Shock tuning advice needed
04-29-2016, 12:15 PM
#1
Thread Starter
Shock tuning advice needed
All,
I'm getting set for a T&T tomorrow but hoped to get some advice to get me started. My goal will be to work on improving the shock settings.
I have been running JRZ double adjustables on my car for about a year now. I had made some initial adjustments, but have pretty much been driving it as is for the last 9 months or so. One of the things I really noticed when comparing it to the OEM shocks on my AP1 (just sold it, BTW), was that there was significantly more pitch during shifting on the street with the JRZ's on the AP2 than the OEM shocks on the AP1. So before my autocross last week, I went around the car and increased the compression settings by 2 clicks on each corner.
I immediately noticed on the street that the change caused me to start chirping the tires during my 1-2 shift when it never would have done so before.
In the autocross, the car performed better than ever. I was FTD out of 99 cars. I got second on PAX. First and third were national champion drivers. But you'll see from my video that I struggled on two of the three 1-2 shifts. Video: https://www.youtube.com/watch?v=wKaXNrB8oF0.
Any advice? Should I take the bad with the good and call this perfect? Or would it seem that I've gone to far on my rear compression and maybe dial it back a click? What about rebound? Other insights?
Tomorrow, I will plan on following the procedure below. But it leaves some room for interpretation. So your input is appreciated!
I'm getting set for a T&T tomorrow but hoped to get some advice to get me started. My goal will be to work on improving the shock settings.
I have been running JRZ double adjustables on my car for about a year now. I had made some initial adjustments, but have pretty much been driving it as is for the last 9 months or so. One of the things I really noticed when comparing it to the OEM shocks on my AP1 (just sold it, BTW), was that there was significantly more pitch during shifting on the street with the JRZ's on the AP2 than the OEM shocks on the AP1. So before my autocross last week, I went around the car and increased the compression settings by 2 clicks on each corner.
I immediately noticed on the street that the change caused me to start chirping the tires during my 1-2 shift when it never would have done so before.
In the autocross, the car performed better than ever. I was FTD out of 99 cars. I got second on PAX. First and third were national champion drivers. But you'll see from my video that I struggled on two of the three 1-2 shifts. Video: https://www.youtube.com/watch?v=wKaXNrB8oF0.
Any advice? Should I take the bad with the good and call this perfect? Or would it seem that I've gone to far on my rear compression and maybe dial it back a click? What about rebound? Other insights?
Tomorrow, I will plan on following the procedure below. But it leaves some room for interpretation. So your input is appreciated!
Suggested Adjustment Procedure for Auto Cross Use
Adjusting the Compression (Bump) Damping Control
Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension such as hitting a bump in the track. It should not be used to control the downward movement of the vehicle when it encounters dips. Also, it should not be used to control roll or bottoming.
Depending on the vehicle, the ideal bump setting can occur at any point within the adjustment range. This setting will be reached when "side-hop" or "walking" in a bumpy turn is minimal and the ride is not uncomfortably harsh. At any point other than this ideal setting, the "side-hopping" condition will be more pronounced and the ride may be too harsh.
1. Set all four dampers on minimum bump and minimum rebound settings. Drive one or two laps to get the feel of the car.
NOTE: When driving the car during the bump adjustment phase, disregard body lean or roll and concentrate solely on how the car feels over bumps. Also, try to notice if the car "walks" or "side-hops" on a rough turn. Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car one or two laps. Repeat this step until a point is reached where the car starts to feel hard over bumpy surfaces. Back off the bump adjustment two clicks. The bump control is now set. NOTE:Â The back off point will likely be reached sooner on one end of the vehicle than the other. If this occurs, keep increasing the bump on the soft end until it too feels too hard. Then back that side off two clicks. The bump control is now set.
Adjusting the Rebound Damping Control
Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound damping. The rebound damping controls the transitional roll (lean) as when entering a turn. It does not limit the total amount of roll; it does limit how fast this total roll angle is achieved. How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center heights, etc.
It should be noted that too much rebound damping on either end of the vehicle will cause an initial loss of lateral acceleration (cornering power) at that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as "jacking down." This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered. This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer.
1. 1. With the rebound set on full soft and the bump control set from your testing, drive the car one or two laps, paying attention to how the car rolls when entering a turn.
