Spring Rates?
07-08-2011, 01:03 AM
#11
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I have been wanting to try out stiffer springs on the rear as well!!
the fact that the Amuse S2K handles better than the J's at Touge Max was probabaly because the damping
if the Amuse had KW like damping feel and the J's are like Tein then it is very reasonable that the Amuse is faster through the bumpy canyon roads~
anybody in So-Cal have stiffer rears for me to get a ride-along sometimes??
the fact that the Amuse S2K handles better than the J's at Touge Max was probabaly because the damping
if the Amuse had KW like damping feel and the J's are like Tein then it is very reasonable that the Amuse is faster through the bumpy canyon roads~
anybody in So-Cal have stiffer rears for me to get a ride-along sometimes??
07-08-2011, 09:15 PM
#12
Registered User
More rear spring rate = less rear grip (generally).
Suspension - you dropped total spring rate from 16k all around to 11.6 front 14.3 rear. Overall you gained compliance by dropping dpring rate despite more rear rate. Is it possible your improved ride quality has more to do with the less rate than rear springrate bias?
I'm not convinced more rear spring is the way to go. Should add relatively more oversteer.
0.02
Suspension - you dropped total spring rate from 16k all around to 11.6 front 14.3 rear. Overall you gained compliance by dropping dpring rate despite more rear rate. Is it possible your improved ride quality has more to do with the less rate than rear springrate bias?
I'm not convinced more rear spring is the way to go. Should add relatively more oversteer.
0.02
07-09-2011, 12:45 AM
#13
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Sorry but your not going to get a definitive answer, because there is no recommended spring rate for our cars. The only answer we can give is that your spring rate will depend on what you have done to your car, how you drive, and where you drive it.
Let me try to explain some of the reasons why:
1. We are all starting with different variables. Even though we all drive S2000s, there are 2 chassis (AP1 & Ap2), and 2 models. They all came with different suspension geometry, tire sizes, sways bars, and curb weights.
2. Tires make a larger difference then most people think. Check out what happens the next time a spec tire changed for a racing class or series, I know that in F1 they had to redesign the cars.
As a general rule stiffer side walls and stickier tires like higher spring rates (or ride frequency), but not always.
3. Weight changes spring rates. The more weight a car has the higher the static spring rate has to be in order to maintain the same wheel spring rate, because the weight compresses the spring more, it affectively become a softer spring. This also applies to wheel weights, spring rates have to be increased to compensate form heavy wheels or tires.
4. High grip surfaces require higher spring rates, and low grip surfaces require lower spring rates. The reason why, is because there is a certain ride frequency that is optimal for tires to grip the road. Ride frequency is how fast a car bounces up and down after hitting a bump, raising a car's spring rates causes it to bounce up and down faster after hitting a bump. Every tire has it own preferred frequency for optimal grip. If we only drove in a straight line it would be easier to keep tires at their optimal rate, but every time we corner the lateral g-force increases the weight on the outside tires (making the spring rate softer) and at the same time reducing weight on the inside tires (making the spring rate higher). This is why higher G-forces require higher spring rates, and the more grip a surface or tire has, the more g-force is created during cornering. Until it rains and the grip level drops. Then spring rates need to be soften to maintain that same preferred frequency for optimal grip on the tires during cornering. On a side note braking and acceleration need to be considered as well, as g-force is generated under braking and acceleration.
5. Aero Dynamic load increases the need for higher spring rates. If you put a splitter and wing on your car don't forget to up your spring rate. Downforce is just that it's a force pushing the car down and it acts just like an increase weight, it will soften the springs. Hitting the bump stops in the middle of a high speed corner would not be a good thing. But on the flip side a car the has high-speed lift will need to soften the springs to compensate for the deceased weight.
6. Front wheels and rear wheels hit obstacles at different times. Most cars have around %15 increase in rear spring rate (wheel rate comparison) to prevent a car from bouncing out of control. Since the rear wheels are bouncing faster it matches up to the ride frequency of the fronts. Although most auto-crossers, rally drivers, and professional drifters, prefer the front spring rate higher then the rear. They find that the cars transition quicker, turn in more stable, track out is more neutral, and are all around faster, but this may not work for a high speed track.
