Suspension settings interaction

[superfist]

I've been thinking about suspension setup recently and wanted to make a couple minor adjustments to my shock. I found this article about tire wear patterns and how they read.  My stock tire was an exact match for "Rebound too Fast" after 5500 miles on the edge tread grooves.  The center tread was gone, so it's not like I didn't get the full life of the tire.
On the FJ-09 rear shock we have preload and rebound adjustment only.  I could be wrong, but I want to think that increasing preload stiffens the spring and helps push the tire back out harder after suspension compression, so less rebound is needed.
I had my stock screw at the standard 1.5 turns out (right in the middle).  My preload was set to two clicks below maximum hardness.  Last night, I changed rebound to 2 turns from max to ease it up.  I also changed preload to 3 clicks from maximum hardness.  I didn't notice any appreciable difference in a commute ride, but I haven't pushed it in any way.
I suppose my questions is:  How does rebound and preload interact and do they affect each other? 

[pattonme]

The OE shock is a useless pile of junk. I've started a thread on that "other" FZ09 forum about comparative analysis of various rear shocks. I'll replicate it here hopefully later this week. It has f'all compression damping and the rebound even at fully closed is about the same as 1/2 way open on the K-Tech or Ohlins.
 
A constant rate spring by definition moves the same X distance for same Y force no matter how much you preload it. What preload does is alter the balance point (pushing war between gravity and spring's potential energy) provided the spring doesn't have so much preload the shock is topped out. At that point then the 'Y' has to be big enough to overcome the potential energy.
 
Some good reading:
http://www.sportrider.com/technicalities-spring-rate-and-preload
http://www.worksperformance.com/html/tpl_desc.html
 

[norcal616]

whats your weight suited up? if your around 175# I can provide my settings for you to try out... biggest improvement for me was setting the tire psi at 30 for front and back...

[koth442]

I've been thinking about suspension setup recently and wanted to make a couple minor adjustments to my shock. I found this article about tire wear patterns and how they read.  My stock tire was an exact match for "Rebound too Fast" after 5500 miles on the edge tread grooves.  The center tread was gone, so it's not like I didn't get the full life of the tire. 
....
 
I suppose my questions is:  How does rebound and preload interact and do they affect each other? 

That's a great article. Dave Moss is a knowledgeable resource and over all a great guy.  
Rebound damping allows the shock to rebound at a fixed speed regardless of pre-load. 
 
The first thing to do while fiddling with suspension is set your sag. This is suspension jargon for adjust the preload, front and rear, for you. This requires two people. This

by Dave Moss goes through the process. 

[superfist]

Thanks for the answers, everyone.
 
Thank you Pattonme for the additional reading and the spring explanation, which makes perfect sense. I was thinking in terms of my old eibach springs from my car-guy days, which were not constant rate.
 
@norcal616 - Thanks! I'm a bit heavier and certainly more than the stock spring was set for at 230 all suited up. I'm running 36 front and rear. For most of the year I was running 36/42 and I'm hearing a lot of people run lower pressures. Dropping from 42 to 36 on the rear made a huge difference, but I've been hesitant to try less.
 
@Koth442 - I was able to set my front sag a while back with the zip tie method. I'll have to revisit the rear since I messed with it. Thank you.

[norcal616]

@superfist
 
the reason I run my tires at 30/30 is because the suspension feels the best for me at 32/32psi when the tires get warmed up.... at first I tried 34/36 from 36/40 when I first got the bike home from the dealership and felt the tires feeling was riding on a knife edge when in the upper speed limits...
 
I advise caution when you start dropping tire pressures, take it easy for first few mins then start getting into normal riding habits...

[pattonme]

a couple PSI low is no big deal. measure cold, go do some decent (not start/stop) riding for 10-15 minutes. measure. If pressure difference is inside 10% you're fine. Check again after another 30 min. If the pressure keeps climbing, add 2 psi. repeat test sequence on next ride. 32/32 or 32/34 cold (~70F)should be plenty fine for 230lbs. It depends on the tire how much they warm up too. But we're talking like 3-4psi range.

[steveb]

I've been thinking about suspension setup recently and wanted to make a couple minor adjustments to my shock. I found this article about tire wear patterns and how they read.  My stock tire was an exact match for "Rebound too Fast" after 5500 miles on the edge tread grooves.  The center tread was gone, so it's not like I didn't get the full life of the tire. 
....
 
I suppose my questions is:  How does rebound and preload interact and do they affect each other? 

That's a great article. Dave Moss is a knowledgeable resource and over all a great guy.  
Rebound damping allows the shock to rebound at a fixed speed regardless of pre-load. 
 
The first thing to do while fiddling with suspension is set your sag. This is suspension jargon for adjust the preload, front and rear, for you. This requires two people. This video by Dave Moss goes through the process. 

So on a very simple & practical note, to adjust the rebound and solve the "Rebound too fast" problem, do I turn the adjustment screw clockwise or counter-clockwise?
 

[koth442]

So on a very simple & practical note, to adjust the rebound and solve the "Rebound too fast" problem, do I turn the adjustment screw clockwise or counter-clockwise?

I'm not sure. That would be a question for @pattonme

[dbeau]

I believe by turning the screw clockwise you are increasing rebound damping meaning there is more resistance for the suspension to return to a non-compressed state.
 
More damping means suspension stays compressed longer.
 
Less damping (counter-clockwise) = "Rebound too fast"
 
 
 
...if that's any less confusing haha

[pattonme]

like most things in life; lefty loosy, righty tighty. You're moving a needle in/out of an orifice.

[koth442]

Less damping (counter-clockwise) = "Rebound faster"

I changed the phrasing a little bit, otherwise I entirely agree.

[superfist]

I believe by turning the screw clockwise you are increasing rebound damping meaning there is more resistance for the suspension to return to a non-compressed state. 
More damping means suspension stays compressed longer.
 
Less damping (counter-clockwise) = "Rebound too fast"
 
 
 
...if that's any less confusing haha

Wow... this means I adjusted it a half turn in the wrong direction!  I didn't take the time to stop and think about what "too fast" meant.  Unfortunately, the owners manual is vague with the harden/soften terminology. 

[betoney]

Think of the word damping as "resistance". CCW is less resistance felt and CW is more resistance felt. Give it a try, open your shock rebound fully CCW and press the seat a few times to feel the level of resistance, now fully close the rebound CW and bounce the seat to feel a dramatic change of resistance.

[dbeau]

Less damping (counter-clockwise) = "Rebound faster" I changed the phrasing a little bit, otherwise I entirely agree.

 
I agree that sounds better but thought OP might understand his own lingo better
 
 

Wow... this means I adjusted it a half turn in the wrong direction!  I didn't take the time to stop and think about what "too fast" meant.  Unfortunately, the owners manual is vague with the harden/soften terminology.

 
So if you're seeing signs that you are "rebounding too fast" then you want to increase rebound dampening by turning the screw clockwise. This will make you rebound less fast. 
 
And yeah, the Harden/soften crap in the manual is ridiculous.