How to tune DA shocks?
02-14-2014, 10:35 PM
#1
Race Director
Thread Starter
How to tune DA shocks?
I put some on, need to learn how to adjust, anyone have a resource on how to do it. Please don't post irrelavent stuff about how great xxx non adjust or xxx SA are.
Thanks!
Thanks!
02-15-2014, 02:36 AM
#2
It's a big job. Huge job if the car fundamentally has bad physics that you are trying to compensate for. A good platform like a c4 with cage or a c5 it's not too bad.
Start full soft front and rear bump and rebound. Figure 8 at 10/10's on a bumpy surface, in on the brakes hard and out on the gas hard. Run a few laps.
Repeat going full stiff front bump. Note feel and times. Then go full stiff one adjustment at a time, noting feel each time until you are full stiff all settings. Now you know the feel of all max settings low and high. Return to full soft all settings.
Adjust bump upwards in small increments one end at a time starting front bump, until you get the most stable smooth consistent and fast figure 8. If the shocks are right you'll be on the mid to low range of the adjustment on both ends.
Then set up an uneven slalom that requires transitions on and off throttle.
Adjust rebound up one end at a time until you get the most stable and consistent transitions.
Then tune for any give course and conditions. The smoother the track the stiffer you can go. The more transitional the track the more rebound you will use, especially in the front. For flowing courses your base setting may under steer - feed in more rear rebound.
There are charts and cheat sheets that may help or just confuse. There are excellent articles that mostly confuse even though they are dead on. Mostly it's trial and error like above, while keeping copious notes at each step.
It's both complicated science and art. It's easier to make your car worse than stock than it is better. But if you get it right you'll be way ahead of most people.
Start full soft front and rear bump and rebound. Figure 8 at 10/10's on a bumpy surface, in on the brakes hard and out on the gas hard. Run a few laps.
Repeat going full stiff front bump. Note feel and times. Then go full stiff one adjustment at a time, noting feel each time until you are full stiff all settings. Now you know the feel of all max settings low and high. Return to full soft all settings.
Adjust bump upwards in small increments one end at a time starting front bump, until you get the most stable smooth consistent and fast figure 8. If the shocks are right you'll be on the mid to low range of the adjustment on both ends.
Then set up an uneven slalom that requires transitions on and off throttle.
Adjust rebound up one end at a time until you get the most stable and consistent transitions.
Then tune for any give course and conditions. The smoother the track the stiffer you can go. The more transitional the track the more rebound you will use, especially in the front. For flowing courses your base setting may under steer - feed in more rear rebound.
There are charts and cheat sheets that may help or just confuse. There are excellent articles that mostly confuse even though they are dead on. Mostly it's trial and error like above, while keeping copious notes at each step.
It's both complicated science and art. It's easier to make your car worse than stock than it is better. But if you get it right you'll be way ahead of most people.
02-15-2014, 10:40 AM
#3
Melting Slicks
Here is a guide done by Bob Tunnell that will help you get started.
http://www.bimmerhaus.com/tech/shocktuningTN.html
Read that first and then, the second thing you need to read and UNDERSTAND is on page 31 of the Bilstein tuning guide here
http://www.bilsteinus.com/uploads/tx...ts_2010_15.pdf
The Bilstein guide is for setting up a circle track car and since they are turning only in one direction they can do things on one corner that won't work on road racing cars where you want a symmetrical setup.
The thing that will get you dialed in faster is understanding what changing jounce and rebound at one end fundamentally does. If you understand that fundamental relationship you can fine tune the car very quickly. Basically, the rule is transferring more vertical load to one end or the other will reduce grip at that end during that transition.
For example, if the car is oversteering just past the apex, as you squeeze on the power, you need to reduce front rebound, or rear jounce to transfer less vertical load to the rear tires and reduce the oversteer. The reducing of the rear jounce is intuitive because the shift of weight aft compresses the rear shock and increasing that makes sense. The front is a bit less intuitive and is a bit more difficult to explain, but higher rebound in the front increases the load on the rear tires during the power on transition and that increases oversteer, so you want to lower the rebound in the front to decrease exit oversteer.
Read the articles, think about what the car is doing as you make changes. Remember that the front settings may be different than the rear when you are all done. Before each change think about what you are going to do and what results you expect. This is important. If for instance you have that rear end stepping out on corner exit and you reduce front rebound, write down what you did and what you got for each change.
