I have a 1969 Chevelle 396 four-speed with a 3.55:1 ratio rear F41 Chevy suspension on air shocks. When I do a burnout I have bad wheel hop. I tried letting the air out of the shocks, but it still hops. I changed the upper and lower bushings to poly bushings, but I still have wheel hop.

Will it stop if I put the QA-1 traction bars on it? I’m trying to keep the car as original looking as possible and also not throw away a lot of money. Everybody says their product will stop wheel hop but nothing so far. Can you help me?

L.B.

We have several suggestions and if done correctly you should not necessarily need to buy any products to solve your problem.

A long time ago when I bought my 1966 SS396, four-speed Chevelle it was popular to stick the rear end higher in the air to give the car a radical rake. I bought a pair of air shocks and, like you, experienced severe wheel hop when launching the car hard from a dead stop.

Unlike your experience, if I lowered the air pressure to near zero, the ride height returned to the near stock position and the wheel hop disappeared. At the time, I did not know why this happened, but knew that if I wanted to run the car hard—I had to bleed all the air out of the shocks.

What I’ve since learned about suspensions is that when you raise the rear ride height, this drastically changes the angles of the rear trailing arms that locate the axle. Raising the body with the air shocks forces the rear trailing arms, especially the upper ones, in a very acute or severe angle.

If we extend a line from the two mounting points of an upper arm until the line intersects a similar imaginary line extended forward from the lower control arm mounting points, these lines will eventually intersect at a point that engineers call the instant center. As you raise the ride height of the car in the rear, this moves the instant center closer to the rear axle. As you can probably guess, this causes the wheel hop under hard acceleration.

The solution is to simply the lower the ride height.

You said you lowered the air in the air shocks but it did not help. This is likely due to a tall ride height with the rear springs. Unfortunately, with 1969 Chevelles, the rear coil springs use a pigtail on both ends to locate the spring in the spring cups on both ends, so you can’t just cut the springs to lower the car. On 1964 through ’66 Chevelles you can just cut the upper portion of the spring to lower the ride height.

You may have to purchase new rear coil springs that will lower the rear ride height. I will hazard a guess that with all the air out of your shocks, the lower control arms are not parallel with the ground. If you look at the lower control arms from the side I’m assuming the front locating point is higher than the rear pivot point. You need to shoot for a ride height where the lower control arm is parallel with the ground.

Once this is achieved, the instant center will be extended further forward, which takes some of the “shock” out of power application from a geometry standpoint. I think this will solve your wheel hop problem, especially since you have replaced all the suspension bushings.

vintage chevelle being driven on a highway
The best way to eliminate a rear wheel hop problem with a Chevelle is to lower the rear ride height so that the lower control arms are parallel with the ground. Plus, in our opinion, Chevelles just look better lower. They also handle better, too. (Image/Jeff Smith)

Frankly I would eliminate the air shocks altogether. One big problem with this idea is that when you put air in the shocks, this transfers load from the coil springs and places this load on the shocks. This is not how the rear suspension was designed. If you continue to drive with air in the shocks, this will eventually crack and break the lower shock mount because it is in single shear and was never designed to withstand the load the shocks are now carrying.

If you feel the need to adjust the ride height, it’s a smarter move to install air bags inside the coil springs and adjust the ride height that way. But just to reinforce the concept that you should not change the ride height is that anytime you raise or lower the rear ride height (besides the wheel hop problem) this also affects the caster in the front suspension.

 As you raise the rear ride height, you lose positive caster in the front alignment. Ask any front alignment specialist and he will tell you this is true. It also affects the other alignment specs, but raising the rear ride height greatly affects caster. You may notice that the steering will feel easier when you raise the rear. That’s because reducing positive caster lowers steering effort. Of course the opposite is also true that if you lower the rear ride height, this adds positive caster to the front alignment. Many things in the suspension are tied together and this is a good example of this point.

Hope this helps solve your wheel hop problem.

Keywords
Ask Away, chevelle, Ride Height, Wheel Hop
Share this Article
Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.