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Download: Datsun 1200 Competition Suspension Manual Online: PDF
Foreward
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Front Suspension Modifications
For road racing, the front suspension of the race car must be modified to improve handling and maneuverability. This is done by: lowering the car (thereby lowering the center of gravity); reducing body roll by increasing roll stiffness; and, by improving high speed stability.Along with the above improvements, the Datsun 1200 is further modified to allow the use of superior brake components and is also converted to a fully adjustable suspension system.
The Datsun 1200 suspension, modified following the procedure in this manual, will provide the following features:
1. Camber Adjustment — the front strut tower is modified to allow the camber to be adjusted as needed. 2. Increased Caster — the tension rods are altered to provide an optimum increase in caster of 4° over stock.
3. Adjustable Ride Height — A threaded collar is added to the strut assembly to allow the height of the car to be varied depending on track conditions.
4. Lower Center of Gravity — The stock front springs are replaced with stiff, lower competition units that reduce front car height by 2 inches.
5. Improved Brakes — The stock 1200 brakes are discard and the competition strut assembly is modified to accept the more efficient 240-Z disc brake components.
6. Roll Stiffness — Replacing the stock springs with stiffer units and adding a heavier sway bar increases suspension stiffness and reduces body roll.
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Front Camber Adjustment
See main article: Camber
Front Camber AdjustmentTo allow for camber adjustments, the holes in the top strut mounting point must be elongated to 9/16-inch in length, as shown in Fig. 1. Note that the outboard mounting hole extends into the large hole provided for the upper portion of the strut assembly. Tin snips can be used to increase the size of the large opening and the outboard mounting hole. The two remaining holes can be elongated with the proper size drill and a round file.
To gain the maximum amount of adjustment, it may be necessary to file down the top strut mounting insulator to obtain the necessary clearance between it and the shock tower. (Fig. 2)
Check the clearance by placing the assembled strut into position and moving the top of it as far inboard as possible within the limits of the mounting holes. If part of the strut mounting insulator hits radius "X" (Fig. 1) of the strut tower, then that portion of the insulator should be filed off.
During final installation of the modified strut assembly, place large (1-inch diameter) washers under the stock strut mounting nuts and lockwashers.
Aside from the possibility of a slight amount of filing (for clearance), the top strut mounting assembly remains stock and is entirely adequate for competition road racing purposes. No modifications are made to the top spring seat or the top pivot bearing.
Fig. 1
Fig. 2
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Adjustable Ride Height
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Modified Strut Caliper Mount
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For competition purposes, the stock 1200 front brakes are replaced with 240-Z disc brakes. In order to adapt the more efficient disc brake components, the competition strut must be modified.
The first step is to cut off a portion of the caliper flange. Scribe a line on the caliper flange as shown in Fig. 7 and cut (hacksaw or bandsaw) the caliper mounting "ear" off. (Strut part numbers 54302-H1024 and 54303-H1024).
Fig. 7 (Zone 2B) Cut 1200 Competition Strut
Fabricate a new ear (caliper mount) from 5/8-inch C1018 mild steel following the specifications given in the blueprints.
Fig. 8 (Zone 1D) Fabricated Caliper Ear
Clamp the new ear to the strut so that the plane of S1 coincides with the plane of S2. It is extremely important that the ear be located very precisely (Fig. 9).
Fig. 9 (Zone 3B) S1 S2 Weld
Using a heliarcᵂ, tack weld the ear to the strut using No. 316 rod and then check the alignment. When the two parts are lined up properly, weld completely around the part line.
Front Hub
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Disc Brake Rotor
Page 9
The disc brake rotor is a modified, stock 240-Z unit (part number 40206-E4101ᴳ).
The first step in adapting the 240-Z rotor to the 1200 is to machine the outside diameter of the rotor to 10.312+-.025 [261.92 mm +- .635 mm. NOTE: 240Z stock rotor diameter is 271mm]
Machine radius "X" (see Fig. 13) to clear the hub flange radius (Radius —.250)
Machine surface S, Fig. 13, to remove casting marks (optional)
Fig. 13 (Zone 4C) Surface S Radius X
Note: The rotor inside diameter must clear the hub by .002 to .004-inch to allow for heat expansion.
Rotor mounting bolts should be fully threaded, 1.0-inch shank length, grade 8. Torque the bolts to 40 lbs. and secure with Lock-Tite and safety wireᵂ (Fig. 14).
Fig. 14 Safety Wire
240-Z Caliper Modification
Page 9
The 240-Z disc brake calipers have to be modified for proper clearance. The outside of each caliper should be ground down slightly to provide adequare wheel clearance. Also approximately 1/8-inch of material must be removed from the bottom of the caliper to clear the brake disc. The shaded areas in Fig. 15 illustrate the areas to be ground down.
