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Bite Me.
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Discussion Starter · #1 · (Edited)
At Tscheezy's urging, I ran some data on the Linkage V2 program- www.angelfire.com/jazz/linkage/ for the following Turner frames - 5 Spot, XCE, Burner and O2. There are also charts for the Burner with the XR rockers. I have the O2 with XR also but I'm at my upload limit.
To understand the charts, the blue line represents the compression of the rear shock as the rear wheel travels vertically. The red line shows the progression rate of the suspension as it compresses the shock. If it moves up from left to right, you have a rising rate suspension. Horizontal line means a linear rate, and a line falling from right to left means a falling rate (duh).
Rising rates mean the suspension must push harder and apply proportionally more force to the shock as it moves through its stroke to get the same amount of travel (the rate of energy input required to compress the shock rises throughout the stroke). Linear suspensions are just that, consistent through the stroke - a 500lb spring needs 500lbs to compress it one inch. To compress it another inch, you add another 500lbs (1,000lbs to compress 2 inches, etc). It's a linear progression. Falling rate suspensions increase the amount of energy applied to the shock as it moves through the stroke (less energy input needed to compress the shock the same distance).
Falling rate suspensions work better with rising rate (progressive) air shocks since these shocks need more energy/force to compress them the farther into the travel you go. Generally speaking, rising rate or linear suspensions work well with coil (linear) shocks since these designs prevent the coil from over-compressing and blowing through its travel at the end of the stroke. l Thought you Homers might like to see this information for selecting shocks, discussions around the water cooler, or after a few too many beers. :D
 

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Bite Me.
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Discussion Starter · #2 ·
Here's the O2 with XR rockers

This is the chart for the O2 with XR rockers. Interestingly enough it's virtually identical to the Burner with the XRs :rolleyes:
 

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Now I know why I ordered XR rockers for my Burner

Nice work Cutthroat! good insights into what's happening with these suspension designs.
There's bound to be discussion on the slope of the curves and how this changes - vis-a-vis progressive suspension... but what strikes me is the different absoolute levels of gradient between the designs...
5-Spot is plush with (relatively low) gradient levels between .33 and .37
The standard Burner is firmer, with gradients between .43 and .45 ...
What I like is to see is that the XR Burner is more plush than the Standard Burner with gradients .36 to .39 - not quite as plush as the 5-Spot but a change in the right direction for my riding preferences.
- I know why I got the 4-inch rockers. - Now it's time to install these things and take them for a spin and test the theory ...

Thanks for your analysis.
 

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Help me understand these charts...

Gentledudes,

First, I want to thank cutthroat for his fine work in publishing this information. I was just about to ask the group if anyone had this data, and it magically appears before I get to the post. What a great friggin board this is!

I have been been noodling on these charts for a few hours (business travel, too much time hanging around in airports and hotel rooms...no dicking around at work for me, no sir.) I am having troubling understanding these charts, or maybe the accompanying explanation. Let me try to explain my hang-up.

In all of the charts, the blue line is said to represent the amount of compression relative to the amount of axle travel. And, in all of the charts (on both this thread and the Horst Link thread that got us started) the blue line is straight. I interpret this to mean that at the beginning of the travel, 1mm of axle travel gives me the same amount of shock compression as 1mm of travel anywhere else in its range of travel.

If the blue line is indeed mm of compression per mm of travel, and is straight, then all of the set-ups we have seen would have linear rates. Dusting off some of my high school math (and this is going back a long way), the rate of the travel would be the first derivative of the travel curve itself, which in this case would be a flat line (the slope of the travel curve).

What would make more sense to me is a travel curve that looks like the red curve. This would show that the amount of compression you get (per mm of axle travel) diminishes late in the stroke...a falling rate. And since the curves look to the naked eye like sections of a classic parabola, the first derivative (the "rate of change" could indeed be a straight line (or close too it).

But the curves are labeled just the opposite...and in the Burner and XCE plots the curves arch back down...so they could not represent the actual mm of travel.

So what am I missing here?

Thanks in advance,

D-man
 

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Bite Me.
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Discussion Starter · #6 ·
Oh God!

Now I've started it - the word parabola was bound to crop into this discussion sometime - gotta go now :D . Dad Man - a couple of caveats are in order here - First, these charts are as good as I could get using Turner's spec diagrams, others have worked from actual photos and informed me that their curves look slightly different - GIGO (garbage in garbage out) as they say. So please don't look at these as absolutes, just general parameters of the suspension rates. Second - I'm no mathematician (that's why I got into law). Here's the direct quote from Gergely Kovacs, the program designer as to what the charts depict:
"Geometry: The thick blue one: shows how much the rear shock compresses with the vertical travel of the rear wheel. Thin red one: show the progressivity of the previous. If it goes upwards from left to right, it's a rising rate design, a horizontal line means linear compression, otherwise it's a falling rate." My limited understanding of how the graphs work is that you need the blue line to be straight to understand, based on the red line, how the suspension behaves to produce that linear compression of the shock. In essence, the blue line is straight on all the graphs because it forms the baseline for determining how that particular suspension will behave in producing a linear compression of the shock's travel. By keeping the blue line the constant (assuming you're comparing a 90mm travel to another 90mm travel, etc) you can effectively compare two different suspension designs to see how they behave to produce the same compression of the shock.
 

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Dad Man Walking said:
Gentledudes,

First, I want to thank cutthroat for his fine work in publishing this information. I was just about to ask the group if anyone had this data, and it magically appears before I get to the post. What a great friggin board this is!

