as discussed on the Internet Z car club.
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1. How do I improve the handling?
2. What are bump steer spacers?
3. How do I cure steering vibration?
4. What goes into making a Z race car handle?
5. Which shocks are best?
6. How do I lower my springs?
7. Do I need a spring compressor to replace the springs?
8. How do I replace my springs?
9. How do you replace your springs without disconnecting the brake hose?
10. How do you remove the spindle pin from the rear control are?
11. My car has too much camber, how do I fix it?
1. How do I improve the handling
A: I installed a kit from Suspension Techniques [also available from Motorsport Auto] that included Tokico adjustable cartridges, all new springs, 25 mm front anti roll bar, 19 mm rear anti roll bar, and solid bushings. I installed 10 mm shorter steering knuckles, solid rack bushings, solid steering coupler, and a tension/compression rod kit. The knuckles quicken the overall steering ratio by about 10%. They require the use of later style ball joints for Zs built up to 6/70. The rack bushings and coupler give you an instant response to the steering wheel, as well as a clear indication of poor road surfaces. Also, since you're under the car doing all of this, replace the steering rack bushings with "performance rack bushings". These resemble the stock rubber bushings but are made from higher durometer rubber, taking out a lot of the slop in the steering due to a shifting rack unit. Twisting the wheel a bit, used to make the nose dive from side to side as you rocked the car. Most of this is gone! The car's anti roll bar takes over much quicker without the play in the spongy rubber bushings. The difference is VERY noticeable. On the negative side, the road noise has increased noticeably, especially the bumps and cracks in the road. But the increase in handling was well worth it. The tension/compression kit stops suspension geometry changes caused by cornering forces. The tension rod is the rod extending from the rear of the wheel well (actually connected to the body/frame) to the lower control arm. Motorsport and others have the teflon/aluminium replacement. This will (nearly) eliminate the front end dive under braking.
B: I've put in 20% stiffer springs from one of the catalogues. The springs are also a bit shorter resulting in the car being lowered by about an inch or so. In addition, I've installed Tokico adjustable strut cartridges. No sooner had these goodies been installed (about 2 years ago) that I realised more was necessary due to changes in the suspension geometry. My solution was to install those aluminium/delrin bushings which allow a reasonable amount of suspension adjustment front and rear. I now have a fairly adjustable car with a very firm ride. This is a car that only a car nut would want to drive on a regular basis. The old Z's rode hard in stock trim and the relatively minor changes I've installed made the ride even harder. BTW, no regrets here, I love it!
2. What are bump steer spacers
Basically it is a 3/4" thick aluminium spacer that mounts between the strut and the lower control arm, allowing the lower control arm to regain a somewhat horizontal position. The spacers that install between the strut housing and ball joint do not cure bumpsteer. I know that several vendors advertise them as doing bumpsteer spacers, but after I installed them, I found out that they do not cure it. They do give you a little negative camber and effectively raise front roll centre and these are good things to do to a lowered Z. The reason these spacers don't cure bump steer is that they don't address the problem. I looked into the definition of bumpsteer and found that is very well covered in (of all things) the Chevrolet Power Manual. Zero bumpsteer results when, on each side of the car, (a) the line connecting the tie-rod ends' centers and (b) the line connecting the inner control arm pivot centre and lower ball joint centre are parallel in the vertical plane and are of the same length. The problem on the Z is that they are not parallel. The bumpsteer spacers lower both the lower ball joint and the outer tie-rod end. Therefore, they don't change the non-parallelism of the lines (a) and (b) above. To fix the bumpsteer, you need to change the angle of one of these lines. An easy fix is (from "Datsun V8 Z conversion manual", by Mike Knell, Classic Motorbooks) to raise the control arm's inner pivot point on the crossmember. Here's how he does it: -Remove the doubler washer in the original crossmember hole with a chisel. -Drill a 9/16" hole in the crossmember 3/4" above the original hole. -Weld in a doubler plate for the new hole. -Grind the part of the control arm near the bushing to prevent interference with the crossmember. You can also raise the pivot by using the offset camber bushings, but when you change the position with these, you have to go back and adjust the toe-in. The spacers don't cure the problem, but it is possible for them to help. With lines a and b not parallel, there will be a position where they will be closest to parallel. If you lower a Z too far, you probably move it away from this ideal point, and get more bumpsteer. The manufacturers of the bumpsteer spacers are probably trying to get the tie rods and control arms back to their stock position so you will only have the stock amount of bumpsteer. (or slightly less because the stiffer suspension will move less over bumps). Another way I've seen on a 510 is to change the effective "length" of the control arm. Take two sets of control arms, cut them in half , then weld the 2 long halves together, thereby increasing the length of them. It also increased the negative camber and has worked like a charm for two auto-x seasons now.