7. Anti-sway bars are springs too. Just because they are not coiled, that doesn't mean you can forget about them. They only come into play through a corner so the braking and accelerating spring rates stay the same. Basically they work by transferring some of the weight from the loaded (outside) wheel to the unloaded (inside) wheel. It is also a torsion spring that stores some of that energy which will be released when the cornering forces are decreased, this of course will need to be damped or the car will be hard to control on corner exit. Anti-sway bars require a twisting force from both sides in order to transfer load. So the spring rate at the bar attachment points has to be high enough to twist it or the inside wheel will lift. (The wheel can also lift if it runs out of drop travel). So wheel lift issues typically require higher spring rates unless it's a lack of drop travel issue then it needs a stiffer bar. For guys running the same size tires all around, tuning with sway-bars will be a better route then trying to compensate by running too much front spring rate.
8. Shocks, damping, and valving can make the difference. Shocks damp the oscillations of the springs and control how a car transitions it's weight through a corner. If this is not tuned correctly that car will never feel right, it will either be over or under dampened, causing it to bounce too much or pack down until the shock bottoms out. Also if the compression and rebound dampening are not balanced correctly the car will either over or under-steer at different parts of the corner. Also, we often forget that some shocks have an air-spring that can be tuned and it can make another difference .
9. Driving style and the type of racing matter a lot. According to what I've seen, smooth drivers prefer the higher spring rate in the rear of the car, and more aggressive driver like them in the front. If you are someone who tosses a car into a corner, snaps on the the throttle, and exits a corner with a little too much wheel spin you may prefer higher front rates. The higher front rates seems to help make the car stay stable under aggressive movements, but in contrast having higher rear rates helps make the car rotate faster, this can be an advantage on tight course, especially if you tend to brake straight and turn in smooth. Braking is also affected by higher front spring rates, this can lead to increased front wheels locking under braking, but better trail braking and allow increased rear brake bias. In general, auto-crossers tend to tune their car's to be neutrally balanced in 2nd gear on full throttle, so there setups seem to under-steer more at a track when driven at higher speeds. Also because every race course has different sized corners the optimal car balance changes from site to site. Where as road racers have tuning laps, practice laps, and time to set their car's up different from track to track, most auto-crossers can do little more then adjust knobs. This means that optimal setups may vary greatly.
If you have read this far in my post maybe I should list my setup:
2003 S2000 AP1
Tires: Hankook RS3 Front: 235/45ZR17, Rear: 255/40ZR17
Wheels: Front & Rear: 04 AP2 rear wheels.
Sway Bar: Front: Saner (adjusted to 2nd hole), Rear stock 03
Shocks: Bilstein PSS re-valved by bilstein
Spring rate: Front: 10k, Rear: 12k
Everything else: Stock...
I autocross on both asphalt and high grip concrete. I have always thought that I'm rather aggressive and sloppy, but lately everybody been telling me that I'm actually a smooth driver.
When I can get ahold of some 255 fronts, I'm think about disconnecting the rear bar...
So in conclusion you can either spend months reading, measuring, testing, and re-testing until you find the correct spring rate, or find someone who is fast with the same car, mods, driving style, and locations; and ask them what spring rate they run.
Let me try to explain some of the reasons why:
1. We are all starting with different variables. Even though we all drive S2000s, there are 2 chassis (AP1 & Ap2), and 2 models. They all came with different suspension geometry, tire sizes, sways bars, and curb weights.
2. Tires make a larger difference then most people think. Check out what happens the next time a spec tire changed for a racing class or series, I know that in F1 they had to redesign the cars.
As a general rule stiffer side walls and stickier tires like higher spring rates (or ride frequency), but not always.
3. Weight changes spring rates. The more weight a car has the higher the static spring rate has to be in order to maintain the same wheel spring rate, because the weight compresses the spring more, it affectively become a softer spring. This also applies to wheel weights, spring rates have to be increased to compensate form heavy wheels or tires.
