Front suspension "locked" - Problem Identified

[JohnLiddle]

Greetings,

I am in the process of changing the front shock absorbers on my daughter's car.

The car is supported on both sides on axle stands under the main chassis members.

I noticed that when, as part of the shock absorber removal, I jacked up the lower suspension arm on the nearside, the suspension moved upwards a small amount, and then "locked" and the whole car started to move upwards, raising it off the axle stand.

At first I thought this might be because the shock absorber had failed in some way which prevented it moving through the full range. However, the symptom is still there after I have disconnected the shock absorber from the king pin.

The offside behaves as expected, jack under the wishbone and the suspension can be moved up and down through the whole range of movement.

Clearly I shall have to dismantle the lower suspension wishbone etc to investigate, but can anyone suggest what the cause might be?

Regards,

John Liddle, Backwell, N. Somerset

[chrisryder]

well you will get to a point where once you put the spring under enough load, the spring will lift the car off the ground, in the same way that the car sits at a given ride height when on the ground. i've probably not explained that well...

it does sound odd that it's different from one side to the other. could it depend on where about you are jacking the suspension from?

if it truly is seizing, the i'd look a the pivot pin in the lower trunnion, and the pin and bushes in the eyebolt at the chassis leg.

worth checking over, and replacing if necessary while you've got the suspension in this many pieces.

[simmitc]

It could be that the arm has been put back on the torsion bar at the wrong angle. Was the ride height level before you started? With the car on stands, and both dampers removed, are the bottoms of the arms the same distance from the ground? It could also be a seized trunnion. As above, definitely worth stripping and checking, it's a simple job and could save a serious failure in the future.

[bmcecosse]

Has the suspension been greased in living memory? Why are you changing the dampers? Were they leaking ? If not leaking - an oil change to more viscous SAE 30 will make a world of difference. While in there you should take the chance to fit polyurethane bushes.

[JohnLiddle]

Greetings once again,

thanks for the helpful replies to my query.

Further dismantling has revealed the cause of the "locking" - see photo below.

[frame][/frame]

Note the position of the pin within the bush - off-centre and towards the top. This means that as the wishbone rotates about the inner pivot (as when I was jacking under the king pin), the top surface of the wishbone was coming into contact with the seam on the main chassis member, thus preventing further rotation.

So its off to Charlie Ware's on Monday for me with a view to purchasing a load of polyurethane bushes (I shall do both sides while I am at it).

Best wishes,

John Liddle

[bmcecosse]

CW may not be the best 'deal' - always shop around.... There are many reputable suppliers of Minor parts. I suggest you may well need a new 'pin' too. But well done for coming back and showing us the problem!

[JohnLiddle]

I spoke of Charlie Ware's because he's local, as is Moss, both being in Bristol.

bmcecosse - you are right about the pin, and a new eybolt is needed as well!

Regards,

John Liddle