What Should I Know About Suspension?

Suspension Tech Session by Don Erb, Comptech USA
Alignment of any car including the NSX can make a jewel or a sow depending on how it is done. There are several setup considerations that need to be looked at before the alignment is done, each one will also affect tire wear. So, do you want MAX mileage or ultimate performance? Is it strictly for the race track or just occasionally the track? As you can see you need to consider all these before you spend your hard earned money.
Today’s new radial tires love camber and the more you five them the better the car will handle. If this is a track only car, we would aim for approximately 3 1/2 degrees to 4 degrees negative camber. This would use up the inside edge of the tires at a rapid pace if driven on the street.
Let’s start with what is adjustable on your car and the effects each one can have on handling. The thing to remember is that everyone drives differently and what is the best setup for your friends NSX could seem evil to you. A good example of this was when Jimmy Vasser changed back to his old setups on his Reynard instead of using Alex’s and he started winning again. Obviously Alex’s setup worked for him but Jimmy’s driving style was different enough that he needed his own.
Camber: This can and will, as said above, be the number one reason for rapid inside tire wear, 2nd is toe setting, but we will come to that later. The more camber you have the more high speed grip you will have, but be realistic, if you are excessively wearing out the inside of the tires, you’re not driving the car hard enough and should reduce what you are using. On a street driven NSX I would recommend setting the front to 1 1/4 degrees to 1 1/2 degrees negative camber and the rear to 2 degrees negative. Typically, the most you can get out of a stock NSX is 2 degree negative on the front and 2 5/8 degrees negative rear. This can be increased with offset bushings if it is track car. It will also change as you lower or change the ride height.
If you want MAX performance and you are going to the track, get yourself a [BJ]PROBE-type[/BJ] tire pyrometer. This is the best way to test your setup. After doing several laps you should test the tire temps at three places across the tire(outside 1/4, middle and 1/4 inside edge). Start from the side of the car that you think the tires will be hottest (usually the most loaded corner of the car). You can tell several things from the temps as follows: hot in middle

too much air pressure; hot on each edge

not enough air pressure; equal temps across tire

not enough camber; hot on outside edge of tire

not enough camber; 5-15 degrees hotter on inside = camber is good!
Caster: the standard setting on the NSX is between 6-7 degrees, this is fine for all models and I would not change. You do however want it to be equal on each side. This in street car terms is 3 times higher than most cars. This is why non-power steering NSX’s have fairly heavy steering. The reason for high caster is to give you more grip on initial turnin into the corner, as you turn the wheel the front end gains camber and this gives you more grip. As you can see the engineers refused to compromise in designing the NSX suspension.
Toe Setting: The toe on the front of the NSX should be approximately 4mm or 3/16″ toe-out. This is a good spot to start with. If the car seems slow on turning into a corner you can add more toe out to give you more aggressive steering. Be careful, there is no such thing as too much toe out, but it will increase the tire wear and will decrease the straight line stability. Remember, what is comfortable for your friend may be different for you. Unless you are racing I would not recommend going over 8mm out.
Rear toe should be about 3-4mm toe in. The more toe in you have on the rear the more stable the car will be down the straight and the more stable understeer you will have in the corner. Some factory settings on certain models had up to 8mm toe in. This was to keep the car more stable. The tire wear was very high and many owners complained about it, so the next year they went back to lower settings in the 4-6mm range. In an ideal world, as the suspension moves the toe would never change, but it does. This is why we make the low compliance rear beam and toe links. If you don’t believe me, do this simple test. Look at the rear wheel out your door and roll you car backwards and hit the brakes, see the wheel move in and out? This is toe change! The less you have the better.

Toe Summary:

More toe out in the front: Turn-in quicker, also called Turn-in oversteer, if excessive.

Car is darty: Reduce toe out in front. Toe in in the rear. If car pushes in mid corner add more toe in.

Remember it is always better to err on the safe side and run too much toe in than not enough.
[BJ]From my experience, Zero “0” front toe makes the car ‘wander’ the road and become more darty, while adding more and more toe OUT in front makes the turn-in slightly more vague and allows the driver to be more aggressive with the wheel without consequence. Somewhat backwards from the above comments.[/BJ]
These are just the basics and as you can see all these settings affect and interact with each other. This can be very difficult to grasp in one easy lesson.

How Do The Various Suspension Packages Compare?

Spring rates

normalized for units (2.2 lb/kg and 25.4 mm/in)

	Front	Front	Rear	Rear	Front/Rear	Lowering
Units	lb/in	kg/mm	lb/in	kg/mm	Percent
Stock ’91 NSX	170	3.04	220	3.94	77%	n/a
Stock ’96 NSX	179	3.20	212	3.80	84%	n/a
Stock ’97 NSX	196	3.50	224	4.00	88%	n/a
Stock ’95 NSX-R	447	8.00	319	5.70	140%	n/a
Stock ’93 NSX-R	447	8.00	336	6.00	133%	n/a
Stock ’97 NSX S / Zanardi	363	6.50	279	5.00	130%	0.4″ ?
Stock ’97 NSX S Zero	448	8.00	336	6.00	133%
Stock ’02 NSX Type-R	582	10.40	465	8.30	125%
Ground (Race)	601	10.74	501	8.95	120%
Ground (Street)	375	6.71	501	8.95	75%
Comptech Pro	1002	17.90	601	10.74	167%
KW Variant 3	343	6.12	343	6.12	100%	20-50mm Front, 25-55mm Rear
Eibach Pro	154-228	2.75-4.07	137-280	2.45-5.00	112%-81%	1″
H&R	260		275		94.5%	1.5″
Tanabe GF210	319	5.7	269	4.8	119%	rated 1.3″/1.3″, actual front is lower than rear
Swift Sport	146-218	2.6-3.9	157-258	2.8-4.6	93%-84.5%	20mm front, 15mm rear (0.8″F, 0.6″R)
TEIN-S	224	4	246	4.4	91%	0.7″F/1.0″R

