Struts and Springs Buying Guide

[ConchZ]

I've been doing a lot of research on this site and others to decide what combination of struts and springs to get. I've never seen a post that summarizes all the options, so I thought I'd write it up. I'm not an expert on the subject, so this post will be information drawn from the posts of notable experts. I'm hoping that writing this summary will help me organize my thoughts and perhaps draw out some advice on something I'm missing. So...here goes. First off, my car is stock, although it has fully poly bushings. My intended use is street use only. I may someday take my car to the track and get some lessons, but I doubt I'd ever be serious about tracking it. My comments will be geared to this usage.

First, let's discuss ride height - my 240z sits on sagging stock springs, and is already about an inch below stock ride height, at just under 6 inches at the rear of the rocker. I like this height, which is good, because it is the expected drop from most aftermarket springs. Many people experience different ride height results with aftermarket lowering springs. Sometimes this difference is attributable to accidentally swapping the front and rear springs, or even from installing them upside down. Some people think the newer gas charged struts will make a car ride higher, even with lowering springs. I guess results will vary a bit.

Next, let's discuss linear vs progressive rate springs - basically, progressive rate springs get stiffer the more they are compressed, while linear springs do not. The consensus opinion seems to be that progressive rate springs are the most comfortable, but they are not popular for track use because of their unpredictable dampening. Some even say they cause unexpected suspension movement, which results in control difficulty. I think this is only a problem if you are pushing your car to the limits on a track.

Coil Overs - these are available from various sources, in either ready to install kits, or a kit that will require you to do some cutting and welding. Prices run from a few hundred to about $1600, with the cheaper ones not including the struts and camber plate you also need to buy. The advantages of these are that you can adjust ride height, swap out springs, and install wider tires. Coil overs are best for someone who wants to race, and are not necessary for my intended usage.

Arizona Zcar springs - these are the only spring I can find that keeps your stock ride height. They are shorter than stock, but stiffer, so it works out to about the same height. I'm interested in dropping my height below stock, and these are also likely too stiff for my tastes. At 180lbs front and 200lbs rear, I believe they have the stiffest spring rate of all the options, although I can't find any numbers on some of the options.

Suspension Techniques springs - these lower the car about an inch. They are linear rate springs. I can't find the spring rates on these.

Eibach Pro-Kit - these lower the car about an inch. They are progressive rate springs. I can't find the spring rates on these.

Tokico Performance Springs - These lower the car about an inch. Be careful, because these are linear in the back, and progressive in the front. I may like this. The linear in the rear would stop acceleration squat, while the progressive front ones would be more comfortable. Their spring rates are 140lbs front and 165lbs in the rear.

That's it for spring options, so now let's discuss strut options.

KYB - they have one option for a 240, and they say they aren't for use with lowering springs. This rules these out, unless you go with the Arizona springs.

Tokico HP - these are the cheapest strut that will work with lowering springs. They are not adjustable. They are commonly referred to as "Blues".

Tokico Illumina - these work with lowering springs, and are adjustable. A set of them will cost roughly $200 more than the HPs. For that extra $200, you can adjust between 5 firmness settings.

Tokico D-Spec - these work with lowering springs, and are infinitely adjustable. Expensive, though.

Tokico springs and struts can be bought together as a kit, at significant savings. A popular Z-specific vendor that has a complete Tokico selection is Beta Motorsports.

When buying struts, it is important to make sure you get the necessary boots and bump stops. Most boots seem to have a bump stop integrated into them. Some kits seem to come with these boots, and some don't.

A final consideration is whether or not to spring for the bump steer spacers, if you are going to use the lowering springs. In terms that I understand, these keep your lower control arm parallel to the ground, which prevents extra under steer at cornering limits. Here's more info on bump steer. They are available from various vendors, and fit between the bottom of the front strut and the control arm. Be aware that many people report that they cause rubbing of the control arm on the inside of a 14 inch wheel (but not on larger wheels). Black Dragon sells some that claim to be ok with a 14 inch wheel. I have 14 inch wheels. I am not sure if want to spend the extra $70 on these, but I probably will unless someone here talks me out of it.

