Yes it will appear to stiffen. If the bike was sitting low and you adjusted the shock to a longer position to accommodate for a heavier load, it moves the swing-arm cage into the neutral position and adds that slight geometric leverage change between the pivot point and shocks. By moving the cage to where it was engineered to be, ride quality improves.

 

About a year ago, I readan article about how to tell if the shock is adjusted properly foryour weight.
You were suppose to take a measurement with the bike standing straight up and then another measurement with your weight ( or you and a passenger), while sitting on the bike.
My wife took the measurements from the rear edge of the rear fender to the pavement, while I stood the bike up and againonce I sat on it.
I don't remember what the ideal measurement was suppose to be.
When ever I decide to adjust the shock settings, I will take these measurements, with the shocks set at their softestand firmest settings and post if the bike height changes.
Tom

 

I hate to do it, but everyone's sort of right.

For a straight-rate (ie, linear) spring, the equation describing force, spring rate and travel is: F = R x L (Force == spring Rate x Length). When you increase the preload length by tightening the adjuster, you are increasing the initial force exerted by the springs (which is why it feels stiffer). It does not, however, increase the spring rate (which does not change because the spring wire diameter and coil diameter do not change ... see next paragraph). If we were to graph this, (picture the rate being a rising slope) the difference between the two adjustments would push the slope to the right but the slope itself would not change because the length changed. Where's the dang chalk board when you need one!

However, to determine "spring rate" we really only need three things ... "mean" diameter (basically outside diameter less inside diameter), free height (length of spring w/ no load), and the number of active coils (the coils in the middle not touching either end or each other). Bigass IF the spring being "preloaded" is of the progressive variety and we remove any coils from our equation because those softer coils get compressed out of service ... yes, you got it ... those "soft" coils will be used either very little or not at all and thus the active/usable spring rate will basically change once we park our big ***** in the saddle. Good Lord, this is hard to explain on here.

Isn't there a mechanical engineer here that can explain this easier by explaining jumping cheeseburgers or something?

Basically, unless someone knows the exact spring type and measurements and/or has the proper equipment to test we're all just speculating and I've done all this typing for myself so I can feel like I've not killed too many brain cells and can go damage a few more this afternoon at happy hour. HA!

 

Thanks for your detailed explanation on preloading the springs.
I think of it more as loosening the adjustment, which allows the spring to lengthen.
Now lets get deeper into these jumping cheeseburgers, that you mentionedand how they affect motorcycle dynamics. This is getting more complicated by the minute.
Tom

 

Quick question here. I have an 02 Fatboy and was looking at the shock as shown on fatbills page. I only have the large nut taht holds the actual part of the shock where you use the spanner in place. (spring I guess) There is not another nut on that part of the shock. The shaft is shaped like a nut at the end where the crossmember of the frame is but that is all. Anyone have shocks like this? I guess I can't adjust preload?

 

My shocksdon't have the extra nut, that is forward of the retainer nut, shown in the Fatbills picture.
I thoughtthey might be a bit different, because the SE Fat Boy comes from the factory lowered in the rear, so the SEmust use a different model number shock.
My owner's manual says to adjust the shocks, while the bike is on the jiffy stand. I had enough room to do this, after I cut a 1 1/16" open end wrench down, so it would be short enough to fit between the nut and the pavement.I just couldn't break the locktited nut loose. Hopefully yours will not have locktite on it.
On the 6 other bikes I have owned (non of them were a Softail, with the hidden shocks)I always set the shocks to the firmest setting and 2 of them I put progressive springs in the front forks. It seemed to me that the firmer the bike was setup, the better it handled.
Tom

 

Sorry but the fatbills is a broken link . Any alternatives?

 

This tread is 10 yrs old, thays probably why it's GONE.

 

As "Cocky" eluded too; the thread is 10 years old so any links are probably a path to nowhere.

If you're looking for the adjustment procedure it's attached.

 

I don't know what information the link contained, but if you are interested in adjusting your shock's preload, there are numerous YouTube videos available.

https://www.google.com/search?q=adju...harley+youtube