I have been been noodling on these charts for a few hours (business travel, too much time hanging around in airports and hotel rooms...no dicking around at work for me, no sir.) I am having troubling understanding these charts, or maybe the accompanying explanation. Let me try to explain my hang-up.

In all of the charts, the blue line is said to represent the amount of compression relative to the amount of axle travel. And, in all of the charts (on both this thread and the Horst Link thread that got us started) the blue line is straight. I interpret this to mean that at the beginning of the travel, 1mm of axle travel gives me the same amount of shock compression as 1mm of travel anywhere else in its range of travel.

If the blue line is indeed mm of compression per mm of travel, and is straight, then all of the set-ups we have seen would have linear rates. Dusting off some of my high school math (and this is going back a long way), the rate of the travel would be the first derivative of the travel curve itself, which in this case would be a flat line (the slope of the travel curve).

What would make more sense to me is a travel curve that looks like the red curve. This would show that the amount of compression you get (per mm of axle travel) diminishes late in the stroke...a falling rate. And since the curves look to the naked eye like sections of a classic parabola, the first derivative (the "rate of change" could indeed be a straight line (or close too it).

But the curves are labeled just the opposite...and in the Burner and XCE plots the curves arch back down...so they could not represent the actual mm of travel.

So what am I missing here?

Thanks in advance,

D-man
The blue lines aren't exactly straight, it's just that the scale makes it look as if they are. Look at the difference in the increments of the scales on the left and right. If the red line used the same scale as the blue line, it would look completely flat.

The Burner is digressive rising rate (the rate at which the suspension rate is increasing decreases as you move through the travel). The XCE is digressive rising rate that turns to falling rate near the end of travel.

The problem is that the suspension rate on the Turner bikes is relatively linear. You need a bike with a rate that's a bit less linear to really see it on the blue line. Here is a Blur:

 

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I don't do PC
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Great info cutthroat, do you guys mind me asking a non Turner question?, can't get this kind of info on other boards.

I ride a FXR and I'm seriously considering an air shock as a backup to the curnutt and to lose a little weight, plan on doing a few races. I know the FXR is a falling rate design but it works great with the curnutt(coil)so will it work with a more progressive air shock? and what about the RP3 which in theory would not work well with the 5 Spot, but does. Is the RP3 more linear than other air shocks and would it work on a falling rate design? I haven't talked to Foes yet but I know they spec the Fox AVA as a shock option on the bike. Thanks for any input.
 

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Backmarker said:
The blue lines aren't exactly straight, it's just that the scale makes it look as if they are. Look at the difference in the increments of the scales on the left and right. If the red line used the same scale as the blue line, it would look completely flat.
Yes, the different scales on the left and right are very misleading. It gets worse when the right hand axis use a different scale from one plot to the next. One bike's red line may only vary by 0.02 (XCE) throughout it's plot but have a huge hump to it because the vertical axis is in such fine increments while another may vary by 0.05 (Spot, XR) and "appear" to have the same magnitude arc because the right axis uses larger increments. And I think we have seen how a slight deviation in defining the pivot locations can have a very large effect on the ultimate curves.

In the end it is just an academic circle-jerk. I have 3 bikes with wildly different rate curves and they all kick butt.
 

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Again, thanks for crunching the numbers and posting the curves. I have had an intuitive feel for the qualities expressed here and want to understand better by putting some numbers to them. I am reading the accompanying site you posted yesterday, trying to get the background. I wish our Instron here at work had a load cell larger than 225 lbs, I'd rig up my frame to get some empirical curves.
One thing that may be confusing in your description is the red line describes a linear rate if it is linear (a straight line), not if it is "horizontal". Maybe I need to study it more, my understanding is on a "rising rate". Anyway, thanks a bunch!
 

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Bite Me.
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Discussion Starter · #12 ·
Ellsworth Truth Chart

Bikezilla said:
This is great stuff folks. Just the thing to ward off norideitis/cabin fever!
Thanks cutthroat and everyone for all the work.
I tried to run the chart for an Ellsworth Truth, but in the middle of the program the seat tube broke! :eek:
 

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Thanks, now I have to clean my keyboard of soda. I'll paypal you 5 bucks if you post that over on the Ellsworth board and send a copy to Tony!!!!!!!!!!!!!!!! :D :D :D :D :D I bet that would be at least 2 pages of responses, 1.5 of Osaklo and a few other chiming in here and there.
 

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Brilliant!!!!!!

cutthroat said:
I tried to run the chart for an Ellsworth Truth, but in the middle of the program the seat tube broke! :eek:
OMG. Coffee everywhere here. Your post represents a serious choking hazard. You really should post a warning and a disclaimer.

Brilliant!!!!!!
 

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Bite Me.
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Discussion Starter · #18 ·
You owe me.

CDMC said:
Thanks, now I have to clean my keyboard of soda. I'll paypal you 5 bucks if you post that over on the Ellsworth board and send a copy to Tony!!!!!!!!!!!!!!!! :D :D :D :D :D I bet that would be at least 2 pages of responses, 1.5 of Osaklo and a few other chiming in here and there.
OK - CDC the deed is done! The Ellsworth board has just been posted. I'll need my flameproof suit now.
 

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.....meanwhile, in the Turner Forum...

viewership in the Turner forum drops from 117 to 0 as all of the Turner homers go over to the Ellsworth board to watch them flame Cutthroat and stab him with a broken seat-tube.

Cutthroat, thanks for taking one for the team :)

Too much fun! Now, back to the Ellsworth forum (beer in hand, and five more in staging)...
 
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