Front Suspension Advice Request

[Jetaway]

Happy New Year Zcar-ers!

My 1972 recently developed steering wheel shake, its way of telling me its time to work on the front suspension. Since it's going to be dissembled anyway, I've decided to: 1) replace all the bushings and: 2) replace the struts.

There is, of course, a possible complication. I sure hope not, but I'm pretty sure the coils aren't stock.

The attached photo is from the left front suspension. There is no compression on the spring when unweighted. It turns easily in the holders, though it won't quite rotate 360 degrees. Maybe it would if I tried harder, but that seems like a pointless exercise. I'm not quite sure how to count the turns, the spring continues at the bottom and ends within an inch of where the top of the spring can be seen to end. I counted this as 7 turns, starting with the hidden turn "zero" at the bottom. The spacing is consistent except at the top and bottom where the spacing is tighter so that the a reasonably level coil end is produced. I measured 10 and 3/4 inches from top of the spring to the bottom of the spring (which is just about where the top of the date-stamp is). The wire is 1/2 inch in diameter. I haven't seen any markings but I haven't had it off the car yet. The ride does _not_ seem to be lowered. It looks stock and ground to body measurements seem right in line with what expected distances based on the tire diameter. Probably rides stiff -- I haven't ridden in any other Z so I couldn't say for sure, but my 150 lbs doesn't seem to make the slightest impression on it when pressing down on the fender.

The first question is about the bushings: rubber (stockish) or urethane? I understand that the urethane bushings are stiffer and more durable, what I don't have a grasp on is how the stiffness will affect ride and handling. Well, handling should be a bit crisper, but what about the ride and noise levels? I don't race it but it does get a lot of use, 15,000 miles / year is not out of the question. Would the stiffer urethane bushings be something that would be noticeable at all times or only when driven hard or on, for instance, rough roads, of which we are becoming increasingly well supplied with here in California?

The second question is what brand of strut. I don't need adjustable struts, so it seems to come down to KYB or Tokico. Prices seem pretty consistent regardless of source, I'll use Black Dragon's prices here: $60.00 for the KYB and $90.00 for the Tokico's. What am I getting for the additional 50% over the KYB price? I wouldn't mind spending more if I got a smoother ride _and_ better handling characteristics but I'd have to think about it quite a bit if the Tokico's only either rode smoother or handled better but not both. And I'd certainly like to hear about other options, though at $220 I do think I'll pass on the Koni's.

First, will stiffer than stock shocks make urethane bushings intolerable for regular street use, or make little difference?

Second, will the non-stock coils mean I have to use a non-240Z strut? I have no idea what kind of strut is in use now.

Thoughts, tips, and experiences appreciated.

Chris

[beermanpete]

Your springs are after market for sure. It is likely a typical "lowering spring" designed to lower the car about 1 inch. The rest looks stock so you should be able to use any replacement strut made for the 240Z. The bumps stop seems to be missing so make sure to get new ones and install them when you change the struts. It makes a big difference in the smoothness when the suspension bottoms.

We have Tokico Blue struts and lowering springs on our car along with poly bushings. The Tokico Blue struts are only slightly more expensive than run of the mill struts from the auto part store but handle better (IMO). Poly bushings do add some harshness and noise compared to the original rubber parts. The ride in town is OK by my standards. The main thing I don't like is the gear noise from the differential is louder with the poly bushings in the mustache bar. Keep the original rubber bushings for the mustache bar if this will bother you.

The poly bushings need to be greased at install and probably should get serviced periodically. Since you plan to drive your car a lot you might want to go with the rubber bushings to ease maintenance issues. Unfortunately, Nissan never sold the bushings separately. Part stores might have replacement bushings however.

Check with John at Beta Motorsports for Tokico prices. http://www.betamotorsports.com/index.php

[Jetaway]

Your springs are after market for sure. It is likely a typical "lowering spring" designed to lower the car about 1 inch. The rest looks stock so you should be able to use any replacement strut made for the 240Z. The bumps stop seems to be missing so make sure to get new ones and install them when you change the struts. It makes a big difference in the smoothness when the suspension bottoms.

It _never_ bottoms.

And I think I know why now.

We have Tokico Blue struts and lowering springs on our car along with poly bushings. The Tokico Blue struts are only slightly more expensive than run of the mill struts from the auto part store but handle better (IMO). Poly bushings do add some harshness and noise compared to the original rubber parts. The ride in town is OK by my standards. The main thing I don't like is the gear noise from the differential is louder with the poly bushings in the mustache bar. Keep the original rubber bushings for the mustache bar if this will bother you.

