ReStackor 2019 KX450 ReStackor Analysis

[Clicked]

What do the modifications "feel like"

To hit the baseline tuning targets the stock damping needs rebound softened to hit the zeta= 0.7 target and compression damping needs to be stiffened to hit the rebound/compression ratio target of 3.25:1. The mods proposed above uses stiffer compression damping and a softer spring rate to keep the final setup from being too stiff. What do those mods "feel like"?

I ran a test case with the stock damping and 0.525 kg/mm spring rate; compared to the proposed modified setup with softer 0.47 kg/mm springs. Both cases hit the same bump; producing the same launch velocity of 4 m/s and are driven into the same 220 mm wheel stroke. So both setups have a similar “stiffness” in terms of the bump driving both setups into the same 220 mm wheel stroke.

Dropping rebound to hit the zeta= 0.7 target gives a faster peak rebound speed and that gets the suspension back to race sag faster, about 25% faster. Faster return keeps the suspension from packing so it should perform better in braking bumps. The softer rebound damping allows the suspension to overshoot race sag by about 5 mm. That is a feature. Overshoot combined with stiffer low speed compression damping keeps the suspension riding “high in the stroke”.

The modified setup with a 0.47 kg/mm spring rate uses stiffer compression damping to control bottoming. That results in a higher bump impact force putting about 1.8 g’s on the rider compared to 1.5 g for the stock setup. Absorbing more energy at the start of the bump makes the peak g-force at the end of the stroke lower. The modified setup produces a peak g-force of 4.8 g at end of stroke compared to 5.1 g’s for the stock setup. Lower peak g-force makes the setup ride “plusher”.

25% faster return to race sag and a 0.3 g reduction in peak force. That is the difference between the setups, but is it enough that you can “feel” it?

There is no way to know without test riding it for yourself.

Any test rides with the stock or 0.525 kg/mm springs?

Edited May 22, 2020 by Clicked

[Johnny_On_The_Spot]

On 5/22/2020 at 11:03 AM, Clicked said:

What do the modifications "feel like"

To hit the baseline tuning targets the stock damping needs rebound softened to hit the zeta= 0.7 target and compression damping needs to be stiffened to hit the rebound/compression ratio target of 3.25:1. The mods proposed above uses stiffer compression damping and a softer spring rate to keep the final setup from being too stiff. What do those mods "feel like"?

I ran a test case with the stock damping and 0.525 kg/mm spring rate; compared to the proposed modified setup with softer 0.47 kg/mm springs. Both cases hit the same bump; producing the same launch velocity of 4 m/s and are driven into the same 220 mm wheel stroke. So both setups have a similar “stiffness” in terms of the bump driving both setups into the same 220 mm wheel stroke.

Dropping rebound to hit the zeta= 0.7 target gives a faster peak rebound speed and that gets the suspension back to race sag faster, about 25% faster. Faster return keeps the suspension from packing so it should perform better in braking bumps. The softer rebound damping allows the suspension to overshoot race sag by about 5 mm. That is a feature. Overshoot combined with stiffer low speed compression damping keeps the suspension riding “high in the stroke”.

The modified setup with a 0.47 kg/mm spring rate uses stiffer compression damping to control bottoming. That results in a higher bump impact force putting about 1.8 g’s on the rider compared to 1.5 g for the stock setup. Absorbing more energy at the start of the bump makes the peak g-force at the end of the stroke lower. The modified setup produces a peak g-force of 4.8 g at end of stroke compared to 5.1 g’s for the stock setup. Lower peak g-force makes the setup ride “plusher”.

25% faster return to race sag and a 0.3 g reduction in peak force. That is the difference between the setups, but is it enough that you can “feel” it?

There is no way to know without test riding it for yourself.

Any test rides with the stock or 0.525 kg/mm springs?

You really went above and beyond here!  

