How do fight with wheel hop?

[kummel]

I have a problem with my rekord C, when accelerating it doesnt spin the wheels but the whole rear end starts jumping, almost impossible the make quick launch.
I have quite hard springs and shocks also the rear end is quite high compared do normal.
Maybe softer springs or lowering helps it?
All ideas how do remove wheel hop are welcome

Harri

[72Rallye]

Harri,
I am by no means an expert on suspension dynamics, but I'll give it a try.
It seems that the root of your problem is the high ride height.
The rear suspension is designed to reduce squatting under acceleration.
The Rekord C has a 5-link rear axle, but for simplicity I'll pretend it has a GT or Manta axle. Imagine a lever between the end of the axle extension (the donut) and the contact patch of the tires. When you accelerate, the reaction force from the pavement pushes on the bottom of this imaginary lever in forward direction. Because the lever is not level, but has an upward slope, there is a force component that pushes up on the donut. This force counteracts the weight shift towards the rear under acceleration and as a consequence the car body stays more or less level.
In your case the car rides higher and the imaginary lever has a much steeper angle. Therefore, the upward force on the donut is much higher. It is probably so high, that it overcomes the squatting tendency and the rear of the car actually gets jacked up under acceleration.
When the tires start spinning, they loose a bit of traction and the jacking of the rear can no longer be maintained. Therefore, the rear axle suddenly folds in under car and loses more traction. Finally, the tires regain traction and the whole cycles starts all over.
I would think that stiffer springs and shocks would help, since they reduce the up and down movement, but they don't solve the principal problem.
You have to get the lever back to a shallower angle. The easiest way to do this is to put the ride height back to stock. If you don't want to do that, because you are going for the drag racer look, then you can lower the cross member that supports the donut. This will reduce the lever angle as well.
Of course on a Rekord C you have to find some other means to do this.
Wheel hop is normally observed on cars with leaf springs. They wind up under acceleration and snap back when the tires start slipping. This can be avoided by traction bars that prevent the rear axle from rotating. I don't think traction bars would help on your coil spring axle, since axle rotation isn't the problem.
Thomas