Buying coilovers: how to pick spring rates?

Hey guys,

So I decided to spring for a set of Ksport coilovers for my old ride . I've been thinking, based on some of the reports that BL guys have had using this coilover, that the stock spring rates may be a little too stiff and wouldn't go well with the current suspension stuff I have on the car (basically, 22mm rsb, and stiffer endlinks upfront w/ 19mm stock fsb).

 

How would you go about picking the spring rates? Would you buy a set that's initially lower front and rear, then work your way up, or should I just start with the recommended rates and work my way down?

 

My main concern is basically ride, and bump absorption, because Detroit and NYC have crappy roads, and I would like to continue rallycrossing (on top of autocrossing) this car, but given that they don't have the rally spec coilovers available, I may just stick to autocrossing.

whoa.. rallycross and autocross have totally different setups.. it's almost impossible to have a setup that would be decent for both.

 

Spring rates are always difficult to decide. I'd say, start on the softer side of things, maybe 6-7 kg/mm and see how you like it. If there is still too much roll, move up from there.

it also depends on the shock itself.. but yes, you should buy your coilovers based on the driving situation and conditions..

 

I run autox and road track and, of course, daily driving.. if I had to go back and get it right, I would up to at least 10/8.. 14/12 is my ideal set up for the GT.. I might do 12/10 just to retain some daily driving comfort.. there's some comprimise of what you need for your car to do and act.

 

stock setup is based with a softer spring rate up front vs rear (we can disregard any "mechancial advantages" differences from McPherson fronts vs Multi-link rears because coilovers are not going to change the suspension design).

 

Springs are like sway bars as well (heck, sway bars are helpers to the springs' function). Springs prevent squatting.. so based on what you already know what the car does stock is what you can change with the new setup.. if you dont want as much head-dive under braking, get stiffer springs up front compared to what the stock spring rates where (afterall, stock form should be your benchmark). If you dont like the squatting in the rear, get stiffer springs in the rear.. if you like the balance of the car in stock form but overall it's too soft, just increase the spring rates proportional as to stock numbers.. it's NOT THAT hard and you are not here to make it a profession to become a suspension tech for a race team, so you can have some slack along the way.

lol Keefe, thanks.

 

I'll...ugh...do the last thing you said .

 

Seriously though. Yes, the current spring rates are soft overall...but with the swaybars setup that I have, I would like to keep the balance as is.

 

The big problem is finding the stock spring rates for the older BE model...

just wondering... how would a car feel if the spring is stiff but the damper is set to the softest? Wouldnt it be comfy and yet very good at cornering?

just wondering... how would a car feel if the spring is stiff but the damper is set to the softest? Wouldnt it be comfy and yet very good at cornering?

It might be too bouncy of a ride if not enough damping is provided. Also, cornering is more of a function of the shocks and how much they are damping the springs, so running at full soft isn't optimal for performance.

oh..?!

btw, some said that the softest coilover would still be stiffer than stock ride, is that true?

I found the stock to be quite stiff already, just bodyroll not acceptable

(Hey, i come from a Honda Accord, it ought to feel this way =)

dampening can be set within the range of the spring's range.... a properly valved shock will work with the spring just fine.. you can always have better shocks and less spring rate (see rally cars with really soft but LONG springs and super crazy shocks). It depends on your suspension travel as well...

dampening can be set within the range of the spring's range.... a properly valved shock will work with the spring just fine.. you can always have better shocks and less spring rate (see rally cars with really soft but LONG springs and super crazy shocks). It depends on your suspension travel as well...

 

You just described my dream suspension...oh..oh...suspension travel...oh helper springs...oooooooohhhh yaaaaaaahhhhhh:lol:

 

I just got an email from Ksport saying they wouldn't recommend 6kg for the front; something about the weight at the front maybe too much for the softer springs. I know the BE's are heavier by a good 200lbs than even a BL (so maybe...100lbs per end)...is that true or should I call BS on their suggestion.

 

I was hoping for either 6/7r or 7/7r...

heavier car.. stiffer springs a good idea.. wow I completely forgot about the nearly 200 lb weight savings between the BL and BE.

You just described my dream suspension...oh..oh...suspension travel...oh helper springs...oooooooohhhh yaaaaaaahhhhhh:lol:

 

I just got an email from Ksport saying they wouldn't recommend 6kg for the front; something about the weight at the front maybe too much for the softer springs. I know the BE's are heavier by a good 200lbs than even a BL (so maybe...100lbs per end)...is that true or should I call BS on their suggestion.

 

I was hoping for either 6/7r or 7/7r...

 

 

it really comes down to the preference of what you want to achieve. I have an GC 2.5RS (2700 lbs by itself) and I run a custom set of Cusco Zero2Rs on them with 10kg front and 7kg rears. On my GT-Limited, I have Zeal Function V6s with 8kg front and 6kg rears (standard off the shelf valving and spring choice, Endless/Zeal did have a HARD version which was 10kg/8kg, but I needed a baseline of how well their valving was.. so on my next rebuild of the coilovers, I'll order a stiffer set of springs to go along with the new valving (after all, they are going to take it all apart anyways, why not just upgrade it in the process?). Personally, spring rates should just indicate how much suspension travel you want to try to eliminate, shocks are the one thing that you need to control the rate of which the spring compresses and release.. that's where your ride firmness really comes from (hence oversprung, undersprung, overdampen, underdampen, etc). Remember that you can surely load up one corner of the car with more than the weight of the car (you can easily put down that kind of weight under braking and turning if your tires can handle that kind of load capacity.. at 3500 lbs car with a 400 lbs/in linear rate spring, your spring can collapse close to 8" (assume it doesnt bind first).. but of course, our car doesnt do that, but even thinking at half the downforce on that one tire is still going to be near 1700 lbs at a 400 lbs/in spring, you're looking at 4" of compression distance.. which is a bit much for me for this car.. leverages and all..

 

I havent even factored in the sway bars that is suppose to share the load as well from side to side.

 

You should take a look of my corner weights thread if you are looking for weight differences and such from your BE vs BL. Not sure how detailed you want to get, but I know the BL can be converted into a shorter suspension travel setup and still be fine for daily driving.