Thoughts on Coilover springs currently on EBay

Art, those spring rates are very high...

If I am doing the math correctly, they are about 400 lb/in front and 500 lb/in rear. For comparison I believe stock X spring rates are something like 160/190. So about 2 1/2 times stiffer than stock. I started with 450/400 for my Scorpion and worked my way down to the 300/250 I have on there now (pretty sure that was what was on the car that day we both drove it). And frankly I'm thinking about going down another 50 lbs to 250/200, as what I have on there now is still plenty stiff. If you get the coil-overs, sell the springs on ebay and get yourself something that's livable for the street.

Also, I bet at this price these don't come with dampers (strut insert cartridges). Find out what kind they are supposed to take and check into their price, that will be a separate expense. Cheaping out here won't help your handling, which I assume is why you want the coilovers in the first place. If they fit, and you keep the spring rate below about 250, you can use KYBs intended for VW rabbits or whatever. But if you want spring rates higher than that, you must shell out the big bucks (probably about $250-300 per corner) for quality dampers such as Koni universals.

Ever see those rediculous lowered Honda's literally pogo-ing down the road? It's because the owner slapped an absurd spring rate on them and then expected the stock dampers to handle it - it does not work.

All that said, I have no experience with the G-force product. I think Plaia's coilovers were right about that price, I would probably go that route if I was in the market to buy (assuming they are still available, which I am not sure of).

Pete
 
KSports...

Yeah, they are sweet looking, but need some creative engineering. The problems I encountered were:

1. Too high spring rate - easy - I bought 250/300lb springs. (I am thinking about 200/250 rates now.

2. Upper perches come with 3 - 1" round spacers to clear the set screw on camber plates - easy - I bought Plaia bigfoots to spread the load.

3. Camber adjustments seem to affect caster because they are not adjustable perpendicular to the thrust angle of the car. When adjusted, they look to affect caster as well. - unknown - I set mine to center. I will at some point have a professional race alignment done at a known Porsche club shop. There also is a slotted upper bolt on the lower mounts to assist with camber adjustment. I really don't know why you would need to have a camber plate and a slotted upper bolt on the lower mounts. One or the other is all you need. Maybe they are there if you don't get the camber plates. Personally, I would like to try Obert's new strut tops with the Ksport struts and modified stock upper spring perches. That should also remove about 1 " from the height of the complete strut.

4. The engineering of the lower mount is a little off. - easy, sort of - I spoke to Ksport and they are not interested in following my suggestion. The lowest point you will get the car with the Ksports and 8" springs is about stock ride height. You will have to go with 7" springs in order to drop the car 1" from stock. The whole problem is the position of the lower mount relative to a stock lower mounts position. If the lower mount could be turned upside down, you would gain another 2" of drop. Because the upper bolt hole on the lower mount is slotted, you can't. Also, you can't flip it upside down because the threads on the lower mount don't go through the entire lower mount body.



Good luck.

Arman
 
And this is why I love this forum!

Thanks Pete and Arman!! You told me exactly what I wanted to know. I'll be passing. After riding in Pete's sweat Scorpion I definitely understand!! I liked the idea of being able to adjust the height but it sounds like it doesn't do what I wanted. Like you Arman I have bought Mark's Big Foot and will be installing them. Thanks to both of you for the input! - Art
 
I'm only bringing this thread back to life because Ksport may have fixed these problems, I just got mine a week ago, haven't installed them yet, but I did hang the fronts on the car for a test fit.

SpidArman said:
Yeah, they are sweet looking, but need some creative engineering. The problems I encountered were:

3. Camber adjustments seem to affect caster because they are not adjustable perpendicular to the thrust angle of the car. When adjusted, they look to affect caster as well. - unknown - I set mine to center. I will at some point have a professional race alignment done at a known Porsche club shop. There also is a slotted upper bolt on the lower mounts to assist with camber adjustment. I really don't know why you would need to have a camber plate and a slotted upper bolt on the lower mounts. One or the other is all you need. Maybe they are there if you don't get the camber plates. Personally, I would like to try Obert's new strut tops with the Ksport struts and modified stock upper spring perches. That should also remove about 1 " from the height of the complete strut.
Click to expand...

I noticed that also, then I moved it to the other side and it was perpendicular to the thrust angle of the car, at least on the ones I have it depends on which side you mount it on. you can have camber only or camber/caster.

