Spring Rate / coilover help - Track only setup
07-31-2014, 08:39 AM
#1
Spring Rate / coilover help - Track only setup
Hi all, ive been doing so much research my head is spinning. I think ive read every post about spring rates in this section. 
Purpose is HPDE, I drive as an instructor. For fun only, no TT or rules to worry about. Car is track only. I am looking for a solid starting point for track suspension.
255 RS3 tires, stock sway bars, white line bushings all around, track alignment. Stock weight Z.
Im looking for a coilover system for about 2k range. My research shows KW Club sports, and BC ER (not the standard BC you commonly see) as the main competitors. AST maybe? KW is the only one in the bunch who use OEM spring setup.
I know there is alot of brand loyalty, but im in this just for the fun to drive with friends and to teach students. Please keep that in mind, I can pick the brand.
The big question I have is SPRING RATES. Assuming true rear coilover setup, I have noticed most off the shelf spring rates are around 110lbs (2k) softer springs in the rear.
Considering I am using 255 tires for the immediate future. My thoughts are 14k (784lbs) FRONT and 12k (672) REAR
What is your experience with different spring rates you have tried? Any advice would be appreciated for my specific setup.
Purpose is HPDE, I drive as an instructor. For fun only, no TT or rules to worry about. Car is track only. I am looking for a solid starting point for track suspension.
255 RS3 tires, stock sway bars, white line bushings all around, track alignment. Stock weight Z.
Im looking for a coilover system for about 2k range. My research shows KW Club sports, and BC ER (not the standard BC you commonly see) as the main competitors. AST maybe? KW is the only one in the bunch who use OEM spring setup.
I know there is alot of brand loyalty, but im in this just for the fun to drive with friends and to teach students. Please keep that in mind, I can pick the brand.
The big question I have is SPRING RATES. Assuming true rear coilover setup, I have noticed most off the shelf spring rates are around 110lbs (2k) softer springs in the rear.
Considering I am using 255 tires for the immediate future. My thoughts are 14k (784lbs) FRONT and 12k (672) REAR
What is your experience with different spring rates you have tried? Any advice would be appreciated for my specific setup.
09-16-2014, 11:14 PM
#4
I'd go KW if you're using your car on the street. Had them on my previous car and they worked flawlessly. Car was used for street/track/autox. Best bang for the buck.
If you're wanting to something a bit more aggressive I'd look at the newer 4150, 4250 ASTs. Past that would be the 5000-series, my brother currently runs 5200s on his G35.
When it comes to coilovers, you get what you pay for. KWs would be my base go-to as they're amazing right out of the box. Teins, and most other cheap 'jdm' coilovers, are crap and should be avoided. I have seen a number of shock dyno tests showing their valving all over the place.
As far as spring rates go, you don't really need to go that stiff. For a 255 street tire I'd look at around 4-500 lbs all the way around (factory rear setup). I'm running hotchkis springs (and sways), rates being 340 front / 330 rear, with 275/305 RE11s. This setup is a touch soft but still works well enough for a dual purpose car.
For reference I believe my brother runs 295/315 R6s and 1000 lb springs, and it works quite nicely. Interestingly, I think his car rides nicer than mine haha.
Shocks are the single most important component in your suspension, don't skimp.
If you're wanting to something a bit more aggressive I'd look at the newer 4150, 4250 ASTs. Past that would be the 5000-series, my brother currently runs 5200s on his G35.
When it comes to coilovers, you get what you pay for. KWs would be my base go-to as they're amazing right out of the box. Teins, and most other cheap 'jdm' coilovers, are crap and should be avoided. I have seen a number of shock dyno tests showing their valving all over the place.
As far as spring rates go, you don't really need to go that stiff. For a 255 street tire I'd look at around 4-500 lbs all the way around (factory rear setup). I'm running hotchkis springs (and sways), rates being 340 front / 330 rear, with 275/305 RE11s. This setup is a touch soft but still works well enough for a dual purpose car.
For reference I believe my brother runs 295/315 R6s and 1000 lb springs, and it works quite nicely. Interestingly, I think his car rides nicer than mine haha.
Shocks are the single most important component in your suspension, don't skimp.
09-17-2014, 10:11 AM
#6
Thank you for the replys. I am fully aware you get what you pay for. For my purposes a full blown race setup is overkill
Car is track only. Not dual purpose. Oe swaybars
Zonemaster. Great specific feedback. You say you prefer softer rates even though it feels too soft? Then comment how you like the 1k springs better? Doesn't sound ideal to me? These details are just based on your feel?
Car is track only. Not dual purpose. Oe swaybars
Zonemaster. Great specific feedback. You say you prefer softer rates even though it feels too soft? Then comment how you like the 1k springs better? Doesn't sound ideal to me? These details are just based on your feel?