2. 2. Increase rebound damping three sweeps or 3/4 of a turn on all four dampers and drive the car one or two laps. Repeat this step until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. Any increase in the rebound stiffness beyond this point is unnecessary and may in fact be detrimental.
EXCEPTION: It may be desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This preference, of course, will vary from one driver to another depending on the individual driving style.
Adjusting the Compression (Bump) Damping Control
Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension such as hitting a bump in the track. It should not be used to control the downward movement of the vehicle when it encounters dips. Also, it should not be used to control roll or bottoming.
Depending on the vehicle, the ideal bump setting can occur at any point within the adjustment range. This setting will be reached when "side-hop" or "walking" in a bumpy turn is minimal and the ride is not uncomfortably harsh. At any point other than this ideal setting, the "side-hopping" condition will be more pronounced and the ride may be too harsh.
1. Set all four dampers on minimum bump and minimum rebound settings. Drive one or two laps to get the feel of the car.
NOTE: When driving the car during the bump adjustment phase, disregard body lean or roll and concentrate solely on how the car feels over bumps. Also, try to notice if the car "walks" or "side-hops" on a rough turn. Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car one or two laps. Repeat this step until a point is reached where the car starts to feel hard over bumpy surfaces. Back off the bump adjustment two clicks. The bump control is now set. NOTE:Â The back off point will likely be reached sooner on one end of the vehicle than the other. If this occurs, keep increasing the bump on the soft end until it too feels too hard. Then back that side off two clicks. The bump control is now set.
Adjusting the Rebound Damping Control
Once you have found what you feel to be the best bump setting on all four wheels, you are now ready to proceed with adjusting the rebound damping. The rebound damping controls the transitional roll (lean) as when entering a turn. It does not limit the total amount of roll; it does limit how fast this total roll angle is achieved. How much the vehicle actually leans is determined by other things such as spring rate, sway bars, roll center heights, etc.
It should be noted that too much rebound damping on either end of the vehicle will cause an initial loss of lateral acceleration (cornering power) at that end which will cause the vehicle to oversteer or understeer excessively when entering a turn. Too much rebound control in relation to spring rate will cause a condition known as "jacking down." This is a condition where, after hitting a bump and compressing the spring, the damper does not allow the spring to return to a neutral position before the next bump is encountered. This repeats with each subsequent bump until the car is actually lowered onto the bump stops. Contact with the bump stops causes a drastic increase in roll stiffness. If this condition occurs on the front, the car will understeer; if it occurs on the rear, the car will oversteer.
1. 1. With the rebound set on full soft and the bump control set from your testing, drive the car one or two laps, paying attention to how the car rolls when entering a turn.
2. 2. Increase rebound damping three sweeps or 3/4 of a turn on all four dampers and drive the car one or two laps. Repeat this step until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. Any increase in the rebound stiffness beyond this point is unnecessary and may in fact be detrimental.
EXCEPTION: It may be desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This preference, of course, will vary from one driver to another depending on the individual driving style.
04-29-2016, 01:57 PM
#2
Do you have dyno plots for the shocks so you know how much movement you get per "click" of compression adjustment? What about rebound?
Spring rates?
Are you picking up time in lateral transitions due to compression but losing it in accel because of the skittishness?
You could back down on compression for traction and add rebound. In lateral transitions, adding rebound to the inside wheel has similar roll-canceling effect to adding compression to the outside wheel without inducing skittishness over choppy pavement.
Spring rates?
Are you picking up time in lateral transitions due to compression but losing it in accel because of the skittishness?
You could back down on compression for traction and add rebound. In lateral transitions, adding rebound to the inside wheel has similar roll-canceling effect to adding compression to the outside wheel without inducing skittishness over choppy pavement.
04-29-2016, 03:44 PM
#3
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Having tested the JRZ RS Pros extensively, and having sold over 30 sets now to customers, hopefully I can provide some decent input for you Will.
I would totally forget about the Koni adjustment procedure for compression that you posted. That probably works for the more linear valving Koni has used throughout the years, but with the digressive JRZs, there's a large range of compression you can use to control the low speed behavior of the chassis, well before any "side-hop" is reached.