After reading up on lots of threads, here's my current thoughts. I plan to order a Tokico Illumina struts and spring kit and bump steer spacers. I probably don't need the adjustability of the Illumines, but for $200, it'll be a neat thing to play with, I guess. I'll always wonder, if I don't get them.

Did I miss anything that I should be considering? Any corrections or additions to the above information? If so, I'll edit it and we'll end up with a nice buying guide that is written in layman's terms.

Matt

[John Coffey]

Since I was mentioned, let me add some information:

Spring Rates and Shocks

The rebound damping in a shock is closely tied to the spring rate. Shocks, even if they are adjustable, are designed to work within a specific range of spring rates. For our S30s the ranges are:

Tokico HP - stock to 200 lb. in.
Tokico Illumina - stock to 250 lb. in.
Tokico HTS (D-spec) - 150 to 300 lb. in.
Koni 8610-1437 - 225 to 400 lb. in.
Koni 8611-1259 - 225 to 400 lb. in.

Shock Adjustments

Shocks control chassis and suspension movement in two directions: bump (compression) and rebound (extension). They do this primarily through internal valving which in the case of the Koni shocks is rebuildable and can be modified. The valving in some shocks is adjustable (within a fairly narrow range) externally without disassembly. These external adjustments affect high speed compression and rebound and some very expensive shocks (Penske, Ohlins) allow adjustment of low speed operations.

Here's a summary of what the external adjustments affect and my opinions on each:

Tokico Illumina (5 settings) - A linear increase in compression and rebound damping from setting 1 to 5. This is typical of a street performance shock where the car is sprung near stock rates. The increase in compression damping helps give the car a tighter, more responsive feel at the expense of compliance and grip (on bumpy surfaces).

Tokico HTS (7 turns) - A linear increase in rebound damping with a very shallow increase in compression damping. Much better when higher rate springs are used that better control the sprung platform. Compression damping doesn't have to be used as a performance crutch for soft springs.

Koni 8610-1437 (2.5 turns) - A linear increase in rebound damping with no change in compression damping. Even better then the Tokico HTS for the reasons listed above.

Koni 8611-1259 (2.5 turns rebound and I forgot how many clicks on compression) - Double adjustable so that compression and rebound can be adjusted separately. The best of the off the shelf shocks for the S30 and really only used for racing.

[John Coffey]

More IMHO stuff:

Tokico Springs

The Advanced Handling spring kit for the 240Z has progressive front springs that have a working rate of 140 lb. in. and linear rate rear springs at 165 lb. in. This is fine for a basically stock 240Z and its what Tokico designed the spring for. I consider these stock replacement springs.

The Advanced Handling spring kit for the 260/280Z has linear rate springs front and rear with rates of 185 lb. in. front and 200 lb. in. rear. These can also be used on the 240Z but you will most likely have to cut coils to get the ride height where you want it. I consider these (and the Arizona Z Car springs) the first level of spring upgrade for the S30.

Eibach ProKit Springs

Progressive front and rear with working rates estimated at 150 lb. in front and 175 lb. in. rear. Again, these are fine for a basically stock 240Z I consider these a light "sport" upgrade.

Coil Over Springs

Hypercoils, Eibachs, etc. in 2.5" diameter. Rates available from 150 to 2,500 lb. in. in 25 lb. increments and lengths from 5" to 18". For our discussion we are looking at a rate range from 150 to 450. For any spring on a S30 from 150 to 250 lb. in. you'll need a 10" tall spring to keep from coil binding on a big bump or long corner. From 300 lb. in. and above an 8" tall spring works fine. An 8" tall 150 lb. spring as part of a coil over kit to clear big tires is a bad idea.

[Arne]

John, any idea what the appropriate spring rates were for the old Koni 82R-1716/82R-1717 inserts? Did they also just adjust rebound, and leave compression alone? Or how about the 86-1811/1812 set?

[John Coffey]

Don't know, never had one in my hands.

[Arne]

OK, just curious. I suspect those old red part numbers were designed for closer to stock spring rates, but have never been certain. Been considering a set for use with my Euro Stage 1 springs (about 110-120 lbs. rate, IIRC) instead of the KYBs I now use.

