KSport Coilovers: All About 'Em

[insite]

Originally Posted by RandallNeighbour

I put a link to the right ones earlier on this thread. I got mine in and they fit perfectly, although I will need washers.

I should have bought ones with washers welded on but didn't know this until it was too late.

thanks; M8 x 1.25. odd thread choice since you can get neither flanged nuts or 10.9 grade hardware with that pitch. not sure what their rationale was there....

[RandallNeighbour]

Originally Posted by insite

thanks; M8 x 1.25. odd thread choice since you can get neither flanged nuts or 10.9 grade hardware with that pitch. not sure what their rationale was there....

They probably got a really good deal on the bolts!

So, will you use washers or what?

I need some guidance on this one.

[insite]

Originally Posted by RandallNeighbour

They probably got a really good deal on the bolts!

So, will you use washers or what?

I need some guidance on this one.

definitely use flat washers. BTW, my KSports will arrive today. i don't think i'll get a chance to install them tomorrow; slammed with work. i'm out of town from tuesday -> labor day; i'll probably install them on tuesday the 2nd. i'll take lots of pics & do an installation write-up.

[Dragonwind]

Great thread! I have been tossing around some ideas too as the left front is creaking now. However, I don't track it (yet) but I do take it on long drives and should get myself to an AX to give it a try. I really don't want a stiff ride either, so the PSS9's might be the best choice albeit a little pricy. Maybe the M030's would be better suited for me? I see Suncoast has the kit for $1088 so that is more doable for me.

How are the KS's for comfort?
Chris

[j.fro]

The KSports are very tolerable at the softest setting. I just recently reminded myself of how much range is in the settings. I had been running them pretty stiff because of a couple of AX's, and yesterday set them back to full soft. What a difference! At full soft, I'd say it's only a bit stiffer then stock. At full stiff, the car is like a go kart, and my wife gets a bit queasy.

[Gary in BR]

I find my Ksports very uncomfortable even at the softest setting.

I was thinking today as I was shopping for the 14th time today preparing for the storm.

Yes I am staying...In Baton Rouge.

Do you guys think that part of the reason I am so unhappy is because I am running 19 inch rims with 30 height tires?

I am going to get the softer springs mentioned earlier.

[insite]

Originally Posted by Gary in BR

I find my Ksports very uncomfortable even at the softest setting.

I was thinking today as I was shopping for the 14th time today preparing for the storm.

Yes I am staying...In Baton Rouge.

Do you guys think that part of the reason I am so unhappy is because I am running 19 inch rims with 30 height tires?

I am going to get the softer springs mentioned earlier.

the 19's have a LOT to do with it. good luck with the weather!

[Gary in BR]

If I went with a higher profile tire would that help?

But, I think I may get rubbing issues if I go taller.

I just need a 996TT to daily drive and save the Boxster for the weekend!!

[RandallNeighbour]

Gary, I think that's a great idea. TT for the DD, keeping the box in the garage for sunny weekends and track use.

Of course, you'll need to do an engine swap on the box so it doesn't feel so pokey compared to the TT.

[Gary in BR]

I would have to do more than an engine swap

Maybe swap in a 3.4 and put a TT kit on it??
Nah...I keep telling myself I am on the last leg of mods, and then I buy her a garage mate to mod.

[whitespyder]

Insite-

Please post pics of ksports installed on boxster with out the tire.

I have 19's installed on my boxster and need to know more about clearance issues. Barely clearing stock set up. 2mm or so from the bottom of spring perch (fronts) and 2mm from rear strut.

[JP-s-in st. louis]

Originally Posted by Gary in BR

I would have to do more than an engine swap

Maybe swap in a 3.4 and put a TT kit on it??
Nah...I keep telling myself I am on the last leg of mods, and then I buy her a garage mate to mod.

OMFG you are my twin! I promise I am done after this.

[insite]

ok, i WILL be doing my installation tomorrow. i will measure clearances with my OEM suspension and also with the coilovers installed. i will take lots of pics and do an installation write-up. i imagine i will be tweaking things for a couple of days to find the right setup; i will have it all laser aligned on monday.

on the 18th, i will take it to the track & do a comparison write-up to M030. i will also have an opportuninty to compare back to back the ksport setup and PSS9 setup. more to come......

[insite]

they're in. took about six hours total. right now the ride height is a little high; i'm going to give it a day of driving to settle and then lower it to around M030 up front and a bit lower than M030 in back. i have not played with the damping at all yet; currently they're all at full soft. the ride is actually pretty comfortable.

i'll try to post an install DIY this weekend. one thing of note: the reason they left the helper springs off the rear struts is that they interfere with the wheels. no matter; there is no slack in the spring at full droop, so the helper isn't really needed back there.