Having played with different chassis and the JRZs, I will say that not every car reacts the same way to certain compression adjustments. Typically, the more front compression you have, the more you may notice front end push. On the S2000, but in STR trim, adding front compression always to me made the car bite really hard. It increased the S2000's responsiveness (and actually made the car too sensitive and difficult to drive). On a car that is already very edgy and responsive, I have found I prefer to dumb it down, and run soft front compression. Again, that is in STR trim with 700-800lb front springs and 255 front tires on a 9" rim. Being you are on stock springs and less front grip, you may actually find you want some compression in the front end to increase response. I have actually found on other chassis lately (the ND), that even though it goes against the literature above, I was able to use compression over rebound to control roll in transitions (running more compression, but less rebound). Even though theoretically you are supposed to use rebound, I found lots of chatter and loss of grip going high rebound and low compression, where the rebound really didn't help roll much at all, and more was gained with compression. Every car seems to react slightly different, so the only way to determine what will benefit you is to go out and test. Make big swings. The JRZs are extremely responsive where just a few clicks are huge. Other dampers don't have that luxury, but I still say, maybe after some runs of really knowing the course well, throw in 3-4 clicks of compression to observe the change, or decrease by a similar amount.. same with all the adjustments really..
For the rear of the S2000 and the JRZs, I have found that more compression has actually helped stabilize the car and make easier to drive. Again, I am talking about STR and not BS, so things may be different here. In STR we do run softer rear bars or no rear bar, so the back end maybe flops around a bit more.. with compression back there, it seems to stabilize the rear much more, where less weight is being transferred, and I use rear compression to control how much I want the rear of the car shifting weight, where more compression typically makes it push, and less, making more loose (both in and out of the corners). This is definitely counter-intuitive, but I use the rear compression all the time to control this behavior, and know it well (again, at least how the car is set up in STR trim). However, referencing the ND chassis, I clearly saw a slightly different trait. Throwing a lot more rear compression did something similar, where on corner entry, it actually caused a lot of push. That does coincide with the S2000. However, on throttle, that extra rear compression acted as if I added a bit more rear bar, and on throttle the car was more loose. In the STR S2000, more compression for some reaons seems to tame the on throttle behavior, at least to a point. There is a point when if you go near full stiff on rear compression it will do the same effect, but there seems to be a large window where that is not the case. This may be due to our soft rear bar/no rear bar setup, so it's possible in BS with the large OEM rear bar that you may experience a similar trait as what I stated with the ND chassis.
The point to all of this again is that you really just have to test each setting independently for a given chassis and setup and experience and note what occurred.
Now reading the Koni rebound adjustment process, throw that out the window too, especially where it says to adjust rebound on all 4 corners. You should be making adjustments at one end of the car at a time. Front rebound I still don't seem to notice doing all that much on the S2000. I typically get to a point where it's too much and I start noticing a loss of grip and then back down. Most of us on the JRZ RS Pros are between 12-17 clicks, where I typically like the lower end of that, but I know others prefer a lot. Front rebound behaves very similar to front bar, but I would rather actually use a lot of front bar and less rebound than the opposite way around. I just seems more effective to me. Now, for rear rebound, that has always done the same for me on every vehicle I have ever owned. Your rear rebound is all about your corner entry behavior on throttle lift. More rear rebound and you make the car more loose on entry. If you are too loose on corner entry, then take rebound out.
As for the unsettled behavior during shifting, that's kind of a trait I have always dealt with on the S. I say set the shocks up for the other stuff, and for the shifting part, don't man handle the shift. I go through a clutch a year in STR trim, probably because I'm always slipping the clutch from 1-2 to make a smooth transition in order to not upset the car.
Also, I'm not claiming to be any expert here, these have just been my observations.. hopefully something here will be of help.
I would totally forget about the Koni adjustment procedure for compression that you posted. That probably works for the more linear valving Koni has used throughout the years, but with the digressive JRZs, there's a large range of compression you can use to control the low speed behavior of the chassis, well before any "side-hop" is reached.
