Rear spring shackles

[MorrisJohn]

Whilst treating my rear springs I noticed some of the rubber bushes on my rear suspension are shot (see photo for an example). I’ve ordered the rear shackle/poly bush kit to put it right -https://www.morrisminorspares.com/rear- ... e-p1238940

Question is should I attempt it myself having little mechanical experience? How difficult a job is it? In theory it looks straightforward.

I’ve got the car going into a garage next month for some other minor work (no pun intended) and could add this on. It would save me grief, but at a financial cost.

[philthehill]

It is a reasonably easy job but can be difficult if the front eye pin and or nuts are seized.
If you are in any doubt I would recommend that you get the garage to do the job.
I also recommend that you fit poly bushes as they will last longer than the rubber bushes and give a better ride.

[MorrisJohn]

It is a reasonably easy job but can be difficult if the front eye pin and or nuts are seized.
If you are in any doubt I would recommend that you get the garage to do the job.
I also recommend that you fit poly bushes as they will last longer than the rubber bushes and give a better ride.

Garage it is then!

[kevin s]

If it's the spring hitting the body at the back you are worried about ours did that with new bushes, never could work out why, the spring mountings in the body are all in the correct place only thing I could think of is the flange is a bit deeper on the replacement panels I used, in the end I made 1/2" longer shackles.

[MorrisJohn]

If it's the spring hitting the body at the back you are worried about ours did that with new bushes, never could work out why, the spring mountings in the body are all in the correct place only thing I could think of is the flange is a bit deeper on the replacement panels I used, in the end I made 1/2" longer shackles.

That hadn’t crossed my mind until recently. Any idea what the normal gap should be? I haven’t measured my current gap (this is before the work begins on rear bushes).

[kennatt]

If the spring shackle is hitting the chassis it is a clear sign that the spring needs changing ,as the spring ages and looses temper it begins to straighten and therefore lengthens,then the shackle his the chassis . With new spring and bush the shackle should point straight down when unloaded.The life can be extended by fabricating slightly longer shackles ,but new spring is the correct way since handling is also effected with a soft spring.

[MorrisJohn]

Thanks for the explanation. That makes sense. The shackle itself is reasonably vertical, though the rubber bush is completely shot on one side. The springs are only six years old. I recently wire brushed them and treated them. Still to grease them up. Photo shows clearance between spring and chassis.

I reckon some new poly bushes and “pads” will suffice for a few years. I considered replacing the whole lot, springs included, but it’s probably a bit overkill?

Might be worth removing the rear dampers and replacing the oil at same time.

[kevin s]

I don't understand how a sagged spring would cause it to hit the body at the shackle, the springs don't grow in length as the age and even new ones hit the bump stop over bumps with a couple of rear seat passengers, it may be they hit more often but they will still hit it seems either there is a fundamental design flaw, the modern springs are too long or the bushes are worn.

[philthehill]

The rear springs fitted to the Minor are not flat they are semi-elliptic - which when looked at from the side appear to have a downward curve.
The front of the spring is fixed by the front eye pin and cannot move in any direction only in rotation around the bush and eye pin.
When the suspension/spring is depressed it flattens. When an elliptic spring flattens it gets longer i.e. the distance between the front and rear eye increases pushing the rear shackles to rotate around the shackle pin located in the body. The spring will get to a point where the flattening process reduces the clearance between the rear spring eye and the body allowing the spring eye and the body to come into contact.
The problem of the rear of the spring hitting the body is a common issue when the spring eye bushes have failed or in poor condition. The spring pads between spring and axle tube have little if any impact on the problem as they are only there to locate the axle on the spring.
I would suggest that you replace all the spring eye bushes with poly bushes whilst leaving the spring pads alone. I would also suggest that you service the rear dampers and fill with a straight EP30 oil.
After replacing the bushes and servicing the rear dampers see what the clearance between the rear spring eye and body is and go from there.
Comparing the measurements of your car with those in the diagram below will determine how much your springs have or have not flattened .

ride height 1.jpg (959.84 KiB) Viewed 678 times

Aftermarket rear Minor springs do not appear to have the longevity of the originals and may start to flatten after a short service life.
Before giving the spring bolts a final tighten - bounce the car a few timed to normalise the position of the components and then give the final tighten.

[kennatt]

The original springs on my old ser11 lasted for 20 years approx,before they hit the chassis,the next new ones lasted about 5 years,the next ones were far too hard (wrong temper ) had virtually no spring, needed to remove the small leaf to get any sort of a reasonable ride.Sold the car a few years back so don't know if they ever softened up, suppose they would eventually,gave the small leaf to the new owner so he could replace it if he needed to.
Very poor quality replacement,depends how lucky you are.

[les]

Some rear springs are supplied with a cheaper, and inferior clamping ring, as opposed to the more conventional clamping device. I have seen the former break, ( there’s a surprise ! ) so the last set I bought were modified back to original. Worth checking if considering buying springs. You can’t let your guard down for one moment, when looking for quality.

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[philthehill]

The clamps shown in Les's photo above do little to effect the spring rate. What they do do is keep the spring leaves in line and help to reduce the spring leaves flexing when under load i.e. starting off where spring wind up and axle tramp may be experienced. The clamps should be fitted to the front half of the spring as spring flexing is maximised between the front spring eye and axle mount. There are usually two clamps forward of the axle and one clamp to the rear of the axle.
What I have done in the past to improve or adjust the spring rate is to fit clamps to the front half of the spring that can be tightened to grip the spring leaves to reduce the movement of the leaves in relation to one another.

[MorrisJohn]

Thanks for all the advice and diagram. I shall replace the rear bushes with poly and add additional spring clamps where necessary.

One question in respect of the rear dampers, are any parts (other than SAE30 oil) required for servicing them?

[philthehill]

No additional parts required when servicing the dampers or changing the oil. Changing the oil is about all you can do anyway.
The rear dampers are best serviced off the car. See wksp man for details.