Unpleasant tramlining coming from the rear

[CB72]

I've been experiencing quite unpleasant tramlining on my NSX.
It comes from the rear of the car when I drive on gutted roads and highways.
I had to really drive very slowly ( 100 km/h) on the highway under very heavy rain as the feeling was quite scary.
It has happened with both my Pirelli P Zero Corsa's and my Avon ZZR's semi-slick tires.
Sizes are the same at 265/35*18.
I wonder if it's due more to the toe or the camber setting?
I read that 1°of camber induces .1° of toe equivalent to .8 mm that adds of course to the measured toe setting!
My specs are:
Camber L:-2°54' R: -2°36'
Toe (in) L:0°21' R: 0°25'
The toe in corresponds to respectively : 2.8 and 3.3 mm on an 18" wheel.
I guess I should go to half those values i.e. a total toe in of 3mm versus the 6 mm currently?

 

[jwmelvin]

That’s odd as I’ve always understood rear toe as a stabilizing effect. But you said heavy rain; does this occur in the dry too? With semi-slick tires, one wouldn’t expect much stability in heavy rain.

 

[CB72]

That’s odd as I’ve always understood rear toe as a stabilizing effect. But you said heavy rain; does this occur in the dry too? With semi-slick tires, one wouldn’t expect much stability in heavy rain.

That's most probably true but when there is a large mismatch in grip on eitheir side of the car, the wheel with the most grip must push the car in the direction it's headed I suppose.
On a motorbike, if the rear wheel is not well aligned with the front, the front steering angle must counteract the turning motion induced from the rear.
I wonder to what extent this was not the cause of a few total loss accidents that happened in a straight line to at least three NSX owners I know personally?
Maybe that when Honda changed the spec on the rear toe in from 6 to 3 mm it wasn't only related to tire wear...