[mark belrose]

Since I was mentioned, let me add some information:

Spring Rates and Shocks

The rebound damping in a shock is closely tied to the spring rate. Shocks, even if they are adjustable, are designed to work within a specific range of spring rates. For our S30s the ranges are:

Tokico HP - stock to 200 lb. in.
Tokico Illumina - stock to 250 lb. in.
Tokico HTS (D-spec) - 150 to 300 lb. in.
Koni 8610-1437 - 225 to 400 lb. in.
Koni 8611-1259 - 225 to 400 lb. in.

FYI John I finally gave up on the Advance Design inserts - never could get them to work correctly with any of the 250-325 lb. spring rates I was using. I'm changing over to Koni 8611-1259s next season.

Mark

'70 240Z C Production restored privateer

[jmortensen]

FYI John I finally gave up on the Advance Design inserts - never could get them to work correctly with any of the 250-325 lb. spring rates I was using. I'm changing over to Koni 8611-1259s next season.

What are you going to do with those crappy Advance Design struts then? Just curious.

[motorman7]

Boy I have a lot to say on this issue. One other factor that must be considered is the tires and rims that accompany the spring shock set-up. These also play an important factor in the ride and handling of the car. Another factor is personal preference, of course. I think my son and I are at opposite ends of the spectrum. He wants a car that rides on rails around the race track, and I want a car that I can drive everyday without getting beat up.

Over the last month I have done one tire set change out, and 4 spring configuration changes (yes, that equates to 16 spring swap outs. I am pretty good at it now). All this was done in the effort to produce a decent ride for my daily driver, a 1971 240Z with an L26, 5 speed and LSD. I was looking for something that was both comfortable and yet sporty.

The initial configuration was the Tokico Illumina adjustable struts, Tokico 5020 Springs,195/50 Yokohama H4’s(AA traction Rating) on Konig 14” rewinds, 1” diameter Anti-sway bars front and rear, and front and rear shock tower support bars. In this configuration, the handling of the car was incredible. I could rip around corners way faster than I thought possible and the tires would not chirp or make a sound. The car remained flat and had no problem doing more than double the posted speed limits around turns. The ride was like that of a go kart, very stiff. The negative of this set-up is that I spent most of my time trying to dodge potholes and maneuver around speed bumps during everyday driving. On speed bumps, I would get the occasional scrapping. Bumpy roads were brutal . On some speed bumps, I would bottom out, so had to be very careful in parking lots. So, the car was great down the backroads, but not practical as a daily driver.

The first change, and very significant, was the tire/rim change. I replaced the 14” Konig Rewind set-up with 16” Panasports and 205/60 Yokahama YK520’s (A traction Rating). This was a big improvement as I no longer had to dodge the speed bumps. They also softened the ride up a bit. In spirited driving, however, I could here the tires groan a bit and also felt a bit of mush that I did not feel with the earlier set-up. I also liked the final 5th gear drive ratio for freeway driving. With the ~15% Diameter increase I now am doing about 2800 RPM and 80 MPH (Typical CA freeway speed). This is pretty nice for gas mileage I am thinking. The Konig set-up was doing 70 at 2800 RPM. In spite of the improvements, I still wanted a softer ride. So, I decided to take off the Tokico springs and put on some Suspension Techniques (ST) Sport Springs.

While putting on the ST springs, I was a little spooked by the loose fit of the springs on the fully expanded strut on the fronts. So, I ended up running the ST rear springs in the front (They fit better) and keeping the Tokico springs in the rear. This was not much different than the four Tokico’s and offered no improvement.

After getting some reassurance on the ST spring fit, I installed all 4 on the car. The front of the car sat about the same height as the Tokico’s but the rears sat way low, about 2” lower. The top half of the tire was hidden in the wheel well (wrong springs?). This definitely would not do, so I put in a two inch spacer to get the rear height correct. With this configuration, the ride was a bit softer than the Tokico’s, but not much. Still not what I wanted. Found myself still dodging potholes and large bumps.