4. High grip surfaces require higher spring rates, and low grip surfaces require lower spring rates. The reason why, is because there is a certain ride frequency that is optimal for tires to grip the road. Ride frequency is how fast a car bounces up and down after hitting a bump, raising a car's spring rates causes it to bounce up and down faster after hitting a bump. Every tire has it own preferred frequency for optimal grip. If we only drove in a straight line it would be easier to keep tires at their optimal rate, but every time we corner the lateral g-force increases the weight on the outside tires (making the spring rate softer) and at the same time reducing weight on the inside tires (making the spring rate higher). This is why higher G-forces require higher spring rates, and the more grip a surface or tire has, the more g-force is created during cornering. Until it rains and the grip level drops. Then spring rates need to be soften to maintain that same preferred frequency for optimal grip on the tires during cornering. On a side note braking and acceleration need to be considered as well, as g-force is generated under braking and acceleration.
5. Aero Dynamic load increases the need for higher spring rates. If you put a splitter and wing on your car don't forget to up your spring rate. Downforce is just that it's a force pushing the car down and it acts just like an increase weight, it will soften the springs. Hitting the bump stops in the middle of a high speed corner would not be a good thing. But on the flip side a car the has high-speed lift will need to soften the springs to compensate for the deceased weight.
6. Front wheels and rear wheels hit obstacles at different times. Most cars have around %15 increase in rear spring rate (wheel rate comparison) to prevent a car from bouncing out of control. Since the rear wheels are bouncing faster it matches up to the ride frequency of the fronts. Although most auto-crossers, rally drivers, and professional drifters, prefer the front spring rate higher then the rear. They find that the cars transition quicker, turn in more stable, track out is more neutral, and are all around faster, but this may not work for a high speed track.
7. Anti-sway bars are springs too. Just because they are not coiled, that doesn't mean you can forget about them. They only come into play through a corner so the braking and accelerating spring rates stay the same. Basically they work by transferring some of the weight from the loaded (outside) wheel to the unloaded (inside) wheel. It is also a torsion spring that stores some of that energy which will be released when the cornering forces are decreased, this of course will need to be damped or the car will be hard to control on corner exit. Anti-sway bars require a twisting force from both sides in order to transfer load. So the spring rate at the bar attachment points has to be high enough to twist it or the inside wheel will lift. (The wheel can also lift if it runs out of drop travel). So wheel lift issues typically require higher spring rates unless it's a lack of drop travel issue then it needs a stiffer bar. For guys running the same size tires all around, tuning with sway-bars will be a better route then trying to compensate by running too much front spring rate.
8. Shocks, damping, and valving can make the difference. Shocks damp the oscillations of the springs and control how a car transitions it's weight through a corner. If this is not tuned correctly that car will never feel right, it will either be over or under dampened, causing it to bounce too much or pack down until the shock bottoms out. Also if the compression and rebound dampening are not balanced correctly the car will either over or under-steer at different parts of the corner. Also, we often forget that some shocks have an air-spring that can be tuned and it can make another difference .
9. Driving style and the type of racing matter a lot. According to what I've seen, smooth drivers prefer the higher spring rate in the rear of the car, and more aggressive driver like them in the front. If you are someone who tosses a car into a corner, snaps on the the throttle, and exits a corner with a little too much wheel spin you may prefer higher front rates. The higher front rates seems to help make the car stay stable under aggressive movements, but in contrast having higher rear rates helps make the car rotate faster, this can be an advantage on tight course, especially if you tend to brake straight and turn in smooth. Braking is also affected by higher front spring rates, this can lead to increased front wheels locking under braking, but better trail braking and allow increased rear brake bias. In general, auto-crossers tend to tune their car's to be neutrally balanced in 2nd gear on full throttle, so there setups seem to under-steer more at a track when driven at higher speeds. Also because every race course has different sized corners the optimal car balance changes from site to site. Where as road racers have tuning laps, practice laps, and time to set their car's up different from track to track, most auto-crossers can do little more then adjust knobs. This means that optimal setups may vary greatly.
If you have read this far in my post maybe I should list my setup:
2003 S2000 AP1
Tires: Hankook RS3 Front: 235/45ZR17, Rear: 255/40ZR17
Wheels: Front & Rear: 04 AP2 rear wheels.
Sway Bar: Front: Saner (adjusted to 2nd hole), Rear stock 03
Shocks: Bilstein PSS re-valved by bilstein
Spring rate: Front: 10k, Rear: 12k
Everything else: Stock...
I autocross on both asphalt and high grip concrete. I have always thought that I'm rather aggressive and sloppy, but lately everybody been telling me that I'm actually a smooth driver.
