VR poor frames

I am getting poor performance in VR.

My specs:
i5 6600k @ 4.1ghz
16gb DDR4 RAM
nvidia 980ti
rf2 installed on SSD

I have turned all game settings to the lowest they can go and have rendertargetmultiplier for Steam VR set to 1.0. PP effects set to None.

Car: USF2000
Track: Nola

I am getting frame drops as when turning my head I can see jittering. This makes it unplayable. Wouldn't like to see what happens with some AI cars added too.

 

What are you Post Effects set to?

 

Oops sorry forgot to post that. None

 

Vive or Rift ?

I can run High to Med on detail settings, but have to run low to off on the rest. Just around the 90 FPS on my Vive @ GTX1080

 

Plugins that render on screen (trackmap, delta ....) disabled?

 

is it ok that the options default and max at 60hz when our headsets are in fact 90hz ????

 

I'm using a Vive and yes all plugins disabled apart from the Steam one.

 

how do we know the fps as I cant get it to show