As far as a ride report - I actually only rode the stock spring/valving once (Aug 2018) . It was at a fast track with some small jumps.  My biggest complaint was heavy pitching during braking/accelerating which makes sense with how underdamped the compression is. There wasn't anything large enough to bottom the bike on at this track so I don't have a comment on that, but I'd expect it would be pretty easy to do! I then installed the 0.525 kg/mm front springs (one stock .50 and one .54 spring), and a 5.9 kg/mm rear spring and rode the bike that way for the remainder of the season.  

In spring 2019 I actually revalved using a reputable tuner who sold me a stack which I installed myself. I rode that all last year and generally felt good except for some packing in braking bumps and I notice some traction issues when the track is dry and choppy. I'm mainly looking for more comfort on corner exit on rear shock, less diving from front and "bucking" through braking bumps without compromising bottoming too much. I also have a "harsh" spot in the forks that I notice on slap-down landings that I suspect is cavitation, but I'm not really sure.

I started response tuning based on your guidelines:

1. Stroke avg rebound zeta to 0.707 over entire suspension travel, some roll-off at low speed OK.
2. Low speed damping ratio at 0.8:1
3. Mid/high speed damping at 3.25:1 for "middle of the road" fast/plush balance
4. Wheel bottoming force: equal peak spring force to peak damping force
5. Chassis bottoming force: Compression peak damping force ~70% of rebound damping force

Rebound Zeta Tuning

I dropped the spring rate down to 0.51 kg/mm based on your suggestion that I am oversprung (and adjusted sag and preload to maintain rider weight). Here are my results from my rebound tuning. I'm pretty happy with how that looks, but I'm surprised I had to soften the rebound stack so much! I ended up opening the d.leak to 1.25 mm and made some large modifications to the stack. I also set my clicker setting to 7 so that it is in the middle of the linear adjustable region of the needle.

Now that the Rebound Zeta is nearly constant at 0.70 over the entire suspension stroke I'm going to move on to the compression tuning.

Damping Ratio

I played with R/C a bit and am struggling to find a setting where I can get the low-speed damping stiff enough with anything more than 2 clicks out on the needle. Any tips on this? I know we went thought the LSV and it looks like it is disabled due to float. Do you think I should pull the float shim and re-enable it? Is it possible to modify the ReStackor software to add an LSV model to the software so the valves can be analyzed simultaneously? 

Side note - I can see how you can get yourself into trouble quickly with cavitation if you make the mid-valve overly stiff!

[Clicked]

Low speed r/c damping ratio

Something you may have overlooked is the mid-valve check spring effect on low speed damping. Check spring stiffness varies widely from bike-to-bike and makes a difference in low speed compression damping force.

A check spring stiffness of 0.1 kg/mm with a preload of 5 mm should get you in the ballpark of the target 0.8:1 rebound/compression damping ratio. The mid-valve check spring is modeled in Shim ReStackor using the HSC inputs. If your check spring is lighter than 0.1 kg/mm, and you can’t get the needed damping out of the base valve shim stack, you will have to tune the LSV.

LSV shim stack tuning

You can use Shim ReStackor to tune LSV damping, but it is a PITA. The first step is figure out how much additional compression damping you need to hit the 0.8:1 rebound/compression ratio target. For the example below an additional 1.5 lbf of compression damping is needed at 0.08 m/sec.

The LSV damping is modeled in a separate Shim ReStackor spreadsheet with the BVc valve geometry setup to match the LSV port configuration. LSV valves typically have a continuous perimeter port so the w.port dimension needs to be setup like a compression adjuster valve. Clicker bleed is set to zero, since the only bleed is through the LSV shim stack, and the LSV port throat diameter (d.thrt) is set to match the clicker throat flow area at the clicker setting you are running. The clicker throat flow area is shown on the bv_ReStackor output tab in column D (A.clk) with zero force on the shim stack.

After setting up the LSV spreadsheet, the process is hack around on the LSV shim stack configuration so the damping force at 0.08 m/sec increases by 1.5 lbf compared to running the LSV with no shim stack. With no shim stack the valve port throat (set to the clicker area) meters the flow.