Damper (Shock) Rates

units are kg @ 0.3 m/s

|

Model	Front Extension	Front Compression	Rear Extension	Rear Compression
1991 NSX	101	98	173	112
1993 NSX-R	319	226	315	222
1995 NSX-R
1997 NSX	115	109	183	125
1997 NSX-S and Zanardi	195	150	230	170
1997 NSX S-Zero	319	226	315	222
2002 NSX-R	321	208	338	244
Bilstein NSX*	163	165	132	193
Koni NSX**	428	275	642	275
*units are kg @ 0.254 m/s, source: goldNSX
** extension (rebound) values are for shocks at full stiff adjustment, source: shrddr

[AWN] One thing that seems universally ignored by all the manufacturers and users of the so-called “progressive” springs is the problem of properly adjusting your shocks to match. Obviously, the ideal shock setting for the “soft” rate will be wrong when the spring gets into its “stiff” range, and vice-versa.
[PM – 99/8/31] The Eibach is progressively wound and will provide a more compliant ride, the H&R is a linear design that will tighten things up. If you concerned with ride quality and don’t care about lowering the car, retain your stock coils.
[PM – 99/1/24] BILSTEIN: Warrants its gas pressure shock absorber against defects in workmanship and materials for as long as the original owner owns the vehicle. If at anytime the shock malfunctions and Bilstein determines it to be defective they will either replace or repair it. Exceptions, improper installation, racing or off road usage, modified shock.
KONI: Warrants all new shocks to the original owner against defects in material and workmanship, excluding mounting rubbers, washers and bushings when used under NORMAL operating conditions for as long as original owner owns the vehicle. Excludes improper installation, modified from intended use or when used for off road, racing or any other driving competition. Heavy duty trucks and busses are warranted for 3 years or 300,000 miles. Would suggest that all quality shock warrantees are basically the same.

KW Variant 3

The KW suspensions coilover for the Acura NSX enables the owner to lower their vehicle 20 to 50mm on the front axle and 25mm to 55mm on the rear axle. The coilover suspension retains enough travel to handle maximum load and dynamic loads during driving. Double adjustable rebound and compression damping allows a truly individual performance driving setup from agressive track to fine tuning the ride quality and comfort for every day driving.
Variant 3: Race technology for the road.
The Variant 3 is state-of-the-art technology for the skilled/experienced driver to the everyday driving enthusiast. The separate and independent compression and rebound damping adjustments allow a truly individual driving set-up. These unique systems with the 3 individually adjustable components (compression, rebound, and ride height) allows for adjustment of the compression of the damper in the low-speed range, while the high-speed set-up, so decisive for driving comfort, has been pre-set by our engineers.
• Independent Compression and Rebound adjustable damping (Double Adjustable)
— Infinitely adjustable rebound damping
— 14-level adjustable compression damping
• Ride height adjustable
— TÜV-tested adjustment range
• “Inox-line“ stainless steel technology
• High-quality components for long term durability
• Detail instructions for ease of use
• Spring rate and valving determined by KW’s state-of-the-art 7-Post rig
• 343lb/343lb front/rear spring rates
[BJ]German brand KW made famous by their efforts in LeMans, ALMS, FIA GT, European Touring Car, BTCC, etc… as well as their links to supplying the factory OEM Mercedes AMG “Black Series” cars and the Nurburgring record holding production car – the Viper ACRX. With near OEM ride quality, KW has proven to be one of the most streetable, compliant, and quality coilovers on the market for the NSX. When used with upgraded swaybars, the KW V3 has the best of both worlds for street comfort and track performance. Its also double-adjustable with separate compression and rebound adjustment for fine tuning of the cars handling.[/BJ]

Comptech Pro Suspension

[BH] If anyone is considering the Comptech Pro Suspension e-mail me at bhogan@ml.com. Even on its softest setting I had a tough time on the rough roads in NY, NJ, and PA. Unless one really, really wants to race the car, I don’t think the $5000 handling upgrade vs. the very rough ride tradeoff is worth it.
For those of you still having trouble with Comptech (or other) suspension upgrades keep reading.
I finally installed the helper springs on my car. They cost $150, and they clearly hold the Eibach 1000 lb linear main spring in place. They stopped the clanking sound that resulted from the main spring slamming against the strut and having to realign itself when it was re-weighted. Small potholes are no longer a problem either. However, the *deeper* potholes now have a deeper *thud* sound intead of the loose sounding metal-on-metal *clank*. The 1000 lb fronts are just too stiff for real bumpy streets.
Also, the helper springs should cure the clanking at the track since that was a result of the spring slapping around and then having to be realigned on the strut when ever the spring was totally unweighted in tight corners.
The helper springs add about 3/4″ total to the height of the spring when they are compressed. The spring itself is about 1/2″ and the coupling that fits between the helper spring and the main spring adds about 1/4″.
Just so there is no confusion, *helper* springs are used to keep the main spring centered on the strut. They do not change the spring rate of the main spring. They are used frequently with stiff springs in racing applications. *Tender* springs are used to change the the initial effective rate of a main spring. They come in various rates (Eibach even carries progressive rate tender springs) and when added to a linear main spring, combine to form a progressive spring.
IMO, Comptech grabbed the stiffest road racing spring Eibach has on their shelf to eliminate the front bodyroll. They then matched a rear spring to the fronts and added the Konis to create their pro package. While the Konis are very adjustable, obviously the springs are not.
My ’95 is a track car that spends some time on the street so I like the go-cart handling, but for those who need more of a compromise, I suggest calling a suspension tuner to learn how much softer the springs can get to make street driving enjoyable and still deliver superior track handling. I suspect the answer will be different for every driver, and I suspect trial and error will be the process. Maybe we will have different setups at NSXPO that we can evaluate, but then again, what works at MidOhio may not be best at your local track…

[BH] OVERVIEW

I installed 750 lb springs in place of the 1000 lb springs Comptech sells with their pro kit to see how the car would feel. The springs cost $55 a piece and I can swap them out in a little over an hour so I did not view this as a big investment. I liked the handling of the 1000/600 combo vs the stock set up, but all the chatter on the list about springs prompted me to experiment. I realize springs are a personal thing, but maybe this will help someone on the list.

