981 Spring Rates
Drifting
Joined: Sep 2019
Posts: 2,959
Likes: 1,454
From: Balt/DC
I think spring rates of 237 / 325 would be good for track and not too stiff for the street; I say that because the Bilstein damptronic (PASM) setup I have installed has 286 / 357 springs and they are great on track and bearable on the street (a little stiff but manageable). If you have PASM, you might consider the Damptronic Bilstein option...
Racer
Joined: May 2018
Posts: 322
Likes: 78
Reviving an old post here, as it seems relevant. I am currently debating options for my 981S PASM/PDK car. I do not have the capability to go with any set of PASM compatible coils in the near future. I've thought about removing PASM and going with a set that is not compatible, however that is a last resort. Current considerations are X73, H&R HAS, and KW HAS. I actually have the KW's but have yet to install.
To the point...what are your thoughts on spring rates of 41.5 n/mm (237lb/in) and 56.9 n/mm (325 lb/in)? I am used to springs using KG, so this is a bit new to me. The conversions are not adding up. On my last 4500 lb behemoth, I was running 10k and 12k, and the car performed very well in the Great Smokey's. The purpose for the spring change is very spirited runs through mountain roads. I have swapped to X73 sways, however I may trade those out for adjustable. The large swing in transition of weight from side to side in very short intervals is not enjoyable with the stock setup. I'd love to hear thoughts and suggestions.
TIA
To the point...what are your thoughts on spring rates of 41.5 n/mm (237lb/in) and 56.9 n/mm (325 lb/in)? I am used to springs using KG, so this is a bit new to me. The conversions are not adding up. On my last 4500 lb behemoth, I was running 10k and 12k, and the car performed very well in the Great Smokey's. The purpose for the spring change is very spirited runs through mountain roads. I have swapped to X73 sways, however I may trade those out for adjustable. The large swing in transition of weight from side to side in very short intervals is not enjoyable with the stock setup. I'd love to hear thoughts and suggestions.
TIA
the important thing is the damping you use with the springs. It doesn’t matter how stiff the spring is if you can’t control it. I personally would never use spring rates that the damper wasn’t designed for or matched with.
how stiff you go ultimate depends on how nice are these roads that you’ll be driving on. Smoother it is, the stiffer you go. Also stiffer suspension isn’t going to make the weight transfer any less, it will just make the weight transfer happen in an even shorter interval (ie faster). So if you find the weight transition happening to quickly, softer springs is what you’re looking for). The point of stiffer springs is so you can run the car lower, reduce alignment changes from pitch/roll, and/or you need it cuz of aero.
Last edited by Squeaky; Oct 11, 2021 at 02:36 PM.
Instructor
Joined: Oct 2020
Posts: 138
Likes: 14
From: NC
well a couple of things here. Spring rates by themselves are irrelevant when comparing different cars (potentially with different suspension geometries) - it all depends on the motion ratio. Also heavier cars will want stiffer springs, all else equal. 10k/12k is likely in kg/m.
the important thing is the damping you use with the springs. It doesn’t matter how stiff the spring is if you can’t control it. I personally would never use spring rates that the damper wasn’t designed for or matched with.
how stiff you go ultimate depends on how nice are these roads that you’ll be driving on. Smoother it is, the stiffer you go. Also stiffer suspension isn’t going to make the weight transfer any less, it will just make the weight transfer happen in an even shorter interval (ie faster). So if you find the weight transition happening to quickly, softer springs is what you’re looking for)
the important thing is the damping you use with the springs. It doesn’t matter how stiff the spring is if you can’t control it. I personally would never use spring rates that the damper wasn’t designed for or matched with.
how stiff you go ultimate depends on how nice are these roads that you’ll be driving on. Smoother it is, the stiffer you go. Also stiffer suspension isn’t going to make the weight transfer any less, it will just make the weight transfer happen in an even shorter interval (ie faster). So if you find the weight transition happening to quickly, softer springs is what you’re looking for)
I appreciate the advice - I ended up returning the KW's and will be picking up the Bilstein's, and will pair them with a DSC controller sometime next year. Thanks!
Instructor
Joined: Oct 2020
Posts: 138
Likes: 14
From: NC
Yup, that's what I am paying. With the $850 credit from the KW, they're downright cheap! lol. The DSC will be a future mod, but I figure it's better to give them a try without just for comparison.
I went with the KW initially because they were (at the time) 4 way adjustable (no longer, and my set was only front adjustable - they just changed designs) and I was only looking to lower a half inch or so and corner balance. The ROA on full coilovers at $3k+ as opposed to the $850 just did not make sense. With the current pricing on the Bilstein's and KW's lack of rear adjustability, it's funny how the table turned lol. I can't wait to get these in and on. Evidently the rears are going to be more problematic than normal given I have the Boxster and not a Cayman.
Rennlist Member
Joined: May 2021
Posts: 135
Likes: 99
From: STL
I would keep your eyes peeled in the classifieds for a DSC controller to see if you can get it at a discount sooner. It really is magical... And I have yet to scratch the surface of tuning it.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
Instructor
Joined: Oct 2020
Posts: 138
Likes: 14
From: NC
I would keep your eyes peeled in the classifieds for a DSC controller to see if you can get it at a discount sooner. It really is magical... And I have yet to scratch the surface of tuning it.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
My plan is to do exactly that with the DSC. I've been lucky enough to get all of my performance mods sans Cobb second hand.
Racer
Joined: May 2018
Posts: 322
Likes: 78
I would keep your eyes peeled in the classifieds for a DSC controller to see if you can get it at a discount sooner. It really is magical... And I have yet to scratch the surface of tuning it.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
Be sure and post how you like the Bilsteins. I was going to go that route but was talked into H&R HAS with all the adjustable bits @brewerbry mentioned first. I am having height issues with the H&RS and am stuck running "aggressive track" -3 camber in the rear so coilovers might have to be sooner rather than later.
Instructor
Joined: Oct 2020
Posts: 138
Likes: 14
From: NC
Rennlist Member
Joined: May 2021
Posts: 135
Likes: 99
From: STL
Yes, you can adjust more than you could ever imagine on the DSC... gforce ramping, braking, speed and also overall stiffness via the max and min voltage sent to the shocks. Thus revalving the shock at the click of a button. Quite a unit, just depends how far you want to go down the rabbit hole.
This is an in depth overview of all the things controlled by the controller.
H&Rs are definitely on the firm side for the street, but nothing crazy. Its a sports car, and I have yet to dive into the DSC. You are correct, height is only adjustable in the fronts with H&Rs. It seems to have dropped my car .8in more than quoted on the site thus camber is more aggressive. I have yet to really figure out why... maybe my car has sport pasm? Not sure if that even changes ride height compared to pasm Who knows. You can see the camber here.
This is an in depth overview of all the things controlled by the controller.
H&Rs are definitely on the firm side for the street, but nothing crazy. Its a sports car, and I have yet to dive into the DSC. You are correct, height is only adjustable in the fronts with H&Rs. It seems to have dropped my car .8in more than quoted on the site thus camber is more aggressive. I have yet to really figure out why... maybe my car has sport pasm? Not sure if that even changes ride height compared to pasm Who knows. You can see the camber here.
Last edited by Turboale; Oct 13, 2021 at 04:03 AM.