Nissan 370Z Forum - View Single Post

MaysEffect · 12-13-2017, 02:25 PM

UPDATED

You are on the money in terms of basic understanding. Bump is also referred as compression which I'm guessing you researched already.

Before you go making damper setups, here are some things that should be done first.

1- set all settings front and rear to 0 (fully open/soft), both rebound and compression.

2- measure the static ride height of each corner fender to wheel center line, or ground. You must be on a perfectly flat ground for this to be even remotely accurate. This test is best done with you in the driver seat or someone of similar weight while the measurements are done.
If the car is not even remotely close to being 5-7mm(7/32-1/4th inch)corner to corner, then you should go get the car corner balanced and aligned. Also if the heights are not remotely equal but the front driver wheel is the highest (with no one in the car) then you might be okay as long as its within 10mm. If you do not have adjustable swaybar endlinks, now would be the time to get some (before corner balancing). This alone can throw off your ride height by 5-10mm if there is too much preload. There are several other car parts people will recommend, but ultimately do no impact overall damper/spring performance (outside of tires/wheels).

3- After the height has been corrected then you can go about testing the cars handling then tuning***.

You will want to test the car first at zero level of adjustments to judge how the car behaves on the springs alone with very little damper intervention.

You will be judging how the car dives, squats, rolls, and absorbs bumps and waves in roads.

Rebound adjustments will change the time it takes for the car to return to center after a bump.
Increasing the front rebound rate will make the car want to hunch down on the nose more. This can make turn-in and bumps feel smoother but with a bit more roll and dive.
Increasing the rear rebound will make the car want to squat down more.Iin conjunction with stiffer front rebound, it will limit dive and roll a bit, but will also increase understeer. Increasing rear rebound in general will increase understeer and/or reduce oversteer.

Compression(bump) reduces the amount of absorption a corner will see. Increasing compression on the front will yield less weight shifting in the form of dive and roll while increasing turning speed and handling feedback. Too much and you will start to limit the spring effectiveness and will make the car jolt more over bumps. This will also increase the load on the front tires and cause them to start to slip, increasing understeer. If you have to increase compression past 75% to keep the car from bottoming out or rolling then your springs are too soft for your ride height. Increased front bump will also cause a bit more understeer mid corner and corner exit, and can be felt immediately after turn in.

Rear bump works pretty much the same as front. But will limit how much the car squats on acceleration and how quickly the car dives all things being equal. More compression in the rear in conjunction with front rebound will make the car turn hard into corners, but will slide quicker and be harder to correct. It will also increase dive sensation and pitch. This can be desirable at low speeds, but disheartening at higher speeds.
______________________________

-It is safest to increase front compression > rear rebound first. Followed by rear compression then front rebound after tests. (In this order)

-Increased front rebound and rear compression will help steering agility but will be less stable and will feel a bit more jolting over bumps and wavy roads. Because of the anti-dive geometry and low caster set on our cars, this setup may yield fairly unstable braking characteristics. Alignment changes may need to be made to help with this.

-More rebound front and rear compared to compression will make the car more floaty' and less stable overall.

-More compression front and rear will make the car sharper and harder over bumps but with less jolting, but will also make the car understeer more after turn in.

From zero adjustment (full soft), make sure the car does not bottom out or roll and wobble out of turns too much. If this is the case, you will need stiffer springs, a stiffer swaybar or raise the ride height. If the springs are preloaded more than 2inches for your given ride height, you should get stiffer springs. If the height is too tall with less than 1/4 inch of preload you need softer springs. And by tall, i mean more than 1-2 inches of wheel clearance and ride height.

12-13-2017, 02:25 PM	#3 (permalink)
MaysEffect Enthusiast Member Join Date: Aug 2016 Location: SoCal Age: 32 Posts: 383 Drives: Infiniti FX35 Rep Power: 36	UPDATED You are on the money in terms of basic understanding. Bump is also referred as compression which I'm guessing you researched already. Before you go making damper setups, here are some things that should be done first. 1- set all settings front and rear to 0 (fully open/soft), both rebound and compression. 2- measure the static ride height of each corner fender to wheel center line, or ground. You must be on a perfectly flat ground for this to be even remotely accurate. This test is best done with you in the driver seat or someone of similar weight while the measurements are done. If the car is not even remotely close to being 5-7mm(7/32-1/4th inch)corner to corner, then you should go get the car corner balanced and aligned. Also if the heights are not remotely equal but the front driver wheel is the highest (with no one in the car) then you might be okay as long as its within 10mm. If you do not have adjustable swaybar endlinks, now would be the time to get some (before corner balancing). This alone can throw off your ride height by 5-10mm if there is too much preload. There are several other car parts people will recommend, but ultimately do no impact overall damper/spring performance (outside of tires/wheels). 3- After the height has been corrected then you can go about testing the cars handling then tuning*. You will want to test the car first at zero level of adjustments to judge how the car behaves on the springs alone with very little damper intervention. You will be judging how the car dives, squats, rolls, and absorbs bumps and waves in roads. Rebound adjustments will change the time it takes for the car to return to center after a bump. Increasing the front rebound rate will make the car want to hunch down on the nose more. This can make turn-in and bumps feel smoother but with a bit more roll and dive. Increasing the rear rebound will make the car want to squat down more.Iin conjunction with stiffer front rebound, it will limit dive and roll a bit, but will also increase understeer. Increasing rear rebound in general will increase understeer and/or reduce oversteer. Compression(bump) reduces the amount of absorption a corner will see. Increasing compression on the front will yield less weight shifting in the form of dive and roll while increasing turning speed and handling feedback. Too much and you will start to limit the spring effectiveness and will make the car jolt more over bumps. This will also increase the load on the front tires and cause them to start to slip, increasing understeer. If you have to increase compression past 75% to keep the car from bottoming out or rolling then your springs are too soft for your ride height. Increased front bump will also cause a bit more understeer mid corner and corner exit, and can be felt immediately after turn in. Rear bump works pretty much the same as front. But will limit how much the car squats on acceleration and how quickly the car dives all things being equal. More compression in the rear in conjunction with front rebound will make the car turn hard into corners, but will slide quicker and be harder to correct. It will also increase dive sensation and pitch. This can be desirable at low speeds, but disheartening at higher speeds. ______________________________ -It is safest to increase front compression > rear rebound first. Followed by rear compression then front rebound after tests. (In this order)** -Increased front rebound and rear compression will help steering agility but will be less stable and will feel a bit more jolting over bumps and wavy roads. Because of the anti-dive geometry and low caster set on our cars, this setup may yield fairly unstable braking characteristics. Alignment changes may need to be made to help with this. -More rebound front and rear compared to compression will make the car more floaty' and less stable overall. -More compression front and rear will make the car sharper and harder over bumps but with less jolting, but will also make the car understeer more after turn in. From zero adjustment (full soft), make sure the car does not bottom out or roll and wobble out of turns too much. If this is the case, you will need stiffer springs, a stiffer swaybar or raise the ride height. If the springs are preloaded more than 2inches for your given ride height, you should get stiffer springs. If the height is too tall with less than 1/4 inch of preload you need softer springs. And by tall, i mean more than 1-2 inches of wheel clearance and ride height. Last edited by MaysEffect; 12-13-2017 at 10:07 PM.