SpidArman said:
4. The engineering of the lower mount is a little off. - easy, sort of - I spoke to Ksport and they are not interested in following my suggestion. The lowest point you will get the car with the Ksports and 8" springs is about stock ride height. You will have to go with 7" springs in order to drop the car 1" from stock. The whole problem is the position of the lower mount relative to a stock lower mounts position. If the lower mount could be turned upside down, you would gain another 2" of drop. Because the upper bolt hole on the lower mount is slotted, you can't. Also, you can't flip it upside down because the threads on the lower mount don't go through the entire lower mount body.

Good luck.

Arman
Click to expand...

the threads on mine do go all the way through, you can screw the lower mount all the way up to the spring land if you want to. Also the spring measures 7.25" relaxed. Photo shows a 1980 stock strut for comparison.

IMG_5201.jpg
 
Thanks for posting...

Bpimm - please keep us posted on your findings after fitment and testing. I was also looking at these some time back and passed because of this thread.

Thanks,
Tim
 
OOOOOOOOH.... let me see....

Could you do me a favor and let me know the following? It would help me out if I could compare yours to mine. I still haven't completed the install. If yours are different to mine, I would like to contact the KSport guys and try to swap out my parts for ones similar to yours.

BTW, when mounted, are the screw heads fully visible to you for adjusting, or do they extend under the cars strut tower?


Take a picture of the lower mount with the threads going all the way through.

Take a picture of the camber plates from the top. I would like to see if the adjustment is different from mine.

Get a dimention from the surface of the camber plate to the bottom of the strut body. I think your strut body may be shorter than mine.

Thanks,

Arman
 
Last edited:
SpidArman said:
Could you do me a favor and let me know the following? It would help me out if I could compare yours to mine. I still haven't completed the install. If yours are different to mine, I would like to contact the KSport guys and try to swap out my parts for ones similar to yours.

BTW, when mounted, are the screw heads fully visible to you for adjusting, or do they extend under the cars strut tower?
Click to expand...

No they are buried under the strut tower, don't really like this but without cutting I don't see a way around it.
IMG_5202.jpg


SpidArman said:
Take a picture of the lower mount with the threads going all the way through.
Click to expand...

Actually when I took it off the threads don't go all the way through but the area where there are no threads is large enough to clear the threads on the body.
IMG_5207.jpg


SpidArman said:
Take a picture of the camber plates from the top. I would like to see if the adjustment is different from mine.
Click to expand...

IMG_5204.jpg


SpidArman said:
Get a dimention from the surface of the camber plate to the bottom of the strut body. I think your strut body may be shorter than mine.

Thanks,

Arman
Click to expand...

16.125" from the top of the plate, not top of spacer.

IMG_5208.jpg

IMG_5210.jpg


Brian
 
I got these rates

After reading many claims as to stock spring rates, I put my struts in my press with my bathroom scale underneath and compressed them one inch, recording the additional weight on the scale, giving time for the shocks to equalize:



Uploaded with ImageShack.us

I got spring rates of 250 front, 275 rear.

The springs have 35,000 miles on them.

Paul Davock
 
I don't think they're that high...

Here is a table I collected from somewhere for the Scorpion, which has similar if not identical rates, along with the rates for the stiffer aftermarket Jamex springs:

FrontRearOriginalJamexOriginalJamexwire diameterinches0.4750.520.520.445coil outer diameterinches4.854.744.994.64# of active turnsno units5.53.56.57.5overall heightinches12.591312coil diameterinches4.3754.224.474.195K value (calculated)lbs/inch158.9399.6181101.8K value (published)lbs/inch147.7179.5load per spring (Scorpion)lbs529647height under loadinches8.197.468.944.44

But if you want, take some basic measurements of the spring (wire diamter, free length, number of coils, etc) and run it through one of the many spring rate calculators on the internet. I don't think you'll come up with rates in the 200's.

Edit: Ok, cut n paste out of Excel looks good until you hit the post button. Let's try this instead:

springrates.jpg


Pete
 
It makes sense to me now

The rates seemed high to me, and now it makes sense.

Likely if I preloaded it, measured the weight and then went down an additional inch, the change in weight would give me a realistic spring rate. I will try it next time they are out of the car.

Thanks,
Paul
 
STOP!!

Do not proceed forward or there will be three domes where the studs are and likely damaged sheet metal on the first solo run bump.

This is a horrible idea K Sport had for trying to make their off the shelf part fit the exxe.

If possible, make a spacer to distribute the load on a larger area of the strut tower's top. Those spacers are going to cause more than a minor headache.

The minimal solution would be to add something like Mark's "Big Foot" plates..

I'm just not comfortable with this lash-up.


Bernice

bpimm said:
No they are buried under the strut tower, don't really like this but without cutting I don't see a way around it.
IMG_5202.jpg



Brian
Click to expand...
 
