Rumble in the Rear

[Faceplant]

Hi All,

Have noticed that morris has developed a bit of a knocking at the rear, its a cross betweek a rattle and knock that is noticable when i go over pot hole/ bump in the road. its not there all the time, i thought it may be the exhaust, but have checked and tightened the bracket and its still there. its probably a result of all the winter pot holes!

the car has had a mini shoc conversion at the rear but has origional leaf springs.

any suggestion on what to check first?

thanks

[bmcecosse]

Well - the Mini rear damper kit is 'not the best' shall I say. The dampers don't really have enough stroke - or enough damping ability! And the beam to which they fasten is prone to cracking - so - plenty to check out there! May simply be loose damper mount bolts - or the rubber eye bushes in the dampers of course.

[Faceplant]

the last owner actually fabricated his own version of the shoc conversion, it goes up into the boot and is fastened to a beam, which allows the shoc to work properly, instead of having it overly compressed and bouncing. i'll get a pic soon.

will have to wait for the weekend to get under it properly

[bmcecosse]

Well - still inspect the beam for cracking, and the bushes/mount bolts - but Mini dampers don't have enough movement to cover the full range of Minor rear suspension - so they may be taking a beating either on bump or rebound. neither of which they are designed to withstand! The back end of a Minor is also a good deal heavier than the back of a MIni.............

[Faceplant]

good point, though with it lowered it only has about 3' of travel!

u think its worth getting uprated gaz/spax adjustable shocks?

[bmcecosse]

I would think it's worth getting larger dampers - not Mini ones! They don't have enough stroke. Although your suspension may be lowered - the suspension can still 'droop' until it is (presumably) hanging on the dampers -which were never designed for that. One answer may be to add straps to retain the droop - as on MGB etc.

[Faceplant]

i had a quick look at the shackles as i read they sometimes knock against the chassis. It looks like there has been some contact with the chassis as its uneven, i have attached pic. can anyone tell me if the shackle is of standard size? the spring is only 10k old and shouldnt be worn, the car doesnt look like it sagging.

If this is the problem, can i trim the chassis to stop it knocking?[frame][/frame]

[bmcecosse]

You said the car had been 'lowered' - how has that been done ? The suspension may have been overtravelling - and the shackle pin may have been bottoming on the chassis. However - that would occur in rear of the shackle mount - and most of the missing underseal etc in that pic is in front of the shackle. The chassis doesn't look too unusual - so really the problem probably is that the car is too low, and/or the spings and dampers are too weak! Are the rubber cone bump stops present and correct ? Whe the car is on the ground - how much space is there from bump stop to chassis plate?

[Faceplant]

its been lowered using 1 1/2 lowering blocks, it sits on top of the spring and longer U clamps hold in place. when i got the car last month i had it up on workshop ramps and there was about 3-4' between the bump stop and chassis.

I'm going to get the back up on some ramps in the morning and have a better look, see if i can spot and fresh metal to metal marks, check exhaust, spring and all nuts, axel/prop, and top of the schocks that are in the lower boot section. i have a leyland workshop manual at hand!

cheers for the help, will report back tomorrow!

[bmcecosse]

Well - normally - on an UNLOWERED car - there would be 1.5" beteween bump stop and chassis plate - so I don't see how yours has 3 - 4" (or do you mean 3/4" ?) clearance. Assuming it is the 3/4" - I suggest you take out the lowering blocks - and get yourself some suspension movement!

[PSL184]

Lowereing blocks will not cause the issue you are having (I've run lowered cars in my younger days without issue). Whilst you have her up on the ramp check all the bushes and mountings carefully. I can't see anything obviously wrong in the pic you posted above, however, Mini dampers, as suggested, are not the most suitable. Spax do some or maybe you could use original LCV rear dampers....?
Also, I know it is a daft suggestion, but take every thing out of the car, ie spare wheel, tools etc - you never know

[Faceplant]

i was looking at spax adjustable shocks, though i need the check that the shocks can cope with the weight and travel of the minor.

i'l pretty sure there was 3' between the bump stop and chassis, if it only had 1.5' as standard, wouldnt the car be bottoming out all the time? put 4 people in and ur riding ur stops?

[bmcecosse]

Yes - that's exactly what happens! Your axle does have bump stops fitted - yes ?[frame][/frame]

[Faceplant]

good new is that once i finished putting the new lock on the book and locked it, the knocking also stopped! must have been loose and ratteling, killed 2 birds with one spanner!

while i was there i had a good look underneath and there is about 3' of travel between the bump stop and chassis. the lowering block is abt 1'. the car only bottoms out when i have someone in the back and going over a big bump. i'll keep an eye on it, but it seems to be working well, even when putting 120bhp through the rear it doesnt jump or bounce when accelerating.

think some spax are on the cards, just for peace of mind.

thanks for the help!!

[bmcecosse]

3 " must be a record! So - without the lowering blocks - you would have 4" - amazing. No wonder you fitted lowering blocks.