Fig. 15 Ground Area
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Fig. 16 Complete Competition Front Brake Assembly
Modified 240-Z Caliper Competition Strut 240-Z Disc Fabricated Hub
Front Springs
Page 11
Lower Link and Steering Gear
The complete lower suspension link can be left stock. The inner chassis mount rubber bushing may also be left stock since it is very rigid and deflects a minimal amount while cornering.
The complete steering linkage assembly is adequate for competition purposes. This includes the steering gear box, tie rods, tie rod ends, all steering arms, idler arm assembly and the lower ball joint.
Tension Rod and Bushing Modification
See Main Article: Castor#Datsun_Competition
Page 11
Sway Bar Assembly
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Front Competition Suspension Assembly
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Sway Bar Installation
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Sway Bar Adjustment
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page 20 (blank page)
Rear Suspension Modifications
Page 21
Like the front, the rear suspension must be modified to improve handling and maneuverability. Steps must also be taken to see that traction is improved to insure that all the available power "gets to the ground."In order to improve handling and traction, the modifications illustrated in this manual are designed to achieve the following results:
1. Control of lateral and fore-and-aft rear axle movement. 2. Prevent spring wrap-up and improve traction.
3. Increase spring rate.
4. Provide a fully adjustable suspension (shocks, ride height, roll stiffness).
5. Lower car height.Since the front and rear suspensions are dissimilar, different steps are needed to achieve the desired results in the rear. These modifications include:
1. Shocks and reworked lower shock mount. 2. Spring modification.
3. Front spring eye bushings.
4. Front spring hanger chassis mount bushings.
5. Traction arm assembly.
6. Reworked rear spring shackle assembly.
7. Sway bar assembly.
page 22 Fig. 1 Complete Rear Competition Suspension
Rear Spring Modification
Rear Spring Modification
The original rear springs are replaced with modified Datsun 1200 Competition units, Part Number 55020-H1024. The competition spring assembly contains three leaves held together by a single bolt.
Before installation, both of the competition springs are modified by removing the bolt and discarding the bottom (short) leaf. Then simply bolt thetwo remaining spring leaves back together. This modification will result in a spring rate reduction of approximately 25% from the unaltered competition spring assembly, but an increas of approximately 10% over the stock 1200 assembly.
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Front Spring Eye Bushing
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Compare to Comp manual:
Shocks and Reworked Lower Mount
Page 24
When the recommended #rear spring modification is performed, only KONI shock absorbers (part number 80-1977-0051) should be used on the rear suspension. Konis are an adjustable shock with approximately 6-1/2 inches of available travel. This is very close to the amount of travel provided by the stock shock. However, at maximum bump, the Konis will run completely out of travel before the axle does. If this occurs and the Konis are forced to collapse completely, the adjustment mechanism can be destroyed.
To prevent this, the shock absorber mounting stud on the bottom of the spring seat must be moved downwards one inch. This will provide enough shock absorber and wheel travel so that the shock does not bottom out before the axle hits the chassis.
The first step in lowering the shock mounting stud is to remove the stock stud with a hacksaw. Note: use the lower coupe spring plate, not the sedan, regardless of the model being modified.
Next fabricate a shock bracket extension from a piece of .150 to .180-inch thick mild steel. Bend it to the proper shape as illustrated on the blueprint, and heliarc or arc weld it to the lower edge of the stock coupe spring seat (Fig. 3). A cutting template and detailed bending instructions are given on the blueprints.
A new shock mount stud should be fabricated from a 1/2-inch by 2.0-inch, grade 8 bolt. Leave the full head thickness of the bolt unaltered as this will properly space the shock away from the bracket surface for proper clearance. Machine and rethread the nose of the bolt as shown in Fig. 4.
Finally, arc weld the bolt to the newly fabricated bracket extension (Fig. 5). Make certain that the bolt is perpendicular to the bracket extension and that the centerline of the new stud (bolt) is 1.0-inch lower and directly in line with, the location of the stock shock mounting stud.
EDITOR'S NOTE: here is a photo of similar mod for a shock with 2" longer compression length:
Rear Traction Bar Mount
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Front Spring Hanger Mount Chassis Bushing
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Front Spring Hanger Assembly
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Traction Arm Assembly
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Rear Shackle
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Rear Sway Bar Assembly
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Rear Competition Suspension Assembly
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Final Adjustments
Page 36
General Handling
Page 37
Parts Lists
Competition Parts Lists
Page 38
Front Suspension
Page 39
Rear Suspension
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