Stiffer springs after sway bar upgrade

[akusuma]

hi,

on EG, after upgrading to ITR sway bar + ASR, is it necessary to change to stiffer springs as well?
current springs are kings which I believe has similar spring rates as OEM EG.

Is it true that having soft spring adds more burden to the subframe? Would the ASR be strong enough for the sway bar and softer spring rate (btw ITR has stiffer stock springs compared to EG)?

thanks for the help

[JohnL]

Changes to ARB (anti roll bar, aka sway bar) can typically be made with no change to spring rates. They (springs and ARBs) are more or less independant of each other, though this doesn't mean that ARB X won't work better with springs Y rather than springs Z (etc).

Softer springs never contribute more stress to the chassis (or any parts thereof, and for purposes of this discussion the subframe can be considered part of the chassis). In fact the opposite is true, unless the softer springs allow more frequent and / or severe bottoming out of the suspension, in which case it's the bottoming out that causes increased momentary loadings (i.e. increased stress), but it would typically need to be substantially worse than before to make much difference.

[akusuma]

thanks John,

so it's the other way around actually. stiffer spring rates may contribute more stress to the chasis rather than softer?

how about when you angle when parking (avoid scraping when going to driveway). sometimes there is a short moment where one of the wheels is in the air? do you need to be careful with this?

[JohnL]

Sorry, it just clicked with me exactly what you're asking and why.

If you fit stiffer rear springs then they'll contribute roll stffness and you'll take some roll loading (and single wheel bump loading) off the rear ARB and thus off it's subframe mounts.

It would be preferable to re-inforce the sub frame in order to use spring rates of your choice rather than have stiffer rates forced upon you. It seems to me that using spring rates to cure a subframe problem associated with the ARB is a very clumsy means of dealing with this. You may end up with more rear roll stiffness than you wanted? (i.e. increaased ARB rate + stiffer rear springs). It may have been enough just to increase the rear spring rate in the first place?

Uneven driveways;
Imagine two identical cars, one very stiffly sprung (A) and one very softly sprung (B).

When crossing the uneven driveway entrance, car A will load up heavily on two diagonally opposed wheels, possibly even teetering on this diagonal axis. This is because the stiff springs don't allow much vertical suspension motion.

This isn't really a problem for the car, it should be easily strong enough to cope with the loads this creates, just don't go across the driveway quickly because the loadings will increase substantially with higher speed.

Car B will still load up more heavily across one diagonal axis than the other (with one diagonal unloading rather than loading), but the loading on the more heavily loaded diagonal will be less than car A because the softer spring rates more equally distribute load over all four corners as the driveay is negotiated. This is because the softer spring rate allows more suspension travel (at least does before the suspension reaches the limits of the bumpstops and / or damper extension, at which point the suspenion rate becomes effectively infinite in any case).

On the road a stiffer spring will impart a greater impact loading into the chassis when the road wheel hits bumps, and damper rate also has a considerable affect here (possibly more so than the spring rate).

[SiReal]

I've read and heard that you will need to share the load of the anti-roll via suspension + RSB combined otherwise goodbye endlinks (for my accord at least).

[55EXX]

on a separate tangent due to the arb adding one springs rate to the other, getting better dampers is a smart move with all that increased energy to be controlled.

[akusuma]

thanks for the replies.

it's the other way around John. I upgraded the ARB from the stock one, I was thinking whether I should change to stiffer springs as well or not.

I have the rear sub-frame reinforcement but since the ARB is dc2r size and my springs are softer than stock dc2r springs, I was thinking to upgrade the springs to stiffer or same as dc2r springs.

Initially I thought that by having stiffer springs can reduce the loads/stress on the chasis (from thicker sway bar). However this is NOT right, as explained before, it is the other way around.

I think I will just change the dampers as well to have better load sharing since my stock dampers are pretty old anyway.

[JohnL]

it's the other way around John. I upgraded the ARB from the stock one, I was thinking whether I should change to stiffer springs as well or not.

I have the rear sub-frame reinforcement but since the ARB is dc2r size and my springs are softer than stock dc2r springs, I was thinking to upgrade the springs to stiffer or same as dc2r springs.

If the subframe is strong enough then the only issue is whether you want stiffer springs for handling purposes, and my first post remains pertinent.


Initially I thought that by having stiffer springs can reduce the loads/stress on the chasis (from thicker sway bar). However this is NOT right, as explained before, it is the other way around.

Stiffer springs will somewhat increase forces fed into the chassis as a whole, but reduce it at the ARB mounting points (the opposite is also true, fitting a stiffer ARB increases force seen at the ARB mounts while taking some roll and single wheel bump loading away from the spring seats). The forces in question are loadings trying to torsionally twist the chassis and acting between diagonally opposed suspension 'corners'.


I think I will just change the dampers as well to have better load sharing since my stock dampers are pretty old anyway.

If the dampers are at all worn then they need to be replaced before anything else. IMO you're wasting your time if the dampers are not up to par, at least as good as stock dampers in near new condition, or preferably upraded to at least somewhat stiffer rates because stock dampers do tend to be as soft as is compatable with a soft ride and merely acceptable spring / chassis control (for non demanding drivers). Of course with stiffer springs the dampers do need to be stiffer to suit the increase in spring rate.

With most cars I've had anything to do with, it's the dampers that are usually the first thing that is in most urgent need of replacement or upgrade (either because as new they are too soft to start with or are more or less worn out). Stiffer dampers will most likely impart more loading (from bumps and other abrupt suspension motions) into the chassis than stiffer springs will.

Personally I'd be checking prices on Bilstein and Koni dampers (in that order).