Ohlins vs KW3 body roll
06-06-2022, 06:11 AM
#1
Ohlins vs KW3 body roll
Hello,
my friend and I both own 2005 S2000 (European AP1).
He has KW V3 (9k/9k) coilovers and I have Ohlins DFV with different rear springs (10k/10k) with similar ride height.
As our S2000s were built in the same year we both have the same OEM anti roll bars, but I also have J's roll center adjusters installed all around.
We have just been comparing both cars on the road and my S2000 seems to have more body roll. How is that possible? I run stiffer springs and RCAs - shouldn't I have less body roll?
I went down to 5 clicks from full stiff which helped a little to control body roll, but his car with the KW V3 still feels more planted and settled.
What are the reasons for this?
Currently, I see the coilovers as the main difference between the cars, but does the damper tuning affect body roll so much?
Thank you for your insights.
JagoBlitz
my friend and I both own 2005 S2000 (European AP1).
He has KW V3 (9k/9k) coilovers and I have Ohlins DFV with different rear springs (10k/10k) with similar ride height.
As our S2000s were built in the same year we both have the same OEM anti roll bars, but I also have J's roll center adjusters installed all around.
We have just been comparing both cars on the road and my S2000 seems to have more body roll. How is that possible? I run stiffer springs and RCAs - shouldn't I have less body roll?
I went down to 5 clicks from full stiff which helped a little to control body roll, but his car with the KW V3 still feels more planted and settled.
What are the reasons for this?
Currently, I see the coilovers as the main difference between the cars, but does the damper tuning affect body roll so much?
Thank you for your insights.
JagoBlitz
06-06-2022, 06:55 AM
#2
I'll take a stab. I'm fairly new to understanding dampers but I think I get this scenario.
Damping has an affect on the rate at which the car rolls but not the total amount of roll. More compression damping will slow the speed at which the damper compresses. Therefore, the outside wheel will have more load on it and take a "set" more slowly. Generally, more compression will feel like less body roll but in a long, steady state corner, it would roll in accordance with the spring rate. The feeling of not enough compression damping is when you turn and feel the car drop suddenly until the wheel "sets" and the "set" shocks the tire because it was so sudden. That makes it sound like more compression is better. There is such thing as too much also and there's a range where things are pretty functional where small differences are just a matter of preference. Too much compression damping and you shock the tire too quickly based on your inputs before it even takes a set.
I find rebound harder to conceptualize. I don't think rebound has an impact on the roll that you feel entering any one corner. However, it will impact how the car feels in transition a bit.
Damping has an affect on the rate at which the car rolls but not the total amount of roll. More compression damping will slow the speed at which the damper compresses. Therefore, the outside wheel will have more load on it and take a "set" more slowly. Generally, more compression will feel like less body roll but in a long, steady state corner, it would roll in accordance with the spring rate. The feeling of not enough compression damping is when you turn and feel the car drop suddenly until the wheel "sets" and the "set" shocks the tire because it was so sudden. That makes it sound like more compression is better. There is such thing as too much also and there's a range where things are pretty functional where small differences are just a matter of preference. Too much compression damping and you shock the tire too quickly based on your inputs before it even takes a set.
I find rebound harder to conceptualize. I don't think rebound has an impact on the roll that you feel entering any one corner. However, it will impact how the car feels in transition a bit.
06-06-2022, 07:22 AM
#3
I cannot measure actual body roll, so it is all subjective, but both of us had the impression that my suspension has more roll/ movement.
The main difference for me are the coilovers.
Other differences I can think of are the tires, the alignment and he runs Powerflex PU bushings in the front.
He has Michelin PS4 and I have Bridgestone Potenza Sport.
He runs less camber at the front (1° front and 2° rear) and a lot of toe in at the rear axle.
I have 2° camber all around.
But none of these differences would really affect body roll.
The main difference for me are the coilovers.
Other differences I can think of are the tires, the alignment and he runs Powerflex PU bushings in the front.
He has Michelin PS4 and I have Bridgestone Potenza Sport.
He runs less camber at the front (1° front and 2° rear) and a lot of toe in at the rear axle.
I have 2° camber all around.
But none of these differences would really affect body roll.
06-06-2022, 07:58 AM
#4
I'll take a stab. I'm fairly new to understanding dampers but I think I get this scenario.
Damping has an affect on the rate at which the car rolls but not the total amount of roll. More compression damping will slow the speed at which the damper compresses. Therefore, the outside wheel will have more load on it and take a "set" more slowly. Generally, more compression will feel like less body roll but in a long, steady state corner, it would roll in accordance with the spring rate. The feeling of not enough compression damping is when you turn and feel the car drop suddenly until the wheel "sets" and the "set" shocks the tire because it was so sudden. That makes it sound like more compression is better. There is such thing as too much also and there's a range where things are pretty functional where small differences are just a matter of preference. Too much compression damping and you shock the tire too quickly based on your inputs before it even takes a set.
I find rebound harder to conceptualize. I don't think rebound has an impact on the roll that you feel entering any one corner. However, it will impact how the car feels in transition a bit.
Damping has an affect on the rate at which the car rolls but not the total amount of roll. More compression damping will slow the speed at which the damper compresses. Therefore, the outside wheel will have more load on it and take a "set" more slowly. Generally, more compression will feel like less body roll but in a long, steady state corner, it would roll in accordance with the spring rate. The feeling of not enough compression damping is when you turn and feel the car drop suddenly until the wheel "sets" and the "set" shocks the tire because it was so sudden. That makes it sound like more compression is better. There is such thing as too much also and there's a range where things are pretty functional where small differences are just a matter of preference. Too much compression damping and you shock the tire too quickly based on your inputs before it even takes a set.