The poly bushings need to be greased at install and probably should get serviced periodically. Since you plan to drive your car a lot you might want to go with the rubber bushings to ease maintenance issues. Unfortunately, Nissan never sold the bushings separately. Part stores might have replacement bushings however.

Check with John at Beta Motorsports for Tokico prices. http://www.betamotorsports.com/index.php

Thanks for the advice, I would not have known I was missing bump stops. And very much for the link. After posting I gave a run at figuring out the spring rate on those bad boys.

I bought a cheap household scale ($9.99, thank you K-Mart!), removed the wheel from the other side, taped a cardboard scale with 1 inch of compression measured off to the top of the coil, put a floor lift under the car and lifted him up. I slid the scale under the tire and slowly lowered the car until the spring had compressed one inch and noted the weight. 305 pounds! Stock is around 90 - 100 lbs and my first thought was that this couldn't be right. I thought that maybe the sway bar and compression rod were exerting a downward pressure as well, so I removed the former and disconnected the latter and repeated the measurement. 270 lbs. I removed the wheel, slipped a small bottle jack under the strut end and used the jack to lift the wheel assembly up the inch. 275 lbs. I haven't disconnected the steering knuckle, but since it isn't designed to control up and down motion while the sway bar is, to some extent, I don't think it can be having much of an effect on the measurement.

Here is where the link to Beta Motorsports proved very interesting. In the description of the Tokco HP shocks (I assume these are the "blues" you have on your car) they call them great shocks for springs up to 200 lbs / inch. Yikes!

The Tokcio HTS shocks, at $180 a shot are the only one of the three types listed for springs over 250 lbs. being rated for 200 to 375 lbs.

The doubts I had about my lbs. / inch measurement methods have been relieved by finding these statements. Rates of 270 lbs / inch aren't out of the realm of possibility and are, in fact, right around the midpoint for race-equipped early Zs. The relief I have in not being completely nuts is someone nullified by thinking that the Tokico HPs might not be a good fit for my car. Is this mismatch between recommended spring rates and my actual rates something to be concerned about or am I worrying too much about something that would have, at most, a small effect that I may never experience?

Although at a little under $100 for the pair, picking up a new set of progressive Tokcio springs with 140 lb rate might not be the worst idea in the world.

Hmmmm.. Thoughts?

Chris

P.S. On the really bright side, all the bolts came loose without much argument after an overnight hit of penetrant. Well, one of the sway bar to control arm nut required a bit of the blue torch, but nothing went up in smoke.

[John Coffey]

Your spring rate measurement technique is wrong. To actually measure spring rate you first compress the spring one inch and then compress an additional inch and measure the rate for that second inch of compression. Also, you're not taking into account the suspension motion ratio, the angle of the strut, and the stock bind/friction in the inner LCA bushing. The stock bushing does not turn, it flexes so you have the hysteresis of the rubber adding to your measured spring rate. The front motion ratio is either .97 or .98, I don't remember which. Cheap bathroom scales get more inaccurate as the weight goes up so figure a 5% variance on that. Basically the 270/275 number is meaningless.

One way to check your measuring process is to jack up that corner (with the car level to begin with) until the spring stops compressing and the chassis starts to rise. That should happen around 650 lbs (if you scale goes that high). At that point measure the compression of the spring. EDIT: you don't need to measure the weight with this check. Just measure total compression of the spring and then divide 650 by the number of inches of compression and you should be able to come close.

Edited January 11, 2012 by John Coffey

[jfa.series1]

Hi Chris,

FWIW, I can offer you my real world experience with Tokico HP shocks and urethane bushings. I don't have the knowledge to speak of spring rates and other technical details, just seat-of-the-pants and steering wheel feedback to pass along.

I finished my resto last fall, full suspension rebuilds included. I have 70's vintage Mulholland springs all round. Unlike OE-style hydraulic shocks, the HP gas shocks provide some amount of suspension lift and seem to keep the car from fully settling onto the springs. The springs are in full contact, not loose on the strut - they just don't seem to be significantly compressed at rest.

On the front, I have eccentric bushings on the LCA's for camber adjustment so no rubber or poly bushings there. I have poly on the T/C rods, steering rack, and steering rod. The front end ride is firm-to-harsh, road feedback thru the steering wheel is harsh and unpleasant - a lot of snap in the wheel from small bumps.