DETAILS

I had previously installed helper springs on the 1000 lb springs so I kept the helper springs on the 750 lb springs also. I did not change the 600 lb rear springs. I did not have the car corner balanced as I did not get the springs on until late Friday night, and Sat was a track day.
I had R1s on the car this weekend, and the Koni coil over shocks were set at the middle of the range for the bounce and on the stiffest setting for the rebound, which is my normal Road Atlanta setup. The alignment was the same as the last track weekend.

CONCLUSION

Guess what…I like this combination much more than the original 1000/600 lb combo. There was just a smidgen of body roll, and the car felt great. There is no doubt in my mind that the 1000 lb front springs are way too stiff for street and track, unless you’re Peter Cunningham. The car still drives like a go-cart, but the softer springs gave me a much better feel for what the car was doing. Once I got used to them, I ended up running quicker times than with the stiffer springs. Basically, in my car, this setup produces a *little* oversteer; where as, the Comptech setup produces a *little* understeer. Would 800 lb springs be perfect? I don’t know, but I like a little oversteer anyway.
The 750 lb springs are also a big help on the street. No more clanking. It actually feels like the springs are compressing up front. I believe this is a great combination for those of us who want lots of track performance and still be able to drive on the street comfortably.

Dali Semi-Pro Suspension

[CA – 99/8/7] In the past, I have experimented with different suspensions, stock, koni’s with stock springs, Bilsteins with stock springs, Bilsteins with H&R springs, and now the DALI Semi Pro Shock/Spring height adjustable kit!
Install: I was able to take my time installing the shocks and springs as I was waiting for a wheel from Forgeline. the kit comes pretty much assembled except for the shock mounts, which are complete custom billet aluminum pieces which were very well done. The kit came with the springs preassembled on the shock at 500ft/lbs rear and 600ft/lbs front, this didnt make too much sense to me, I made some phone calls, and the concesus was the same, so I reversed them, 600 rear, 500 front (more on this later!). My logic for this is the engine and most of the weight is in the rear, I know Comptech and many others have theirs the other way, I also hear that ctech doesnt use sways so maybe this is to compensate, I dunno. I will try it this way and see what happens. The Shock is constructed extremely well, as are the springs. I thought I would preassemble the shocks to the billet mounts, I had a *&%)*&%*_&% of a time getting the bushings into the billet mounts, the good thing here is you know they arent going to move around and make noise.
Getting the shock and mounts into the car was very easy, no problems, it is somewhat awkward bolting the mounts to the car though, the stock setup has the 3 bolts set into the mount like lugs so its easy to put the nuts on, the DALI setup has you holding the screw in while putting the nut on, uncomfortable if you are doing this by yourself, but not impossible to do.
Getting the lower bushings into the A-arms was also very easy, in fact you have to hold the A-arm up enough to slide the retainer bolts through, this was light years easier than the stock or Koni’s which was short of an all out delaration of war! If you have a spare jack, use this to hold the A-arm up, makes life alot easier.
I wasnt sure where I wanted the ride height to be, so I figured it would be easier to start low and raise the height if I wanted, so I loosened the retaining allen screw far enough to turn the lower spring perch, and adjusted it enough so it was firmly against the spring. This would be a good starting point. You will also notice that installing the fronts can be interesting due to the A-arm being very close to the springs, I had to adjust the camber to give the spring clearance, at first this freaked me out…after calling Mark, he said this was normal, and once you put weight on the wheels, the clearance opens up quite a bit, he was right.
I finally recieved the last Forgeline wheel ( thanks Andie Lin), and it is essentially brand new, they even called me to notify me it was on its way this is what customer service is about!), I was going top get some AVS Intermediates for the rear, but I got a killer price on some SO2 PP’s…wow are these things awesome…!
Test: I finally get the car on the ground this morning and decide to take a spin, the alignment is of course off, so I will get it redone, but the tires stick well, the front shocks feel “bouncy” and the wheels hit the fender liner even after I adjusted the height twice…hmmmm…
I decided to swap the front springs with the rears…I figured it would be fairly simple IF I can take the springs off while not removing the shocks…luckily I was able to do this, all in under an hour (very cool!), I again run the spring retainer/height adjuster thingies up as far as I could get them by hand, and lowerd the NSX once again, the ride height was a bit higher than before, which is good as the rears were at max camber….I took the NSX out to my “testing grounds” and it rode MUCH better, not bouncy at all, very smooth, yet stiff. I am looking for a good race alignment shop here in Dallas and will have it corner balanced and then aligned.
Overview: I have only one complaint about the DALI semi pro suspension, it NEEDS to include a “wrench” to adjust the height of the springs when it is too tough to do by hand…otherwise, it is very awesome and am looking forward to getting it corner balanced and aligned.

Eibach Springs

Eibach part number 4025.140 for the Pro Kit springs.
[KP] I got started with the Eibach install at about 9am. Finished at 4pm. What a pain in the butt! It’s sure not as easy as the shop manual would lead you to believe. “Remove bolts, disconnect brake line hanger, remove damper
assembly.” Yeah, right!
All in all, it wasn’t *that* bad. I guess I just got optimistic from reading the easy description in the shop manual the night before. If any of you are planning to do an install soon, give me a holler, and I’ll give you some better input that *may* save you a minute or two. Perhaps requiring one less Advil than I popped tonight.
Well, I promised some before/after top-of-the wheelwell measurements, so here they are: Oh, please note that I bought my springs used from Randy with about 4K miles on them. I’m assuming they’re settled. I did take the car out to stretch its legs before collecting the *after* measurement.