Mid-Valve check spring and LSV do the same thing

The kx450 base valve clicker throat area is around 1.6 mm2 based on Johnny’s needle geometry at 7 clicks. A 20mm LSV valve matches that flow area with a shim lift of 0.000,2 inches. That makes the LSV operate like a check valve that increases compression damping force at low speed and blows-off as soon as the LSV shim stack cracks open. A check spring on the mid-valve operates the same way and can probably be setup to achieve the same effect.

[Johnny_On_The_Spot]

19 hours ago, Clicked said:

Low speed r/c damping ratio

Something you may have overlooked is the mid-valve check spring effect on low speed damping. Check spring stiffness varies widely from bike-to-bike and makes a difference in low speed compression damping force.

A check spring stiffness of 0.1 kg/mm with a preload of 5 mm should get you in the ballpark of the target 0.8:1 rebound/compression damping ratio. The mid-valve check spring is modeled in Shim ReStackor using the HSC inputs. If your check spring is lighter than 0.1 kg/mm, and you can’t get the needed damping out of the base valve shim stack, you will have to tune the LSV.

LSV shim stack tuning

You can use Shim ReStackor to tune LSV damping, but it is a PITA. The first step is figure out how much additional compression damping you need to hit the 0.8:1 rebound/compression ratio target. For the example below an additional 1.5 lbf of compression damping is needed at 0.08 m/sec.

The LSV damping is modeled in a separate Shim ReStackor spreadsheet with the BVc valve geometry setup to match the LSV port configuration. LSV valves typically have a continuous perimeter port so the w.port dimension needs to be setup like a compression adjuster valve. Clicker bleed is set to zero, since the only bleed is through the LSV shim stack, and the LSV port throat diameter (d.thrt) is set to match the clicker throat flow area at the clicker setting you are running. The clicker throat flow area is shown on the bv_ReStackor output tab in column D (A.clk) with zero force on the shim stack.

After setting up the LSV spreadsheet, the process is hack around on the LSV shim stack configuration so the damping force at 0.08 m/sec increases by 1.5 lbf compared to running the LSV with no shim stack. With no shim stack the valve port throat (set to the clicker area) meters the flow.

Mid-Valve check spring and LSV do the same thing

The kx450 base valve clicker throat area is around 1.6 mm2 based on Johnny’s needle geometry at 7 clicks. A 20mm LSV valve matches that flow area with a shim lift of 0.000,2 inches. That makes the LSV operate like a check valve that increases compression damping force at low speed and blows-off as soon as the LSV shim stack cracks open. A check spring on the mid-valve operates the same way and can probably be setup to achieve the same effect.

Interesting point. I assumed the check spring was so light that it could be ignored but that makes sense at low fork velocities that it provides additional damping. 

On this fork the mid-valve check spring is 0.04 kg/mm and there is only 0.75 mm available to increase preload before coil-bind, so I would have to go to a custom piano-wire spring or something. I checked a few sources and it doesn't seem like something I'll be able to buy off the shelf.

How did you determine that 1.5 lbf additional damping is required? I assumed it was a ratio of damping coefficient, but after manually trying to solve for R/C based on the Resp_Dat output I can't seem to get numbers that match.

Assuming I have to use the LSV: I already have the LSV modeled with a lookup for clicker to throat settings. Since the restriction is upstream of the ports, do I enter the d.thrt as clicker area, and N.thrt as 1, or do I split the flow area into 4 equivalent diameters with N.thrt equal to 4.  I wasn't clear on how the restriction would be handled with N.thrt =1 or if wetted perimeter losses are factored in at all. 

I did a test-case where I simply took the bleed shim out and it does seem that the stack is extremely soft (like a check valve, like you said) so blows open as soon as pressure is applied.

Do you see any possibility of a new version of Restackor including the LSV in the analysis to make it less cumbersome to work with? I was thinking a simple map lookup of shim area vs clicker position vs bleed pressure or something could be a way to do it without a huge tear up on the code.  I took a crack at mapping something like this out for the stock LSV here.