Having played with different chassis and the JRZs, I will say that not every car reacts the same way to certain compression adjustments. Typically, the more front compression you have, the more you may notice front end push. On the S2000, but in STR trim, adding front compression always to me made the car bite really hard. It increased the S2000's responsiveness (and actually made the car too sensitive and difficult to drive). On a car that is already very edgy and responsive, I have found I prefer to dumb it down, and run soft front compression. Again, that is in STR trim with 700-800lb front springs and 255 front tires on a 9" rim. Being you are on stock springs and less front grip, you may actually find you want some compression in the front end to increase response. I have actually found on other chassis lately (the ND), that even though it goes against the literature above, I was able to use compression over rebound to control roll in transitions (running more compression, but less rebound). Even though theoretically you are supposed to use rebound, I found lots of chatter and loss of grip going high rebound and low compression, where the rebound really didn't help roll much at all, and more was gained with compression. Every car seems to react slightly different, so the only way to determine what will benefit you is to go out and test. Make big swings. The JRZs are extremely responsive where just a few clicks are huge. Other dampers don't have that luxury, but I still say, maybe after some runs of really knowing the course well, throw in 3-4 clicks of compression to observe the change, or decrease by a similar amount.. same with all the adjustments really..
For the rear of the S2000 and the JRZs, I have found that more compression has actually helped stabilize the car and make easier to drive. Again, I am talking about STR and not BS, so things may be different here. In STR we do run softer rear bars or no rear bar, so the back end maybe flops around a bit more.. with compression back there, it seems to stabilize the rear much more, where less weight is being transferred, and I use rear compression to control how much I want the rear of the car shifting weight, where more compression typically makes it push, and less, making more loose (both in and out of the corners). This is definitely counter-intuitive, but I use the rear compression all the time to control this behavior, and know it well (again, at least how the car is set up in STR trim). However, referencing the ND chassis, I clearly saw a slightly different trait. Throwing a lot more rear compression did something similar, where on corner entry, it actually caused a lot of push. That does coincide with the S2000. However, on throttle, that extra rear compression acted as if I added a bit more rear bar, and on throttle the car was more loose. In the STR S2000, more compression for some reaons seems to tame the on throttle behavior, at least to a point. There is a point when if you go near full stiff on rear compression it will do the same effect, but there seems to be a large window where that is not the case. This may be due to our soft rear bar/no rear bar setup, so it's possible in BS with the large OEM rear bar that you may experience a similar trait as what I stated with the ND chassis.
The point to all of this again is that you really just have to test each setting independently for a given chassis and setup and experience and note what occurred.
Now reading the Koni rebound adjustment process, throw that out the window too, especially where it says to adjust rebound on all 4 corners. You should be making adjustments at one end of the car at a time. Front rebound I still don't seem to notice doing all that much on the S2000. I typically get to a point where it's too much and I start noticing a loss of grip and then back down. Most of us on the JRZ RS Pros are between 12-17 clicks, where I typically like the lower end of that, but I know others prefer a lot. Front rebound behaves very similar to front bar, but I would rather actually use a lot of front bar and less rebound than the opposite way around. I just seems more effective to me. Now, for rear rebound, that has always done the same for me on every vehicle I have ever owned. Your rear rebound is all about your corner entry behavior on throttle lift. More rear rebound and you make the car more loose on entry. If you are too loose on corner entry, then take rebound out.
As for the unsettled behavior during shifting, that's kind of a trait I have always dealt with on the S. I say set the shocks up for the other stuff, and for the shifting part, don't man handle the shift. I go through a clutch a year in STR trim, probably because I'm always slipping the clutch from 1-2 to make a smooth transition in order to not upset the car.
Also, I'm not claiming to be any expert here, these have just been my observations.. hopefully something here will be of help.
05-04-2016, 08:27 PM
#4
I agree with Brian. I'm no expert but after fiddling with these revealed Motons, I've discovered the same. Unless I'm on a bumpy surface, I like rear compression pretty stiff. Too much front compression and I'm wanting to dial down the Swaybar, but then I lose corner exit traction. Front rebound is the hardest to figure out. More rear rebound definitely helps bring the back around under braking. That said, I've heard more rear rebound can settle the back through slaloms, but I haven't tried it yet. I'm still working on the driver though 
05-05-2016, 05:40 AM
#6
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There could be other things causing that (too much front compression).. But that is definitely a trait I notice with a lot of rebound in elements where you really have to lock the car down for a corner. I will say it's not limited to straight line braking. Those are the situations where I don't like a lot of front rebound and will rather use more front bar. That's just me though, as I know plenty guys who love running a ton of front rebound.