1.00

	Stock Height (in.)	Eibach Height (in.)	Difference (in.)
Front Left	25.75	24.75	-1.00
Front Right	25.68	24.68
Rear Left	26.68	25.75	-0.93
Rear Right	26.75	25.75	-1.00

[BP] I also have the Eibach’s a. It looks perfect now. I think Honda had to compromise with the ride height.
As for ride, I see NO DIFFERENCE in ride qualities with just the Eibach’s. I have driven two other cars with Eibach’s and Koni’s and they are MUCH stiffer. Therefore, it must be the Koni’s. IMO, I like the same ride with the Eiback/Stock Shock and maybe put a stiffer sway bar for increased limits with wider tires.
[AV] I second Kendall’s observations as well. I have been driving with Eibachs and stock shock setup for several years with good results. The ride is almost indistinguishable from a stock car. And the handling is improved, probably due mostly to the lower center of gravity. The stock shocks are quite firm as it comes out of the box, thank you, certainly a lot firmer with more control than shocks that come with luxury 4-door automobiles.
[AV] The Eibach pro-kit suspension (part # 4025.140) lowers the car 1″ and has a progressive spring rate. This gives the car has a very compliant ride on highway travel, but firms-up nicely in the turns. The initial compression rate is lower than factory springs, but rapidly increases to around 30% higher than stock.
[BP] I watched the guys at Motorsports Tech in Houston do my springs and I’m REAL glad that I paid them to do it. It cost me $150 and it was well worth it. Now that I have added Dali sway bars, the car feels totally glued to the road! Man, this is how the car should come from the factory! Koni’s would be over kill! Nothing more is needed besides Eibach’s, 19mm sway bars, and wider tires.
[AWL – 99/10/19] I feel that the best way to lower a car and retain/improve handling, is to lower the car with struts, and not with springs. I found that lowering the car with Eibach’s only and running 17/18 wheels/tires, results in unpredictable handling when driving aggressively. The OEM struts have a rebound damping rate that simply cannot keep up with the increased weight of the aftermarket wheels/tires, especially in the rear; when driving around turns, the
rear suspension will bunch up and break loose unpredictably. Most people install aftermarket springs for a firmer ride and for improved aesthetics.
I feel you improve looks by lower the car with springs, but you kill performance…you don’t get a much firmer ride, but you will get a bouncier ride, since the OEM struts are too soft to “keep up” with the stiffer/lower springs. In order to improve handling, lower the car with struts and keep your OEM springs. The best route would be to upgrade springs AND struts. Just doing springs is less expensive, but I don’t think you’ll be happy with the result in terms of handling. Of course, it all depends on how you drive, so it’s a matter of opinion. Some NSXers have dropped in springs alone and attest to how much better the car handles. I personally felt the handling sucked big chalupas with just springs.

H&R

[NM] I bought the H&R springs from Chuck’s Brakes for $300 (including shipping) and used the stock shocks with them. I did the install myself (as you might remember) and it was a PAIN! Remember to get your car aligned when you do this as the process required moving a lot of stuff around and potentially changing (slightly) the relative ride height from front to back. Anyway – here is what I think…
Looks: I think they make the car look awesome. I measured and they delivered the 1.25″ lower that they promised. I really hated how “high” the wheel wells were and now it looks aggressive. Note: be carefull with aftermarket wheels as they may rub now where they didn’t before. I have stock 91′ wheels that are chromed and it looks killer.
Ride: Kind of a mixed bag. On the track or smooth pavement – I think they work great to keep your center of gravity down and the stock shocks work fine (not to stiff, not too loose). If you are a novice – you should be concentrating on the line and your driving – and not your shock dampening settings. If you are more advanced, you have probably already deleted this email and you are trying to get your supercharger tuned one last time before another southern California street endurance race!
As for the street – I think I liked the stock spring / shock setup better. The after market springs are about the same height as the stock springs, but with slightly less thickness. With this lower spring coefficient, the car tends to “bounce” more with the stock shocks. This is especially noticeable when you have a harness and are strapped in. Also, you will never look at another speed bump the same way again as (at least with the stock wheels) you will hit anything over 2″ from top of the road. I’m believe the adjustable shocks could dial in more stiffness and correct some of this – but am not sure.
All in all – if you are going to upgrade the springs only – do it for looks first, smooth driving second, and general ride quality third.

Ground Control

[DH] I installed the Ground Control stuff right before the Virginia City Hill Climb due to:
I had to fit the big rims and tires under the front of my car, and with the adjustible Koni’s and Eibach springs(both about 5 years old or so), the front tires rubbed. NOTE: The Comptech Tecnomagnesio Wheels fit fine with their recommended tire setup, but I went up one size to 245/45/17 to get the big Hoosiers underneath. The Ground Control allows you to adjust ride height, which is what I think I needed to make sure I get the Hoosiers underneath.
The car felt great, with unbelievable “stick” with this setup(along with Dali bar and Comptech Toe links/bushings). The Hill Climb was the first time I ever ran with this setup, so I never even really to got to “shake it out”, but it really worked great.
My Caveats are:
GC was patient with me on the phone, answer all the questions my suspension guy had
Seemed weird that they had wrong recommendation on springs, the dual spring setup in the front was way too high the first time, so now I just have single spring in front. You would THINK they could send out a sheet saying, “Buy this spring setup for the street, buy this spring setup if you are track oriented, buy this spring setup with this size rims, etc.”. It seems like they are winging it when you call them, depending on who picks up the phone.
My dual rear springs are clunking a lot, and I got my car with Larry the Riverside NSX mechanic who is going through the car, putting new fuel regulator on the supercharger, etc. I told him to check out the springs and see what the scoop is. It wasn’t clunking like this at the Hill Climb, so maybe something needs adjusting.
I was thinking that since these are ride height adjustible, I would raise height slightly infront for track events when I use the 17/18 inch rims, and when I get back home I put the 15/16 stock rims on and lower the height. However, Harry said that raising and lowering the height screws up the rest of the alignment, so I just have it aligned for the track at all times, and I don’t screw with the height…
[BH] I have had pretty good success with Ground Control, but I just order springs from them. I do not ask their opinions.
Unfortuntately, based on my success with them I referred two Atlanta NSXers to them to buy their ride height adjustable Konis. The Konis looked okay, not nearly as nice as the Konis that Comptech sells with their Pro kit, but they also cost quite a bit less than the Comptech Konis so everyone was happy until they felt the harsh ride and heard the loud clanking sounds that the dual spring (main + tender) setup produced. Customer support was initially less than satisfactory but I believe ultimately GC helped the guys out. Hopefully one or both of the guys will comment further. I believe even Doug ‘the flame’ Hyashi had an interesting experience with them over the phone.