When I can get ahold of some 255 fronts, I'm think about disconnecting the rear bar...
So in conclusion you can either spend months reading, measuring, testing, and re-testing until you find the correct spring rate, or find someone who is fast with the same car, mods, driving style, and locations; and ask them what spring rate they run.
07-09-2011, 08:02 AM
#15
are you looking at the HKS Hippermax III Sports? They're single adjustable with a range of 30 clicks from full soft to full stiff and are rated 13kg front and 11kg rear.
They're the coilovers i have on my CR, which is why i ask. i've had them for a year and they've proven to work quite well in both auto-x and on the track.
The car is in STR trim for auto-x with a 255mm squared setup on all 4 corners. if you were going to autocross, i wouldn't advise running more spring in the rear than the front, but for the track, i guess it depends upon how much oversteer you can handle. i have a Saner front bar on the middle setting and no rear bar in the back and the car feels pretty neutral. it pushes a bit on corner entry, but i can still throttle steer on corner exit and get the car to rotate. keep in mind i've got some power add-ons and a tune - Flash Pro, so i picked up an additional 20whp which makes a big difference when putting power down.
since your car is mostly stock, with no power upgrades, try the spring rates you want with the rear bias and try it out. if the car is too loose at your next track day, you can always disconnect the rear bar between sessions, then go out and try as a comparison.
i'm actually looking for a little more turn in on corner entry, so i'm going to try keeping the front springs, going softer in the rear, and putting the rear bar back on. i'm hoping for better initial turn in with the rear bar back in place, with a more compliant back end so it doesn't step out when i'm on throttle coming out of the corners.
They're the coilovers i have on my CR, which is why i ask. i've had them for a year and they've proven to work quite well in both auto-x and on the track.
The car is in STR trim for auto-x with a 255mm squared setup on all 4 corners. if you were going to autocross, i wouldn't advise running more spring in the rear than the front, but for the track, i guess it depends upon how much oversteer you can handle. i have a Saner front bar on the middle setting and no rear bar in the back and the car feels pretty neutral. it pushes a bit on corner entry, but i can still throttle steer on corner exit and get the car to rotate. keep in mind i've got some power add-ons and a tune - Flash Pro, so i picked up an additional 20whp which makes a big difference when putting power down.
since your car is mostly stock, with no power upgrades, try the spring rates you want with the rear bias and try it out. if the car is too loose at your next track day, you can always disconnect the rear bar between sessions, then go out and try as a comparison.
i'm actually looking for a little more turn in on corner entry, so i'm going to try keeping the front springs, going softer in the rear, and putting the rear bar back on. i'm hoping for better initial turn in with the rear bar back in place, with a more compliant back end so it doesn't step out when i'm on throttle coming out of the corners.
07-10-2011, 09:11 AM
#16
Originally Posted by Suspension' timestamp='1309960779' post='20751182
90% of the guys here run stiffer front springs than rear. I am part of the other 10%. I am currently running spring rates very close to yours: 650 lb/in (11.6 kg/mm) front and 800 lb/in (14.3 kg/mm) rear and I feel like the ride has improved over the 16 kg/mm springs I used to use all around.
I run stock anti-roll bars and have used 255 R compounds and 255 street tires all around on the street and the track. Go for it, try it out. It's not going to be an oversteering nightmare like some may suggest, especially since yours is an AP2 and mine is an AP1.
I run stock anti-roll bars and have used 255 R compounds and 255 street tires all around on the street and the track. Go for it, try it out. It's not going to be an oversteering nightmare like some may suggest, especially since yours is an AP2 and mine is an AP1.
My last car was an EG and I had 10k F and 14k rear on Tein RA suspension.
. . .
07-10-2011, 10:35 PM
#17
Registered User
3. Weight changes spring rates. The more weight a car has the higher the static spring rate has to be in order to maintain the same wheel spring rate, because the weight compresses the spring more, it affectively become a softer spring. This also applies to wheel weights, spring rates have to be increased to compensate form heavy wheels or tires.