3. How do I cure steering vibration
I've (partially, in some cases) solved this persistent problem in several Zs by addressing several areas: Wheel balance, roundness, and trueness, alignment, tire inflation, rack play, mushiness in the steering chain, and worn front struts. In particular, the first thing to check is tire inflation. Both of my current cars will vibrate severely if inflation is even a couple of PSI different. In fact, I use this fact to remind me when to check the air. Next, check the alignment. Toe out will ALWAYS cause the car to hop. I generally put about 1/2" more toe in than specified. This seems to give more tolerance to wear and other influences. You will find that a by product of this adjustment is more steering resistance at slow speed/stopped. Nothing you can do other than maybe install a power steering unit from a later model so be prepared. Check wheel roundness and trueness. If you've spun the car and flattened the tires, they WILL hop at some speed. Live with it or replace them. Check runout, preferably with a dial indicator indicating against a clean and locally unbent area of the rim. Any warpage here is unacceptable. Check radial as well as axial runout. If you find runout, be sure and check the trueness of the hub. I've found one hub where the lug holes were slightly out of centre. Nothing we did stopped that damn hopping until I replaced the hub. Make sure, of course, that you don't have any ball joint wear or rubber deterioration in the suspension. Check the manual. One area to pay particular attention to is the rubber rack-&-pinion mounting bushings. These bushing soften up fairly rapidly. While it is popular to replace these bushings with solid plastic ones, I don't recommend it unless you are driving in competition. I've found that wrapping the bushing with a piece of split gas line or coating it with Shoe Goo and then clamping it while still wet will take up almost all the slop without making the steering harsh like the plastic bushings tend to do. Check the slop in the rest of the steering system, particularly the vibration bushing in the steering shaft near the firewall. Again, while many people replace this bushing with plastic or metal, I find the rubber bushing to do just fine if it is as firm as a new one. Finally, if all else fails, consider mounting a dampener cylinder on the steering arm. There is a nice little one made for volkswagens that i've used on one particular car that absolutely insisted on hopping regardless of what else I did. You can probably find a universal kit at an off-road shop.
4. What goes into making a Z race car handle
My experience with high speed zcars comes mostly from a GT2 240Z that topped out at a bit over 150 on a long track. The car probably was capable of more given the right gears and a long enough straight. The suspension was pretty standard stuff for this type of car. Carrera(?) struts with ride height adjustment using threaded collars and coilover springs. All pivot points were set up with rod ends and were fully adjustable. All mounting points on crossmembers had strengthening pads wielded on. Anti roll bars were tilton/electromotive goodies. The suspension arms themselves were all braced. This car used extremely stiff springing. In order to accommodate the radical lowering the pivot points of the front a arms were moved upward and, I believe, inwards in the crossmember. All four struts did have camber adjustment from the top but the lower pivot had to move just to get things into the ballpark. This put the front crossmember pretty close to the ground. The rubber at the top of the struts and at the differential mounts was retained. Removing these rubbers tends to make the cars crack up. Another trick to get the car lower was to cut out the floors to level and raise them. In this case they were replaced with aluminium. A box was built into the passenger side floor to accommodate a 3.5" flowmaster with the outlet going through the rocker panel. The bottom of the frame rails where they extend below the floor were also raised. Aside from the lowering the aerodynamic mods were pretty mild with a huge air dam hanging to the ground in front and the standard 3" rear spoiler in back. This car was not fast enough to get into the places where aero stuff gets really strange. From the people I've talked with it seems that it turns into real black magic somewhere around 170 - 180 mph.