[AV] I’ve had the Ground Control suspension for about two years now, and I can say I am happy with the results. The first setup I had had a single main spring at each corner. Ride was acceptable, handling was significantly better.
After a few months, I replaced the front springs with stiffer main springs, and added tender springs at all corners. The result was a more comfortable ride, but with much more aggressive and taut handling when needed. Combined with the Dali sway bars, Al T.’s collars, stiffened up Konis and R1s at the track, it is an AWESOME handling machine. You’d have to drive it to believe it. And I’m not just being arrogant 😉
Of course it is not as nice as the Konis Comptech has with their pro kit. The GC Konis are the same yellow bodied Koni sport shocks you could buy almost anywhere. And the whole GC shock/spring/conversion setup costs about $1000, while the Comptech pro kit lists for close to $5000 nowadays.
The front lower perches (that are adjustable up and down) will rub the upper suspension arm when it is at its lowest position, AND when in full droop, AND when you are using the longer tender and main spring setup.
Possible solutions to this are:
Raise the front end a little bit, so the lower perch is high enough to clear the upper suspension arm in full droop.
Depending on how much ribbing there is, you can have the lower perch machined to take off the lower corner. This will give you about a quarter inch or so additional clearance, which is sometimes enough to clear the upper arm. This is what I ended up doing (GC also advised me to try this first), and I was able to clear the arm.
Limit the suspension travel so it does not go all the way down in full droop. I have seen, on some of the racing Porsches, a strap that they install on the lower A-arm that is bolted to a sturdy point on the body or a stationary part of the suspension, for the purpose of limiting the travel of the suspension during “droop.” I don’t see why we can’t do it on our cars. ICBW.
Change springs to a shorter length. However, I understand that I already have the shortest main spring possible, at 6″ long, 2.5″ diameter. Tenders are 2″ long, so unloaded length of the whole spring setup is 8″. Though it is possible to eliminate the tenders up front, you just lose its benefit.
Other parts of the suspension do not hit anything else. This is only the potential problem area, and it only involves the front suspension. There is no problem whatsoever with the rear suspension.

Bilstein Shocks

[WME – 98/10/25] After about 1.000 kilometers on the road and 180 km on a track I can say the yellow-blue Bilstein shocks (for NA 1 and NA 2) are an astonishing compromise for NSX drivers who want enough comfort on the street and good handling on the track.
They have a possibility to lower the car (with stock springs) that I didn’t use – so there’s no change for the spring rates.

Street: The first hit when you drive over a bumpy road is softer as it is with stock shocks. But the rest of the way is stiffer (kind of progressive). That effect gives you good control up to top speed in autobahn curves with bumps or other obstacles. The car won’t jump aside (you can notice that bad effect with cars with a suspension that is too stiff). The relation between front and rear suspension seems to be more close to the S-type version: Front a bit softer than stock, rear a bit stiffer. Very important: Your passenger (i. e. girl friend) won’t complain about the new shocks.