Finally, I opted for the stock springs in this set-up. This is what I want! Soft enough to drive every day, but solid enough to take a spirited drive down the long windy roads. It is a very nice compromise. In addition, I can now use the adjustability of the Illumina’s. On all the previous set-ups, I had them on the softest setting (1) . Now I can dial them in. I currently have the fronts set at 3 and rears on 2.

So, just thought I’d share my thoughts on this for anyone interested.

[mark belrose]

What are you going to do with those crappy Advance Design struts then? Just curious.

Jon, I gotta very very good deal for you. Seriously though, they'll probably get put on Ebay; they'll buy anything over there.

Mark

[motorman7]

ST Springs with 2" spacer

[jmortensen]

ST Springs with 2" spacer

You ought to seriously consider returning that poly isolator. It's a bad idea to use polyurethane in that spot. It is too stiff, and requires too much force to change the angle of the strut. Rubber isolators are much better.

Mark, I'll be running spring rates that work better with the AD struts. Let me know when you put them on ebay.

[ztattoo]

............ Finally, I opted for the stock springs in this set-up. This is what I want! Soft enough to drive every day, but solid enough to take a spirited drive down the long windy roads. It is a very nice compromise. In addition, I can now use the adjustability of the Illumina’s. On all the previous set-ups, I had them on the softest setting (1) . Now I can dial them in. I currently have the fronts set at 3 and rears on 2.

So, just thought I’d share my thoughts on this for anyone interested.

Motorman7, I am so glad you took the time to share this. It saves me (probably many others) from having to go through several experiments to get what we want with our suspension.
My car is completely stock and I have been planning to do some tweaking of the suspension as I enjoy going up to the canyons of Malibu (used to be a sportbiker). I won't be doing any overly aggressive driving, but it will be nice to know and feel that my suspension will be reliable and can take some corners better than stock.
I think I am going to stick to the stock springs and install Tokico Illimuminas. I also need to replace other suspension components like bushings, tie rods and ball joints up front. I will also stay with my 14" wheels until the tires wear out, then I am going to shift to 16" Panasports but probably with slightly lower profile. This is more for the "looks".
Thanks again!

[kjphilippona]

One quick question, i am looking at the Tokico HP/spring combo that is suppose to lower the car 1", will i have to install a camber correction kit to insure proper wheel alignment ?

[ConchZ]

The initial configuration was the Tokico Illumina adjustable struts, Tokico 5020 Springs,195/50 Yokohama H4’s(AA traction Rating) on Konig 14” rewinds, 1” diameter Anti-sway bars front and rear, and front and rear shock tower support bars.

I'm thinking that a 1" front/rear sway bars, combined with front/rear shock tower support bars, plus 50 series tires would make any set of springs ride really rough.

In any case, I'm assuming my stock springs are shot, given that my rear bottoms out on nearly every bump with two people in the car, so I don't think I should re-use them. Does this make sense? Any chance its just the struts? I doubt it, as the car doesn't have any extra bounce, and the struts have only about 20k miles on them (they're almost 20 years old, though).

Attached are two pics, demonstrating the car's ride height. The one with the tape measure is showing the lowest point of the frame rail just inside the dog leg, without me sitting in the car. It's well under 6 inches. The wheels/tires are 185/70/14s. I'm refinishing the center caps. I'd like bigger wheels, but I sorta like having these old Keystones, because the seem rare.

If I could be sure that the Tokico springs wouldn't lower the thing any more than it already is, I think I'll get them. At its current ride height, the rear mud flaps drag on speed bumps, damaging them. This might not be so bad if the rear didn't sag so much with my 200lbs sitting in it.

Thanks for the input, nice discussion...

Matt

[TomoHawk]

Mine is sagging at the back, probably 2 inches lower than the front. What's worse is that you can now hear the springs groan when you accelerate and it settles down lower.

thxZ

[Zs-ondabrain]

I don't know guys, I've had KYB struts with my Eibach PR springs for over 4 years of daily driving, racing around town and small tracks, and they still seem to be holding up great. Freeways are smooth, corners are tight and the wife never bitches about her "Precious Butt" after a long road trip.

I know that KYB says "NO" but I've had NO problems. And as a matter of fact, I've already bought and installed the same combo into the 260Z. Can't tell you how they feel as the car won't be on the road till about April and they'll need some break in time as well.

