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[Datsun 1200 encyclopedia]

Knuckle Arm

From Datsun 1200 Club

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Category: Front Axle And Front Suspension

The "Knuckle arm" (steering arm) is sandwiched between the Ball Joint and the Strut assembly.



Knuckle arm also known as "steering arm". It turns the strut to which the front wheel is bolted, thus steering the vehicle. The arm is pushed/pulled by the tie-rod of the Steering Linkage.
29464.jpgAlbum 29464

Steering arm. The threaded bolt is to adjust the steering angle stop
13022_4e3cbb95cad29.jpgUpload click to view

Knuckle arm bolts to the bottom of the Strut
174_5ca6e20bd6a2a.jpgPost 491099

Special shoulder bolt required to take up shear load
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Datsun knuckle arms come in two basic sizes, 75mm & 80mm:

  • 75mm narrow bolt spacing for 45mm strut tubes (used by B110)
  • 80mm wide bolt spacing for 50.8 mm strut tubes (used by most other Datsuns including 280ZX)
  • 91mm spacing on 240Z

23761.jpgAlbum 23761

There is only one size for 1200, to fit 45mm strut type. But it comes in two versions: 1970-1975, and 1976-up.

H10 balljoint (small taper)
* for small-bolt-pattern LCA (B110, early 120Y)
H74 balljoint (large taper)
* fits large-bolt-pattern LCA (late  120Y/B120/B310) 

casting marks identify
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25612.jpgAlbum 25612 25613.jpgAlbum 25613 29470.jpgAlbum 29470

Bolted to the balljoints
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Quick Ratio Arm

Consider the length of the arm: long arm gives a slower steering response, but less effort is required to turn the wheels. Shorter arms give faster response.

Change the length of the steering arm without changing the steering idle arm length will impact the front suspension bump steer characteristics.

Unfortunately the large-size B310 arm (commonly used when swapping struts) will change your 15:1 steering to an effective 16:1 as the arm is 7% longer. Even worse, when putting 2" struts in a 45mm B310 vehicle, the stock B310 16.4:1 steering will effectively turn into a slow 17.6:1.

Short-arm Modified for use with 2" struts
23760.jpgAlbum 23760

Pitroad sells modified quick steering arms.


It seems B310 with W5000/W5060 steering arm uses the same size tie-rod ends as the smaller units (B110 and B210).

* B310 small: rounded 
  23728.jpgAlbum 23728
* B310 large: knobbed area around the ball joint hole
  16973_5541cf499778a.jpgUpload click to view

Knuckle Arm

B120 early +H1000/H1025 rod assy
B120 7510- +H1025 rod assy
H7400 -8507
H7440 8508-

23726.jpgAlbum 23726 23727.jpgAlbum 23727 23728.jpgAlbum 23728

B210 early +H5025
H7400 late van
B210 late +H5025 rod assy
PB210/USA B210 +H5800 rod assy
B310 +W5025 rod assy
H7400 regular cars

23723.jpgAlbum 23723 23724.jpgAlbum 23724 23725.jpgAlbum 23725

W5000/W5060 power cars

B310 Steering Knuckle Arms
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Part Numbers

steering arm
40052 = Knuckle Arm RH 
40053 = Knuckle Arm LH
Knuckle Arm RH
 B10: 40052-18000 (different from newer models)
 B110: 40052-H1000 < 40052-H5000
PB110: 40052-H2501
  510: 40052-H2501 from 1972 510 > 40052-H2500 > 40052-A8600
 B120: 40052-H5000 to 1974
 B120: 40052-H7400 7510- <> 40052-H7440
 B210: 40052-H5000 (74-75 A12)
 B210: 40052-H7400 (1976-up A engine, except USA)
 B210: 40052-U0101 (USA, also PB, also L16)
 B310: 40052-W5000 (All US, all A15, most A14) <> 40052-W5060
 B310: 40052-H7400 (A12, A13, and budget A14 models)
  A10: 40052-W5000 ALL <> 40052-W5060

Knuckle arms bolted to ball joints
23731.jpgAlbum 23731


* 1977-1981 A10 Stanza/510
* 1978-1982 B310 fitted with 13" wheels


H74 - A12A cars
W50 - A14/A15
25892.jpgAlbum 25892
40052-H7400 ARM-KNUCKLE RH
  ALL round headlight except GX#,Wagon
  S,K.A12A/A13 square headlight
40052-W5000 <> 40052-W5060
  GX# round headlight (OPTION)
  S,K.A14/A15 square headlight
USA B310
W50 - all [including A12A-powered cars]
Compare W50 arm use with the 13" wheel fitment
12 x 4J GRAY
12 x 4J SILVER
13 x 4.5J SILVER
  40300-W8300 S,K,W square headlight S/# 40300-W5700
              GX# round headlight
              W.GL round headlight
  40300-U7400 W.DX round headlight
13 x 5 alloy Type B 40300-U7527/40300-U7528 (W/KEY)
  OPTION for W
  OPTION for GX round headlight
  OPTION for S,K.A14/A15
13 x 5 alloy Type C 40300-W6027/40300-W6028 (W/KEY)


40055-H1000 BOLT-KNUCKLE ARM 44mm
08911-64010 NUT-HEX M10x1.25 High, medium carbon steel (2 each side)
08915-14010 WASHER-SPRING lock medium M10 (2 per side)

The 44mm bolt replaced the earlier 38mm long version which was used on one side. After 1973 February the long bolt was used on each side.
14333_65928ea9afc60.jpgPost 498145 14333_65928eb86736b.jpgPost 498145

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When Lowering the front suspension, if going ultra-low, strut spacers (roll center adapters) are used. They are intended to correct the lower arm angle when the vehicle height is dropped to address the change in front roll instant center.

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