Dear forum member Hoghead,
Great post! Im going to make this brief, but you can write or call, anytime you wish.
Q: What is a spring? A :A spring is an energy storage device. Ergo: A smaller spring will absord and dissipate less energy.
Let us clarify what we mean. In as far as a RSU fork with an outdated damper "turkey baster tubes (1970) the correct spring tate witj Longer spings that are dual rate (not to be confused with progressive) and shorter pre load tubes = Plusher Ride.
RSU forks with less spring and more spacer tubes will yield a shorter stroke. A shorter stroke means you are going to absord less energy and lose suspension travel.
If Im riding my "sport bike" with approx 17" wheels. @ 60 miles per hour and hit a 1" high right angle bump; How many inches do you suppose the Forks witll go up and down in 1 second? Or the time to recover from the bump?
When you do that math or stick a Go Pro to your frame and tape the Fork on VDO and play it back in slow motion.... You will have your answer.
As far as " Modern Bikes" Im not quite sure what you mean..... If you mean RSD forks that employ Stacked Valves for Rebound and compression dampening, as well as cartrdges that are open, closed or pressureized with Nitrogen Gas.......????
Then its a whole other design and ball game..... Typically, you are right! the springs are smaller but a larger diameter...they are also matched to the manufacturers cartridges or Forks and come in many spring rates and are only Single or Linera rates.
Let me wrap this post with this info: As far as any springs used in motorcycles for the last 40 years, There are 3 types: Linear, Dual and Progressive
Linear in you machine is for racing or strest. Yes you will have great feedback and handeling. Im too old now and I dont want to feel anything.
Dual Rate absorbs the roads inconsistancies and is not used for racing....or I would not recommend it. Its great for touring and carving up the mountains.
A progressive rate is almost never used up front as load calculations are difficult to calculaye sag and squat the bike. Again, many people and advertisers use this "Buzz word" for DUAL Rate springs.
Last note: If your happy with Sonic, Cannon, Viking, Eibach, Ohlins, or anyother manufacturer .... Stay with them since you know the quality of the Spring, the spring type, rate and stroke that you like.
Personally: I like a Ohlins because they are right in our back yard .... but they dont make every shock nor spring for every motorcycle.
Enjoy the Ride and be seen!