5. Which shocks are best
NOT SO GOOD (YOU GET WHAT YOU PAY FOR): On the KYB's: my personal experience with the "garden variety" KYB's is that they are valved too stiffly. (Or at least that was the driver's seat feel...) Unlike other performance shocks though, not only did the ride degrade (from stock) but the handling was not improved over the Mulholland's that I was replacing. (In other words, they -might- be better than stock but for a few dollars more, there are lots of alternatives.) Also, the KYB's gave up the ghost prematurely. BETTER (MODERATE COST): While we're talking about this price range (give/take) shock absorber, I had very good luck with Kontrolle...don't start asking about these at your local parts counter however, this brand no longer exists. The good news is that these were OEM'd by Kontrolle/FAR from TOKICO! (This all happened before Tokico's were direct imported under their own name.) Now, Tokico's aren't exactly cheap but they're certainly not as high as Koni, GAB, Bilstein, etc. BEST (HIGH COST): Now a lot will depend on what the ultimate use of your car is but if it's performance you want, you can't go too far wrong with most of the Koni's or Bilsteins. I've had Koni adjustables on one Z car and they were great (for that particular application). I've used Bilsteins in all of my European cars (BMWs, Volvos) and wouldn't go with anything less, although they're not available for 240/260 Zs anymore. Alternatively consider Tokico Illuminas. These are 5 way adjustable for compression and rebound stiffness. They are rather common among autoXers and beginning road racers. Note; Konis require their removal from the strut in order to adjust them, the Tokico's require only a screwdriver.
6. How do I lower the springs
The safest, albeit time-consuming, way to judge how much to trim is to proceed in half coil increments, then reassemble and measure. Note that the rate change will be proportional to the change in length of the spring. While the material of the spring remains constant, shortening the spring reduces the torque arm length of forces applied against it, effectively increasing the spring rate. You can cut the spring with a hacksaw or an angle grinder. We cut the (already short and stiff) springs on my friend's 510 with a carbide cutting wheel on a little air powered grinder. It went through the springs in about a minute each. I think we took off about a coil and a half (counting the close wound coil on the end!) and ended up with a very low 510. This is of course with aftermarket springs on a different car, so it means nothing to you. I would try 1/2 coil at first, and then 1/4 coil increments until you get it right. I suggest driving it for about a week between cuttings so you can adjust to the new stiffness and be sure you want to go farther. Do not cut the springs so short that they are loose when the strut is at full extension - this would cause them to jump off of the spring perches while driving. The short springs on the 510 were also "too short", but it never seemed to be a problem. With the suspension at full droop you could pull the spring out of the seat, but for some reason we never had problems with it coming out on its own. I have seen the car pick up an inside front wheel when cornering very hard (this was on a 200 hp rotary engined 510 from hell), but the springs never came out of the seats (we checked frequently). I suspect this is because the front anti roll bar was keeping the front springs compressed a little under these conditions, even though the wheel was off the ground (1" front anti roll bar can do that). We also noticed some softening of the suspension after a while but attributed it to wear on the Tokico shocks that we installed at the same time. Could be wrong, but shocks do seem like much more of a wear item than springs, especially "good" ones.
