Pontiac Solstice Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
96 Posts
Discussion Starter · #1 · (Edited)
I had to hunt around and collect information from lots of different places to come up with all of the parts and pieces to put together Koni-based coilovers, so I figured that I'd save some poor soul in the future the same ordeal and post up what I built, all of the part numbers, and where I sourced them.

Here goes...this is what I've built:



Koni SA shocks with 400lb/in 2.5" coil springs front and 450lb/in rear.

Exploded it looks like this:



Top to bottom (um, left to right), the parts are:

- Koni-provided nut and lock washer

- Stock top washer drilled to 12mm (actually 31/64" since I didn't have a 12mm bit)

- Stock upper mount drilled to 12mm (sourced new ones via eBay for $28 each)

- Stock lower washer drilled to 12mm

- Techno Toy Tuning 2.5" aluminum upper hat (22mm center bore); available here

- Bronze flanged bearing from McMaster-Carr w/22mm OD and 16mm ID to center the top hat on the shock shaft; McMaster part number 6659K34

- Stock bump rubbers

- QA1 7"x2.5" coilover springs (I'm hoping 7" isn't too short) sourced from Summit

- Vorshlag motorsports spring adapter (one side sanded down to 3/16" deep); Vorshlag part ID "25DualSpacer"

- Hyperco CS100 4" tender springs sourced from Amazon

- Koyo torrington bearings and races; bearings part number NTA-4052 and races TRA-4052, both sourced from Amazon

- Koni 50mm threaded sleeve and lower perch; sleeve part number 30.0000.0005, lower perch part number 30.0000.0006, sourced from Performance Shock Inc.

- Koni SA shocks, Koni part numbers 8241-1247 & 8241-1248; sourced from NOPI online (about $35 cheaper than anywhere else)

All told I have right about $1500 into the set of four, including all shipping and tax.

Time will tell if my spring rates are OK and if the spring length is enough. I may need to go to a longer spring and/or higher rates, but this is a start. Swapping springs will be cake compared to getting them put together the first time!

I hope this is helpful...enjoy!

Chris
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #4 ·
Quick update...the 7" QA1 springs in the front are too short, at least at a 400lb/in rate. At static ride height they have very little compression left before they'd bind. I have some 8" 425lb/in Hypercos on order to see how they do.

I'm also considering having additional snap-ring grooves cut into the shocks. The fronts I'd do 1" lower than stock and the rears probably 5/8" lower. The rears can't go much lower on the sleeves due to possible interference with the CV boot.

More to come...

Cheers,

Chris
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #5 ·
Custom Coilovers - Take 2

The front shocks have had new snap ring grooves cut (I went with 2" lower) and I switched to Hyperco springs at all four corners. The Hypercos are not wound anywhere near as tightly as the QA1 springs, which gives them substantially more compression before they would bind. I am now at 425lb/in in the front and 500lb/in in the rear. Everything looks pretty good at this point. I may still need to have new snap ring grooves cut in the rears to give them a bit more lowering potential but I think I'm OK for now. All that is left is to finish dialing in the ride height and get the car corner-weighted.

New, lower snap ring groove on the front shock (thanks to Marty at Block Head Machine!):


Complete revised unit installed up front:


Revised rear with Hyperco spring (this is actually a 450lb/in spring; I ended up going with the 500s in the same length):


The rear unit in place:
 

·
Registered
Joined
·
34 Posts
Custom Koni coilovers

Nice work. I find it interesting the spring rates your using are almost identical to mine. I've got 425 lbs/in - 8" Hypercoil in the front and 550 lbs/in - 7" Hypercoil in the rear. I started off with 700/900 in the front & rear, but found those way to loose. I next tried 550/700 front/rear, better but still loose. So far I'm pleased with the 425/550 combination.

Optimizing Spring Rates

La Sanguine

Cheers!
:cheers:
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #7 ·
Nice work. I find it interesting the spring rates your using are almost identical to mine. I've got 425 lbs/in - 8" Hypercoil in the front and 550 lbs/in - 7" Hypercoil in the rear. I started off with 700/900 in the front & rear, but found those way to loose. I next tried 550/700 front/rear, better but still loose. So far I'm pleased with the 425/550 combination.