The reason it is important is that you need to learn how much each change effects the car and in what way. Once you learn this you will be able to make small changes in the right direction and you will keep the car in the sweet spot without changing it in the wrong way of getting it really screwed up.
http://www.bimmerhaus.com/tech/shocktuningTN.html
Read that first and then, the second thing you need to read and UNDERSTAND is on page 31 of the Bilstein tuning guide here
http://www.bilsteinus.com/uploads/tx...ts_2010_15.pdf
The Bilstein guide is for setting up a circle track car and since they are turning only in one direction they can do things on one corner that won't work on road racing cars where you want a symmetrical setup.
The thing that will get you dialed in faster is understanding what changing jounce and rebound at one end fundamentally does. If you understand that fundamental relationship you can fine tune the car very quickly. Basically, the rule is transferring more vertical load to one end or the other will reduce grip at that end during that transition.
For example, if the car is oversteering just past the apex, as you squeeze on the power, you need to reduce front rebound, or rear jounce to transfer less vertical load to the rear tires and reduce the oversteer. The reducing of the rear jounce is intuitive because the shift of weight aft compresses the rear shock and increasing that makes sense. The front is a bit less intuitive and is a bit more difficult to explain, but higher rebound in the front increases the load on the rear tires during the power on transition and that increases oversteer, so you want to lower the rebound in the front to decrease exit oversteer.
Read the articles, think about what the car is doing as you make changes. Remember that the front settings may be different than the rear when you are all done. Before each change think about what you are going to do and what results you expect. This is important. If for instance you have that rear end stepping out on corner exit and you reduce front rebound, write down what you did and what you got for each change.
The reason it is important is that you need to learn how much each change effects the car and in what way. Once you learn this you will be able to make small changes in the right direction and you will keep the car in the sweet spot without changing it in the wrong way of getting it really screwed up.
02-15-2014, 05:51 PM
#5
Race Director
Thread Starter
I have sheets & a base setup from the builder which felt great today, but I don't know if they can be even better.
62.0 in my group & the local fast guy was 59.9. The other fast guy was a 61. I think.
02-20-2014, 11:19 PM
#10
Race Director
Thread Starter
I ran the shocks with baseline settings from the builder , new a6 all around & beat my bud by .7 or .8 sec, he also on new slicks.
The suggestions re: dialing in from scratch are great, but I don't have a skid pad & can't rent a lot so I will have to do the fine tune from the baseline.
I get the concept (I think) of more/less bump & rebound and now need to feel the car which I think I can. Or will develop that more as the season goes.
It will take a while since most of the clubs (5) in my region do the practice wrong. You take all your practice runs in a big rush and do your work duty in the am or pm. So almost zero time to adjust shocks. This also sucks for driver development as most of us get pretty good on the 6th or 7th run (so what) and get tired by the 10/11/12 run.
Thanks again guys!
Will post up what I do.
The suggestions re: dialing in from scratch are great, but I don't have a skid pad & can't rent a lot so I will have to do the fine tune from the baseline.
I get the concept (I think) of more/less bump & rebound and now need to feel the car which I think I can. Or will develop that more as the season goes.
It will take a while since most of the clubs (5) in my region do the practice wrong. You take all your practice runs in a big rush and do your work duty in the am or pm. So almost zero time to adjust shocks. This also sucks for driver development as most of us get pretty good on the 6th or 7th run (so what) and get tired by the 10/11/12 run.
Thanks again guys!
Will post up what I do.
02-20-2014, 11:44 PM
#11
Drifting
Koni's suggested setup guide (Penske's is similar):
Just be careful about too much compression damping. It is like crack, ESPECIALLY in the slaloms. I kept going faster and faster with more and more compression damping, but I made the car too stiff and it wouldn't turn in on bumpy surfaces.
Adjusting The COMPRESSION (Bump) Damping Control (Very Important to do this FIRST!)
Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension as when 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.
STEP 1: Set all four dampers on minimum bump and minimum rebound settings.
STEP 2: 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.
STEP 3: Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car one or two laps. Repeat Step 3 until a point is reached where the car starts to feel hard over bumpy surfaces.
STEP 4: Back off the bump adjustment two clicks. The bump control is now set. Note: The back off point will probably 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 hard. Then back it off 2 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. 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, ride heights, etc.
It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering grip) a 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.
STEP 1: With rebound set on full soft and the bump control set from your earlier testing, drive the car one of two laps, paying particular attention to how the car rolls when entering a turn.
STEP 2: Increase rebound damping three sweeps (or 3/4 turn) on all four dampers and drive the car one or two laps. Repeat Step 2 until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. An increase in the rebound stiffness beyond this point is unnecessary and may result in a loss of cornering power. Note: As with the bump settings, this point will probably be reached at one end of the car before the other.
However, individual drivers may find it desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This can be easily "dialed-in" using slightly excessive rebound settings at either end.