I uploaded the LSV model here: https://drive.google.com/drive/folders/1sisyrsdUrDYW8Krthf_33isTrEC_VNX9?usp=sharing 

 

 

 

[Johnny_On_The_Spot]

For now I'm going to continue ahead with the assumption that I can't source a stiffer MVc check spring and will instead have to use the LSV to tune the low-speed comp.  I added the 0.04 kg/mm spring to the model to capture the low-speed contribution to compression damping.

Clicked shared the LSV configuration in his post above. I unfortunately didn't take pictures of the actual hardware when I had it apart for measurements, so I'll just put up the valve geometry on my sketch

I used VLOOKUP in excel to lookup the d.thrt diameter based on the clicker flow area. This lets me quickly adjust the valve to a new clicker setting. 

ran the LSV model with my clicker setting at 8, and a 13 1.0 bleed shim to solve for the damping of the valve without any shims stack. This is how the model is treating my needle bleed in the main mid-valve sheet. I then set this to my "baseline" curve with the "Make_Baseline" button.

Simply pulling the bleed shim out of the stack got me close (about 1.1 lbf additional force), so I just made some small face shim adjustments to bring that up.

I ended up making some more adjustments to base and mid stacks to get my response results to look like this:

Rebound zeta = 0.7

I'm assuming my low speed R/C is actually closer to 0.8:1 now that I have the LSV enabled and modified. Mid-speed R/C is = 3.25. The high speed R/C has a little bit of a stiff "hook" above 3 m/s. I'm not sure if it will cause any issues, but I think im going to leave it as is unless anyone has experience saying that it will cause some undesirable feeling.  

As Clicked said, chassis bottoming is still 4 m/s and wheel bottoming is 10.5 m/s even with the stock springs.

My peak wheel bottoming compression force is nearly equal to peak spring force.

Chassis bottoming compression force is 75% of chassis bottoming rebound force.

Now I'm wondering if there is a way to sum this damping force with the mid-valve spreadsheet results to get my response curve to capture the LSV contribution.

I do have some concerns that this setup will feel too plush based on the "Enduro and MX Setups" section of the ReStackor manual HERE, but I guess the only way to know is to make the modifications and test it out!  Before I do this I'll go through the same activity for the shock (it's already done, I just haven't posted yet) so that the bike does not feel "stink-bugged" with a stiff rear spring and soft front.

More to come

[Johnny_On_The_Spot]

Onto the shock now.

Reservoir Pressurization System

Bump height - I based this estimate off of the same input as the fork. A 5" bump hit at 30 mph.  This bike has a 19" rear wheel, so I used this plot which ReStackor provides to determine wheel velocity.  I then assumed a 3:1 linkage-shock motion ratio to come up with approximately a 40 mm shaft stroke at 2.5 m/s.  I overestimated slightly because the plot below is for a 120/90-19, and I'm using a 120/80-19, which has a slightly shorter side-wall.

Oil

I'm using Showa SS-25 oil. I found 40 C and 100 C viscosity specs here: http://mahonkin.com/~milktree/motorcycle/fork-oil.html. I'm assuming the same 50C oil condition as the fork, although it probably should be a little warmer seeing as I tend to notice my shock heating up more than the forks.

ICS

This is all set to zero since the shock uses a bladder system

Bladder

P.res - 1034 kPa (150 psig)

L.Blad - 100 mm

OD.blad - 54.5 mm

ID.blad - 0 mm

Spreadsheet:

  

[Johnny_On_The_Spot]

BVc Shock

The HSC adjuster is modeled as the base valve.  I had never had a shock compression adjuster apart before, so I made this diagram to help understand the functions:

You can see the shock BVc piston has an odd geometry that isn't intuitively modeled in ReStackor. The outer seat surface is actually the rebound check washer, not the piston itself. The ports bisect the "step" in the piston that we would normally call r.port, so some work has to be done to figure out the actual r.port. This didn't match anything on the ReStackor site, so I brute-forced the solution with CAD. I'll show how I did this below.