Track: Reduces body roll a bit (still waiting for the Dali sway bars for more reduction), prevents the well-known counter swings of the rear completety (maybe also an effect of the Bridgestone SO-02 PP, don’t know), gives you a slight understeer with stock alignment you can control easy with the throttle to neutral or oversteer, warns you long before the car gets uncontrollable, a very safe feeling also if you go to extremes in corners or on the brakes (Guus Toth – who has koni shocks on his one and drove my car for some laps yesterday – told me that the konis are way stiffer and give you only a little time to react if something goes wrong). Maybe real experts are faster with the konis – rookies like me should prefer the Bilsteins.
[PM – 98/10/26] As I’ve mentioned in previous posts, we’ve been testing with BILSTEIN dampers specifically to ensure that they would compliment and enhance the already superb handling of the NSX. Those of us who enjoy our cars as grand-tourers but also dedicate a percentage of their use to track events/driver’s schools have pretty much been restricted to stock shocks or KONI’s at the price of sacrificing ride quality. Those of us who wanted to lower the car for cosmetic or performance reasons have been required to invest in lowering springs as well as shocks.
I’m excited about announcing that CGI MOTORSPORTS, has entered into an agreement with BILSTEIN to market the CGI-BILSTEIN shock absorber. This product will not only enhance the dampening of the suspension, but will also allow you to custom design your ride height without incurring the cost of aftermarket springs. It should be noted that the shocks will carry the full BILSTEIN “lifetime” factory warranty. As a side note, it’s not unheard of for the BILSTEIN shock to exceed a 100,000 mile life span.
The selling price for the custom ride height shock is $169.00 each versus a list price of $219.00 plus shipping. This is approximately $250.00 – $350.00 less than KONI/EIBACH setup or $44.00 per set less than the discounted OEM shock. As always, we have an automotive engineer on duty to assist you with any technical questions you might have and, he can also help to determine if the KONI/EIBACH setup may be preferred based upon your priorities. He can be contacted at 630.262.0063. Phil Mirenda, CGI MOTORSPORTS DIVISION, THE COALITION GROUP, INC.
[DNG – 98/12/10] They’re exactly like the ones seen on the Hyper Rev NSX edition. These are adjustable to a predefined ride height by simply adjusting the lock ring in which the bottom spring plates rest on. These costs less than half as those found in Japan and about the same as the non-adjustable Konis here.
I ordered mine with stock ride height, .5″ lowered (my prefered setting), and 1.25″ lowered. This is in addition to the lowered springs (1.25 drop) that I have now, thus giving me about 1.5″ total drop. The best part is that you can use your existing springs and don’t have to worry about tinkering with the spring rates or helper springs. If you’re looking to replace your shocks, take a look at the Bilstein’s when doing your comparisons. BTW, CGI can be reached at 708-301-9595 or tailgater@orbitel.com
[DNG – 98/12/18] I had the adjustable Bilsteins installed last weekend. Nice. The damping rates are perfect. The high speed compression damping is not too hard as to slam your kidneys, but it’s still firm. The high speed rebound damping is firmer than the compression damping so that your car won’t ‘hop’ back. I’m not sure how it is in cars, but in racing motorcycles you always want less compression damping and more rebound damping. Under acceleration, the bike/car will ‘squat’ (compress) to prevent hopping thus increasing traction. You also want it to take it’s time going back to normal position (rebound) so as not to disturb the suspension geometry in corners.
Both low speed compression/rebound feels similar to another good shocks around.
The best thing about the Bilsteins is that they can be set at any predefined height before installing the springs. Thus, you can keep your current spring rates.
[WME – 99/1/24] Bilstein Germany (the headquarters) told me, that the HD-version is the only shock they have for the NSX, I don’t think they make any OEM-versions for it because of the rare number.
[CA – 99/2/24] I installed CGI Motorsports Bilstein shocks with H&R lowered linear rate springs. The ride is great, you dont get beat up when normal driving, but under slightly (and more) agressive driving, the shocks firm up a bit and really keep the NSX on the ground. The H&R springs have lowered the car about an inch and a half, I have not witnessed, nor do I expexct any clearance problems, they arent near as liver and kidney jarring harsh either, firm, but not too firm…just right! I think they compliment the Bilsteins well.
[PM – 99/1/26] Bilstein does use stacked washers or as the engineers call them, damping curve defining devises. The primary cause of degradation is foaming of the oil. Gas pressurized dampers in general, minimize foaming and it’s resulting wear. Material quality also dictates longevity.
The Bilstein shock utilizes high pressure gas which all but eliminates foaming. They also use high grade materials significantly enhancing build quality. These shocks regularly exceed 100,000 miles without degradation.
In spite of Bilstein’s claim regarding heat, it should be noted that all dampers will experience some oil viscosity change with heat; however, the Bilstein’s mono tube design exposes the oil to direct cooling airflow via the single wall of the damper. A twin tube design, generates heat within the inner cylinder and the heat must therefore pass through 2 walls and the reservoir to dissipate.
Once again, it should be noted that unless good records are maintained ala race teams, and the driver is experienced and sensitive to vehicle dynamics, adjustable dampers could actually deteriorate handling if improperly adjusted.
[CMI – 99/4/15] I decided on the CGI Bilstein shocks for a number of reasons. First, ride quality. One of my friends here has the adjustable Koni’s and said they were a big improvement on the track over stock, but the ride quality on the street really deteriorated, even on the softest setting. After trying his car, I agreed.
The CGI Bilstein’s again are a great choice for those of us who don’t want to give up the finer points of our cars yet need more than the factory gave the masses. These shocks, being self adjusting (ask Kern Fisher from CGI for the technical explanation how this works) give the firmness when needed along with improved rebound dampening. Add the Eibach springs, RM sway bars and Hoosier tires on stock 16/17′ wheels you will have a great handling (very neutral), easy to live with ride.
On the track, it went where you pointed it and when you stepped on the loud pedal coming out of the turn, it plants and takes off. My car is the most neutral it has ever been. Easy to control drifts in the corners and when you get too aggressive, it telegraphs perfectly what is about to happen and more importantly, lets you correct it. I am *very* happy with this setup!
[AWL – 99/10/19] For struts, I have to recommend custom-indexed Bilsteins from CGI Motorsports, which are self-adjusting. They are firm, yet compliant on the street, and on the track, they firm up very quickly, while still keeping the tires planted, and thus allowing more traction around turns and transitions, which allows you to carry more speed.
[goldNSX – 07/08/08]
General/Quality:
Bilstein shocks are very streetable shocks and a direct replacement for OEM shocks, together with OEM or aftermarket springs (Eibach, H&R). Due to their self-adjusting mechanism they usually last more than 100k miles. They use gas pressure to prevent the damping oil from foaming. The weight of a Bilstein (shock only, no spring or mounting hardware) is about 2.2 kg.
Characteristics:
Their damping characteristics (has been measured *pictures here*) reveal soft damping forces at low speeds (of the shock/wheel) and high damping forces at high speeds. This gives you an even more comfortable ride than with the OEM shocks at the sake of loosing a little bit turn-in-feeling. But this effect is cancelled out by choosing the lowering option on them which is 1 by using the lower perch (0.875).
Customizing (advanced feature):
Bilsteins offers a service to customize/revalving the shocks. You send them your shocks, let them know what spring rates you are using and how you like to have them customized: track-orientated or remain some street-comfort. You can also choose a rebound on the dampers to keep very short springs in place or let machine more (lower) perches to adjust the ride height. Bilstein will calculate the damping forces needed to fulfill your wishes and sends your shock back. If you don’t trust them you could even let them know at what speed (0.01, 0.05, 0.1, 0.3 m/s) the damping forces (N) have to be.
Machining lower perches adds more flexibility to the ride height. A common setting for lower perches have been an additional perch at 0.6 below the lower perch in the front and one at 0.4 in the rear. Be careful with lower perches as the shock may rub against the tire.

