The polys do transmit more harshness into the ride. My experience was that with the 235/60-15s on the Demon 318 on rubber, I could feel the front end twitch through the steering just a bit. The /6 Custom on rubber bushings and 205/60-15s do not exhibit this. When I put the polys in the Demon, the twitch disappeared. It now steers better without and twitchyness.
