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Discussion Starter · #1 ·
Hello, so I've been doing a little research on coilover setups for this car, one of the suggestions I received was if I swap the front end suspension with a Silvia one I'd have an easier time getting an affordable and better adjustable coilover setup.

But I'd like to hear some more good suggestions for an affordable and well performing setup that can suit the track + daily driving, since the ready made ones from BC racing or raptor racing for example are super pricey.

Thanks.
 

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You can get better-performing coilovers by DYI.

First, get Ground Control coilover kit. They use Eibach springs which is better stuff than anyone else has. Used by racing Porsches and Ferraris. And you can pick exact spring-rate you want. Remove factory springs, trim lower spring perch and install kit and that's it!

Then use Koni Motorsports 8611 double-adjustable strut inserts. Nobody else gives you independent adjustment of rebound AND compression damping without spending $$$$. A lot of times when dialing in suspension for specific needs, street vs track or changing spring-rate, optimum adjustments often requires changing rebound and compression in opposite directions. Or changing just one while holding other same. Other than Penske or Ohlins, you're not gonna get that feature.
 

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Discussion Starter · #3 ·
You can get better-performing coilivers by DYI.

First, get Ground Control coilover kit. They use Eibach springs which is better stuff than anyone else has. Used by racing Porsches and Ferraris. And you can pick exact spring-rate you want. Remove factory springs, trim lower spring perch and install kit and that's it!

Then use Koni Motorsports 8611 double-adjustable strut inserts. Nobody else gives you independent adjustment of rebound AND compression damping without spending $$$$. A lot of times when dialing in suspension for specific needs, street vs track or changing spring-rate, optimum adjustments often requires changing rebound and compression in opposite directions. Or changing just one while holding other same. Other than Penske or Ohlins, you're not gonna get that feature.
Thank you so much for the write up, I'll look into those 👍🏻
 

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Discussion Starter · #4 ·
You can get better-performing coilivers by DYI.

First, get Ground Control coilover kit. They use Eibach springs which is better stuff than anyone else has. Used by racing Porsches and Ferraris. And you can pick exact spring-rate you want. Remove factory springs, trim lower spring perch and install kit and that's it!

Then use Koni Motorsports 8611 double-adjustable strut inserts. Nobody else gives you independent adjustment of rebound AND compression damping without spending $$$$. A lot of times when dialing in suspension for specific needs, street vs track or changing spring-rate, optimum adjustments often requires changing rebound and compression in opposite directions. Or changing just one while holding other same. Other than Penske or Ohlins, you're not gonna get that feature.
Quick question, are those two parts just for the front suspension? Or both the front and rear? And do I use the coilover conversion kit together with the Koni adjustable struts?
 

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Most affordable just buy them and bolt them on option are T3:


Protip if you wait a few months for black friday they have like a 10+% off sale. They also sell the kit to do the fronts if you're more DIY.
 
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Quick question, are those two parts just for the front suspension? Or both the front and rear? And do I use the coilover conversion kit together with the Koni adjustable struts?
yes, this is just for front. You re-use factory strut housings. Coilover kit goes on outside to replace springs. Koni double-adjustable strut inserts goes inside factory strut housings. Need to drill hole in bottom for compression-adjustment. Rebound adjustment is by usual knob on top.
 

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Thank you so much for the write up, I'll look into those 👍🏻
You're welcome! I also don't recommend lowering car without roll-centre adjustment. Due to geometry of strut suspension, lowering will lower roll-centre more than amount car was lowered. This increases distance between C.o.G. and roll-centre, causing car to lean more than before, which puts tyres onto outside edge more than stock, thus reducing grip.





So you end up having to increase spring-rate more than necessary to combat this extra lean. Also need camber plates to match lean angle.

Unless all you're doing this for is lowering looks. In which case, cheapest is to just cut factory springs.
 

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Discussion Starter · #8 ·
You're welcome! I also don't recommend lowering car without roll-centre adjustment. Due to geometry of strut suspension, lowering will lower roll-centre more than amount car was lowered. This increases distance between C.o.G. and roll-centre, causing car to lean more than before, which puts tyres onto outside edge more than stock, thus reducing grip.

So you end up having to increase spring-rate more than necessary to combat this extra lean. Also need camber plates to match lean angle.

Unless all you're doing this for is lowering looks. In which case, cheapest is to just factory springs.
My intention here is to have it perform well as a daily and have that freedom to adjust the suspension for track days and drifting.
 

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That's tough 3-way combo as optimum suspension settings for those 3 tasks vary substantially! Difference between track & drift is HUGE! You'll want front compression close to max and soft rebound for drift while track would have lighter compression and stiff rebound. Luckily with dual-adjustable dampers, you can make these adjustments.

I started out this way with my '82 MKII in '84. Here's good comparison article at one of my favourite tracks. C&D - Best Handling Cars 1984. I found their actual lap-times on Ferrari chat forum.

1. Lotus Esprit Turbo 87.1 MPH 1:43.3s
2. Ferrari 308 QV euro 86.8 MPH 1:43.7s
3. Porsche 911 Carrera 86.7 MPH
4. Porsche 928S 85.1 MPH
5. Porsche 944 84.4 MPH 1:46.6s
6. Audi Quattro 82.8 MPH
7. Toyota Celica Supra 81.5 MPH 1:50.4s
8. Honda Prelude 78.8 MPH

Interesting that top 4 best-handling cars in that comparison had the slowest times at Willow Springs. Goes to show that pure speed isn't all there is to handling. Feel and control makes it easier to get the car to its limits, and more fun too!

