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[Datsun 1200 encyclopedia]

Datsun 1200 Competition Suspension Manual

From Datsun 1200 Club

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Categories: Documentation | Racing | Suspension Modifications

Download: Datsun 1200 Competition Suspension Manual



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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 Adjustment

To 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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Front Hub

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240-Z Caliper Modification

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Front Springs

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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

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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

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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
22.png 27694.jpgAlbum click to view

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:
16273.jpgAlbum click to view

Shocks and Reworked Lower Mount

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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.

27693.jpgAlbum click to view

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:
19038.jpgAlbum click to view

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

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General Handling

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Parts Lists

Competition Parts Lists

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Front Suspension

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Rear Suspension

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