05-05-2016, 06:35 AM
#7
Originally Posted by sillyboybmxer
Is straight line braking skipping/lock up too much front rebound???I was testing this weekend and it felt great except for when i had to shut it down at the end.
The rear shocks are in extension (which does not explain Brian's experience that more rear compression hurts rear lift during corner entry) In your scenario, the front shocks are in compression.
So, if under breaking you are skipping the front tires, I would reduce front compression.
I'v also had a different experience, with rear rebound and corner entry, from Brian.
With rebound at full soft, the rear pitches up under braking too quickly. Using rebound as a timing device slows the pitching and settles the rear as it lifts for turn in.
I suspect more rebound, beyond what is necessary to slow the rear lift sufficiently, may have the effect that Brian wrote about.
So, all the advice depends on your starting point, namely spring rates and shock valving.
Consider that I have large bore Koni twin tube shocks with a revalve for large amounts of bump and a fairly normal STR build (800/600 springs, 1.25 front bar, Karcepts rear bar 4x255 tires, 17x9 wheels, aggressive alignment).
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05-05-2016, 09:08 AM
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I know a lot of the observations I stated go against the grain of shock tuning. And in my example, two different chassis reacted a little differently. I will say when I was on the Koni 3011, the point of chatter was easy to find per the Koni example. On the JRZ/MCS/Moton, it seems there is more usable compression range in there, where I get different low speed chassis behaviors out of the vehicle before there is discomfort from too much.
I can't explain the corner entry behavior with more rear compression, but if you ever had a JRZ in your hand and try to bench test it, when full soft compression, you can just barely compress it with your body weight. Bump it up a few clicks, and you cannot budge it. The forces they output from the high gas charge are incredible. I felt like I was relearning how to adjust the chassis when going from a Koni to a JRZ.
As for the rear rebound characteristic I stated, I do feel this is an extremely universal behavior for most dampers, where more rebound will promote corner entry looseness, and backing it down fixes the behavior. I would just argue that due to whatever setup is on the car, the weight is going to transfer to the front. I don't see the rear dampers preventing the pitch. If the rear rebound is high, the rear shocks will not extend fast enough, preventing the inside rear tire from staying in contact with the ground (promoting a loose corner entry characteristic). Softening the rear rebound for a throttle lift or braking event on corner entry will then allow that inside rear to drop down fast enough, keeping the tire in contact when the weight transfers. This is one of my go-to adjustments where I'm always trying to balance it on that fine line.
Could not agree any more with this! I don't think you can go off text book examples. There are so many variables going on with suspension dynamics. Key point is to test back to back to back, and make big swings, then you can learn the behaviors that suit your driving style, and use the adjustments to your advantage when experiencing different course designs or surface conditions.
I can't explain the corner entry behavior with more rear compression, but if you ever had a JRZ in your hand and try to bench test it, when full soft compression, you can just barely compress it with your body weight. Bump it up a few clicks, and you cannot budge it. The forces they output from the high gas charge are incredible. I felt like I was relearning how to adjust the chassis when going from a Koni to a JRZ.
As for the rear rebound characteristic I stated, I do feel this is an extremely universal behavior for most dampers, where more rebound will promote corner entry looseness, and backing it down fixes the behavior. I would just argue that due to whatever setup is on the car, the weight is going to transfer to the front. I don't see the rear dampers preventing the pitch. If the rear rebound is high, the rear shocks will not extend fast enough, preventing the inside rear tire from staying in contact with the ground (promoting a loose corner entry characteristic). Softening the rear rebound for a throttle lift or braking event on corner entry will then allow that inside rear to drop down fast enough, keeping the tire in contact when the weight transfers. This is one of my go-to adjustments where I'm always trying to balance it on that fine line.
Could not agree any more with this! I don't think you can go off text book examples. There are so many variables going on with suspension dynamics. Key point is to test back to back to back, and make big swings, then you can learn the behaviors that suit your driving style, and use the adjustments to your advantage when experiencing different course designs or surface conditions.
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