Sunshine on leaf

Hop, squat, lift, wrap and other issues in leaf spring, live axle rear suspension

- MARK ORTIZ

Q I am building a ‘somewhat vintage reproduction’ track car for the Barber Road Course. It would be best compared to the Camaros and Mustangs that raced the Trans-Am circuit in 1969-’70.

The brake package and front steering / suspension is modern and very robust. However, the rear suspension is slidermounted, 200lb/in, Chrysler-style stacked leaf springs with a Panhard (though I plan to try a composite monoleaf at some point in time).

The sliders on the rear of the springs will give me up / down and / or angular adjustment, and are within the rules. Bird cages / links and floating calipers seem unnecessarily complicated to me and are more than I want to deal with, or package on this car.

I know there are probably better ways to skin the cat, but I have always had a fascination with leaf springs and the tuning thereof (ie changing wheel rate / linearity etc. by changing mount geometry and the possibility of ‘tuning’ wheel rates without changing the springs).

I have been warned that brake hop could be an issue (?) and so, having talked to the engineers at Landrum and Hypercoil, have included brackets for ‘anti-hop’ shocks. These will allow for two shocks per rear assembly for up / down and either one or two, probably 90/10s, to ‘anti’ the brake torque.

Some guys swear a leaf set-up will induce rear-end steer ie the more loaded side of the car will have a longer wheelbase than the less loaded side. Supposedly, nonparallel leaf springs enhance this effect.

Although, I would add that Bobby Allison had the track record at Huntsville Speedway (asphalt) from about 1975 to 1985 with a quarter elliptic leaf spring set-up, and everyone said that was a rear-end steer car.