On the rear I have full poly except for the moustach bar mounts - I did not want to fool with cutting out the original bushings with the pressed steel inserts. The OE bushings were in good shape, so I left them alone. The ride on the rear is equally as harsh as the front - every small bump is transmitted into the body as impact and noise.

This summer I plan to begin replacing poly bushings with rubber to get the harshness out of the ride. My car is not a daily driver, just primarily a fun car for club events, shows, ...etc.

Hope this helps in some way.

Jim

[LeonV]

FWIW, you can get a close approximation that spring's rate with a spring rate calculation.

k = Gd⁴/8nD³

Where,

k = spring rate (lb/in)

G = Shear Modulus (about 11.5 X 10⁶ lb/in² for spring steel)

d = wire diameter (in)

n = # of active coils (total coils - 2) for that spring

D = average coil diameter (in)

That should get you close.

Edited January 11, 2012 by LeonV
Clarity

[Mike W]

Chris,

I went through the same mental exercise about a year ago when trying to decide on a strategy for my suspension refresh. In the end, I went rubber every place that I could and I also opt'ed for the KYB's. My expectation was a close to stock ride with as little noise as possible, but with more responsive handling based on the newness of the bushings and shocks. I also run an aftermarket spring that I purchased many years ago and it does lower the car by about an inch.

I completed the rear end refresh back in the spring and was very satisfied with the results. It performed as expected and now gives me a ride that is as close to what it was when the car was new (I am the original owner) . Going with rubber did complicate the process as I had to remove the rubber and metal parts of the bushings on the control arms and this was tedious. I also had to find a way to flare the OEM bushings on the moustache bar and ended up having a tool made to do this (I have also loaned this tool to other CZCC members and will make the same offer to you if you go this route). The only bushings that I was not able to source in rubber from Nissan were the rod end bushings for the sway bars and the rack and coupling bushing for the steering system. I managed to source everything else directly from Nissan. In fact I ended up developing a spread sheet with all of the Nissan parts numbers that I needed for this and would be happy to share that with you as well. Just PM me and I will send it along. This was for a late build 260Z not an earlier 240 like yours, but many of them will be the same and I believe that I even created a column for the 240 part numbers as well.

I am now in the middle of finishing the front end refresh and am really looking forward to having this done and getting my handling to an improved state as well.

Hope this helps.

Mike.

[5thhorsemann]

Just as a side note, there are several threads here about the "dreaded death wobble" steering wheel shake. My front end had it and I made changes to the suspension but all any individual modification or upgrade was able to do was change the speed and intensity of the steering wheel shake.

I took the wheels off and speed / match balanced the wheels, tires and rotors on the front. That cured the shakes. I would recommend you go that route FIRST to make sure the balance is right so you aren't chasing problems that don't exist. Might save alot of time and money once you start modifing your suspension gear. Read this FWIW. http://www.classiczcars.com/forums/showthread.php?43905-Death-to-the-death-wobble&highlight=death+wobble

[Oiluj]

Back in the very distant past, (mid-1980's), my 1st 240Z got the front-end wobblies. Not bad, just enough to be annoying.

After talking with a tech guy at MSA, I replaced the streeing rack bushings. Completely solved the problem.

[black gold man]

A bad steel belt even on the back can cause the shake.

Feel up your tires.

[Bonzi Lon]

My front end wobble was caused by a loose self locking nut on the top of the shock rod. It ruined the 'D' shape in the insulator & the shock rod was 1/2 eaten through. It was found by jacking the car up & down on that side & watching the whole assembly move in & out. The black cap covered the nut that was held on by about 4 turns.

Bonzi Lon

[Jetaway]

Thanks all,

I've been slowly dismantling the front end, giving the magic of penetrant plenty of time to work, with the happy side effect of dampening my OCD tendencies.

LeonV and John Coffey: I'll get back to you on spring rates in a new thread in this area.

MikeW and Jim: You've got me leaning heavily towards rubber rather than urethane. Frankly, urethane, if it was a stiff as I would think it is (and apparently is) never seemed like a great idea for the street. There ain't a lot between you and the street in an early Z and replacing most of the buffers with basically solid pieces seemed unnecessarily brutal.

I've got a couple of questions somewhat buried in here. I'll label them "Question" if you don't want to wade through the verbal rubble.

