Sunday, 8 February 2015

E60: Replacing the Rear Trailing-arm / Bushes

REMOVAL:
  1. Jack car, remove wheel.
  2. Remove anti-roll bar link [14] by undoing both the upper and lower nut. Upper nut is 16mm and you need to hold the threaded-bolt by inserting a T30-Torx socket down the end of bolt itself. Lower nut is 18mm and the bolt-end is held by a T40-Torx. Use an open-ended spanner or place a ring-spanner over the Torx-socket before inserting it.
  3. Loosen the eccentric-bolt [11] that aligns the rear suspension, making a note of its position. This is the bolt connecting the trailing-arm to the subframe lowest to the rear of the car. The bolt-head is 18mm and the nut, to the rear, is 21mm.
  4. Loosen off the front bolt [9] connecting the trailing-arm to the subframe using an 18mm socket and spanner. You do not need to remove the hard plastic cover next to it, there is just enough room to hold the obscured bolt with a spanner.
  5. Loosen off the long bolt [5] connecting the trailing-arm to the wheel-hub. The bolt-head is 18mm again and the nut, to the front, is 24mm.
  6. Fully remove the 3 bolts and wiggle the trailing arm out, usually from the subframe end first. The bolts may need helping out with a drift and hammer.
REPLACING BUSHES:
Replacing the rubber-bushes and refitting your existing trailing-arm is the cheapest option. The bushes are really tight in the arm and the old ones can be removed by any means necessary - cutting, burning, whatever gets them out. The new bushes however, are nigh on impossible to fit and will likely need shoving in with a hydraulic-press. Your local garage or mechanic mate will do this for buttons. If your on your own at home, as I was, then replacing the whole arm with bushes already in will save a lot of hassle.






REFITTING:
  1. Offer the trailing-arm up, wheel-hub first, and reinsert the long bolt [5] through the hub, loosely screwing the nut [6] on a few turns.
  2. Manoeuvre the arm up to slide the foremost bush back into the subframe mount and reinsert the bolt [9], screwing the nut [10] on a few turns. The arm may need a bit of twisting and jimmying to get in due to the geometry of the raised suspension.
  3. Manoeuvre the trailing-arm up to fit the rearmost bush back into the subframe mount. This will be difficult and you will likely need a second car-jack and a fair bit of working to get it in so the eccentric-bolt will slide through. Reinsert the eccentric-bolt [11] and tighten it up so it is reasonably tight.
  4. Tighten up the other two bolts s they are reasonably tight.
  5. Replace the wheel and lower the car off the jack to rest the weight back on the axles and reset the suspension geometry.
  6. Fully tighten all the bolts while the car is not raised off the wheels. The correct torques are [5] - 240Nm, [9] - 100Nm, [11] - 165Nm.  [BMW recommend tightening the bolts while the car is under 'normal load'. This involved placing 50kg weights on each of the seats. ** on ** used multiple bags of cement to properly set his, but if you consider this going too far then just tighten them with the car sat on its wheels as I did. You will need to back the car onto ramps to get access to the bolts without removing the wheel, so if you absolutely can't do that then just tighten them as much as possible with the car raised.]


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