I'm moving forward with the idea that the r.port should be the area-averaged inner radius that acts on the shim. Using the inner radius of the port will overestimate the pressure area on the shims and give unrealistic results.

I had to solve for w.port the same was as I did for the LSV perimeter throat. The final results are:

 

The KX450 has a 16 mm shaft, so D.rod is 16 mm on all 3 tabs. 

Spreadsheet input:

 

Edited May 29, 2020 by Johnny_On_The_Spot

[Johnny_On_The_Spot]

High Speed Compression Adjuster

As shown before, the HSC adjuster simply increases the preload on the HSC spring, which then applies force through a collar onto the shim stack.  I took measurements of the HSC to figure out the dimensional stack. See the sketch below:

I then measured the spring to estimate its stiffness and solve for the preload.  This was then mapped to number of adjuster turns to create a preload lookup.

The "collar ID" in the spreadsheet above is the D.hsc which will be used to determine which shim in the stack has the spring force applied to it.

I then made made a linear curve fit of the spring preload vs adjuster turns, and added a little calculation to allow me to enter the adjuster turns and automatically calculate the adjuster preload.

Low Speed Compression Adjuster

The LSC adjuster is a simple pointed tapered needle which throttles the bleed orifice. I created a geom file for this.  ReStackor documentation says that pointed needles should have 0 dia (wide open) when clicker is backed fully out. Based on the external metering behavior I saw on the forks, I wanted to see if the LSC needle would also go wide-open earlier than expected.  

It took some trig, but I found that this LSC needle actually doesn't fully retract when the clickers are backed out fully. You end up with 0.7 mm of the tip still inside the bleed bore, which gives you a 0.25 mm dia restriction.

This needle only meters internally

The geom file for this is below:

 

After all that, the BCv spreasheet looks like this:

The output is below:

Edited May 29, 2020 by Johnny_On_The_Spot

[Johnny_On_The_Spot]

MVc

The Mid-valve compression on the shock is the stack that is on the shock shaft. Nothing non-standard here. ReStackor documentation has an equation to solve for the equivalent d.thrt if the piston has a trapezoidal throat.

 

Side note - there was some odd annular grooving on the radial sections of the seat.  The grooving was pretty deep and almost looked like the piston or shims were spinning on the shaft. Anyone know what would cause this?  I was thinking maybe some contamination went through it when I ground the shaft peening off, but my buddy had Pro Circuit do his extremely low hour shock and they replaced the stock piston with one of their own. His had similar markings, but not as deep. Luckily he let me have his old stocker!

This stack has a crossover so you can see the knee in the flow area, lift, and force plots

Edited May 29, 2020 by Johnny_On_The_Spot

[Johnny_On_The_Spot]

MVr

Again, nothing special here. Same annular damage to the straight radial section of the seat, though!

MVr Needle

I had never had a shock clevis off before, so this seemed like an excuse to give it a shot.  It actually wasn't too bad to do!  After disassembling and trying to figure out how to map needle height to clicker position, I realized the easy way to get height was to drop a drill bit down the shaft and measure the change in needle height that way.

I then measured the needle diameter and height of the tapered section. I then solved for 1/2 the needle taper by breaking the needle into a right triangle

I measured the bleed diameter to be 3.7 mm, and I know the needle seals the bleed when closed. This means that the base of the triangle when clicker = 0 is 3.7 mm. I already solved for the needle taper, so now I can solve for the height of the tip that is inserted into the bleed bore.

I measured the travel of the needle over the clicker range to be 1.0 mm. This means that I need to subtract 1.0 from 2.84 to find the "full out" needle position within the bore. It is clear that the needle does not fully retract from the bleed, so it does not have a wide-open setting!

The diameter of the needle when clickers are full-out is 2.4 mm.