7. Do I need a spring compressor to replace the springs
You can get away with not renting a spring compressor. When removing the old springs, undo the nut that holds the strut insert to the car (the big one buried in grease and whatever else has fallen in there in the last 15 years or so), then slowly and carefully jack up the front of the car (actually it is best to remove the nut when the car is partially jacked up with the front wheels just touching the ground so the strut inserts are fully extended (unless you have gas pressurised shocks, which will extend on their own when you jack up the car)). When the strut insert has reached the top of its travel, it will pull out of the strut tower and, with a few more inches of jacking, the springs will be completely unloaded and the strut can be removed (the upper spring perch will still be bolted to the car). When you put in your new shorter springs, if they are short and stiff enough, they will mount on the strut without compressing. Don't try removing the strut assembly and then removing the spring unless you have a compressor, the pre-load on the spring can be enough to shoot the upper spring perch across the garage!
8. How do I replace my springs
I didn't use the strut spring compressor to remove them. While on the ground I removed the large bolt at the top of each strut (not the 3 that hold the cap to the body!) Then jack up the vehicle. For front suspension, I had to remove the Tension/Compression bar bolts from the front member to allow the front suspension bar to drop enough (I have urethane bushings that make it very tight). The rear (from past experiences) I found that I couldn't get the spindle pin out (just below the brake drum) Instead, I placed a jack under the A frame hinge bolt and removed the 4 bolts holding the rear A frame in place. Then removed the 3 bolts holding the upper strut in place. Lower the jack settles everything to the ground gently. I also removed the front support member off the differential. The anti roll bar keeps it from dropping and allowed me to get the front A frame bolt under that support piece easier. Anyway, I found that the springs fit just inside the strut extension, both front and rear, without the need of the strut spring compressor. HOWEVER: DON'T EVER THINK OF REMOVING THE BOLT ON a stock spring without the compressor off the ground, or out of the car. I'm sure they pack a hell of a wallop. I reinstalled the brake lines and bled them, hooked up the tension rods, rear half shafts, etc.
9. How do you replace your springs without disconnecting the brake hose
I've been using a trick somebody showed me ten years ago for the Z. To do this job without breaking open any brake line or hose fittings, you can do the following:
10. How do you remove the spindle pin from the rear control are
The options are:
A: I soaked the lock bolt and the big pin(spindle) in WD-40 over night. Next day I pounded out the lock bolt (easy part). Now, replace the nut and washer on the large bolt(pin) on one side or the other. Tighten. Tighten more. With any luck the pin will start to move in the bore. When the nut bottoms out on the threaded portion of the pin, remove the nut and use some sort of spacer(s) between the nut/washer and the control arm. Repeat this process using increasingly longer spacers.
B: I could only get 3 of the 4 pins out. I had to knock
the pins out with a 3 lb hammer and large punch trying to minimise damage. The 4th pin mushroomed and will never come out now. None of them were held in by rust. It looks like the little bolt in the middle that holds the pins in place distorts the edges of the pin. The bolt is sort of a tapered wedge that matches up to a flat spot on the pin. The corners of this flat spot get distorted and prevent the pin from coming out. The distortion in the pins scored the bores but not enough to make them unusable. It is possible that this distortion is caused by over tightening the bolt. When I put them back together, I used locktite and tightened the bolt just enough to take the play out of the lock washer. I guess I will not know if this worked until I have to take them apart as some future date.
C: I had a piece of tool steel round bar stock, just slightly smaller in diameter to the spindle pin, drilled on the end and threaded to mate the threaded end of the spindle pin. The hole is deep enough such that the end of the tool mates with the shoulder of the spindle pin. I just threaded the tool on the spindle pin and used a small 2 lb. sledge hammer to drive out the pin. The spindle pins were not damaged and both were reusable. Oh yeah, this was done after the strut/control-arm assembly was removed from the car. The reason I did this was to replace the 20 year old rubber bushings at the outside of the control arm with urethane bushings.
D: I had the spindles cut with a band saw and pressed out with a 20000 lb press. When putting the new spindles back in wire brush the spindle cavity and put "Never seize" on the spindle. This way it will come out easy next time you want it to. By the way I just bought a new spindle and it cost ~$20. I guess Nissan is hurting and their making us pay.
11. My car has too much camber, how do I fix it
If it's too much negative camber:
If it's un-even camber:
To fix it:
Edited by Salman SHAMI