It depends on the purpose to which you intend to use the bike, and the weight you carry on the seat. The softer the springs are, the more travel you get as you accelerate and brake. As the back of the bike goes down and the front comes up the rake changes, and consequently the trail increases. If you have a lot of travel, the bike will usually turn more in the correct direction as you accelerate out of corners. On my Seeley 850, I use 80 pound inch springs on the softest settings. I have too much travel, but the bike handles extremely well. For a road bike, when you carry a pillion passenger, the handling can become very strange, if you have very soft springs.