Koni Adjustable Shocks

[AV] The part numbers for Koni adjustable shocks are: 82411117 front, 82411118 rear.
[BSD] Recently, I fix my worn shocks by replacing them with Koni Yellows. I had the car at Heartland Park over the weekend and this was the first time there with the fixed shocks. I am totally blown away by the difference that good shocks make. I had them on “2 turns” out of a max of “2.5 turns” towards full firm.
I am used to the NSX being a car that has good handling, but one that is also not terribly revealing as far as the rear end grip is concerned. For the last 2 years (only 2) of driving my NSX, the rear end was always hard to judge on the track as to when it was approaching its limit. It would go from turning sharp to suddenly letting go. There was very little, if any, time to correct the oversteer situation. This resulted in my driving in a way as to minimize the time I was at max grip at the rear end and is not the line that is best for an NSX. (It might have been best for my case, but not for how good and NSX should be.)
Note that I knew that my right rear shock was more than worn and on the way to busted before. I just never knew how busted. And, I had assumed that a bad right rear shock would not hurt right hand turns that much.
Anyway, fixed shocks on a pretty stiff setting made a huge difference. I can go through turns and increase the turn rate or increase the speed and, as oversteer is reached, the rear end politely starts to let go and it can be felt through the seat. And, you can then decrease steering input or decrease throttle input slightly to correct. It did not feel like the rear end was going to snap to the outside and that, in turn, did not make me feel like I needed to correct with a sudden decrease in steering input.
The result is a confidence inspiring ride that made me look forward to turns where I could really lean on the rear end, thereby maximizing my turning, while knowing that I’d be able to hold it there without risking life and limb (and aluminum.) My lap times were 2 seconds faster than before at the track but the smile on my face was even better.
In one of the turns, there were some large cracks in the pavement that caused ker-chunk, ker chunk as you drove over. This caused my steering wheel to almost jerk out of my hands, due partly to the stiff shock settings. At the end, I decreased my front shocks to 1 or 1.5 turns towards stiff and left the rears at a full 2. This reduced the steering wheel jerks but still kept the quick responsive feel.
I am re-impressed with the NSX after this weekend and stiffer shocks make a huge improvement.
[BSD] I bought mine from Performance Parts Inc, aka, PPI. They are a hi-po speed shop sort of a thing and they do a lot of Mustang business. There is lots of competition in that market. The prices on Konis from them were good to me. Ask for Jim Dingle, tell him I sent you. He’ll get you a set of 4 for $470.80. http://www.mustangparts.com or (703) 742-6207.

Koni vs. Bilstein
[PM – 99/1/21] The issue of which is better, Koni or Bilstein has no simple answer. As with many things in life, it depends on what compromises are important.
The Konis are adjustable and this can be important to some drivers. If you want to set the car very stiff to run competitive events and then soften it up somewhat for the drive home, the adjustable feature is nice. The adjustable feature also allows some correction for any decrease in dampening control due to wear over time. My associate Kern Fischer (former engineer for GM, Ford, Director of engineering for Maremont Corp. manufacturers of Gabriel and other private label shocks and former pro rally driver) and I, discussed this issue in depth over lunch today. I asked Kern to document his comments as my short hand stinks. He offers the following:
“The adjustment is on jounce (wheel moving down relative to body) control only. If too much jounce control is introduced, the wheel cannot adequately follow uneven surfaces and handling can actually be decreased. Ride quality also suffers. The adjustable feature also requires some experimentation and expertise to optimize the settings front to rear for any particular track/road situation. What works well at one track may not work well at another.
My experience of having Bilstein dampers on four vehicles and working with numerous customers on custom applications is that they are very tolerant of variations in spring rate and vehicle weight. They also offer excellent ride/handling compromise. In all cases the ride quality has been very acceptable and the handling control is excellent.
The Bilsteins have also proven to be very long lived. Of the four personal cars, one was sold with 105,000 on the dampers and it went to 140,000 before losing track of the car. One currently has 80,000 on the dampers. It is used on the street and track and is very stable and controllable while still being a treat to drive.
Car 3 had no listing in the Bilstein catalogue so we built some special dampers using the factory strut tubes with inserts that were physically correct but were designed for other (lighter) cars. The front inserts were for one car and the rears were for another. This effort was expended because I knew that the installation would be a “install and forget” situation. The car was sold with 12 years of use and 120,000 miles on the dampers. It had been used primarily as a street car but also had in excess of 20 track weekends on it. Just before the sale it had been to two track events and felt like new. The purchaser, coming back from the test drive, commented that he was amazed at the handling, given the miles on the car. His second comment was “can I take it home now!” It is still being used three years later, same dampers – current mileage unknown.
The experience with these 3 cars led to the choice of Bilstein for the 4th car. The car as delivered from the factory had good handling but was slightly soft for my taste. It also had some nose rise under acceleration and dip under braking. The installation of Bilsteins resulted in a more stable chassis while the ride quality remained relatively unchanged even with the sport setting.” (end of commentary)
Several years ago, Road and Track performed a damper test. At that time, Koni and Bilstein were the leaders of the pack by a fair margin. The Konis set on full stiff were slightly faster than the Bilstein on the track but the car could not be driven comfortably on the street with that setting. The Bilsteins were very acceptable for both environments with their single dampening setting.
CGI MOTORSPORTS offers both Bilstein and Koni to NSX drivers so we have no preference which we sell. We do feel that the ride/handling compromise of the Bilstein is better and we can offer you CGI-Bilstein with custom ride height capability so you can lower your car without having to buy special springs.
Oh one last thing, guess what damper is being used on the REALTIME NSX?