So far, so good, as far as the dismantling has gone. Only had to borrow one tool from a neighbor, a 19 mm 1/2 socket and when he offered his foot-longer than my 1 and 1/2 foot breaker bar, I gladly accepted. Diesel mechanics tend to have some big tools on hand. Nothing has broken or snapped off, though some of the bolts/nuts definitely need to be replaced.

I've made mental note of the suggestions as to the cause of wheel wobble but I think I've found enough worn parts to, hopefully, solve the problem.

Both ball joints flopped over on removal. I've been told that is not good, so both ball joints will be replaced.

One of the the main transverse link / control arm bushing appears shot and the other wounded, if not dead. The link is to control up and down movement, so I'm assuming that fore / aft movement (that is, in the direction of the travel) should be minimal. On the driver's side the link can swing 15 / 20 degrees fore / aft. Passenger side less, but probably more than it should.

QUESTION: The FSM covers removal of the main bushing, but seems to be referring only to the metal tube in middle because it says "if rubber and inner/outer tube joints (adhered) are sticky (melted) or cracked, replace the transverse link as an assembly." I'm not sure if the bushing is adhered or melted, but I'm sure it is shot, so does this mean I have to find the whole transverse link / control arm? What are the control arm bushings available at Black Dragon then? Something else? I couldn't find any other bushings that I would call transverse link / control arm bushings.

Both of the sway bar bushing mounts were split clear through. There may be another equally large problem with the sway bar assemblage.

QUESTION: (See attachment Sway Bar Strut).

Not sure of this thing's name, "Rod Connection Assembly" is from the on-line parts catalog, but this is one of the two rods/ struts that connect the sway bar to the control arm. They looked symmetrical to me, so I didn't make note of which side connected to the sway bar and which side to the control arm. It was only later when degreasing did I discover this notch / indentation (there is one on the other rod/strut as well, but not quite as large.). The notch/indent only appeared on one side of the strut. I don't think it was designed with a notch, which brings up the question, is this something to be concerned about?

Oh -- one of the engine mount nuts was only 1/2 way down the bolt.

Nothing to do with the wobble, but both steering rack boots need replacing.

QUESTION: I degreased and de-rusted the control arms and ended up with bare metal. They should be painted, right? Is there a special high-impact paint that should be used?

I used Evapo-Rust for the first time on this project. I'll give it a solid 3/4s thumbs up at this point with a full thumb awaiting it's long-term rust removing abilities.

Good Points:

1) OK, this point is from their promotional material, I haven't tested it myself, but it does not affect plastic and is non-toxic.

2) Truly is a "lazy-man's" rust remover. Let the parts soak overnight, an easy water rinse in the morning, and yes, you are done and the rust is indeed gone.

3) Possibly less expensive than common alternatives like Naval Jelly or other such removers as it can be used over and over and over again.

Less than Good Points:

1) It takes its time. The promotional material suggests as little as a half hour for light rust. Maybe, and maybe because it seems to be quite sensitive to temperature it would work much faster at 80 -- 90 degrees than 50 -- 60. I still think they are being a bit optimistic about its speed. And make no mistake, let it work overnight and it will do an excellent job for you.

2) Not a big fan of grease. Of course you should remove all the grease before using a rust remover, but some of that stuff, like the greaserust is pretty hardy stuff. Naval Jelly, while not removing it per se, at least weakens it sufficiently to enable removal. Evapo-Rust has little or no effect, and may even be inhibited in the if a grease spot is in the area. Not entirely sure about the latter point.

3) Largish up-front cost. They do sell it in quart bottles, but other than fasteners and other small pieces, I can't see much use for a quart. You don't brush it on, you immerse the part in it. I had a just about optimal sized container for the transverse link and it took an entire gallon to barely get it all covered. True, I could throw in a few fasteners as well, but not another part of similar size. If I were in a hurry on this project, and want to get everything derusted in one night, I could easily use three / four gallons at $25 -- $30 a pop. True, that might last me a year or even two years, but then again, I may be dead in a year and a fat lot of good four gallons of nearly new deruster would do me then.

Odd Point: The website makes a point of its reusability, explaining the chemistry of it and saying use it till it turns pitch black and doesn't work anymore. (I believe it said a gallon can hold two pounds of rust in suspension) but the package itself says nothing of this, which I think is one of its strongest selling points.

Thanks for the input, all.

Chris