Snap oversteer on drift transitions

Haven’t written in a while so let’s give this a go with some setup theory. This past weekend I got to drive quite a few cars. But the two that stuck out were an E36 and E30. The E36 was an M3 model with basically no modifications outside of some springs/shocks up front. The E30 had an M3 motor and solid subframe bushings with a J stock style coilover setup. Both had issues with snap oversteer on switch back. Entries weren’t too bad to figure out after a bit (I’m used to massive angle kits).

I’ve been googling around for a while and here’s some general bullet points I’ve come across.

Z-link and Trailing arms change toe massively. Both of these cars had stock (OLD) bushings for their “RTABs”. To quote the great Mike Kojima:

…causes the car to toe out under roll. Lifting the throttle or really heeling the car into a turn will causes instability and snap oversteer.

This leads me to think that both the E30 the M3 were having toe issues due to the really old bushings that deflected on accel/side loading/decel.

The fix here is to swap to better bushings. Spherical preferred but more than likely poly.

Sway bars are exponential in their stiffness. This is really for the M3 and not the E30. Bend a ruler as far as you can. At first, it’s easy but it gets harder the more it bends. That’s basically how sway bars work. With the M3’s stock rear suspension, the sway bar was likely loading the sway bar to toss the weight the other direction when unloaded.

The fix is to stiffen up the suspension in general but mainly the rear.

Suspension settings. The E30 has one way adjustable coilovers with unknown settings. Perhaps stiffening the rear shocks will cause resistance to the snap back and make transitions simpler. E36s and E46s have the toe arms. With some added toe in, the rear won’t be as snappy.

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