Softail preload rear shock adjustment
6th Gear
Joined: Aug 2007
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From:
RE: Softail preload rear shock adjustment
ORIGINAL: STUNU
all i know is that when u turn in it makes the shock and the ride stiffer. (period)
all i know is that when u turn in it makes the shock and the ride stiffer. (period)
Elite HDF Member
Joined: Sep 2006
Posts: 3,718
Likes: 11
From: Punta Gorda,FL
RE: Softail preload rear shock adjustment
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
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
Advanced
Joined: Sep 2007
Posts: 75
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From:
RE: Softail preload rear shock adjustment
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!
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!
Elite HDF Member
Joined: Sep 2006
Posts: 3,718
Likes: 11
From: Punta Gorda,FL
RE: Softail preload rear shock adjustment
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
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
Banned
Joined: Jan 2006
Posts: 17,265
Likes: 21
From: Los Angeles, CA
RE: Softail preload rear shock adjustment
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?
Elite HDF Member
Joined: Sep 2006
Posts: 3,718
Likes: 11
From: Punta Gorda,FL
RE: Softail preload rear shock adjustment
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
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
Stellar HDF Member
Joined: Jun 2014
Posts: 2,062
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From: Midlands of SC
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Joined: Jul 2012
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From: Omaha
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.
If you're looking for the adjustment procedure it's attached.
Last edited by Bluraven; May 7, 2017 at 07:27 AM.
Seasoned HDF Member
Joined: Oct 2012
Posts: 13,104
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From: Texas, USA
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
https://www.google.com/search?q=adju...harley+youtube