7. Anti-sway bars are springs too. Just because they are not coiled, that doesn't mean you can forget about them. They only come into play through a corner so the braking and accelerating spring rates stay the same. Basically they work by transferring some of the weight from the loaded (outside) wheel to the unloaded (inside) wheel. It is also a torsion spring that stores some of that energy which will be released when the cornering forces are decreased, this of course will need to be damped or the car will be hard to control on corner exit. Anti-sway bars require a twisting force from both sides in order to transfer load. So the spring rate at the bar attachment points has to be high enough to twist it or the inside wheel will lift. (The wheel can also lift if it runs out of drop travel). So wheel lift issues typically require higher spring rates unless it's a lack of drop travel issue then it needs a stiffer bar. For guys running the same size tires all around, tuning with sway-bars will be a better route then trying to compensate by running too much front spring rate.
0.02
07-11-2011, 12:03 AM
#18
Sorry but your not going to get a definitive answer, because there is no recommended spring rate for our cars. The only answer we can give is that your spring rate will depend on what you have done to your car, how you drive, and where you drive it.
Let me try to explain some of the reasons why:
1. We are all starting with different variables. Even though we all drive S2000s, there are 2 chassis (AP1 & Ap2), and 2 models. They all came with different suspension geometry, tire sizes, sways bars, and curb weights.
2. Tires make a larger difference then most people think. Check out what happens the next time a spec tire changed for a racing class or series, I know that in F1 they had to redesign the cars.
As a general rule stiffer side walls and stickier tires like higher spring rates (or ride frequency), but not always.
3. Weight changes spring rates. The more weight a car has the higher the static spring rate has to be in order to maintain the same wheel spring rate, because the weight compresses the spring more, it affectively become a softer spring. This also applies to wheel weights, spring rates have to be increased to compensate form heavy wheels or tires.
4. High grip surfaces require higher spring rates, and low grip surfaces require lower spring rates. The reason why, is because there is a certain ride frequency that is optimal for tires to grip the road. Ride frequency is how fast a car bounces up and down after hitting a bump, raising a car's spring rates causes it to bounce up and down faster after hitting a bump. Every tire has it own preferred frequency for optimal grip. If we only drove in a straight line it would be easier to keep tires at their optimal rate, but every time we corner the lateral g-force increases the weight on the outside tires (making the spring rate softer) and at the same time reducing weight on the inside tires (making the spring rate higher). This is why higher G-forces require higher spring rates, and the more grip a surface or tire has, the more g-force is created during cornering. Until it rains and the grip level drops. Then spring rates need to be soften to maintain that same preferred frequency for optimal grip on the tires during cornering. On a side note braking and acceleration need to be considered as well, as g-force is generated under braking and acceleration.
5. Aero Dynamic load increases the need for higher spring rates. If you put a splitter and wing on your car don't forget to up your spring rate. Downforce is just that it's a force pushing the car down and it acts just like an increase weight, it will soften the springs. Hitting the bump stops in the middle of a high speed corner would not be a good thing. But on the flip side a car the has high-speed lift will need to soften the springs to compensate for the deceased weight.
6. Front wheels and rear wheels hit obstacles at different times. Most cars have around %15 increase in rear spring rate (wheel rate comparison) to prevent a car from bouncing out of control. Since the rear wheels are bouncing faster it matches up to the ride frequency of the fronts. Although most auto-crossers, rally drivers, and professional drifters, prefer the front spring rate higher then the rear. They find that the cars transition quicker, turn in more stable, track out is more neutral, and are all around faster, but this may not work for a high speed track.
7. Anti-sway bars are springs too. Just because they are not coiled, that doesn't mean you can forget about them. They only come into play through a corner so the braking and accelerating spring rates stay the same. Basically they work by transferring some of the weight from the loaded (outside) wheel to the unloaded (inside) wheel. It is also a torsion spring that stores some of that energy which will be released when the cornering forces are decreased, this of course will need to be damped or the car will be hard to control on corner exit. Anti-sway bars require a twisting force from both sides in order to transfer load. So the spring rate at the bar attachment points has to be high enough to twist it or the inside wheel will lift. (The wheel can also lift if it runs out of drop travel). So wheel lift issues typically require higher spring rates unless it's a lack of drop travel issue then it needs a stiffer bar. For guys running the same size tires all around, tuning with sway-bars will be a better route then trying to compensate by running too much front spring rate.