[insite]

ok, took the car to get it aligned yesterday. i couldn't get the numbers i wanted with the top mount settings i used. for now, i'm going to recommend leaving them in their center positions like they came from KSport.

another note, the rear helper springs WILL fit and allow reasonable ride height without interfering with the wheels. i recommend using them.

still trying to find the 'right' street setup. the adjustment knobs DO have 'clicks'; there are 36 of them. i think running the front around 30 and the rear around 24 gives a reasonable street / performance ride.

i am having some issues with wierd bounciness on the street. i decided to run some calculations to figure out why. turns out i'm having some issues with harmonic amplitudes due to the combination of spring rates i chose. usually, this is a non-issue, but since our cars are rear weight biased, it becomes an issue. i will start another thread on suspension design and link to it here. i will post shock dyno plots and setup analysis in that thread.

my installation notes for the rear are complete; i have to break it into multiple parts since i'm limited as to the size of document i can post. i'll put it up in just a minute. i hope to have the write-up on the fronts done shortly.

[insite]

here are the install notes for the rear. FYI, M030 RoW ride height puts the front fenders 25.25" off the ground and the rears 25.75" off the ground. i set mine up to be 25.25" front and rear. 1" of adjustment at the coilover equals 1" of ride height change.

[insite]

here are the instructions for installing the fronts.

[RandallNeighbour]

Originally Posted by insite

i am having some issues with wierd bounciness on the street. i decided to run some calculations to figure out why. turns out i'm having some issues with harmonic amplitudes due to the combination of spring rates i chose.

Um, I have matched my spring rates to yours. Should I use the ones that came with the set instead or what?

My control arms will be in next week and I need to get this all sorted out before I send the car to the mechanic or I'll be in for a lot of extra time and costs to get it right.

Thanks for all your help here and experimenting in advance of my installation, by the way!

[Boxsterund914]

insite,

Thanks for posting the pdf's showing the procedure from start to finish. I know that it was a lot of work to put together and I just wanted you to know how much I appreciate your effort.

I did note that the strut is not adjustable for ride height independent of the spring perch like you thought in your original comparative analysis. Is this something that is just not available on the 986? It does not seem that any coilover systems offer this. Would the absence of this feature lead you to go for a different brand (ie the PSS9) if you were doing it again?

[insite]

Originally Posted by RandallNeighbour

Um, I have matched my spring rates to yours. Should I use the ones that came with the set instead or what?

did you get the 400/500 setup, or the 300/400 setup? i thought you traded out your rear springs for 7kg.

i'll try to explain the harmonic issue i'm talking about. when we design suspension for a car, one of the first things we do is to choose the natural frequency of the suspension. this is the rate that, if undamped, the car would bounce up and down at. higher natural frequencies make the car respond faster while lower natural frequencies make the car respond slower (and they make it more comforable).

the natural frequencies for road cars tend to be in the .5 - 1.3Hz range. street / track cars and some formula cars tend to be in the 1.3 - 2.0 range. high downforce formula cars are over 2.0. these frequencies are determined by the spring rate.

we actually want to choose slightly DIFFERENT frequencies for the front and rear axles. the reason for this has to do with how the car reacts over bumps. if the frequencies are the same, the rear of the car is at maximum height when the front of the car is at minimum height. this excessive pitch / dive is felt as bounciness at lower speeds. ideally, we want the rear frequency to be about 10% - 20% higher than the front.

the frequency is based on the motion ratio of the suspension (this is the distance the wheel travels compared with the distance the shock compresses in the y direction), the SPRUNG mass, and the spring rate. for our cars, the motion ratio is about 1.43. if i assume a 3000lb car with 100lb unsprung mass per front corner and 115lb unsprung mass per rear corner, then the sprung mass at each front corner is about 600lb and each rear corner is 680lb. the springs i received are 7.0mm/kg (392 lb / in) up front and 8.7 mm/kg (486 lb/in) in back.

this works out to a frequency of 1.76 up front and 1.85 in back. this is a difference of only 5%. the car would ride much better on the street if this were greater than 10%.

FYI, the stock KSport frequencies are 1.53 and 1.88; this is a 23% difference and is too great.

the softer spring rates i recommended (5.3 / 7.0) would work out to 1.53 and 1.66, an 8% difference.

usually this problem isn't so tough to overcome; the rear biased nature of our car means we have to compromise: the best spring rates for balance (under/oversteer) aren't necessarily the best for ride quality

if one uses the 5.3kg stock KSport front springs, they'd want a rear spring rate between 403 lb (7.2kg/mm) and 440 lb (7.9kg/mm) for a 'flat' ride.

if one were to use the 9.0kg rear springs (mine showed up as 8.7 rather than 9.0), they'd want a front spring rate between 322 lb (5.8 kg/mm) and 360 lb (6.4 kg/mm).