Suspension Modification FAQ

[JMortensen]

This is one of the most commonly asked questions asked here and it is also a tough one to answer, due largely to the varied usage of our cars. From the factory the only adjustable alignment angle available is the front toe. One of the main features of a high performance suspension is the ability to adjust the suspension angles, so as the stages progress the adjustablity increases.

 

IF YOU INTEND TO RACE YOUR CAR, GET THE APPROPRIATE RULEBOOK BEFORE YOU START ANY MODIFICATIONS TO MAKE SURE YOU REMAIN LEGAL!!!

 

REFURBISHING A STOCK Z CAR

 

If the car is a street driver and the intent is to have a cushy ride, it may be that a simple refurbish of the stock suspension is all that is necessary. A typical rebuild of the stock suspension will include:

1. New outer tie rod ends

2. New ball joints

3. New rubber bushings and steering coupler

4. Repack/retighten front wheel bearings

5. Replace rear wheel bearings if needed

6. New shocks (KYB GR2, Monroe, etc)

7. New springs OEM replacements and slightly stiffer Euro springs are available from http://www.courtesynissan.com

 

These few things will restore the ride to close to factory stock.

 

MODIFYING A Z CAR FOR BETTER HANDLING

 

If the goal is to stiffen up the car for better handling, then a lot more can be done. I'm going to attempt to show "Stages" of modifications. These are loose guidelines and parts can be mixed and matched, but these are what I feel are typical mods on the Z's that I've come in contact with over the years.

 

STAGE 1 replaces all old parts with stiffer components. This will give you a firmer sporty ride.

1. New outer tie rod ends

2. New ball joints

3. Polyurethane bushings

4. Repack/tighten front wheel bearings

5. Replace rear wheel bearings if needed

6. Aftermarket front and rear swaybars

7. Lowering springs (Eibach, Suspension Techniques, Tokico, MSA, AZC)

8. Aftermarket shocks (Tokico HP, Tokico Illumina, Koni Red)

9. Bumpsteer spacers

 

STAGE 2 is similar to Stage 1 but starts to allow adjustment of alignment angles.

1. New outer tie rod ends

2. New ball joints

3. Polyurethane bushings and Gmachine control arm bushings and TC rod kit (these allow camber adjustment front and rear and also toe adjustment in rear)

4. Repack/tighten front wheel bearings

5. Replace rear wheel bearings if needed

6. Aftermarket front and rear swaybars

7. Lowering springs (Eibach, Suspension Techniques, Tokico, MSA, AZC)

8. Aftermarket shocks (Tokico HP, Tokico Illumina, Koni Red)

9. Bumpsteer spacers

 

STAGE 3 takes adjustability a step further.

1. New outer tie rod ends

2. New ball joints

3. Polyurethane bushings and Gmachine control arm bushings and TC rod kit (these allow camber adjustment front and rear and also toe adjustment in rear)

4. Repack/tighten front wheel bearings

5. Replace rear wheel bearings if needed

6. Aftermarket front and rear swaybars

7. Coilover spring conversion to 2.5" springs. Street springs generally under ~250 in/lbs.

8. Aftermarket shocks (Tokico HP, Tokico Illumina, Koni Red)

9. Bumpsteer spacers

10. Biscuit style bolt in camber/caster plates (EMI, DP racing)

11. Strut tower bars front and back, preferrably triangulated to the firewall in front

 

STAGE 4

1. New outer tie rod ends

2. New ball joints

3. Adjustable control arms (Modern Motorsports, AZC, Z Select)

4. Repack/tighten front wheel bearings

5. Replace rear wheel bearings if needed

6. Aftermarket front and rear swaybars

7. Coilover spring conversion to 2.5" springs. Street springs generally under ~250 in/lbs.

8. Aftermarket shocks (Tokico HP, Tokico Illumina, Koni Red), might be thinking about sectioning strut housings and getting appropriate shorter shocks to fit at this stage

9. Bumpsteer spacers

10. Biscuit style bolt in camber/caster plates (EMI, DP racing)

11. Adjustable TC rods (TTT, AZC, Z Select)

12. Strut tower bars front and back, preferrably triangulated to the firewall in front

13. Roll bar

 

STAGE 5 - at this point you're pretty much race only

1. New outer tie rod ends

2. New ball joints

3. Adjustable control arms (Modern Motorsports, AZC, Z Select)

4. Repack/tighten front wheel bearings

5. Replace rear wheel bearings if needed

6. Aftermarket front and rear swaybars

7. Coilover spring conversion to 2.5" springs. Springs generally over ~250 in/lbs.

8. Aftermarket shocks in sectioned strut housings(Koni 8610-1437RACE single adjustable, Koni 8611-1259 double adjustable, Ground Control Advance Design, Bilstein Sport VW non adjustable P30-0032)

9. Bumpsteer spacers

10. Cut to fit camber plates (DP racing, Carrera, Ground Control, AZC, TTT)

11. Adjustable TC rods (TTT, AZC, Z Select)

12. Strut tower bars front and back, preferrably triangulated to the firewall in front

13. Roll cage with tie ins to front strut towers

 

Above and beyond Stage 5 you get into modifying the chassis itself to allow for modification of the suspension pickup points. There are also people who have adapted suspensions from entirely different cars into the Z chassis. We've had members install 240SX IRS, Corvette C4 rear suspensions. Also for drag racing there have been quite a few "backhalves" where the entire rear section of the frame is cut off and a new frame built in the rear to allow installation of a solid rear end. Popular choices seem to be Ford 8.8 and 9 inch and Chevy 12 bolt rears.

 

Front suspension swaps aren't as popular as of yet, but many GT2 Z racers have fabricated their own SLA (short and long arm) front suspensions.

 

Modifying your suspension is potentially dangerous and you do so at your own risk.

[Michael]

In what category would we classify the JTR-type steering crossmember mod for bumpsteer reduction/camber increase? This used to be [relatively] popular some years ago, but seems to be getting rarer.

[JMortensen]

I didn't cover everything, the JTR mod and short steer knuckles were two that I didn't mention in particular. You could do them pretty much anywhere along the way, I don't think that those mods are too terribly common before about Stage 2.

 

In my experience with slotting the front crossmember to get rid of the bumpsteer I found that I only needed to move the pivots up 7/16" before the bumpsteer went away on a bumpsteer gauge. I don't know how the 3/4" was caculated by JTR, but I have my doubts about the accuracy of that number. The effect on camber is similar to installing a 3/4" bumpsteer spacer. Another issue to consider is using the JTR mod with camber bushings. The camber bushings allow the pivot height to be raised and lowered, and the JTR mod raises the height as well. This could lead to potentially really high pivot heights, which might have a pretty strong effect on bumpsteer too.

 

For more on bumpsteer: http://forums.hybridz.org/showthread.php?t=103886