8. Shocks, damping, and valving can make the difference. Shocks damp the oscillations of the springs and control how a car transitions it's weight through a corner. If this is not tuned correctly that car will never feel right, it will either be over or under dampened, causing it to bounce too much or pack down until the shock bottoms out. Also if the compression and rebound dampening are not balanced correctly the car will either over or under-steer at different parts of the corner. Also, we often forget that some shocks have an air-spring that can be tuned and it can make another difference .
9. Driving style and the type of racing matter a lot. According to what I've seen, smooth drivers prefer the higher spring rate in the rear of the car, and more aggressive driver like them in the front. If you are someone who tosses a car into a corner, snaps on the the throttle, and exits a corner with a little too much wheel spin you may prefer higher front rates. The higher front rates seems to help make the car stay stable under aggressive movements, but in contrast having higher rear rates helps make the car rotate faster, this can be an advantage on tight course, especially if you tend to brake straight and turn in smooth. Braking is also affected by higher front spring rates, this can lead to increased front wheels locking under braking, but better trail braking and allow increased rear brake bias. In general, auto-crossers tend to tune their car's to be neutrally balanced in 2nd gear on full throttle, so there setups seem to under-steer more at a track when driven at higher speeds. Also because every race course has different sized corners the optimal car balance changes from site to site. Where as road racers have tuning laps, practice laps, and time to set their car's up different from track to track, most auto-crossers can do little more then adjust knobs. This means that optimal setups may vary greatly.
If you have read this far in my post maybe I should list my setup:
2003 S2000 AP1
Tires: Hankook RS3 Front: 235/45ZR17, Rear: 255/40ZR17
Wheels: Front & Rear: 04 AP2 rear wheels.
Sway Bar: Front: Saner (adjusted to 2nd hole), Rear stock 03
Shocks: Bilstein PSS re-valved by bilstein
Spring rate: Front: 10k, Rear: 12k
Everything else: Stock...
I autocross on both asphalt and high grip concrete. I have always thought that I'm rather aggressive and sloppy, but lately everybody been telling me that I'm actually a smooth driver.
When I can get ahold of some 255 fronts, I'm think about disconnecting the rear bar...
So in conclusion you can either spend months reading, measuring, testing, and re-testing until you find the correct spring rate, or find someone who is fast with the same car, mods, driving style, and locations; and ask them what spring rate they run.
Let me try to explain some of the reasons why:
1. We are all starting with different variables. Even though we all drive S2000s, there are 2 chassis (AP1 & Ap2), and 2 models. They all came with different suspension geometry, tire sizes, sways bars, and curb weights.
2. Tires make a larger difference then most people think. Check out what happens the next time a spec tire changed for a racing class or series, I know that in F1 they had to redesign the cars.
As a general rule stiffer side walls and stickier tires like higher spring rates (or ride frequency), but not always.
3. Weight changes spring rates. The more weight a car has the higher the static spring rate has to be in order to maintain the same wheel spring rate, because the weight compresses the spring more, it affectively become a softer spring. This also applies to wheel weights, spring rates have to be increased to compensate form heavy wheels or tires.
4. High grip surfaces require higher spring rates, and low grip surfaces require lower spring rates. The reason why, is because there is a certain ride frequency that is optimal for tires to grip the road. Ride frequency is how fast a car bounces up and down after hitting a bump, raising a car's spring rates causes it to bounce up and down faster after hitting a bump. Every tire has it own preferred frequency for optimal grip. If we only drove in a straight line it would be easier to keep tires at their optimal rate, but every time we corner the lateral g-force increases the weight on the outside tires (making the spring rate softer) and at the same time reducing weight on the inside tires (making the spring rate higher). This is why higher G-forces require higher spring rates, and the more grip a surface or tire has, the more g-force is created during cornering. Until it rains and the grip level drops. Then spring rates need to be soften to maintain that same preferred frequency for optimal grip on the tires during cornering. On a side note braking and acceleration need to be considered as well, as g-force is generated under braking and acceleration.
5. Aero Dynamic load increases the need for higher spring rates. If you put a splitter and wing on your car don't forget to up your spring rate. Downforce is just that it's a force pushing the car down and it acts just like an increase weight, it will soften the springs. Hitting the bump stops in the middle of a high speed corner would not be a good thing. But on the flip side a car the has high-speed lift will need to soften the springs to compensate for the deceased weight.