This needle also only internally meters

Geom file below. This geom is also used on the MVc tab.

Again, this stack has a crossover so the curves have discontinuities

Edited May 29, 2020 by Johnny_On_The_Spot

[Johnny_On_The_Spot]

Mid-valve Analysis

Combined output shows that while the rebound pressure never drops into vacuum, the mid valve is stiffer than the base valve which results in a larger pressure drop across it.  I don't think this is a problem, but the trend I'm seeing is that this pressure balance could cause cavitation at higher shaft speeds.

 

 

[Johnny_On_The_Spot]

Response

Now the fun stuff.  

We already entered in the weight split and chassis weight when I did the fork analysis. These values remain the same here. 

While I weighed all the fork components individually to get the unsprung mass, the combination of rotating and translating components in the rear suspension make this method less desirable.  I used a much simpler method - I removed the shock, and put a bathroom scale under the rear wheel. This ignores the clevis, shaft, and shock spring masses - but because there is a link ratio these masses should be dominated by wheel, swingarm, brake, chain, etc. I got 13.97 kg (this was with a 120/80-19 Dunlop MX-33 rear tire, Talon aluminium 50t sprocket, and RK X-ring chain)

As with the front I'm running a stiffer rear spring 5.9 kg/mm rear spring. Sag is set to 105 mm, and 3.5 mm of preload is required to get to my rider weight.  I repeated the measurement 5 times as I did with the forks, but found the measurement to be much more repeatable.

Max Stroke and Wheel Position Data are a little more complicated on the shock than they were on the fork. I need to figure out the motion ratio from vertical rear wheel motion to shock shaft motion, as well as the vertical wheel travel that causes contact to the shock bottoming bumper. I reassembled a "dummy" shock without any oil, spring, nitrogen, compression adjuster so that I could easily compress it.

The dummy shock was installed on the bike, I put a floor jack under my rear wheel, used my Slacker digital sag scale to measure vertical wheel motion, and used my telescoping gauge to measure from the bumper to the shock seal dust cover. (Note - the picture shows no bumper installed. I had to repeat the measurement, but forgot to take new photos )

I have a Ride Engineering +1 mm link installed, but I repeated the measurement for the stock linkage as well.

I created a y.wheel vs y.shock table by moving the rear wheel 20 mm and recording the shock displacement. Comparisons of both are below

And since I took these measurements with the shock bumper installed, I know the "Max Stroke" of the rear wheel before the shock begins to bottom. For the Ride Engineering link it is 214 mm.

My response inputs for the Ride Eng link and 5.9 kg/mm spring are below:

 

[Johnny_On_The_Spot]

Response Output

Linkage Data

You can see 2 green dots - ReStackor has flagged these as outlier points. Since the bike is reassembled and I plan on riding tomorrow (and they're both at points where suspension is above race sag) they're going to have to be good enough for now! I don't see this affecting results too much judging by how close they are to the curve fit. Maybe some slight error on chassis bottoming for the first 40 mm of compression.

 

Wheel bottoming occurs at 8.5 m/s, chassis bottoming occurs at 2.2 m/s.  I'm assuming this is OK since the anti-squat behavior of the chain acting on the swingarm is ignored, so actual bottoming velocity is likely higher.  (That could be an interesting add-on in the future!)

Rebound zeta actually looks pretty damn good at the stock clicker position.  R/C ratio is also close, and just needs a little work at mid/high speed.

Wheel and chassis bottoming force needs some work.

 

Edited May 29, 2020 by Johnny_On_The_Spot

[Creeature]

Wow. Nice thread..

Maybe that shim spinning thats why some guys are surfacing their pistons

Edited May 30, 2020 by Assy man

[DEATH_INC.]

4 hours ago, Assy man said:

Maybe that shim spinning thats why some guys are surfacing their pistons

Surely not , shims are clamped in place, and well lubricated, they would never spin enough, or fast enough to do that. It'd be interesting to see a brand new piston and see if it's a manufacturing defect.