Agreed

Even with the stock strut mounts, where the whole surface of the steel part of the mount transfers the load to the body, domes get distrorted, hence the development of the Plaia plates. Imagine what will happen when you concentrate this load on the three little spacers.
Remember that the full suspension load gets transfered from the suspension to the car at this point.

Is there no way to redesign this setup so that the camber plates are above the strut towers?

I am not going to say what I think of this "design" out of respect for those who have purchased this setup.
 
What do you mean by "preload"?

Hi,

I would argue your "preload" argument is irrelevant, unless I don't understand correctly.

The spring is assumed to be linear, F = kx.
k is constant, at any x.

Yes, the spring is preloaded when you install it on the strut, but once installed on the car, this becomes irrelevant. The weight of the car compresses the spring even further than the preload, there is no energy stored in the spring through the preloading beyond that energy that is stored in the spring through the compressiono due to the weight of the car.
If you used a shock with a much longer rod, such that the spring is not preloaded when installed on the strut, once you install this strut on the car, it is identical to the first strut with the shorter rod.

Recently, the stock springs were tested on a (very) professional spring tester. Here is the curve for the front spring:



The spring rate is the pink curve.
x-axis: overall spring length in mm
y-axis: spring rate in N/mm
(black curve is the compression force in N)
(the blue lines can be ignored)

The spring is fairly linear through much of its range.
What needs to be done is determine the range of force (or x) that the spring sees while in use on the car, and maybe convert the spring rate in that range to lbs/in. I haven't gotten around to that yet, anybody interested?
 
Do not worry, I would not consider driving it that way, I agree it is a horrible idea. it will have some kind of plate in there. This is the biggest drawback to this top mount, but with the small hole in the tower it would be difficult to get much adjustment with the top mount mounted above the tower.

Not familiar with "Mark's "Big Foot" plates.." I'll search for them.



Rupunzell said:
STOP!!

Do not proceed forward or there will be three domes where the studs are and likely damaged sheet metal on the first solo run bump.

This is a horrible idea K Sport had for trying to make their off the shelf part fit the exxe.

If possible, make a spacer to distribute the load on a larger area of the strut tower's top. Those spacers are going to cause more than a minor headache.

The minimal solution would be to add something like Mark's "Big Foot" plates..

I'm just not comfortable with this lash-up.

Bernice
Click to expand...

No Need to pull punches, this "feature" is pure S**T! in defense of those that have bought these, including myself, the pictures don't show the actual coilover so you don't get to see this until you take them out of the box.

As for redesign? haven't got that far yet, it will depend on where it needs to be for the adjustment I want. it will either be underhung or moved to the top if space is available. it will be a b^*ch to adjust like it is.

This is not that surprising to me, I consider all aftermarket parts to be a good starting point to work from, and if they work as advertised, big plus.

Brian

Ulix said:
Is there no way to redesign this setup so that the camber plates are above the strut towers?

I am not going to say what I think of this "design" out of respect for those who have purchased this setup.
Click to expand...
 
But where does this matter?

Yes, the spring will only compress another 2" if it is already precompressed/preloaded, but in spring rate calculations or in actual application this is of no interest.

When the strut is on the car, there is no more preload.
There is only load which will be higher than the preload.
The lenght of the shock rod, that caused a preload when uninstalled, now only causes a limit in travel in extension. Nothing more.

The only factor where this comes into play is in full droop of the suspension.
1) when the suspension unloads over a bump and the shock fully extends, the tire will lose ground contact - bad.
2) the spring is not fixed correctly on the strut since at full droop the spring is not preloaded - hence the need for helper springs

But in terms of spring rate, in the discussion above, how much you preload the spring by installing it on the strut is irrelevant unless you make the shock rod so short that it preloads the spring more than the corner weight of the car - which would be rediculous.
 
Rupunzell said:
STOP!!

Do not proceed forward or there will be three domes where the studs are and likely damaged sheet metal on the first solo run bump.

This is a horrible idea K Sport had for trying to make their off the shelf part fit the exxe.

If possible, make a spacer to distribute the load on a larger area of the strut tower's top. Those spacers are going to cause more than a minor headache.

The minimal solution would be to add something like Mark's "Big Foot" plates..

I'm just not comfortable with this lash-up.


Bernice
Click to expand...


Bernice, I beg to differ about the spacers. I've been racing my X for 3-4 years like this with absolutely no problems and lets just say, I'm not gentle with it either. Thats not including the spirited thrashings/turbo testing on weekends.

My only suggestion is to take the camber plates off, revers the studs and mount them on top with the spacers. This way, you can adjust them without any difficulty.

cimg2181xv0.jpg
 
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