Simple question, looking for an answer. I've seen that they are adjustable but wondering how to do it. I often bottom out over damn railroad tracks while riding 2 up. Bike is a 2012 FXDC

 

Your shocks should have 5 positions.

 

Sorry mate. You can't stiffen a spring by compressing it, unless it is progressively wound. And then only when coils bind. I know, everyone says stiffen, but they are just plain wrong.

All adjusting the preload does is raise or lower the bike. If you need it stiffer, change springs.

 

I would not usually comment on a OEM suspension post but I guess I must. Too much wrong info on the internet on these chat site.
Adjusting pre-load by shortening/compressing the spring increases the force the spring exerts. Two types of springs out there, progressively & linear wound.

*A progressive spring only should have enough pre-load to keep it from rattling around, usually 3 mm. The progressive spring is chosen for the job you want it to do. It really is not adjustable, you just get a different spring.

* A linear wound spring is pre-load adjustable which is the case of that ramp system OEM shock. Don't expect anything but somewhat of a damper that is worn out in less than 10K miles. Doubt what I say than bring it to me an my next show and we will put it on our shock Dyno.

Here are exact measurements we took before we ever offered shocks for sale.
Comparison of one spring to another. (X) V/S (Y) value and is measured in Newtons.


23nm / 25nm
10mm preload on 23nm = 8mm preload on 25nm
15mm preload on 23nm = 13mm preload on 25nm
20mm preload on 23nm = 18mm preload on 25nm
25mm preload on 23nm = 22mm preload on 25nm

25nm / 27nm
10mm preload on 25nm = 8mm preload on 27nm
15mm preload on 25nm = 13mm preload on 27nm
20mm preload on 25nm = 18mm preload on 27nm
25mm preload on 25nm = 22mm preload on 27nm

23nm / 27nm
10mm preload on 23nm = 6mm preload on 27nm
15mm preload on 23nm = 12mm preload on 27nm
20mm preload on 23nm = 17mm preload on 27nm
25mm preload on 23nm = 21mm preload on 27nm



lbf/in to N/mm Chart
100 = 17.5
120 = 21
130 = 22.75
140 = 24.5
150 = 26.25
160 = 28
170 = 29.75
180 = 31.5
190 = 33.25


This means that for every inch the spring compresses the spring exerts (I will keep it in terms that the USA is familiar with) the spring exerts (X) foot pounds or N/mm. A 100 foot pound spring that is compressed 2 inches exerts 200 foot pounds or force, 3" = 300 foot pounds and so on.


A ramp system that is on your (OP) "OEM spring on a stick" compresses the spring to add spring pre-load and in turn your spring exerts more force than without adding spring pre-load because it starts off with more force.
A simple manual spring testing/measuring machine




In no way can you try to emulate a real shock set up method because the performance of an OEM shock absorber is no where the same and does not have the power to sustain movement through the shock alone.

 

I'm no physics major here but I would have to disagree with this. I understand what your saying that the springs don't actually get stiffer when you adjust the pre-load however, when you raise or lower the setting on the shock you are effectively increasing or decreasing the length that the spring and compress and decompress. Therefore, you are creating the feeling that the spring is stiffer or less stiff.

I think that was the OP's question. And... With that said the second poster seemed you have summed it up.

 

Replace them is the answer. Stock shocks are just horrible.

 

Exactly..

Thanks for addressing this common misconception so thoroughly...

 

Diet?

 

i went to tourign shocks over the stock shocks durign last winters build up, and i just finished doign a full air ride. the stock shocks sucked, the tourign shocks sucked but nto as much. the air ride is worlds better then both of them. obviously its a matter of personal tastes and budgets, i would recomend replacign them completly

 

On the bottom of your shocks you will see a bunch of holes. Use a spanner wrench.or i have carefully run a small screwdriver threw two of the holes also while grabbing the the bottom of the shock with you other hand and twist the shock.
Make sure you are turning in the correct way. Example if you on setting #1 turn it the correct way to setting #2.

On the link below, look at the the bottom of the shock you will see the different notches on the shock. Yours is just like that only it has a chrome cover over that part.
http://www.burlybrand.com/slammershocks/index.aspx

Take a flashlight and look up under the chrome cover on the bottom of the shock. You will see the different settings.

By adjusting the shocks, you can make the ride stiffer. It will help with your problem.