How can I make Koni shocks easier to adjust?

Factory Adjustment Knob
[MJ] I’ve seen people use vice grips, pliers, even custom dental appliances 😉 to adjust their shocks – you name it, but adjusting the damping on the KONI SPORT SHOCK can be a pain without the right tool for the job, our adjuster ! dial in some attitude ! Billet aluminum with sure grip knurled edge, looks cool, fits perfectly, works great, priced right! ($25 includes UPS ground available from Dali Racing)
[AT] I devised simple add on extension to the original adjustment knobs which came with the Konis. I hope I can explain how I created it for you. Follow the steps listed below:
Get a short 1/4″ socket extension roughly 3 to 4 ” in length. Usually you can buy this from Sears or any tool supply store. Quality is not critcal here.
Cut off the square end (the one that goes into the socket) and this will leave you with the ratchet side and a long slender straight rod like piece.
Use a small grinding wheel or cutting wheel (ususally found for air tools grinders) and grind a slot in the cut end of the ratchet rod where you made your original cut. If you get the smallest grinding/cutting wheel available, the slot should be the perfect size needed for the Koni shock.
Now measure the diameter of the ratchet side of this new tool, and drill out the inside area of the Koni adjustment knob where the old adjustment slot is. Drill this out only about 2/3 the depth of the knob itself. The new hole should be just slightly larger than the ratchet side diameter.
Now buy some two part expoxy glue and mix enough to glue this new ratchet into the Koni knob.
Let the glue set 24 hours and there you have it.

What About NSX-R Suspension?

[YH] You need an NSX-R registration certificate to order any NSX-R parts. You’ll also need a friend in Japan if you don’t live there yourself. If you can manage those two things, you can order: NSX-R Suspension Kit: Front Set 177,800. yen / Rear Set 203,600. Yen (plus shipping)
There are many used NSX-R suspensions in the market place – Daliracing, Yahoo Auction Japan, etc.
The NSX-R suspension is 0.7 in. lower than the stock suspension. Each of the rear suspension has a reservoir.
NA1 Type R is more stiff than NA2 Type R Suspension.
(NA2 Type R is faster than NA1 on the track is mostly due to the Aero upgrade, transmission upgrade, and improved power to weight ratio).
NA2 Type S Zero is similar, if not, the same as NA1 Type R Suspension.

What about Zanardi or NSX Type-S Suspension?

There are 2 types of Type-S suspensions, the pre -02 (USDM Zanardi) suspension, and the 02+ Japanese only Type S. The Zanardi is available at US dealers in component form – springs, dampers and sway all separate. Zanardi springs lower the car by 1/2″, are stiffer than stock and are a linear spring. The 02+ Type-S is progressive and only available in the US through aftermarket vendors as a shock/spring combo.
You can easily buy the Zanardi suspension (springs, shocks, etc.) from any Acura dealer. They are stiffer (esp. in the front) versions of the regular NSXs come with and are fairly expensive. The one advantage of the Zanardi setup is that it does not lower the car as much (-0.5″ overall) as aftermarket springs for anyone looking to stay close to stock height. It’s a good compromise between the stock and the Type-R suspension. Later has been too harsh for many people as a daily driver.

How Should Roll Stiffness Be Improved?

[AWN] Ideally, you want to limit roll with anti-roll bars. While it’s true that a car’s roll resistance can come from either the springs or the bars, increasing the spring rate to limit roll isn’t such a good idea. Here’s why:
Let’s say that you can live with a HUGE amount of roll… Like 10 degrees or so. How far does the outboard spring compress when the chassis rolls that much? An inch, maybe? I have no idea how stiff the stock springs are, exactly, but for the sake of argument, let’s say that they’re 150-pound-per-inch springs (they probably have a lower rate, but I’ll give them the benefit of the doubt).
Ok… This means that, at 10 degrees of roll (which compresses the spring an inch), each outboard spring is only contributing 150 pounds of roll resistance to the chassis. Your car wants a whole lot more than 150 pounds of roll-resistance at each axle, especially if you want to limit roll to a more-reasonable value, like 5 degrees or less. To get your desired roll-resistance numbers from the springs alone, your springs will be so stiff that the tires will hardly spend any time on the ground; every little bump on the track will send them into the air.
If, on the other hand, you put relatively soft springs on the car and use a stiff sway bar, you’ll get good tire compliance AND good roll resistance. You’ll also be able to quickly adjust the car’s over/understeer balance, since it’s a whole lot easier to move a swaybar droplink (or even to replace the bar) than to replace springs.
In general, it’s best NOT to use one suspension component (the springs, in this case) to perform multiple tasks… If you can split the suspension control among multiple components (springs for keeping the car off the ground, sway bars for limiting roll), you don’t have to compromise one aspect of the car’s handling for another. Well… You don’t have to compromise MUCH, anyway.

Any Other Tips?

[HM] After replacing the springs, the front end started “clanking.” The clanking sound happens at slow speeds when the front end is not loaded. The sound seemed to come from the middle of the front end and happened when either the left or right tire hit a firm bump.
Randy Marchetti (RM Racing) solved the problem for my clanking. There is a black rubber strip on the old springs (front only) that is kinda hard to see since the old springs were black also. These rubber strips pull right off. If you jack your car up and take off the front wheels, the rubber strips can be put back on WITHOUT taking the spring off the car. Put a little silicone on the rubber to keep it on. It wraps around approx 1 1/2 times. Be sure to place it on the spring in the same location. Took me 15 minutes….no noise!! BTW, I can’t really blame the Acura dealer for this one. I think it was easy to miss if you had not replaced the springs with aftermarket ones before.
Performance