I find rebound harder to conceptualize. I don't think rebound has an impact on the roll that you feel entering any one corner. However, it will impact how the car feels in transition a bit.
think of high rebound as the car not wanting to roll and low rebound as willingness to roll as it lets go of the inside wheel easier.
compression is like spring and affects response, high compression increases the speed of weight transfer, while to a degree also resisting roll initially.
the OP's experience is likely the feeling of roll, and the damping curves of the 2 shocks being different.
ohlins are singles dont have a lot of low speed compression, and if the kw v3's are doubles the relationship of rebound/compression can differ.
06-06-2022, 09:25 AM
#5
Thanks for the correction. I do make the error of mostly considering compression because it's easier for me to think about the mechanics of the outside being loaded than the inside becoming unloaded. After reading your write up and thinking to myself what a swaybar does, it makes more sense.
I've gotten fairly comfortable using rear rebound to slightly adjust corner entry behavior but don't have a great grasp of using front rebound. I can tell somewhat when it's way off but I don't really use it as slight adjustment. I'm much more comfortable with front swaybar.
Relevant to OP, I have used rear compression to help my car stabilize in slaloms. I have a very stiff front end with springs and swaybars so I really don't feel much roll up there. The rear, I've been working on managing the roll in a reasonable way. With too little rear compression, It felt that the rear outside tire did not have enough pressure on it until the car took a set. Adding rear compression helped add pressure on that tire before the weight settled to the outside spring/sway. This was a specific adjustment geared towards an autocross slalom. Regardless, the rear of the car was "rolling" just as much theoretically but adding some compression helped load up the tire more while the car was in transition. I did not experience as much of a shock throwing the weight around because of the added compression. It felt like less roll but the roll was really just transferring weight in a more controlled manner.
I've gotten fairly comfortable using rear rebound to slightly adjust corner entry behavior but don't have a great grasp of using front rebound. I can tell somewhat when it's way off but I don't really use it as slight adjustment. I'm much more comfortable with front swaybar.
Relevant to OP, I have used rear compression to help my car stabilize in slaloms. I have a very stiff front end with springs and swaybars so I really don't feel much roll up there. The rear, I've been working on managing the roll in a reasonable way. With too little rear compression, It felt that the rear outside tire did not have enough pressure on it until the car took a set. Adding rear compression helped add pressure on that tire before the weight settled to the outside spring/sway. This was a specific adjustment geared towards an autocross slalom. Regardless, the rear of the car was "rolling" just as much theoretically but adding some compression helped load up the tire more while the car was in transition. I did not experience as much of a shock throwing the weight around because of the added compression. It felt like less roll but the roll was really just transferring weight in a more controlled manner.
06-06-2022, 06:39 PM
#6
I've seen kw suspension listed in several sources as having progressive rate springs. That always seemed odd. But if true, it'd completely explain difference in body roll.
Many progressive springs you can tell just looking at them they are progressive. Coils at one end all bunched together, other end all stretched out. But they aren't all like that. Some are barely progressive, and you'd almost need to measure distance between coils at one end vs other to tell.
Even barely progressive springs will have noticeable effect on body roll. What happens with straight rate springs is outside gets pushed down at same rate as inside pushes up.
With progressive springs, outside pushes up way more than inside. Level cornering.
That and the hybrid nature of soft rate for comfort and harder for performance are the advantages of progressive springs. They work great on the street.
But on track, their inconsistency, how car responds varies based on how far each spring is compressed at any given moment, makes their street benefit a liability.
It would be useful to confirm once and for all if kw really does use progressive rate springs for some of their S2000 products, and of so which ones.
Many progressive springs you can tell just looking at them they are progressive. Coils at one end all bunched together, other end all stretched out. But they aren't all like that. Some are barely progressive, and you'd almost need to measure distance between coils at one end vs other to tell.
Even barely progressive springs will have noticeable effect on body roll. What happens with straight rate springs is outside gets pushed down at same rate as inside pushes up.
With progressive springs, outside pushes up way more than inside. Level cornering.
That and the hybrid nature of soft rate for comfort and harder for performance are the advantages of progressive springs. They work great on the street.
But on track, their inconsistency, how car responds varies based on how far each spring is compressed at any given moment, makes their street benefit a liability.
It would be useful to confirm once and for all if kw really does use progressive rate springs for some of their S2000 products, and of so which ones.
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06-07-2022, 10:43 AM
#8
Probably just a case of higher damping setting on your buddies shocks, so less initial body roll is apparent, but actual total body lean at steady state is more on his car. More damping will slow down the spring movement so during quick transitions like dodging cones in a parking lot, the body never has a chance to settle and feels stiffer then actually is if you were to say going around a long high speed sweeper.
06-08-2022, 12:12 PM
#9
Your friend's KW's are probably sitting on/close to their bumpstops. They don't have a ton of travel.
Damper settings could also be different between your setups. Stiff shocks won't prevent steady state roll...BUT they will slow down the transition into rolling. So perception from inside the car is that the car is flatter. Its not. But the mind is a terrible thing.
Damper settings could also be different between your setups. Stiff shocks won't prevent steady state roll...BUT they will slow down the transition into rolling. So perception from inside the car is that the car is flatter. Its not. But the mind is a terrible thing.
06-08-2022, 12:13 PM
#10
Probably just a case of higher damping setting on your buddies shocks, so less initial body roll is apparent, but actual total body lean at steady state is more on his car. More damping will slow down the spring movement so during quick transitions like dodging cones in a parking lot, the body never has a chance to settle and feels stiffer then actually is if you were to say going around a long high speed sweeper.