|In the interest of sorting out what the application differences are for Nissan & Nismo Rear Arm / Knuckle Bushings
These come factory color coded with a paint marker dot to help differentiate them. The metal "casing" is about 32mm wide on all of them fwiw.
Nissan 55157-33P00 (blue) aluminum 40mm wide x 30mm diameter (fits Z32 knuckle and rear arms)
Nismo 55157-RS521 (green) steel 40mm wide x 30mm diameter
Nismo 55157-RS580 (red) aluminum 40mm wide x 30mm diameter
Nismo 55157-RS590 (white) steel 50mm wide x 30mm diameter (fits S14 R33 R34 etc. non-HICAS toe arm only)
The Z32 rear knuckle is aluminum - the bushings pressed into it from the factory have an aluminum outer shell. Use 55157-33P00 or 55157-RS580 as replacements.
The S13/S14/S15/R32/R33/R34 (non HICAS) rear knuckle is iron - the bushings pressed into it from the factory have a steel outer shell. 55157-RS521 should be used. Original grade S13 bushing 55157-0P000 is NLA.
This is done to prevent corrosion and oxidation from forming between dissimilar metals. Dimensionally 33P00 RS580 and RS521 are the same.
For the rear knuckles on a Z32 I would recommend either original grade 55157-33P00 (blue) or higher durometer (firmer) Nismo 55157-RS580 (red).
Diameter of all 4 bushings is the same:
33P00 RS521 RS580:
Bernie Bilski email@example.com
President of Z-Car Club of Northern Virginia
1995 Nissan 300ZX TwinTurbo in Cobalt Green
1997 Nissan 240SX SE in Ultra Red
2006 Nissan Frontier SE in Ultra Black