Opinions?
Dave.

[mark belrose]

Mark, I'll be running spring rates that work better with the AD struts. Let me know when you put them on ebay.

Will do Jon. I'm always open for interesting trades on performance equipment too. The old struts are still on the car, though hopefully not much longer.

FYI a local Corvette club is running an autocross this weekend here in Lompoc. I'm going to take my red street 240Z with Ground Control coil-overs and heat-cycled-out RR compound Hoosiers and have some fun. Too bad you're not back in Cali to enjoy the fun! I give you credit for explaining to me the whole coil-over theory some years back at Buttonwillow.

Mark

[motorman7]

In any case, I'm assuming my stock springs are shot, given that my rear bottoms out on nearly every bump with two people in the car, so I don't think I should re-use them. Does this make sense? Any chance its just the struts? I doubt it, as the car doesn't have any extra bounce, and the struts have only about 20k miles on them (they're almost 20 years old, though).

Attached are two pics, demonstrating the car's ride height. The one with the tape measure is showing the lowest point of the frame rail just inside the dog leg, without me sitting in the car. It's well under 6 inches. The wheels/tires are 185/70/14s. I'm refinishing the center caps. I'd like bigger wheels, but I sorta like having these old Keystones, because the seem rare.

Hi Matt,

Just did a check on my two Z's here. Both are equipped with stock springs (both nearly 40 years old). The Silver Z has the Illumina's with 205/60/16 tires. The Gold Z has stock shocks (1 year old) and 185/70/14 tires. I measured at the same location you did for both cars. On the Gold, the height is 5 5/8". On the Silver the height is 6 1/4". The difference in height is definitely a result of the difference in tire size. Not sure if the shocks impact the height at all.


Regarding the car bottoming out, I would say it is definitely the shocks. 25 years ago, I drove the Gold Z up to Idaho for my folks and it was the sweetest drive of my life. It was the perfect road trip. I drove it back from Idaho last April and it was pure misery. The shocks were toast. It was like driving a boat. Add 50 mile an hour winds along the Columbia River and you have a recipe for disaster. The car bottomed out numerous times on the 1200 mile trip. Due to the shocks being so bad we did not take the car much above 60 mph.
Once back in San Diego, I installed the new shocks and it was like a new car. The ride is soft compared to the Illumina's, but definitely a great improvement in the handling and no bottoming out at all; even with two people.

Attached are some pics of the ride height for both cars.

Rich

[jmortensen]

Will do Jon. I'm always open for interesting trades on performance equipment too. The old struts are still on the car, though hopefully not much longer.

Don't know that I have much anymore, most of my stuff is all custom these days, but if you're looking for something in particular PM me. If you need stock parts too, my brother-in-law basically bought a Z junkyard and owes me, so I can get you engine parts, doors, hatches, etc. Not performance stuff, but stock stuff...

FYI a local Corvette club is running an autocross this weekend here in Lompoc. I'm going to take my red street 240Z with Ground Control coil-overs and heat-cycled-out RR compound Hoosiers and have some fun. Too bad you're not back in Cali to enjoy the fun! I give you credit for explaining to me the whole coil-over theory some years back at Buttonwillow.

Autox in Lompoc? How convenient for you! I'll let some friends know and maybe you'll get a couple more Datsuns down there. I wish I could join you. We just hit the rainy season here. We won't hardly see the sun for another 6 or 7 months.

[mark belrose]

Autox in Lompoc? How convenient for you! I'll let some friends know and maybe you'll get a couple more Datsuns down there. I wish I could join you. We just hit the rainy season here. We won't hardly see the sun for another 6 or 7 months.

Here's the link: http://vaportrailvettes.com/forms-fl...ocross2009.jpg Don't know how many cars they're accepting or whether the field is full.

Mark

[Darrel]

Great info guys.

John,


Wouldn't using stock 280z springs on a 240z lower the ride height along with the benefit of having a stronger spring rate?

[kjphilippona]

Are there any special tools required besides a spring compressor to replace the strut cartridges front and rear on my '77 280z ?