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09-17-2014, 11:59 PM
#8
Short of throwing shock potentiometers and a full data aq system on a Z, all I have to give you is my butt's preferences.
That being said, I prefer a softer spring rate simply because it allows the chassis to absorb more before becoming upset. It isn't the fastest setup, but it is more forgiving.
From a purely mechanical/control system standpoint, it is generally better to error on the side of under sprung and a touch over damped. I'll have to dig out a textbook if you want me to back this claim up haha.
Also something to think about when going with higher spring rates is that every rubber bushing in your car has and an effective spring rate. The stiffer your springs, the more the bushings' contribution to the system. The closest example I can think of would be static noise on your radio. The louder you turn up the volume the more static you get, until ultimately it overpowers what you're trying to listen to. Likewise, at a some point your fancy dampers and stiff springs will be negated by the rubber in the system. Either practice moderation, or be equally excessive everywhere
As far as the ride difference between my softly sprung Z versus my brother's stiff G35, it simply comes down to damper quality and being excessive. The G35 has had all of the rubber bushings replaced by solid spherical bushings, eliminating all compliance in the suspension. This allows for the dampers to most effectively control the system. The ASTs are also a much higher caliber damper than most, including the twin-tube KWs/Konis. So despite the significantly stiffer spring his car does not have the harshness or bounciness typical of throwing uber stiff springs and low quality dampers on an otherwise stock car.
Sorry for my rambling...
That being said, I prefer a softer spring rate simply because it allows the chassis to absorb more before becoming upset. It isn't the fastest setup, but it is more forgiving.
From a purely mechanical/control system standpoint, it is generally better to error on the side of under sprung and a touch over damped. I'll have to dig out a textbook if you want me to back this claim up haha.
Also something to think about when going with higher spring rates is that every rubber bushing in your car has and an effective spring rate. The stiffer your springs, the more the bushings' contribution to the system. The closest example I can think of would be static noise on your radio. The louder you turn up the volume the more static you get, until ultimately it overpowers what you're trying to listen to. Likewise, at a some point your fancy dampers and stiff springs will be negated by the rubber in the system. Either practice moderation, or be equally excessive everywhere
As far as the ride difference between my softly sprung Z versus my brother's stiff G35, it simply comes down to damper quality and being excessive. The G35 has had all of the rubber bushings replaced by solid spherical bushings, eliminating all compliance in the suspension. This allows for the dampers to most effectively control the system. The ASTs are also a much higher caliber damper than most, including the twin-tube KWs/Konis. So despite the significantly stiffer spring his car does not have the harshness or bounciness typical of throwing uber stiff springs and low quality dampers on an otherwise stock car.
Sorry for my rambling...
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Desert Z (12-29-2019)
09-22-2014, 03:31 PM
#10
Rode in a few cars over the weekend at pocono. Theres a big dip there, but its very smooth. I was able to do it WOT every time but the cars with stiff springs would get very upset by the bump. I was able to catch most cars at that point. Gives me some real perspective about a softer sprung setup.
Inputs?
Inputs?
10-19-2014, 06:19 PM
#13
I currently run 12k/14k on FunctionX True Coulover and the car seems overly stiff. Drifts real nice but not so great for AutoX which is what I mainly use the car for. I was considering having the rears sent off to get new spring rates and revalved. I'll be curious how this turns out. I also have Hotchkis Sway set full stuff up front and full soft in back and still lots of oversteer running 275f 295 rear.
10-20-2014, 04:56 AM
#15
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I currently run 12k/14k on FunctionX True Coulover and the car seems overly stiff. Drifts real nice but not so great for AutoX which is what I mainly use the car for. I was considering having the rears sent off to get new spring rates and revalved. I'll be curious how this turns out. I also have Hotchkis Sway set full stuff up front and full soft in back and still lots of oversteer running 275f 295 rear.
10-20-2014, 01:36 PM
#16
Sorry about the typo. I believe it is 14k/12k or is could be the 12k/10k hard spring version. Never the less they are very stiff. I bought them used and after the last race of the season next weekend I'm planning to pull them off and send them out to be rebuilt. I guess Ill find the truth then.
I am curious what springs rates front and rear are recommend for roadcourse/outcross as well though.
Here is a rundown of my current setup.
