applied to many different front suspensions beyond the typical GM design. For example, our first negative-roll package was for early Mustangs, since the original OE Ford design places the spring above the upper control arm instead of between the two arms. The Ford negative-roll system requires a few minor pickup point changes to be optimal but overall still uses the same front-suspension design combined with much more durable components that won't flex under load.
For your Tempest, Global West has created a combination of parts, including the upper control arm, shocks, springs, and antiroll bars, that creates a very reliable and durable package and greatly improves handling and steering response with simple bolt-on parts. Of course, once you improve the front suspension, there are a few simple modifications that need to be made to the rear suspension in order to take maximum advantage of all the changes. But we'll save those recommendations for when we have space to talk about the rear suspension. Hope this helps you, John.
Doug Norrdin has been designing and building musclecar suspension components since 1979 an
It's All In The Ratio
Gigunseen via CarCraft.com: I'm new to the car scene, and I was thinking about putting a TH700-R4 in my '71 Cutlass because of gas prices and the fact that I have to drive it 70 miles a day. My problem is that I have 2.77 gears. I checked on a speed calculator, and it said at 67 mph I would be at about 1,600 rpm. This would be great for gas, but is it too low? I was once told that 1,500 rpm should be the lowest rpm recommended on the highway, but I'm not sure if that's true. I have a stock torque converter, and the car is running 205/65R15 tires.
Jeff Smith: Your math is right on target. The formula for determining engine cruise rpm is as follows: RPM = mph x gear ratio x 336 / tire diameter RPM = 65 x (2.77 x 0.7) x 336 / 26RPM = 1,628