Optimizing Spring Rates

La Sanguine

Cheers!
:cheers:
I may end up with higher rates in the rear, but we'll see how these work out. I have the new WERKS adjustable bar in the rear so I can likely get similar results with 500s if that bar is set to full stiff (it's set full soft right now).

Did you have new snap-ring grooves cut into your rear shocks? I'm right at the bottom of the threaded sleeve with the perch height and could still use to come down just a touch. There doesn't appear to be much room to bring the perch down on the rear shocks. Much more than 1/2" to 5/8" would mean the bottom of the threaded sleeve would contact the axle CV boot.

Chris
 

·
Registered
Joined
·
34 Posts
Did you have new snap-ring grooves cut into your rear shocks?
Chris:

I had the snap ring grooves lowered 1" on mine. I'm using 7" springs on the rear and don't have any interference problems.

:cheers:
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #9 ·
Chris:

I had the snap ring grooves lowered 1" on mine. I'm using 7" springs on the rear and don't have any interference problems.

:cheers:
Good to know, thanks!

Chris :thumbs:
 

·
Registered
Joined
·
34 Posts
Chris:

The main reason I had new snap rings cut was to prevent interference problems if the suspension ever bottoms out. I used KONI components for the upper spring perches and they interfere with the threaded sleeve when fully compressed.

:cheers:
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #11 ·
Chris:

The main reason I had new snap rings cut was to prevent interference problems if the suspension ever bottoms out. I used KONI components for the upper spring perches and they interfere with the threaded sleeve when fully compressed.

:cheers:
Makes sense. I used Techno Toy Tuning top hats that are more shallow, so I'm not all that worried about them bottoming. In the rear I could just use a touch more range to adjust them down.

Chris
 

·
Registered
Joined
·
96 Posts
Discussion Starter · #12 ·
Some updates...

After a season of autocrossing on these I decided to revise the design and spring rates a bit.

For the coming season I'm going to start by moving the 500lb/in springs to the front and lowering the rear rate to 450lb/in. The car has been a bit looser than I'd like so I'm going to see if I like a stiffer front bias a bit better.

Along with that, I wasn't entirely happy with the fact that I'm losing about an inch of shock travel due to the way the upper mounts are put together. Step one is replacing the existing upper mount arrangement with a fixed spring flange that fits over the bottom portion of the upper mounts. I had a buddy machine them for me on his Smithy lathe/mill.

The new spring locators are essentially just aluminum cups that fit over the bottom of the stock mounts and that the spring seats onto:



This arrangement allows for full travel of the shock and puts the compression load on the flange of the upper mount rather than on the center portion of the mount which is designed to have compliance. With that in mind, what pushed me this direction was discovering that the mount has enough compliance in it that under heavy cornering loads I was actually pushing the spring top hat up and into contact with the bottom of the mount. You can see in the picture below that despite how much space there is between the top hat and the mount, there is rubber transference on the top hat from compression contact. That's a lot of compliance! I can only imagine what that was doing to the consistency of the suspension control.



With the new spring locators you can now see that the shock gets full travel back and there is no longer such a large compression load on the center of the mount. Goodbye compliance problem!



This is really only an interim step however. The compromise of this new setup is that the springs will no longer remain square to the shock shaft as the suspension compresses and the angle of the shock changes slightly. It may not be a huge amount of deflection, probably in the range of 2*-6*, but ideally I don't want any deflection at all. What that brings me to is the creation of custom upper mounts with integrated spherical bearings so that I can eliminate both the compliance issue *and* the deflection issue (something like what's discussed here). More to come on that!

Cheers,

Chris
 

·
Premium Member
Joined
·
4,262 Posts
Nice set up I purchased a set of Koni Sport shocks last fall and will be installing them this spring so I will be following this set up Thanks for the info Chris :thumbs:
 
1 - 13 of 13 Posts
Top