Wheels and Tires:
Enkei RPF1s Front: 9.5x18+15 Rear: 10.5x18+15
BFG KDW2 Front: 275/35/18 Rear: 295/35/18
Brakes:
Akebono BBK w/ 2Piece Front Rotors
Hawk HPS Pads
SS Brake Lines
Driveline:
Quaife LSD Differential
4.08 Gears
Nismo Diff Cover
SPL Diff Bushings
Avid Racing Trans Mount
RJM Cluch Pedal System (Haven't installed this yet but plan too)
Suspension:
Zeal Function X Coilovers (Currently f14k/r12k???, would like to go to a 7 or 8k rate if anyone has suggestions on doing that I'm open to them aside from sending them back to Zeal)
Stillen Sway Bars Front and Rear
Whiteline Sway Bar Bushings
SPL PRO Front Endlinks
SPL PRO Rear Endlinks
SPL Titanium Rear Camber Links
SPL Titanium Rear Toe Links
SPL Eccentric Lock Out Bolts
SPL Titanium Rear Traction Links
SPL FKS Front Compression Rod Bushings
SPL FKS Front Lower Inner Arm Bushings
SPL FKS Front Lower Arm Shock Mount Bushings
I am curious what springs rates front and rear are recommend for roadcourse/outcross as well though.
Here is a rundown of my current setup.
Wheels and Tires:
Enkei RPF1s Front: 9.5x18+15 Rear: 10.5x18+15
BFG KDW2 Front: 275/35/18 Rear: 295/35/18
Brakes:
Akebono BBK w/ 2Piece Front Rotors
Hawk HPS Pads
SS Brake Lines
Driveline:
Quaife LSD Differential
4.08 Gears
Nismo Diff Cover
SPL Diff Bushings
Avid Racing Trans Mount
RJM Cluch Pedal System (Haven't installed this yet but plan too)
Suspension:
Zeal Function X Coilovers (Currently f14k/r12k???, would like to go to a 7 or 8k rate if anyone has suggestions on doing that I'm open to them aside from sending them back to Zeal)
Stillen Sway Bars Front and Rear
Whiteline Sway Bar Bushings
SPL PRO Front Endlinks
SPL PRO Rear Endlinks
SPL Titanium Rear Camber Links
SPL Titanium Rear Toe Links
SPL Eccentric Lock Out Bolts
SPL Titanium Rear Traction Links
SPL FKS Front Compression Rod Bushings
SPL FKS Front Lower Inner Arm Bushings
SPL FKS Front Lower Arm Shock Mount Bushings
Last edited by SirMichael; 10-22-2014 at 10:15 AM.
10-21-2014, 05:45 AM
#17
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SirMichael, first is power, how much are you running or planning to run. If NA I suggest getting rid of the tire stagger.
What kind of tires are you planning, tires and spring rate go hand in hand.
Do you plan on aero, spring rate will also depend on aero.
What kind of tires are you planning, tires and spring rate go hand in hand.
Do you plan on aero, spring rate will also depend on aero.
10-22-2014, 10:14 AM
#18
Tires I'm probably going to stick with what I have for the next season (till driver mod improves) then switching to an R-Compound tire but I would like to go ahead and get the car ready for R-Compounds incase I make the switch sooner. I don't want to be mid season trying to get my suspension rebuilt.
Still havent figured out what size wheels to go with to get the widest option under the factory fender and over the brake calipers. The RPF1s I have now scraped the power coating of the akebono calipers in the front so they are tight and would like to avoid that.
I have considered a aero package but really like the way the car looks as it is now.
As of right now traction is terrible. Tons of over steer even in a strait line traction is iffy on occasion in second. Obviously some of this is due to the gear change but it seems overly excessive for that.
I am open to suggestions as to what sequence to pursue as to what to do next. As far as SCCA is concerned I'm staying in SSM and have no intention of demodding the car to try and fit into a class that seems to change every year.
Apologizes OP for thread jacking.
I do run a full interior as well and for not don't plan to remove it. Ultimately over time it will be a car I build to do a little of everything. Just for no the emphasis is on tracking, I like turning.
10-22-2014, 07:46 PM
#19
^Those tires are holding you back immensely, especially with all those mods. If you get a good set of tires (you dont need rcomps, RS3s are fine), it will transform everything. That should be the next thing you do...unless I am reading your posts wrong it sounds like you have more than enough experience to warrant the upgrade.
Revising your spring rates is the last thing you should be looking at right now. Unless you have the thing setup already and haven't told us yet...and even then your setup is based around a paltry amount of grip
Revising your spring rates is the last thing you should be looking at right now. Unless you have the thing setup already and haven't told us yet...and even then your setup is based around a paltry amount of grip
10-24-2014, 05:22 PM
#20
^Those tires are holding you back immensely, especially with all those mods. If you get a good set of tires (you dont need rcomps, RS3s are fine), it will transform everything. That should be the next thing you do...unless I am reading your posts wrong it sounds like you have more than enough experience to warrant the upgrade.
Revising your spring rates is the last thing you should be looking at right now. Unless you have the thing setup already and haven't told us yet...and even then your setup is based around a paltry amount of grip
Revising your spring rates is the last thing you should be looking at right now. Unless you have the thing setup already and haven't told us yet...and even then your setup is based around a paltry amount of grip
I may looking to rs3s don't come as wide as I would like. I would really like to go 305 - 315 squared.
