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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"

Steering arm
13022_4e3cbb95cad29.jpgUpload click to view

Knuckle arm bolts to the bottom of the Strut
174_5ca6e20bd6a2a.jpgPost click for topic

Special shoulder bolt required to take up shear load
26250.jpgAlbum click to view

14637.jpgAlbum click to view 15173.jpgAlbum click to view

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 click to view

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
25611.jpgAlbum click to view

25612.jpgAlbum click to view 25613.jpgAlbum click to view H7400.jpg

25891.jpgAlbum click to view 40052-W50-3.jpg 40052-W50-2.jpg 40052-W50-1.jpg

Quick Ratio Arm

Consider the length of the arm -- long arm give 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

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
* B310 large: knobbed

Knuckle Arm

B120 early +H1000/H1025 rod assy
B120 7510- +H1025 rod assy
H7400 -8507
H7440 8508-
23726.jpg 23727.jpg 23728.jpg 
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.jpg 23724.jpg 23725.jpg 
W5000/W5060 power cars

B310 Steering Knuckle Arms
16436.jpg :post


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



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


H74 - A12A cars
W50 - A14/A15
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)


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.

See main article: Roll Center Adjusters

16496.jpg 23732.jpg

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