I ended up taking 10-sec. off Supra's lap-times by upgrading just swaybars, dampers (Koni 8610 Sport), stickier tyres and brake-pads. Faster than all those Porsches and Ferraris! :) Swaybars makes bigger difference in handing & cornering performance than coilovers (worth maybe 2-3 sec). And preserves ride-comfort for street use. I'd recommend upgrading swaybars 1st; best bang-for-the-buck in performance-increase.

Partly based on that article, I ended up buying 944 TurboS decade later. Here's my 1st time @ Willow Springs with it. In bone-stock trim, it did same times as my upgraded MKII ~1:40!!! :p


White 944 NA that passed me after 1st lap was driven by Rick White, chief driving-instructor of POC. Here's article comparing 944 TurboS vs. classic 911 Turbo
 

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For rear, you can get QA1 double-adjustable coilover shock. Many people like to completely remove rear spring, but I think that's putting too much load on shock-mount. Perhaps trim stock spring slightly, then use coilover shock to supplement factory spring-rate with double-adjustable damping. QA1 - coilover shocks

Again, after getting swaybars.

Some good reference material:

Physics of Racing - Beckman
How to Make Your Car Handle - Puhn
An Introduction to Race Car Engineering - Rowley
Tune to Win - Carroll Smith
Tyre and Vehicle Dynamics - Pacejka
Fundamentals of Vehicle Dynamics - Gillespie
Race Car Vehicle Dynamics - Milliken
Chassis Design: Principles and Analysis - Milliken
Vehicle Handling Dynamics - Masato Abe (should have MatLab to make most of this)
 

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Eventually I went to coilovers on my MKII and Porsche. Both using Ground Control kit. If possible, better to get 10-12" springs rather than 8". They'll have more preload, won't fully extend and "fall-out" or rattle at full-extension, thus requiring helper-springs to take up gap.



Remove spring-perch leaving ledge for coilover sleeve. On 944 this opened up additional 40mm space for phat wheels & tyres!


There's slight gap between sleeve & strut that can cause some noise. I fill that gap with PVC shim.


Epoxy in place.


Paint...


and we're done!



On newer cars with sealed struts, I'll convert to rebuildable kind to allow use of larger variety of performance inserts.






Or build my own from scratch. Bilstein Motorsport upside-down dampers are really, really good. These bolt in at bottom, so no gland-nut needed on top of strut-housing. Just sleeve to hold seal and that's it.

 

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Discussion Starter · #12 ·
Eventually I went to coilovers on my MKII and Porsche. Both using Ground Control kit. If possible, better to get 10-12" springs rather than 8". They'll have more preload, won't fully extend and "fall-out" or rattle at full-extension, thus requiring helper-springs to take up gap.



Remove spring-perch leaving ledge for coilover sleeve. On 944 this opened up additional 40mm space for phat wheels & tyres!


There's slight gap between sleeve & strut that can cause some noise. I fill that gap with PVC shim.


Epoxy in place.


Paint...


and we're done!



On newer cars with sealed struts, I'll convert to rebuildable kind to allow use of larger variety of performance inserts.






Or build my own from scratch. Bilstein Motorsport upside-down dampers are really, really good. These bolt in at bottom, so no gland-nut needed on top of strut-housing. Just sleeve to hold seal and that's it.

Thanks again for the detailed write up, will keep it as reference. Quick question tho; from what part of the strut housing did you cut out that threaded barrel?

I'll PM you once I get to assembling my setup, many thanks!
 

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I scrounged junkyards for old struts with threaded top. Usually Volvos, VW, old Datsun/Nissans, many Toyotas. Most common to have 50x1.5mm threading. I prefer external threads rather than internal. Then chop 2-3" off top and weld to existing struts. Can also make my own with lathe, but takes longer & more effort than junkyard car.

Can also buy them pre-made for this purpose, but can get expensive @ +$150/pr.
 

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Discussion Starter · #14 ·
I scrounged junkyards for old struts with threaded top. Usually Volvos, VW, old Datsun/Nissans, many Toyotas. Most common to have 50x1mm threading. I prefer external threads rather than internal. Then chop 2-3" off top and weld to existing struts. Can also make my own with lathe, but takes longer & more effort than junkyard car.

Can also buy them pre-made for this purpose, but can get expensive @ +$150/pr.
Do you fabricate these pre-made assemblies? Seems interesting.
 

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Do you mean making just the threaded tops? No.

If you mean the complete strut housings? Then yes.

You shouldn't have to do anything other than slide GC coilover kit on. Don't even have to trim spring-perch. Strut-housing already has threaded top for inserts.
 

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You can get better-performing coilovers by DYI.

First, get Ground Control coilover kit. They use Eibach springs which is better stuff than anyone else has. Used by racing Porsches and Ferraris. And you can pick exact spring-rate you want. Remove factory springs, trim lower spring perch and install kit and that's it!

Then use Koni Motorsports 8611 double-adjustable strut inserts. Nobody else gives you independent adjustment of rebound AND compression damping without spending $$$$. A lot of times when dialing in suspension for specific needs, street vs track or changing spring-rate, optimum adjustments often requires changing rebound and compression in opposite directions. Or changing just one while holding other same. Other than Penske or Ohlins, you're not gonna get that feature.
This is great information. Thank you for this! Also, when I'm looking at those Koni 8611 I notice there is a few options. Do you have any advice on which is the best fit?
 

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Those come in different lengths and strokes. Depending upon if you have stock ride height, stock spring-rate or lowered with stiffer spring. Measure factory parameters and select 8611 that has length/stroke that best matches your final configuration.

You don't have to go overboard with spring-rate, lots of people overdo it due of lack of compression damping. Koni 8611 has separate compression & damping adjustments for fine-tuning opions.
 
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