Koni claims this is for road racing and autocross can be different (which is true), but doing this first with a slalom (8 cones, 67.5 feet spacing) then going to a TNT course worked well for me to get mine in the ballpark. Bump damping controls the unsprung weight of the vehicle (wheels, axles, etc.). It controls the upward movement of the suspension as when 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.
STEP 1: Set all four dampers on minimum bump and minimum rebound settings.
STEP 2: 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.
STEP 3: Increase bump adjustment clockwise 3 clicks on all four dampers. Drive the car one or two laps. Repeat Step 3 until a point is reached where the car starts to feel hard over bumpy surfaces.
STEP 4: Back off the bump adjustment two clicks. The bump control is now set. Note: The back off point will probably 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 hard. Then back it off 2 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. 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, ride heights, etc.
It should be noted that too much rebound on either end of the vehicle will cause an initial loss of lateral acceleration (cornering grip) a 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.
STEP 1: With rebound set on full soft and the bump control set from your earlier testing, drive the car one of two laps, paying particular attention to how the car rolls when entering a turn.
STEP 2: Increase rebound damping three sweeps (or 3/4 turn) on all four dampers and drive the car one or two laps. Repeat Step 2 until the car enters the turns smoothly (no drastic attitude changes) and without leaning excessively. An increase in the rebound stiffness beyond this point is unnecessary and may result in a loss of cornering power. Note: As with the bump settings, this point will probably be reached at one end of the car before the other.
However, individual drivers may find it desirable to have a car that assumes an oversteering or understeering attitude when entering a turn. This can be easily "dialed-in" using slightly excessive rebound settings at either end.
Just be careful about too much compression damping. It is like crack, ESPECIALLY in the slaloms. I kept going faster and faster with more and more compression damping, but I made the car too stiff and it wouldn't turn in on bumpy surfaces.
04-29-2014, 12:59 PM
#14
Drifting
04-29-2014, 01:19 PM
#16
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Okay that makes sense. That being said, in the rear when I hit bumps at highway speed it seems like the back wants to jump. Would I want to tighten or loosen the rear? Also since pfadt is gone what is a good swaybar combo with this set up? T1 or just keep the stock zo6?
04-29-2014, 02:21 PM
#17
Okay that makes sense. That being said, in the rear when I hit bumps at highway speed it seems like the back wants to jump. Would I want to tighten or loosen the rear? Also since pfadt is gone what is a good swaybar combo with this set up? T1 or just keep the stock zo6?
04-30-2014, 02:00 PM
#18
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I have only had the car for a little over a year and haven't been to the track yet, but it may be in my future. I have the stock goodyear rubber on it. The driving I do is "spirited" but not track speed.
04-30-2014, 02:13 PM
#19
the front hotchkiss/eibach/addco bars are all roughly the same stiffness as the front 33mm Zr1 bar
Then the rear adjustable bars that come with the aftermarket kits range from z51 rear stiffness to zr1 rear stiffness.
Going stiffer than that would require using the T1 kit. Some racers choose to go with T1 while others go for the first ones listed. The reason being the idea of the heavier bars limiting wheel travel and the fact that some use very stiff aftermarket leaf springs - this is with racing rubber not street.
Also worth noting - Vansteel and Strano parts make 35mm bars that are in between t1 and zr1 front bars, however I havent seen ratings on their stiffness to give a comparison
If youre going with street tires, Id go for any of the above except the t1, however there are folks that have good reviews of the t1 bars on street tires...
You may want to check under the car to see what parts it has, in case part of the suspension has been upgraded already.
Good luck!
Then the rear adjustable bars that come with the aftermarket kits range from z51 rear stiffness to zr1 rear stiffness.
Going stiffer than that would require using the T1 kit. Some racers choose to go with T1 while others go for the first ones listed. The reason being the idea of the heavier bars limiting wheel travel and the fact that some use very stiff aftermarket leaf springs - this is with racing rubber not street.
Also worth noting - Vansteel and Strano parts make 35mm bars that are in between t1 and zr1 front bars, however I havent seen ratings on their stiffness to give a comparison
If youre going with street tires, Id go for any of the above except the t1, however there are folks that have good reviews of the t1 bars on street tires...
You may want to check under the car to see what parts it has, in case part of the suspension has been upgraded already.
Good luck!
Last edited by el es tu; 04-30-2014 at 02:16 PM.
04-30-2014, 02:22 PM
#20
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Location: Baltimore County, Maryland
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That's a great answer, thank you. I know that it hasn't been yet, and I don't think I want to go with the t-1 as I am doing mostly street driving for the time being. I am just interested in the right weight transfer between the front and rear. Maybe I should just upgrade to poly bushings and better end links.