[J Shara]

I don't know guys, I've had KYB struts with my Eibach PR springs for over 4 years of daily driving, racing around town and small tracks, and they still seem to be holding up great. Freeways are smooth, corners are tight and the wife never bitches about her "Precious Butt" after a long road trip.

I know that KYB says "NO" but I've had NO problems. And as a matter of fact, I've already bought and installed the same combo into the 260Z. Can't tell you how they feel as the car won't be on the road till about April and they'll need some break in time as well.

Opinions?
Dave.

What were the part numbers stamped on your 240's eibach springs, as i have a set (came with my parts car uninstalled) and am planning on using them with kyb gas struts (also came with my parts car uninstalled), i am glad to hear that they work fine together, are you happy with the stance and ride hieght as well?

[Zs-ondabrain]

Question.....

If I throw my Tokico HP's in a pile. How do I tell front from rear. Which one is which?

Anyone?
Dave

[John Coffey]

HZ3015 front, HZ3016 rear.

[Zs-ondabrain]

That makes sense. And only the rears have the tube spacer? Correct?
So the rears are taller?

Just trying to lock it in my brain for future reference.
Thanks John,
Dave

[John Coffey]

The actual shocks are identical - same body, same shaft, same pistons, same valving. The only difference in the spacer. You could knock the spacer off the 3016 and put it on the 3015.

[Zs-ondabrain]

That's AWESOME news John!! MSA Sent me 4 rears because they had no fronts in stock (I ordered 2 complete sets for both Z's) So per your info, I can just knock the spacers off the other 2 rears and turn them into fronts. So I can finsh the job in a day, not days or a week.

Great news, Thank You.

Now does anyone have a set of rear Cylinders for an Early 72'??? My Bleeders are broke off.
Dave.

[woytovich]

Ok... so I've read this thread, carefully, and I have a couple of questions:

I am running 195/70R14 (stock size) tires on my 71 240z. I am not interested in any serious sport upgrade to the suspension. It rides hard now. The springs LOOK shiny and new. (I just bought this car in the fall and it is only now on the road for me - after 25+ years of being stored). There is some evidence that the PO made some (mostly minor) sport upgrades: camber adjust kit, expensive tires, Cibie headlights, Vitaloni mirrors...

1. Is there any way, short of pulling them out, to tell what shocks are installed?

2. Likewise with the springs...

I am looking for a stock height ride that is comfortable - not to the point of sloppy cornering but I won't be doing anything more than twisty mountain roads for my "fun" driving. I don't want to have to do any mods to make shocks/springs work.

Is there a basic "accepted" stock replacement combo I should look at?

Thanks,
Mark

[S30Driver]

I don't think you will be able to tell the brand of the strut inserts without disassembling the suspension & pulling them out of the tubes.
Unless the springs are marked by the mfg, & you can see them with a visual inspection, no way to tell that either, possibly you can take pictures & someone like John C. may be able to id them.
You may want to consider the Tokico Illumina's if you replace the cartridges. They are 5 position adjustable & position 1 and 2 will allow you to adjust for a softer ride than the fixed tokico blues or kyb's. Easy to change the setting with just a small slot screwdriver.

[Zs-ondabrain]

KYB's are a great "STOCK" suspension replacement strut. Tokico HP's and Ilumina's are better for altered suspensions (lowered).

Most stock rubber is available but urethane upgrades are every where.

I don't think it's possible to ID the struts until they are out. But I could be wrong. You'll find that the Top strut nut is a 17mm if it's aftermarket and 19mm if it's stock. Look under the strut tower cap.

[erectorset]

I find the 6" stock ride height mentioned to be confusing and the picture even more so. My 1971 240Z with Koni 82R-1716/82R-1717 shocks installed last year (I paid less for them in 2009 vs. 1976 when I last replaced them) with 175R14 tires on 4 1/2" J rims (I replaced the original 4" J rims when I crowned out my 185-14 Michelin XAS's: I was young then and did not know better.) measures +/- 26 1/8" from the ground up vertically through the centerline of the rear wheel to the underside of the rear quarter panel fender. The +/- depends on your tire pressure. How close is this to the stock ride height?

PS: It's too bad Michelin stopped making the XAS's. They were the best for the Z's.