6. Front wheels and rear wheels hit obstacles at different times. Most cars have around %15 increase in rear spring rate (wheel rate comparison) to prevent a car from bouncing out of control. Since the rear wheels are bouncing faster it matches up to the ride frequency of the fronts. Although most auto-crossers, rally drivers, and professional drifters, prefer the front spring rate higher then the rear. They find that the cars transition quicker, turn in more stable, track out is more neutral, and are all around faster, but this may not work for a high speed track.
7. Anti-sway bars are springs too. Just because they are not coiled, that doesn't mean you can forget about them. They only come into play through a corner so the braking and accelerating spring rates stay the same. Basically they work by transferring some of the weight from the loaded (outside) wheel to the unloaded (inside) wheel. It is also a torsion spring that stores some of that energy which will be released when the cornering forces are decreased, this of course will need to be damped or the car will be hard to control on corner exit. Anti-sway bars require a twisting force from both sides in order to transfer load. So the spring rate at the bar attachment points has to be high enough to twist it or the inside wheel will lift. (The wheel can also lift if it runs out of drop travel). So wheel lift issues typically require higher spring rates unless it's a lack of drop travel issue then it needs a stiffer bar. For guys running the same size tires all around, tuning with sway-bars will be a better route then trying to compensate by running too much front spring rate.
8. Shocks, damping, and valving can make the difference. Shocks damp the oscillations of the springs and control how a car transitions it's weight through a corner. If this is not tuned correctly that car will never feel right, it will either be over or under dampened, causing it to bounce too much or pack down until the shock bottoms out. Also if the compression and rebound dampening are not balanced correctly the car will either over or under-steer at different parts of the corner. Also, we often forget that some shocks have an air-spring that can be tuned and it can make another difference .
9. Driving style and the type of racing matter a lot. According to what I've seen, smooth drivers prefer the higher spring rate in the rear of the car, and more aggressive driver like them in the front. If you are someone who tosses a car into a corner, snaps on the the throttle, and exits a corner with a little too much wheel spin you may prefer higher front rates. The higher front rates seems to help make the car stay stable under aggressive movements, but in contrast having higher rear rates helps make the car rotate faster, this can be an advantage on tight course, especially if you tend to brake straight and turn in smooth. Braking is also affected by higher front spring rates, this can lead to increased front wheels locking under braking, but better trail braking and allow increased rear brake bias. In general, auto-crossers tend to tune their car's to be neutrally balanced in 2nd gear on full throttle, so there setups seem to under-steer more at a track when driven at higher speeds. Also because every race course has different sized corners the optimal car balance changes from site to site. Where as road racers have tuning laps, practice laps, and time to set their car's up different from track to track, most auto-crossers can do little more then adjust knobs. This means that optimal setups may vary greatly.
If you have read this far in my post maybe I should list my setup:
2003 S2000 AP1
Tires: Hankook RS3 Front: 235/45ZR17, Rear: 255/40ZR17
Wheels: Front & Rear: 04 AP2 rear wheels.
Sway Bar: Front: Saner (adjusted to 2nd hole), Rear stock 03
Shocks: Bilstein PSS re-valved by bilstein
Spring rate: Front: 10k, Rear: 12k
Everything else: Stock...
I autocross on both asphalt and high grip concrete. I have always thought that I'm rather aggressive and sloppy, but lately everybody been telling me that I'm actually a smooth driver.
When I can get ahold of some 255 fronts, I'm think about disconnecting the rear bar...
So in conclusion you can either spend months reading, measuring, testing, and re-testing until you find the correct spring rate, or find someone who is fast with the same car, mods, driving style, and locations; and ask them what spring rate they run.
Thanks for writing that. Some great points there. There is a really fast AP1 on Motons in my race club and he "forgets" the spring rate. So now I am on here. Personally I think I am going to go with the 12k, 14k and if it has too much rotation I'll flip the springs. I understand that this is a preference type question, so Im looking to guys that are running something similar.
How would you describe your cars handling? Any videos online? Why did you add the front sway bar and was it done after the suspension upgrade?
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butterbeer (03-24-2021)
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TheClutchKicker
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06-26-2012 05:59 AM