I do agree this is a great thread, it's helped Me get My head around a couple of things.

[Clicked]

Fork bleed shim stack

Getting rid of the LSV 18mm bleed shim is the right thing to do. But the LSV needs some bleed to prevent hydraulic lockup when the suspension is returning to race-sag.

To prevent lockup put a small notch in the LSV 23mm face shim using a dermal cutoff wheel, or a triangle file.

[Johnny_On_The_Spot]

On 5/31/2020 at 8:36 AM, Clicked said:

Fork bleed shim stack

Getting rid of the LSV 18mm bleed shim is the right thing to do. But the LSV needs some bleed to prevent hydraulic lockup when the suspension is returning to race-sag.

To prevent lockup put a small notch in the LSV 23mm face shim using a dermal cutoff wheel, or a triangle file.

OK good to know!  How big of a notch are we talking? I'm envisioning something around 1 mm deep x 1 mm wide, but want to check before I do it!  Should I be concerned with this shim cracking?

[Johnny_On_The_Spot]

On 5/30/2020 at 6:49 PM, DEATH_INC. said:

Surely not , shims are clamped in place, and well lubricated, they would never spin enough, or fast enough to do that. It'd be interesting to see a brand new piston and see if it's a manufacturing defect.

I do agree this is a great thread, it's helped Me get My head around a couple of things.

Yeah I don't think it is actually rotation since the clamp load is so high.  I was thinking it was maybe some sort of fluid cavitation or contamination damage, but I'd expect the pattern to be more radial than annular.  Manufacturing defect is possible too...

[Johnny_On_The_Spot]

Response Tuned Shock Update

I spent some time on the shock valving with the 5.5 kg/mm rate and came up with the following output:

 

Looking for feedback on a few things:

1) Any thoughts on the "bump" in my damping R/C ratio? Is that something that I should correct, or it is good enough to move forward with? I don't have a good feel for if that is a "hack job" stack and I need to spend more time, or if I'm just splitting hairs trying to get exactly to the target.

2) Spring force seems extremely low on wheel bottoming force plot. I also went back and tried the 5.9 kg/mm rate that I am currently using and it didn't seem to significantly increase the force, even when I correct preload to maintain rider weight. Is it just a matter of now re-tuning reb zeta for the new rate, then re-tuning the R/C ratio?

3) How do I get a feel for the "balance" of the bike front to rear? I'm thinking I should target a force balance that is the same ratio as the weight balance, but that's just more of a gut feel/guess.  

[DEATH_INC.]

7 hours ago, Johnny_On_The_Spot said:

Response Tuned Shock Update

I spent some time on the shock valving with the 5.5 kg/mm rate and came up with the following output:

 

Looking for feedback on a few things:

1) Any thoughts on the "bump" in my damping R/C ratio? Is that something that I should correct, or it is good enough to move forward with? I don't have a good feel for if that is a "hack job" stack and I need to spend more time, or if I'm just splitting hairs trying to get exactly to the target.

2) Spring force seems extremely low on wheel bottoming force plot. I also went back and tried the 5.9 kg/mm rate that I am currently using and it didn't seem to significantly increase the force, even when I correct preload to maintain rider weight. Is it just a matter of now re-tuning reb zeta for the new rate, then re-tuning the R/C ratio?

3) How do I get a feel for the "balance" of the bike front to rear? I'm thinking I should target a force balance that is the same ratio as the weight balance, but that's just more of a gut feel/guess.  

(1) The bump looks fairly minimal, if you don't feel like figuring out what is causing it it's probably good enough to try.

(2) I had the same thing when I did the 500 shock, I run a 6.25kg spring, and the spring force seemed very low. Maybe it isn't what we think?

(3) I'd say the balance comes automatically, restackor has the % ratio you entered, plus Clickeds rider weight distribution built in, so it'll do all the calculations to take that into account?

Edited June 1, 2020 by DEATH_INC.