Trailing / semi-trailing arm (BMW E36 / E30 rear)
A big trailing arm pivots at a forward bushing and carries the hub at its rear end; the whole arm+hub swings together on travel. On the E36 it’s really a multilink with a trailing arm (BMW’s “central-link” axle) — a trailing arm plus lateral camber/toe links. So you build it like the multilink, with the trailing arm as one (special) Arm.
Parts → roles
| Real part | Marker | Role | Settings |
|---|---|---|---|
| upright / hub carrier | RL_Hub |
Hub | Wheel Rotation = SteerCamber |
| trailing arm | RL_TrailingArm |
Arm | Inner Pivot = forward bushing · Outer Target = RL_TrailingArm_end · Telescopes ON |
| upper/camber link | RL_CamberLink |
Arm | Pivot = chassis · Target = RL_CamberLink_end |
| lower/lateral link | RL_LowerArm |
Arm | Pivot = chassis · Target = RL_LowerArm_end |
| toe link | RL_ToeLink |
Arm | Pivot = chassis · Target = RL_ToeLink_end |
| halfshaft | RL_Halfshaft |
Arm | Pivot = diff · Target = RL_Halfshaft_end |
| coilover | RL_Spring |
Shock | Tophat = body · Lower Mount = on the trailing/lower arm · Body Anchored At Tophat = ON |
Hierarchy
RL
├── RL_Hub Hub · SteerCamber
│ ├── RL_TrailingArm_end (no component)
│ ├── RL_CamberLink_end (no component)
│ ├── RL_LowerArm_end (no component)
│ ├── RL_ToeLink_end (no component)
│ └── RL_Halfshaft_end (no component)
├── RL_TrailingArm Arm (pivot = FORWARD bushing)
│ └── RL_Shock_low (no component — coilover Lower Mount, if it mounts on the arm)
├── RL_CamberLink / RL_LowerArm / RL_ToeLink / RL_Halfshaft (Arms)
├── RL_Tophat (Shock Tophat — fixed)
└── RL_Spring Shock
What makes it different
- The defining part is the trailing arm: its Inner Pivot is a bushing ahead of the hub, so it swings up/down through travel (and on a semi-trailing arm, that angled pivot makes the wheel gain camber/toe — which the game already bakes into the wheel, so the Hub shows it via SteerCamber).
- Everything else is the multilink recipe — camber/toe links + halfshaft + coilover, all Arms/Shock.
Type gotchas
- Big casting twist: the E36 trailing arm is a chunky casting bolted to the hub, so in reality it cambers with the wheel. A plain Arm only aims (it won’t visibly twist). For a faithful look use the planned “Rigid to Hub (casting)” Arm option (ROADMAP #4) — it pivots at the bushing but rotates with the hub. Until then, a plain telescoping Arm reads fine for most shapes.
- Same shock rule as multilink: keep the shock body off the telescoping arm; only the Lower Mount marker rides it.
- E30 (pure semi-trailing arm, fewer links): drop the extra lateral links — just the trailing arm + coilover + halfshaft.